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Sample records for walking speeds flows

  1. Modulation of walking speed by changing optic flow in persons with stroke

    Directory of Open Access Journals (Sweden)

    Lamontagne Anouk

    2007-06-01

    Full Text Available Abstract Background Walking speed, which is often reduced after stroke, can be influenced by the perception of optic flow (OF speed. The present study aims to: 1 compare the modulation of walking speed in response to OF speed changes between persons with stroke and healthy controls and 2 investigate whether virtual environments (VE manipulating OF speed can be used to promote volitional changes in walking speed post stroke. Methods Twelve persons with stroke and 12 healthy individuals walked on a self-paced treadmill while viewing a virtual corridor in a helmet-mounted display. Two experiments were carried out on the same day. In experiment 1, the speed of an expanding OF was varied sinusoidally at 0.017 Hz (sine duration = 60 s, from 0 to 2 times the subject's comfortable walking speed, for a total duration of 5 minutes. In experiment 2, subjects were exposed to expanding OFs at discrete speeds that ranged from 0.25 to 2 times their comfortable speed. Each test trial was paired with a control trial performed at comfortable speed with matching OF. For each of the test trials, subjects were instructed to walk the distance within the same time as during the immediately preceding control trial. VEs were controlled by the CAREN-2 system (Motek. Instantaneous changes in gait speed (experiment 1 and the ratio of speed changes in the test trial over the control trial (experiment 2 were contrasted between the two groups of subjects. Results When OF speed was changing continuously (experiment 1, an out-of-phase modulation was observed in the gait speed of healthy subjects, such that slower OFs induced faster walking speeds, and vice versa. Persons with stroke displayed weaker (p 0.05, T-test. Conclusion Stroke affects the modulation of gait speed in response to changes in the perception of movement through different OF speeds. Nevertheless, the preservation of even a modest modulation enabled the persons with stroke to increase walking speed when

  2. Brisk walking speed in older adults who walk for exercise.

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    Parise, Carol; Sternfeld, Barbara; Samuels, Steven; Tager, Ira B

    2004-03-01

    To determine the self-selected exercise intensity of older adults who report that they walk briskly for exercise. An additional aim of the study was to assess the contribution of self-reported physical activity to self-selected exercise intensity. Observational. walking path. Subjects consisted of 212 participants in the Study of Physical Performance and Age-Related Changes in Sonomans who stated in a detailed home interview that they walked briskly for exercise. Observed brisk walking speed was measured as the time it took participants to walk half a mile at "normal brisk walking speed." Self-reported physical activity was categorized as metabolic equivalent of the task (MET) in minutes of exercise reported in the previous 7 days. Physiological measures and body composition were obtained through laboratory evaluation. Men walked at an average speed+/-standard deviation of 5.72+/-0.69 km/h and women walked at an average speed of 5.54+/-0.64 km/h. Self-reported physical activity was not associated with brisk walking speed when adjusted for age and ratio of lean to fat mass. This study found that older adults who report that they walk briskly for exercise do so at a pace considered moderate or greater in absolute intensity as indicated by their walking speed (4.83 km/h). Ninety-eight percent of men (93/95) and 97% of women (113/117) had an observed walking speed equivalent to 3 or more METs based on their calculated walking speed.

  3. Establishing the Range of Perceptually Natural Visual Walking Speeds for Virtual Walking-In-Place Locomotion

    DEFF Research Database (Denmark)

    Nilsson, Niels Christian; Serafin, Stefania; Nordahl, Rolf

    2014-01-01

    to virtual motion. This paper describes two within-subjects studies performed with the intention of establishing the range of perceptually natural walking speeds for WIP locomotion. In both studies, subjects performed a series of virtual walks while exposed to visual gains (optic flow multipliers) ranging...

  4. Speed dependence of averaged EMG profiles in walking

    NARCIS (Netherlands)

    Hof, AL; Elzinga, H; Grimmius, W; Halbertsma, JPK

    Electromyogram (EMG) profiles strongly depend on walking speed and, in pathological gait, patients do not usually walk at normal speeds. EMG data was collected from 14 muscles in two groups of healthy young subjects who walked at five different speeds ranging from 0.75 to 1.75 ms(-1). We found that

  5. Sounding better: fast audio cues increase walk speed in treadmill-mediated virtual rehabilitation environments.

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    Powell, Wendy; Stevens, Brett; Hand, Steve; Simmonds, Maureen

    2010-01-01

    Music or sound effects are often used to enhance Virtual Environments, but it is not known how this audio may influence gait speed. This study investigated the influence of audio cue tempo on treadmill walking with and without visual flow. The walking speeds of 11 individuals were recorded during exposure to a range of audio cue rates. There was a significant effect of audio tempo without visual flow, with a 16% increase in walk speed with faster audio cue tempos. Audio with visual flow resulted in a smaller but still significant increase in walking speed (8%). The results suggest that the inclusion of faster rate audio cues may be of benefit in improving walk speed in virtual rehabilitation.

  6. Maximum walking speed is a key determinant of long distance walking function after stroke.

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    Awad, Louis N; Reisman, Darcy S; Wright, Tamara R; Roos, Margaret A; Binder-Macleod, Stuart A

    2014-01-01

    Walking dysfunctions persist following poststroke rehabilitation. A major limitation of current rehabilitation efforts is the inability to identify modifiable deficits that, when improved, will result in the recovery of walking function. Previous studies have relied on cross-sectional analyses to identify deficits to target during walking rehabilitation; however, these studies did not account for the influence of a key covariate - maximum walking speed. To determine the relationships between commonly studied poststroke variables and the long-distance walking function of individuals poststroke when controlling for maximum walking speed. Correlation analyses of cross-sectional data from 57 individuals more than 6 months poststroke measured the relationships between standing balance, walking balance, balance self-efficacy, lower extremity motor function, and maximum walking speed versus long-distance walking function. For a subgroup of subjects who completed training, the relationship between changes in maximum walking speed versus changes in long-distance walking function was assessed. Each measurement of interest strongly correlated with long-distance walking function (rs from 0.448 to 0.900, all Ps ≤ .001); however, when controlling for maximum walking speed, none of the other measurements remained related to long-distance walking function. In contrast, when controlling for each of the other measurements, maximum walking speed remained highly related. Moreover, changes in maximum walking speed resulting from training were highly related to changes in long-distance walking function (r = .737, P ≤ .001). For individuals in the chronic phase of stroke recovery, improving maximum walking speed may be necessary to improve long-distance walking function.

  7. Optimal walking speed following changes in limb geometry.

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    Leurs, Françoise; Ivanenko, Yuri P; Bengoetxea, Ana; Cebolla, Ana-Maria; Dan, Bernard; Lacquaniti, Francesco; Cheron, Guy A

    2011-07-01

    The principle of dynamic similarity states that the optimal walking speeds of geometrically similar animals are independent of size when speed is normalized to the dimensionless Froude number (Fr). Furthermore, various studies have shown similar dimensionless optimal speed (Fr ∼0.25) for animals with quite different limb geometries. Here, we wondered whether the optimal walking speed of humans depends solely on total limb length or whether limb segment proportions play an essential role. If optimal walking speed solely depends on the limb length then, when subjects walk on stilts, they should consume less metabolic energy at a faster optimal speed than when they walk without stilts. To test this prediction, we compared kinematics, electromyographic activity and oxygen consumption in adults walking on a treadmill at different speeds with and without articulated stilts that artificially elongated the shank segment by 40 cm. Walking on stilts involved a non-linear reorganization of kinematic and electromyography patterns. In particular, we found a significant increase in the alternating activity of proximal flexors-extensors during the swing phase, despite significantly shorter normalized stride lengths. The minimal metabolic cost per unit distance walked with stilts occurred at roughly the same absolute speed, corresponding to a lower Fr number (Fr ∼0.17) than in normal walking (Fr ∼0.25). These findings are consistent with an important role of limb geometry optimization and kinematic coordination strategies in minimizing the energy expenditure of human walking.

  8. The association between habitual walking speed and medial femoral cartilage deformation following 30minutes of walking.

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    Harkey, Matthew S; Blackburn, J Troy; Davis, Hope; Sierra-Arévalo, Leslie; Nissman, Daniel; Pietrosimone, Brian

    2018-01-01

    Habitual walking speed is a key functional outcome that has implications for knee biomechanics that occur during gait. Lower extremity biomechanics during walking affects the loading of the femoral cartilage. Ultrasonography (US) can be used to assess resting femoral cartilage thickness and acute cartilage deformation in response to walking. The purpose of this study was to determine the association between habitual walking speed and both resting femoral cartilage thickness and deformation. Twenty-four healthy participants with no history of knee injury volunteered for this study. Habitual walking speed was assessed with a 20-m walk test. Femoral cartilage thickness was assessed with US in the medial condyle, lateral condyle, and intercondylar regions prior to and immediately following 30min of walking. Femoral cartilage deformation was calculated as the percent change in cartilage thickness acutely following the walking protocol. Separate Pearson product moment correlations were used to assess the association between habitual walking speed and each US cartilage variable. Slower habitual walking speed was significantly associated with greater medial femoral cartilage deformation (r=0.48, P=0.018), but not with lateral and intercondylar deformation. Habitual walking speed was not significantly associated with the resting cartilage thickness in any cartilage region. These findings highlight the in vivo association between walking speed and medial femoral cartilage deformation. When controlling for body mass index, the association between walking speed and medial cartilage deformation was weakened (Δr=-0.12). Future studies are needed to determine the extent to which BMI influences the association between walking speed and cartilage deformation. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Prediction of walking speed using single stance force or pressure measurements in healthy subjects

    NARCIS (Netherlands)

    Keijsers, N.L.W.; Stolwijk, N.M.; Renzenbrink, G.J.; Duysens, J.

    2016-01-01

    Walking speed is one of the best measures of overall walking capacity. In plantar pressure measurements, walking speed can be assessed using contact time, but it is only moderately correlated with walking speed. The center of pressure might be of more value to indicate walking speed since walking

  10. IMU-based ambulatory walking speed estimation in constrained treadmill and overground walking.

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    Yang, Shuozhi; Li, Qingguo

    2012-01-01

    This study evaluated the performance of a walking speed estimation system based on using an inertial measurement unit (IMU), a combination of accelerometers and gyroscopes. The walking speed estimation algorithm segments the walking sequence into individual stride cycles (two steps) based on the inverted pendulum-like behaviour of the stance leg during walking and it integrates the angular velocity and linear accelerations of the shank to determine the displacement of each stride. The evaluation was performed in both treadmill and overground walking experiments with various constraints on walking speed, step length and step frequency to provide a relatively comprehensive assessment of the system. Promising results were obtained in providing accurate and consistent walking speed/step length estimation in different walking conditions. An overall percentage root mean squared error (%RMSE) of 4.2 and 4.0% was achieved in treadmill and overground walking experiments, respectively. With an increasing interest in understanding human walking biomechanics, the IMU-based ambulatory system could provide a useful walking speed/step length measurement/control tool for constrained walking studies.

  11. Walking speed, processing speed, and dementia: a population-based longitudinal study.

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    Welmer, Anna-Karin; Rizzuto, Debora; Qiu, Chengxuan; Caracciolo, Barbara; Laukka, Erika J

    2014-12-01

    Slow walking speed has been shown to predict dementia. We investigated the relation of walking speed, processing speed, and their changes over time to dementia among older adults. This study included 2,938 participants (age 60+ years) in the population-based Swedish National study on Aging and Care in Kungsholmen, Sweden, who were free from dementia and severe walking impairment at baseline. Walking speed was assessed with participants walking at their usual pace and processing speed was defined by a composite measure of standard tests (digit cancellation, trail making test-A, pattern comparison). Dementia at 3- and 6-year follow-ups was diagnosed according to Diagnostic and Statistical Manual of Mental Disorders-IV criteria. Of the 2,232 participants who were reassessed at least once, 226 developed dementia. Logistic regression models showed that each standard deviation slower baseline walking speed or decline in walking speed over time increased the likelihood of incident dementia (odds ratios 1.61, 95% confidence interval [CI] 1.31-1.98; and 2.58, 95% CI 2.12-3.14, respectively). Adjustment for processing speed attenuated these associations (odds ratios 1.26, 95% CI 1.01-1.58 and 1.76, 95% CI 1.33-2.34). Mixed-effects models revealed statistical interactions of time with dementia on change in walking and processing speed, such that those who developed dementia showed accelerated decline. At baseline, poorer performance in processing speed, but not in walking speed, was observed for persons who developed dementia during the study period. Processing speed may play an important role for the association between walking speed and dementia. The slowing of walking speed appears to occur secondary to slowing of processing speed in the path leading to dementia. © The Author 2014. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  12. Tempo and walking speed with music in the urban context

    Directory of Open Access Journals (Sweden)

    Marek eFranek

    2014-12-01

    Full Text Available The study explored the effect of music on the temporal aspects of walking behavior in a real outdoor urban setting. First, spontaneous synchronization between the beat of the music and step tempo was explored. The effect of motivational and non-motivational music (Karageorghis et al. 1999 on the walking speed was also studied. Finally, we investigated whether music can mask the effects of visual aspects of the walking route environment, which involve fluctuation of walking speed as a response to particular environmental settings. In two experiments, we asked participants to walk around an urban route through various environments in the downtown area of Hradec Králové. In Experiment 1, the participants listened to a musical track consisting of world pop music with a clear beat. In Experiment 2, participants were walking either with motivational music, which had a fast tempo and a strong rhythm, or with non-motivational music, which was slower, nice music, but with no strong implication to movement. Musical beat, as well as the sonic character of the music listened to while walking, influenced walking speed but did not lead to precise synchronization. It was found that many subjects did not spontaneously synchronize with the beat of the music at all, and some subjects synchronized only part of the time. The fast, energetic music increases the speed of the walking tempo, while slower, relaxing music makes the walking tempo slower. Further, it was found that listening to music with headphones while walking can mask the influence of the surrounding environment to some extent. Both motivational music and non-motivational music had a larger effect than the music from Experiment 1. Individual differences in responses to the music listened to while walking that were linked to extraversion and neuroticism were also observed. The findings described here could be useful in rhythmic stimulation for enhancing or recovering the features of movement

  13. Tempo and walking speed with music in the urban context.

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    Franěk, Marek; van Noorden, Leon; Režný, Lukáš

    2014-01-01

    The study explored the effect of music on the temporal aspects of walking behavior in a real outdoor urban setting. First, spontaneous synchronization between the beat of the music and step tempo was explored. The effect of motivational and non-motivational music (Karageorghis et al., 1999) on the walking speed was also studied. Finally, we investigated whether music can mask the effects of visual aspects of the walking route environment, which involve fluctuation of walking speed as a response to particular environmental settings. In two experiments, we asked participants to walk around an urban route that was 1.8 km in length through various environments in the downtown area of Hradec Králové. In Experiment 1, the participants listened to a musical track consisting of world pop music with a clear beat. In Experiment 2, participants were walking either with motivational music, which had a fast tempo and a strong rhythm, or with non-motivational music, which was slower, nice music, but with no strong implication to movement. Musical beat, as well as the sonic character of the music listened to while walking, influenced walking speed but did not lead to precise synchronization. It was found that many subjects did not spontaneously synchronize with the beat of the music at all, and some subjects synchronized only part of the time. The fast, energetic music increases the speed of the walking tempo, while slower, relaxing music makes the walking tempo slower. Further, it was found that listening to music with headphones while walking can mask the influence of the surrounding environment to some extent. Both motivational music and non-motivational music had a larger effect than the world pop music from Experiment 1. Individual differences in responses to the music listened to while walking that were linked to extraversion and neuroticism were also observed. The findings described here could be useful in rhythmic stimulation for enhancing or recovering the features of

  14. Tempo and walking speed with music in the urban context

    Science.gov (United States)

    Franěk, Marek; van Noorden, Leon; Režný, Lukáš

    2014-01-01

    The study explored the effect of music on the temporal aspects of walking behavior in a real outdoor urban setting. First, spontaneous synchronization between the beat of the music and step tempo was explored. The effect of motivational and non-motivational music (Karageorghis et al., 1999) on the walking speed was also studied. Finally, we investigated whether music can mask the effects of visual aspects of the walking route environment, which involve fluctuation of walking speed as a response to particular environmental settings. In two experiments, we asked participants to walk around an urban route that was 1.8 km in length through various environments in the downtown area of Hradec Králové. In Experiment 1, the participants listened to a musical track consisting of world pop music with a clear beat. In Experiment 2, participants were walking either with motivational music, which had a fast tempo and a strong rhythm, or with non-motivational music, which was slower, nice music, but with no strong implication to movement. Musical beat, as well as the sonic character of the music listened to while walking, influenced walking speed but did not lead to precise synchronization. It was found that many subjects did not spontaneously synchronize with the beat of the music at all, and some subjects synchronized only part of the time. The fast, energetic music increases the speed of the walking tempo, while slower, relaxing music makes the walking tempo slower. Further, it was found that listening to music with headphones while walking can mask the influence of the surrounding environment to some extent. Both motivational music and non-motivational music had a larger effect than the world pop music from Experiment 1. Individual differences in responses to the music listened to while walking that were linked to extraversion and neuroticism were also observed. The findings described here could be useful in rhythmic stimulation for enhancing or recovering the features of

  15. Effect of walking speed on gait sub phase durations.

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    Hebenstreit, Felix; Leibold, Andreas; Krinner, Sebastian; Welsch, Götz; Lochmann, Matthias; Eskofier, Bjoern M

    2015-10-01

    Gait phase durations are important spatiotemporal parameters in different contexts such as discrimination between healthy and pathological gait and monitoring of treatment outcomes after interventions. Although gait phases strongly depend on walking speed, the influence of different speeds has rarely been investigated in literature. In this work, we examined the durations of the stance sub phases and the swing phase for 12 different walking speeds ranging from 0.6 to 1.7 m/s in 21 healthy subjects using infrared cinematography and an instrumented treadmill. We separated the stance phase into loading response, mid stance, terminal stance and pre-swing phase and we performed regression modeling of all phase durations with speed to determine general trends. With an increasing speed of 0.1m/s, stance duration decreased while swing duration increased by 0.3%. All distinct stance sub phases changed significantly with speed. These findings suggest the importance of including all distinct gait sub phases in spatiotemporal analyses, especially when different walking speeds are involved. Copyright © 2015 Elsevier B.V. All rights reserved.

  16. Treadmill Adaptation and Verification of Self-Selected Walking Speed: A Protocol for Children

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    Amorim, Paulo Roberto S.; Hills, Andrew; Byrne, Nuala

    2009-01-01

    Walking is a common activity of daily life and researchers have used the range 3-6 km.h[superscript -1] as reference for walking speeds habitually used for transportation. The term self-selected (i.e., individual or comfortable walking pace or speed) is commonly used in the literature and is identified as the most efficient walking speed, with…

  17. Assessment of walking speed by a goniometer-based method.

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    Maranesi, E; Barone, V; Fioretti, S

    2014-01-01

    A quantitative gait analysis is essential to evaluate the kinematic, kinetic and electromyographic gait patterns. These patterns are strongly related to the individual spatio-temporal parameters that characterize each subject. In particular, gait speed is one of the most important spatio-temporal gait parameters: it influences kinematic, kinetic parameters, and muscle activity too. The aim of the present study is to propose a new method to assess stride speed using only 1-degree-of-freedom electrogoniometers positioned on hip and knee joints. The model validation is performed comparing the model results with those automatically obtained from another gait analysis system: GAITRite. The results underline the model reliability. These results show that essential spatio-temporal gait parameters, and in particular the speed of each stride, can be determined during normal walking using only two 1-dof electrogoniometers. The method is easy-to-use and does not interfere with regular walking patterns.

  18. Vaulting mechanics successfully predict decrease in walk-run transition speed with incline.

    Science.gov (United States)

    Hubel, Tatjana Y; Usherwood, James R

    2013-04-23

    There is an ongoing debate about the reasons underlying gait transition in terrestrial locomotion. In bipedal locomotion, the 'compass gait', a reductionist model of inverted pendulum walking, predicts the boundaries of speed and step length within which walking is feasible. The stance of the compass gait is energetically optimal-at walking speeds-owing to the absence of leg compression/extension; completely stiff limbs perform no work during the vaulting phase. Here, we extend theoretical compass gait vaulting to include inclines, and find good agreement with previous observations of changes in walk-run transition speed (approx. 1% per 1% incline). We measured step length and frequency for humans walking either on the level or up a 9.8 per cent incline and report preferred walk-run, walk-compliant-walk and maximum walk-run transition speeds. While the measured 'preferred' walk-run transition speed lies consistently below the predicted maximum walking speeds, and 'actual' maximum walking speeds are clearly above the predicted values, the onset of compliant walking in level as well as incline walking occurs close to the predicted values. These findings support the view that normal human walking is constrained by the physics of vaulting, but preferred absolute walk-run transition speeds may be influenced by additional factors.

  19. Walking speed of normal subjects and amputees: aspects of validity of gait analysis.

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    Boonstra, A M; Fidler, V; Eisma, W H

    1993-08-01

    This study investigated some aspects of the validity of walking speed recording in 15 normal subjects, 16 trans-femoral amputees and 8 knee disarticulation amputees. The variability and test-retest reliability of walking speed and the influence of simultaneous recording of EMG and goniometry on comfortable and fast walking speeds were studied. The variability between sessions was mainly determined by the variance within each session. The variance of speed within sessions while walking with fast speed, was higher when walking without equipment than when walking with equipment. The variances of speed within sessions of the normal subjects were higher than those for both amputee groups. The test-retest reliability, expressed by the intra-class correlation coefficient, was good: between 0.83 and 0.98. The speed when walking without equipment was significantly higher both in normal subjects and amputees than the speed when walking with equipment.

  20. Arm Swing during Walking at Different Speeds in Children with Cerebral Palsy and Typically Developing Children

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    Meyns, Pieter; Van Gestel, Leen; Massaad, Firas; Desloovere, Kaat; Molenaers, Guy; Duysens, Jacques

    2011-01-01

    Children with Cerebral Palsy (CP) have difficulties walking at a normal or high speed. It is known that arm movements play an important role to achieve higher walking speeds in healthy subjects. However, the role played by arm movements while walking at different speeds has received no attention in children with CP. Therefore we investigated the…

  1. Your brain on speed: cognitive performance of a spatial working memory task is not affected by walking speed.

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    Kline, Julia E; Poggensee, Katherine; Ferris, Daniel P

    2014-01-01

    When humans walk in everyday life, they typically perform a range of cognitive tasks while they are on the move. Past studies examining performance changes in dual cognitive-motor tasks during walking have produced a variety of results. These discrepancies may be related to the type of cognitive task chosen, differences in the walking speeds studied, or lack of controlling for walking speed. The goal of this study was to determine how young, healthy subjects performed a spatial working memory task over a range of walking speeds. We used high-density electroencephalography to determine if electrocortical activity mirrored changes in cognitive performance across speeds. Subjects stood (0.0 m/s) and walked (0.4, 0.8, 1.2, and 1.6 m/s) with and without performing a Brooks spatial working memory task. We hypothesized that performance of the spatial working memory task and the associated electrocortical activity would decrease significantly with walking speed. Across speeds, the spatial working memory task caused subjects to step more widely compared with walking without the task. This is typically a sign that humans are adapting their gait dynamics to increase gait stability. Several cortical areas exhibited power fluctuations time-locked to memory encoding during the cognitive task. In the somatosensory association cortex, alpha power increased prior to stimulus presentation and decreased during memory encoding. There were small significant reductions in theta power in the right superior parietal lobule and the posterior cingulate cortex around memory encoding. However, the subjects did not show a significant change in cognitive task performance or electrocortical activity with walking speed. These findings indicate that in young, healthy subjects walking speed does not affect performance of a spatial working memory task. These subjects can devote adequate cortical resources to spatial cognition when needed, regardless of walking speed.

  2. Walking speed and subclinical atherosclerosis in healthy older adults: the Whitehall II study

    OpenAIRE

    Hamer, M.; Kivimaki, M.; Lahiri, A; Yerramasu, A; Deanfield, J. E.; Marmot, M G; Steptoe, A

    2010-01-01

    Objective Extended walking speed is a predictor of incident cardiovascular disease (CVD) in older individuals, but the ability of an objective short-distance walking speed test to stratify the severity of preclinical conditions remains unclear. This study examined whether performance in an 8-ft walking speed test is associated with metabolic risk factors and subclinical atherosclerosis.Design Cross-sectional.Setting Epidemiological cohort.Participants 530 adults (aged 63 +/- 6 years, 50.3% ma...

  3. Economy, Movement Dynamics, and Muscle Activity of Human Walking at Different Speeds

    DEFF Research Database (Denmark)

    Raffalt, Peter Christian; Guul, Martin Kjær; Nielsen, A. N.

    2017-01-01

    The complex behaviour of human walking with respect to movement variability, economy and muscle activity is speed dependent. It is well known that a U-shaped relationship between walking speed and economy exists. However, it is an open question if the movement dynamics of joint angles and centre...... of mass and muscle activation strategy also exhibit a U-shaped relationship with walking speed. We investigated the dynamics of joint angle trajectories and the centre of mass accelerations at five different speeds ranging from 20 to 180% of the predicted preferred speed (based on Froude speed) in twelve...

  4. The clinical meaning of walking speed as measured by the timed 25-foot walk in patients with multiple sclerosis.

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    Cohen, Jeffrey A; Krishnan, Arun V; Goodman, Andrew D; Potts, James; Wang, Ping; Havrdova, Eva; Polman, Chris; Rudick, Richard A

    2014-11-01

    Walking impairment, a common clinical manifestation of multiple sclerosis (MS), is often measured in clinical practice and clinical trials using the Timed 25-Foot Walk (T25-FW). To evaluate the relationship between walking speed measured by the T25-FW and the Physical Component Summary (PCS) score of the 36-Item Short Form Health Survey (SF-36) to better understand the clinical meaning of T25-FW walking speed in MS. We retrospectively analyzed data from 3 clinical trials (Natalizumab Safety and Efficacy in Relapsing-Remitting Multiple Sclerosis [AFFIRM], Safety and Efficacy of Natalizumab in Combination With Interferon Beta-1a in Patients With Relapsing-Remitting Multiple Sclerosis [SENTINEL], and International MS Secondary Progressive Avonex Controlled Trial [IMPACT]) that included T25-FW and SF-36 scores as outcomes in patients with MS. Patients had secondary-progressive MS and an Expanded Disability Status Scale score of 3.5 to 6.5 or relapsing-remitting MS and an Expanded Disability Status Scale score of 0 to 5.0. We used Spearman rank correlation and Pearson product moment correlation (r ) and descriptive statistics to evaluate retrospectively the relationship between the SF-36 PCS score and T25-FW walking speed at baseline and the 2-year changes from baseline. Among all 2549 patients from the 3 trials, walking speed and SF-36 PCS score at baseline were significantly correlated (n = 2333; r = 0.48; P walking speed was significantly correlated with the change from baseline in SF-36 PCS score (r = 0.35; P walking speed at 2 years also were observed in groups receiving active treatment (r, 0.13-0.28; P ≤ .005). Among placebo-treated patients, 27.5% had a clinically meaningful worsening (≥ 5-point decrease) in SF-36 PCS scores during the 2 years. Walking speed declined by 21.8% in these patients after 2 years, but only by 5.4% in those without worsening of SF-36 PCS scores. In patients with MS, walking speed measured using the T25-FW correlated with SF-36 PCS

  5. Measuring walking speed in COPD: test-retest reliability of the 30-metre walk test and comparison with the 6-minute walk test.

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    Andersson, Mikael; Moberg, Linda; Svantesson, Ulla; Sundbom, Ann; Johansson, Henrik; Emtner, Margareta

    2011-12-01

    To examine test-retest reliability of the 30-metre walk test (30mWT) in patients with chronic obstructive pulmonary disease (COPD) and to compare the 30mWT with the 6-minute walk test (6MWT). Forty-nine subjects with stable COPD were included. The 30mWT consists of walking at different walking intensities over a distance of 30 metres - self-selected speed (ss-30mWT) and maximal speed (ms-30mWT). The test was conducted twice and the time to walk 30 metres was recorded. The 6MWT was performed in duplicate on the same day. Test-retest reliability was high: intraclass correlation coefficient (ICC(2.1)) = 0.93 (95% CI 0.87 to 0.97) for maximal walking speed and 0.87 (95% CI 0.78 to 0.93) for self-selected walking speed. Both maximal and self-selected speed had a standard error of measurement (SEM) of 0.07 m/s and SEM% was 4.4 for maximal speed and 5.9 for self-selected speed. The correlation, criterion validity, between ms-30mWT and the 6MWT was r=0.78 (pwalking ability) in patients with COPD. It may be well suited for primary care settings.

  6. Walking, running, and resting under time, distance, and average speed constraints: optimality of walk-run-rest mixtures.

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    Long, Leroy L; Srinivasan, Manoj

    2013-04-06

    On a treadmill, humans switch from walking to running beyond a characteristic transition speed. Here, we study human choice between walking and running in a more ecological (non-treadmill) setting. We asked subjects to travel a given distance overground in a given allowed time duration. During this task, the subjects carried, and could look at, a stopwatch that counted down to zero. As expected, if the total time available were large, humans walk the whole distance. If the time available were small, humans mostly run. For an intermediate total time, humans often use a mixture of walking at a slow speed and running at a higher speed. With analytical and computational optimization, we show that using a walk-run mixture at intermediate speeds and a walk-rest mixture at the lowest average speeds is predicted by metabolic energy minimization, even with costs for transients-a consequence of non-convex energy curves. Thus, sometimes, steady locomotion may not be energy optimal, and not preferred, even in the absence of fatigue. Assuming similar non-convex energy curves, we conjecture that similar walk-run mixtures may be energetically beneficial to children following a parent and animals on long leashes. Humans and other animals might also benefit energetically from alternating between moving forward and standing still on a slow and sufficiently long treadmill.

  7. VALIDATION OF THE MYWELLNESS KEY IN WALKING AND RUNNING SPEEDS

    Directory of Open Access Journals (Sweden)

    Marco Bergamin

    2012-03-01

    Full Text Available This study was performed to assess the validity of the MyWellness Key (MWK accelerometer during a treadmill-based protocol. The identification of different exercise intensities is imperative to objectively measure time spent at a specified exercise intensity. Thirty subjects, 15 men and 15 women (age = 24.5 ± 2.6 years; body mass index = 22.5 ± 2.5 kg·m-1, participated in a 4-phase treadmill protocol (5 minutes each one using three different walking velocities (3, 4.5, and 6 km·h-1 and run (8 km·h-1 while outfitted with a MWK uniaxial accelerometer. Oxygen consumption was measured by indirect calorimetry (ICVO2. Results: The relationship between VO2 predicted from MWK (MWKVO2 and oxygen consumption (VO2 (ICVO2, yielded a high and significant correlation (r = 0. 944; p < 0.001 with standard error of estimate (SEE = 2.42 mL·kg-1·min-1. The average differences between the two methods (MWKVO2 - ICVO2 were -0.79 (-8. 8% at 3 km·h-1, -0.02 (-0.2% at 4.5 km·h-1, 0.51 (3.3% at 6 km·h-1 and -0.74 (-2.7% at 8 km·h-1 ml·kg-1·min-1. Only the 3 km·h-1 speed showed a difference when compared to the criterion measure (p < 0.001. Bland and Altman analysis revealed less than a 1 MET difference in the mean at each point estimate and relatively tight distribution with the standard errors, especially with the 2 moderate walking speeds. Conclusions: We found a high correlation between oxygen utilization and the MWK with low standard errors estimates. This indicates that this accelerometer can be used to identify exercise intensities that are related to walking and running.

  8. Energy cost of walking: solving the paradox of steady state in the presence of variable walking speed.

    Science.gov (United States)

    Plasschaert, Frank; Jones, Kim; Forward, Malcolm

    2009-02-01

    Measurement of the energy cost of walking in children with cerebral palsy is used for baseline and outcome assessment. However, such testing relies on the establishment of steady state that is deemed present when oxygen consumption is stable. This is often assumed when walking speed is constant but in practice, speed can and does vary naturally. Whilst constant speed is achievable on a treadmill, this is often impractical clinically, thus rendering an energy cost test to an element of subjectivity. This paper attempts to address this issue by presenting a new method for calculating energy cost of walking that automatically applies a mathematically defined threshold for steady state within a (non-treadmill) walking trial and then strips out all of the non-steady state events within that trial. The method is compared with a generic approach that does not remove non-steady state data but rather uses an average value over a complete walking trial as is often used in the clinical environment. Both methods were applied to the calculation of several energy cost of walking parameters of self-selected walking speed in a cohort of unimpaired subjects and children with cerebral palsy. The results revealed that both methods were strongly correlated for each parameter but showed systematic significant differences. It is suggested that these differences are introduced by the rejection of non-steady state data that would otherwise have incorrectly been incorporated into the calculation of the energy cost of walking indices during self-selected walking with its inherent speed variation.

  9. The development of an estimation model for energy expenditure during water walking by acceleration and walking speed.

    Science.gov (United States)

    Kaneda, Koichi; Ohgi, Yuji; Tanaka, Chiaki; Burkett, Brendan

    2014-01-01

    The aim of this study was to develop an estimation equation for energy expenditure during water walking based on the acceleration and walking speed. Cross-validation study. Fifty participants, males (n=29, age: 27-73) and females (n=21, age: 33-70) volunteered for this study. Based on their physical condition water walking was conducted at three self-selected walking speeds from a range of: 20, 25, 30, 35 and 40 m/min. Energy expenditure during each trial was calculated. During water walking, an accelerometer was attached to the occipital region and recorded three-dimensional accelerations at 100 Hz. A stopwatch was used for timing the participant's walking speed. The estimation model for energy expenditure included three components; (i) resting metabolic rate, (ii) internal energy expenditure for moving participants' body, and (iii) external energy expenditure due to water drag force. When comparing the measured and estimated energy expenditure with the acceleration data being the third component of the estimation model, high correlation coefficients were found in both male (r=0.73) and female (r=0.77) groups. When walking speeds were applied to the third component of the model, higher correlation coefficients were found (r=0.82 in male and r=0.88 in female). Good agreements of the developed estimation model were found in both methods, regardless of gender. This study developed a valid estimation model for energy expenditure during water walking by using head acceleration and walking speed. Copyright © 2013 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

  10. LEGS AND TRUNK MUSCLE HYPERTROPHY FOLLOWING WALK TRAINING WITH RESTRICTED LEG MUSCLE BLOOD FLOW

    Directory of Open Access Journals (Sweden)

    Mikako Sakamaki

    2011-06-01

    Full Text Available We examined the effect of walk training combined with blood flow restriction (BFR on the size of blood flow-restricted distal muscles, as well as, on the size of non-restricted muscles in the proximal limb and trunk. Nine men performed walk training with BFR and 8 men performed walk training alone. Training was conducted two times a day, 6 days/wk, for 3 wk using five sets of 2-min bouts (treadmill speed at 50 m/min, with a 1-min rest between bouts. After walk training with BFR, MRI-measured upper (3.8%, P < 0.05 and lower leg (3.2%, P < 0. 05 muscle volume increased significantly, whereas the muscle volume of the gluteus maximus (-0.6% and iliopsoas (1.8% and the muscle CSA of the lumber L4-L5 (-1.0 did not change. There was no significant change in muscle volume in the walk training alone. Our results suggest that the combination of leg muscle blood flow restriction with slow walk training elicits hypertrophy only in the distal blood flow restricted leg muscles. Exercise intensity may be too low during BFR walk training to increase muscle mass in the non- blood flow restricted muscles (gluteus maximus and other trunk muscles.

  11. WALKING SPEED OF NORMAL SUBJECTS AND AMPUTEES - ASPECTS OF VALIDITY OF GAIT ANALYSIS

    NARCIS (Netherlands)

    BOONSTRA, AM; FIDLER, [No Value; EISMA, WH

    This study investigated some aspects of the validity of walking speed recording in 15 normal subjects. 16 trans-femoral empathics and 8 knee disarticulation amputees. The variability and test-retest reliability of walking speed and the influence of simultaneous recording of EMG and goniometry on

  12. Vaulting mechanics successfully predict decrease in walk?run transition speed with incline

    OpenAIRE

    Hubel, Tatjana Y.; Usherwood, James R.

    2013-01-01

    There is an ongoing debate about the reasons underlying gait transition in terrestrial locomotion. In bipedal locomotion, the ?compass gait?, a reductionist model of inverted pendulum walking, predicts the boundaries of speed and step length within which walking is feasible. The stance of the compass gait is energetically optimal?at walking speeds?owing to the absence of leg compression/extension; completely stiff limbs perform no work during the vaulting phase. Here, we extend theoretical co...

  13. Walking training associated with virtual reality-based training increases walking speed of individuals with chronic stroke: systematic review with meta-analysis

    OpenAIRE

    Rodrigues-Baroni, Juliana M.; Nascimento, Lucas R.; Ada, Louise; Teixeira-Salmela, Luci F.

    2014-01-01

    OBJECTIVE: To systematically review the available evidence on the efficacy of walking training associated with virtual reality-based training in patients with stroke. The specific questions were: Is walking training associated with virtual reality-based training effective in increasing walking speed after stroke? Is this type of intervention more effective in increasing walking speed, than non-virtual reality-based walking interventions? METHOD: A systematic review with meta-analysis of rando...

  14. Reliability and Validity of Ten Consumer Activity Trackers Depend on Walking Speed.

    Science.gov (United States)

    Fokkema, Tryntsje; Kooiman, Thea J M; Krijnen, Wim P; VAN DER Schans, Cees P; DE Groot, Martijn

    2017-04-01

    To examine the test-retest reliability and validity of ten activity trackers for step counting at three different walking speeds. Thirty-one healthy participants walked twice on a treadmill for 30 min while wearing 10 activity trackers (Polar Loop, Garmin Vivosmart, Fitbit Charge HR, Apple Watch Sport, Pebble Smartwatch, Samsung Gear S, Misfit Flash, Jawbone Up Move, Flyfit, and Moves). Participants walked three walking speeds for 10 min each; slow (3.2 km·h), average (4.8 km·h), and vigorous (6.4 km·h). To measure test-retest reliability, intraclass correlations (ICC) were determined between the first and second treadmill test. Validity was determined by comparing the trackers with the gold standard (hand counting), using mean differences, mean absolute percentage errors, and ICC. Statistical differences were calculated by paired-sample t tests, Wilcoxon signed-rank tests, and by constructing Bland-Altman plots. Test-retest reliability varied with ICC ranging from -0.02 to 0.97. Validity varied between trackers and different walking speeds with mean differences between the gold standard and activity trackers ranging from 0.0 to 26.4%. Most trackers showed relatively low ICC and broad limits of agreement of the Bland-Altman plots at the different speeds. For the slow walking speed, the Garmin Vivosmart and Fitbit Charge HR showed the most accurate results. The Garmin Vivosmart and Apple Watch Sport demonstrated the best accuracy at an average walking speed. For vigorous walking, the Apple Watch Sport, Pebble Smartwatch, and Samsung Gear S exhibited the most accurate results. Test-retest reliability and validity of activity trackers depends on walking speed. In general, consumer activity trackers perform better at an average and vigorous walking speed than at a slower walking speed.

  15. Energetic consequences of human sociality: walking speed choices among friendly dyads.

    Directory of Open Access Journals (Sweden)

    Janelle Wagnild

    Full Text Available Research has shown that individuals have an optimal walking speed-a speed which minimizes energy expenditure for a given distance. Because the optimal walking speed varies with mass and lower limb length, it also varies with sex, with males in any given population tending to have faster optimal walking speeds. This potentially creates an energetic dilemma for mixed-sex walking groups. Here we examine speed choices made by individuals of varying stature, mass, and sex walking together. Individuals (N = 22 walked around a track alone, with a significant other (with and without holding hands, and with friends of the same and opposite sex while their speeds were recorded every 100 m. Our findings show that males walk at a significantly slower pace to match the females' paces (p = 0.009, when the female is their romantic partner. The paces of friends of either same or mixed sex walking together did not significantly change (p>0.05. Thus significant pace adjustment appears to be limited to romantic partners. These findings have implications for both mobility and reproductive strategies of groups. Because the male carries the energetic burden by adjusting his pace (slowing down 7%, the female is spared the potentially increased caloric cost required to walk together. In energetically demanding environments, we will expect to find gender segregation in group composition, particularly when travelling longer distances.

  16. Perceived Walking Speed, Measured Tandem Walk, Incident Stroke, and Mortality in Older Latino Adults: A Prospective Cohort Study.

    Science.gov (United States)

    Zeki Al Hazzouri, Adina; Mayeda, Elizabeth Rose; Elfassy, Tali; Lee, Anne; Odden, Michelle C; Thekkethala, Divya; Wright, Clinton B; Glymour, Maria M; Haan, Mary N

    2017-05-01

    Walking speed is associated with functional status and all-cause mortality. Yet the relationship between walking speed and stroke, also a leading cause of disability, remains poorly understood, especially in older Latino adults who suffer from a significant burden of stroke. A total of 1,486 stroke-free participants from the Sacramento Area Latino Study on Aging, aged 60 and older at baseline in 1998-1999, were followed annually through 2010. Participants reported their usual walking speed outdoors which was classified into slow, medium, or fast. We also assessed timed tandem walk ability (unable or eight or more errors vs less than eight errors). We ascertained three incident stroke endpoints: total stroke, nonfatal stroke, and fatal stroke. Using Cox proportional hazards models, we estimated hazard ratios (HRs) for stroke at different walking speed and timed tandem walk categories. Over an average of 6 years of follow-up (SD = 2.8), the incidence rate of total strokes was 23.2/1,000 person-years for slow walkers compared to 15.6/1,000 person-years for medium walkers, and 7.6/1,000 person-years for fast walkers. In Cox models adjusted for sociodemographics, cardiovascular risk, cognition and functional status, and self-rated health, the hazard of total stroke was 31% lower for medium walkers (HR: 0.69, 95% confidence interval [CI]: 0.47, 1.02) and 56% lower for fast walkers (HR: 0.44, 95% CI: 0.24, 0.82) compared with slow walkers. We found similar associations with timed tandem walk ability (fully adjusted HR: 0.66, 95% CI: 0.45, 0.98). Our findings suggest perceived walking speed captures more than self-rated health alone and is a strong risk factor for stroke risk in Latino older adults.

  17. Walking training associated with virtual reality-based training increases walking speed of individuals with chronic stroke: systematic review with meta-analysis.

    Science.gov (United States)

    Rodrigues-Baroni, Juliana M; Nascimento, Lucas R; Ada, Louise; Teixeira-Salmela, Luci F

    2014-01-01

    To systematically review the available evidence on the efficacy of walking training associated with virtual reality-based training in patients with stroke. The specific questions were: Is walking training associated with virtual reality-based training effective in increasing walking speed after stroke? Is this type of intervention more effective in increasing walking speed, than non-virtual reality-based walking interventions? A systematic review with meta-analysis of randomized clinical trials was conducted. Participants were adults with chronic stroke and the experimental intervention was walking training associated with virtual reality-based training to increase walking speed. The outcome data regarding walking speed were extracted from the eligible trials and were combined using a meta-analysis approach. Seven trials representing eight comparisons were included in this systematic review. Overall, the virtual reality-based training increased walking speed by 0.17 m/s (IC 95% 0.08 to 0.26), compared with placebo/nothing or non-walking interventions. In addition, the virtual reality-based training increased walking speed by 0.15 m/s (IC 95% 0.05 to 0.24), compared with non-virtual reality walking interventions. This review provided evidence that walking training associated with virtual reality-based training was effective in increasing walking speed after stroke, and resulted in better results than non-virtual reality interventions.

  18. Compass gait mechanics account for top walking speeds in ducks and humans.

    Science.gov (United States)

    Usherwood, James R; Szymanek, Katie L; Daley, Monica A

    2008-12-01

    The constraints to maximum walking speed and the underlying cause of the walk-run transition remains controversial. However, the motions of the body and legs can be reduced to a few mechanical principles, which, if valid, impose simple physics-based limits to walking speed. Bipedal walking may be viewed as a vaulting gait, with the centre of mass (CoM) passing over a stiff stance leg (an 'inverted pendulum'), while the swing leg swings forward (as a pendulum). At its simplest, this forms a 'compass gait' walker, which has a maximum walking speed constrained by simple mechanics: walk too fast, or with too high a step length, and gravity fails to keep the stance foot attached to the floor. But how useful is such an extremely reductionist model? In the present study, we report measurements on a range of duck breeds as example unspecialized, non-planar, crouch-limbed walkers and contrast these findings with previous measurements on humans, using the theoretical framework of compass gait walking. Ducks walked as inverted pendulums with near-passive swing legs up to relative velocities around 0.5, remarkably consistent with the theoretical model. By contrast, top walking speeds in humans cannot be achieved with passive swing legs: humans, while still constrained by compass gait mechanics, extend their envelope of walking speeds by using relatively high step frequencies. Therefore, the capacity to drive the swing leg forward by walking humans may be a specialization for walking, allowing near-passive vaulting of the CoM at walking speeds 4/3 that possible with a passive (duck-like) swing leg.

  19. Wake flow characteristics at high wind speed

    DEFF Research Database (Denmark)

    Aagaard Madsen, Helge; Larsen, Torben J.; Larsen, Gunner Chr.

    2016-01-01

    Wake flow characteristic at high wind speeds is the main subject of this paper. Although the wake losses decrease at high wind speeds it has been found in a recent study that for multiple wake inflow the increase in loading due to wake effects are substantial even at wind speeds well above rated ...

  20. Economy, Movement Dynamics, and Muscle Activity of Human Walking at Different Speeds

    DEFF Research Database (Denmark)

    Raffalt, Peter Christian; Guul, Martin Kjær; Nielsen, A. N.

    2017-01-01

    The complex behaviour of human walking with respect to movement variability, economy and muscle activity is speed dependent. It is well known that a U-shaped relationship between walking speed and economy exists. However, it is an open question if the movement dynamics of joint angles and centre...... of mass and muscle activation strategy also exhibit a U-shaped relationship with walking speed. We investigated the dynamics of joint angle trajectories and the centre of mass accelerations at five different speeds ranging from 20 to 180% of the predicted preferred speed (based on Froude speed) in twelve...... healthy males. The muscle activation strategy and walking economy were also assessed. The movement dynamics was investigated using a combination of the largest Lyapunov exponent and correlation dimension. We observed an intermediate stage of the movement dynamics of the knee joint angle and the anterior...

  1. Preliminary exploration of the measurement of walking speed for the apoplectic people based on UHF RFID.

    Science.gov (United States)

    Huang Hua-Lin; Mo Ling-Fei; Liu Ying-Jie; Li Cheng-Yang; Xu Qi-Meng; Wu Zhi-Tong

    2015-08-01

    The number of the apoplectic people is increasing while population aging is quickening its own pace. The precise measurement of walking speed is very important to the rehabilitation guidance of the apoplectic people. The precision of traditional measuring methods on speed such as stopwatch is relatively low, and high precision measurement instruments because of the high cost cannot be used widely. What's more, these methods have difficulty in measuring the walking speed of the apoplectic people accurately. UHF RFID tag has the advantages of small volume, low price, long reading distance etc, and as a wearable sensor, it is suitable to measure walking speed accurately for the apoplectic people. In order to measure the human walking speed, this paper uses four reader antennas with a certain distance to reads the signal strength of RFID tag. Because RFID tag has different RSSI (Received Signal Strength Indicator) in different distances away from the reader, researches on the changes of RSSI with time have been done by this paper to calculate walking speed. The verification results show that the precise measurement of walking speed can be realized by signal processing method with Gaussian Fitting-Kalman Filter. Depending on the variance of walking speed, doctors can predict the rehabilitation training result of the apoplectic people and give the appropriate rehabilitation guidance.

  2. Effects of obesity on the biomechanics of walking at different speeds.

    Science.gov (United States)

    Browning, Raymond C; Kram, Rodger

    2007-09-01

    Walking is a recommended form of exercise for the treatment of obesity, but walking may be a critical source of biomechanical loads that link obesity and musculoskeletal pathology, particularly knee osteoarthritis. We hypothesized that compared with normal-weight adults 1) obese adults would have greater absolute ground-reaction forces (GRF) during walking, but their GRF would be reduced at slower walking speeds; and 2) obese adults would have greater sagittal-plane absolute leg-joint moments at a given walking speed, but these moments would be reduced at slower walking speeds. We measured GRF and recorded sagittal-plane kinematics of 20 adults (10 obese and 10 normal weight) as they walked on a level, force-measuring treadmill at six speeds (0.5-1.75 m.s(-1)). We calculated sagittal-plane net muscle moments at the hip, knee, and ankle. Compared with their normal-weight peers, obese adults had much greater absolute GRF (N), stance-phase sagittal-plane net muscle moments (N.m) and step width (m). Greater sagittal-plane knee moments in the obese subjects suggest that they walked with greater knee-joint loads than normal-weight adults. Walking slower reduced GRF and net muscle moments and may be a risk-lowering strategy for obese adults who wish to walk for exercise. When obese subjects walked at 1.0 versus 1.5 m.s(-1), peak sagittal-plane knee moments were 45% less. Obese subjects walking at approximately 1.1 m.s(-1) would have the same absolute peak sagittal-plane knee net muscle moment as normal-weight subjects when they walk at their typical preferred speed of 1.4 m.s(-1).

  3. The Effect of Priming with Photographs of Environmental Settings on Walking Speed in an Outdoor Environment.

    Science.gov (United States)

    Franěk, Marek; Režný, Lukáš

    2017-01-01

    This study examined the effect of priming with photographs of various environmental settings on the speed of a subsequent outdoor walk in an urban environment. Either photographs of urban greenery, conifer forests, or shopping malls were presented or no prime was employed. Three experiments were conducted (N = 126, N = 88, and N = 121). After being exposed to the priming or no-priming conditions, the participants were asked to walk along an urban route 1.9 km long with vegetation and mature trees (Experiment 1, Experiment 3) or along a route in a modern suburb (Experiment 2). In accord with the concept of approach-avoidance behavior, it was expected that priming with photographs congruent with the environmental setting of the walking route would result in slower walking speed. Conversely, priming with photographs incongruent with the environmental setting should result in faster walking speed. The results showed that priming with the photographs with vegetation caused a decrease in overall walking speed on the route relative to other experimental conditions. However, priming with incongruent primes did not lead to a significant increase in walking speed. In all experimental conditions, the slowest walking speed was found in sections with the highest natural character. The results are explained in terms of congruency between the prime and the environment, as well as by the positive psychological effects of viewing nature.

  4. A Gaussian process regression model for walking speed estimation using a head-worn IMU.

    Science.gov (United States)

    Zihajehzadeh, Shaghayegh; Park, Edward J

    2017-07-01

    Miniature inertial sensors mainly worn on waist, ankle and wrist have been widely used to measure walking speed of the individuals for lifestyle and/or health monitoring. Recent emergence of head-worn inertial sensors in the form of a smart eyewear (e.g. Recon Jet) or a smart ear-worn device (e.g. Sensixa e-AR) provides an opportunity to use these sensors for estimation of walking speed in real-world environment. This work studies the feasibility of using a head-worn inertial sensor for estimation of walking speed. A combination of time-domain and frequency-domain features of tri-axial acceleration norm signal were used in a Gaussian process regression model to estimate walking speed. An experimental evaluation was performed on 15 healthy subjects during free walking trials in an indoor environment. The results show that the proposed method can provide accuracies of better than around 10% for various walking speed regimes. Additionally, further evaluation of the model for long (15-minutes) outdoor walking trials reveals high correlation of the estimated walking speed values to the ones obtained from fusion of GPS with inertial sensors.

  5. Walking speed estimation using a shank-mounted inertial measurement unit.

    Science.gov (United States)

    Li, Q; Young, M; Naing, V; Donelan, J M

    2010-05-28

    We studied the feasibility of estimating walking speed using a shank-mounted inertial measurement unit. Our approach took advantage of the inverted pendulum-like behavior of the stance leg during walking to identify a new method for dividing up walking into individual stride cycles and estimating the initial conditions for the direct integration of the accelerometer and gyroscope signals. To test its accuracy, we compared speed estimates to known values during walking overground and on a treadmill. The speed estimation method worked well across treadmill speeds and slopes yielding a root mean square speed estimation error of only 7%. It also worked well during overground walking with a 4% error in the estimated travel distance. This accuracy is comparable to that achieved from foot-mounted sensors, providing an alternative in sensor positioning for walking speed estimation. Shank mounted sensors may be of great benefit for estimating speed in walking with abnormal foot motion and for the embedded control of knee-mounted devices such as prostheses and energy harvesters. Copyright 2010 Elsevier Ltd. All rights reserved.

  6. Preferred gait and walk-run transition speeds in ostriches measured using GPS-IMU sensors.

    Science.gov (United States)

    Daley, Monica A; Channon, Anthony J; Nolan, Grant S; Hall, Jade

    2016-10-15

    The ostrich (Struthio camelus) is widely appreciated as a fast and agile bipedal athlete, and is a useful comparative bipedal model for human locomotion. Here, we used GPS-IMU sensors to measure naturally selected gait dynamics of ostriches roaming freely over a wide range of speeds in an open field and developed a quantitative method for distinguishing walking and running using accelerometry. We compared freely selected gait-speed distributions with previous laboratory measures of gait dynamics and energetics. We also measured the walk-run and run-walk transition speeds and compared them with those reported for humans. We found that ostriches prefer to walk remarkably slowly, with a narrow walking speed distribution consistent with minimizing cost of transport (CoT) according to a rigid-legged walking model. The dimensionless speeds of the walk-run and run-walk transitions are slower than those observed in humans. Unlike humans, ostriches transition to a run well below the mechanical limit necessitating an aerial phase, as predicted by a compass-gait walking model. When running, ostriches use a broad speed distribution, consistent with previous observations that ostriches are relatively economical runners and have a flat curve for CoT against speed. In contrast, horses exhibit U-shaped curves for CoT against speed, with a narrow speed range within each gait for minimizing CoT. Overall, the gait dynamics of ostriches moving freely over natural terrain are consistent with previous lab-based measures of locomotion. Nonetheless, ostriches, like humans, exhibit a gait-transition hysteresis that is not explained by steady-state locomotor dynamics and energetics. Further study is required to understand the dynamics of gait transitions. © 2016. Published by The Company of Biologists Ltd.

  7. The application of multilevel modelling to account for the influence of walking speed in gait analysis.

    Science.gov (United States)

    Keene, David J; Moe-Nilssen, Rolf; Lamb, Sarah E

    2016-01-01

    Differences in gait performance can be explained by variations in walking speed, which is a major analytical problem. Some investigators have standardised speed during testing, but this can result in an unnatural control of gait characteristics. Other investigators have developed test procedures where participants walking at their self-selected slow, preferred and fast speeds, with computation of gait characteristics at a standardised speed. However, this analysis is dependent upon an overlap in the ranges of gait speed observed within and between participants, and this is difficult to achieve under self-selected conditions. In this report a statistical analysis procedure is introduced that utilises multilevel modelling to analyse data from walking tests at self-selected speeds, without requiring an overlap in the range of speeds observed or the routine use of data transformations. Copyright © 2015 Elsevier B.V. All rights reserved.

  8. Factors associated with maximal walking speed among older community-living adults

    DEFF Research Database (Denmark)

    Sallinen, Janne; Mänty, Minna; Leinonen, Raija

    2011-01-01

    07330512) involving 605 community-living ambulatory adults aged 75-81 years. Maximal walking speed, leg extensor power, standing balance and body mass index were measured at the research center. Physical activity, smoking, use of alcohol, chronic diseases and depressive symptoms were self-reported using...... standard questionnaires. Results: The mean maximal walking speed was 1.4 m/s (range 0.3-2.9). In linear regression analysis, age, gender and body mass index explained 11% of the variation in maximal walking speed. Adding leg extensor power and standing balance into the model increased the variation...

  9. Speed-related spinal excitation from ankle dorsiflexors to knee extensors during human walking

    DEFF Research Database (Denmark)

    Iglesias, Caroline; Nielsen, Jens Bo; Marchand-Pauvert, Véronique

    2008-01-01

    Automatic adjustments of muscle activity throughout the body are required for the maintenance of balance during human walking. One mechanism that is likely to contribute to this control is the heteronymous spinal excitation between human ankle dorsiflexors and knee extensors (CPQ-reflex). Here, we....../h, then increased with walking speeds about 3-4 km/h, and reached a plateau without any further change at walking speeds from 4 to 6 km/h. The reflex showed no modulation when the stride cycle was varied at constant speed (4 km/h; short steps versus long steps). These changes were unlikely to be only caused...

  10. Cortisol Awakening Response and Walking Speed in Older People.

    Directory of Open Access Journals (Sweden)

    Matias M Pulopulos

    Full Text Available In older people, less diurnal variability in cortisol levels has been consistently related to worse physical performance, especially to slower walking speed (WS. The cortisol awakening response (CAR is a discrete component of the hypothalamic-pituitary-adrenal axis that has been related to several health problems, such as cardiovascular disease and/or worse performance on executive function and memory. The relationship between the CAR and physical performance in older people is poorly understood. In this study, in 86 older people (mean age = 64.42, SD = 3.93, we investigated the relationship between the CAR and WS, a commonly used measure of physical performance in the older population that has also been related to health problems, such as cardiovascular disease and executive function performance in older people. Additionally, we studied whether the relationship between the CAR and WS was independent from cortisol levels on awakening and several possible confounders. Results showed that a CAR of reduced magnitude (measured with 3 samples each day, for two consecutive days, and calculated as the area under the curve with respect to the increase, but not cortisol levels on awakening, was related to slower WS. In addition, this relationship was independent from cortisol levels on awakening. It is possible that a CAR of reduced magnitude would contribute to less diurnal cortisol variability, affecting physical performance. Additionally, it is possible that a CAR of reduced magnitude affects WS through a possible negative effect on executive function, or that the association between the CAR and WS is due to the fact that both are related to similar health problems and to changes in cognitive performance in older people.

  11. Carbohydrate and fat oxidation in persons with lower limb amputation during walking with different speeds.

    Science.gov (United States)

    Gjovaag, Terje; Mirtaheri, Peyman; Starholm, Inger Marie

    2017-11-01

    Studies suggest that the energy expenditure of healthy persons (control) during walking with the preferred walking speed in steady-state conditions is dominated by fat oxidation. Conversely, carbohydrate and fat oxidation during walking is little investigated in transfemoral amputees. To investigate carbohydrate and fat oxidation, energy cost of walking, and percent utilization of maximal aerobic capacity [Formula: see text]during walking. Eight transfemoral amputees and controls walked with their preferred walking speed and speeds 12.5% and 25% slower and faster than their preferred walking speed. Energy expenditure and fuel utilization were measured using a portable metabolic analyzer. Metabolic values are means ± standard deviation. For transfemoral amputees (37.0 ± 10.9 years) and controls (39.0 ± 12.3 years), fat utilization at the preferred walking speed was 44.8% ± 7.2% and 45.0% ± 7.2% of the total energy expenditure, respectively. The preferred walking speed of the transfemoral amputees and controls was close to a metabolic cross-over speed, which is the speed where carbohydrate utilization increases steeply and fat utilization decreases. When walking fast, at 90 m min-1 (preferred walking speed plus 25%), transfemoral amputees utilized 70.7% ± 5.6% of their [Formula: see text], while the controls utilized 30.9% ± 4.5% ( p fat, dominates energy expenditure of both transfemoral amputees and controls. For the transfemoral amputees, consequences of fast walking are very high [Formula: see text] utilization and rate of carbohydrate oxidation. Clinical relevance Research on the relationships between physical effort and fuel partitioning during ambulation could provide important insights for exercise-rehabilitation programs for lower limb amputees (LLA). Regular endurance exercise will improve maximal aerobic capacity and enable LLA to walk faster and at the same time expend less energy and improve fat utilization.

  12. Reliability and Validity of Ten Consumer Activity Trackers Depend on Walking Speed

    NARCIS (Netherlands)

    Fokkema, Tryntsje; Kooiman, Thea J. M.; Krijnen, Wim P.; Van der Schans, Cees P.; De Groot, Martijn

    Purpose: To examine the test-retest reliability and validity of ten activity trackers for step counting at three different walking speeds. Methods: Thirty-one healthy participants walked twice on a treadmill for 30 min while wearing 10 activity trackers (Polar Loop, Garmin Vivosmart, Fitbit Charge

  13. Inertial sensor-based methods in walking speed estimation: a systematic review.

    Science.gov (United States)

    Yang, Shuozhi; Li, Qingguo

    2012-01-01

    Self-selected walking speed is an important measure of ambulation ability used in various clinical gait experiments. Inertial sensors, i.e., accelerometers and gyroscopes, have been gradually introduced to estimate walking speed. This research area has attracted a lot of attention for the past two decades, and the trend is continuing due to the improvement of performance and decrease in cost of the miniature inertial sensors. With the intention of understanding the state of the art of current development in this area, a systematic review on the exiting methods was done in the following electronic engines/databases: PubMed, ISI Web of Knowledge, SportDiscus and IEEE Xplore. Sixteen journal articles and papers in proceedings focusing on inertial sensor based walking speed estimation were fully reviewed. The existing methods were categorized by sensor specification, sensor attachment location, experimental design, and walking speed estimation algorithm.

  14. Inertial Sensor-Based Methods in Walking Speed Estimation: A Systematic Review

    Directory of Open Access Journals (Sweden)

    Qingguo Li

    2012-05-01

    Full Text Available Self-selected walking speed is an important measure of ambulation ability used in various clinical gait experiments. Inertial sensors, i.e., accelerometers and gyroscopes, have been gradually introduced to estimate walking speed. This research area has attracted a lot of attention for the past two decades, and the trend is continuing due to the improvement of performance and decrease in cost of the miniature inertial sensors. With the intention of understanding the state of the art of current development in this area, a systematic review on the exiting methods was done in the following electronic engines/databases: PubMed, ISI Web of Knowledge, SportDiscus and IEEE Xplore. Sixteen journal articles and papers in proceedings focusing on inertial sensor based walking speed estimation were fully reviewed. The existing methods were categorized by sensor specification, sensor attachment location, experimental design, and walking speed estimation algorithm.

  15. Adaptations to changing speed, load, and gradient in human walking: cost of transport, optimal speed, and pendulum.

    Science.gov (United States)

    Gomeñuka, N A; Bona, R L; da Rosa, R G; Peyré-Tartaruga, L A

    2014-06-01

    It has been observed that the optimal speed (OPT) of human walking is independent of load on level surfaces because of the unaltered trajectory of the center of mass and consequent conservation of the pendular mechanism. However, the role of the inverted pendulum mechanism that combines speed, load, and gradient during walking remains unknown. In the present study, 10 subjects walked on a treadmill, with and without loading (25% of the body mass), at different speeds and slopes (0%, +7%, and +15%). The three-dimensional motion and VO2 were simultaneously registered. The mechanical external and internal work and the cost of transport (C) changed with the speed and gradient, but the load only affected C. OPT decreased with increasing gradient, and the pendular mechanics (R) was modified mainly as a result of changes in speed and gradient. OPT and R were independent of the load in these gradients. Remarkably, R increased with increasing speed and decreased (to 30%) with an increasing gradient; moreover, R was independent of load. Therefore, the energy-saving strategy by the pendular mechanism persists, although at a diminished level, in loaded walking on gradients and partially explains the OPT in this condition. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  16. Negative perceptions of aging and decline in walking speed: a self-fulfilling prophecy.

    Directory of Open Access Journals (Sweden)

    Deirdre A Robertson

    Full Text Available Walking speed is a meaningful marker of physical function in the aging population. While it is a primarily physical measure, experimental studies have shown that merely priming older adults with negative stereotypes about aging results in immediate declines in objective walking speed. What is not clear is whether this is a temporary experimental effect or whether negative aging stereotypes have detrimental effects on long term objective health. We sought to explore the association between baseline negative perceptions of aging in the general population and objective walking speed 2 years later.4,803 participations were assessed over 2 waves of The Irish Longitudinal Study on Ageing (TILDA, a prospective, population representative study of adults aged 50+ in the Republic of Ireland. Wave 1 measures - which included the Aging Perceptions Questionnaire, walking speed and all covariates - were taken between 2009 and 2011. Wave 2 measures - which included a second measurement of walking speed and covariates - were collected 2 years later between March and December 2012. Walking speed was measured as the number of seconds to complete the Timed Up-And-Go (TUG task. Participations with a history of stroke, Parkinson's disease or an MMSE < 18 were excluded.After full adjustment for all covariates (age, gender, level of education, disability, chronic conditions, medications, global cognition and baseline TUG negative perceptions of aging at baseline were associated with slower TUG speed 2 years later (B=.03, 95% CI = .01 to 05, p< .05.Walking speed has previously been considered to be a consequence of physical decline but these results highlight the direct role of psychological state in predicting an objective aging outcome. Negative perceptions about aging are a potentially modifiable risk factor of some elements of physical decline in aging.

  17. The effect of walking speed on local dynamic stability is sensitive to calculation methods

    DEFF Research Database (Denmark)

    Stenum, Jan; Bruijn, Sjoerd M; Jensen, Bente Rona

    2014-01-01

    % and 140% of preferred walking speed) for 3min each, while upper body accelerations in three directions were sampled. From these time-series, λS was calculated by three different methods using: (a) a fixed time interval and expressed as logarithmic divergence per stride-time (λS-a), (b) a fixed number...... of strides and expressed as logarithmic divergence per time (λS-b) and (c) a fixed number of strides and expressed as logarithmic divergence per stride-time (λS-c). Mean preferred walking speed was 1.16±0.09m/s. There was only a minor effect of walking speed on λS-a. λS-b increased with increasing walking...

  18. Chronic venous disorders and injection drug use: impact on balance, gait, and walk speed.

    Science.gov (United States)

    Pieper, Barbara; Templin, Thomas N; Birk, Thomas J; Kirsner, Robert S

    2008-01-01

    Injection drug users are at high risk for chronic venous disorders (CVD), a condition resulting in a progressive deterioration of venous function of the legs. However, the effects of CVD on walking mobility in this population have not been studied. We examined a causal model of the relationship between injection drug use, CVD, and Walking Mobility. The validity of the Tinetti Balance and Gait scales and walk speed as a composite measure of Walking Mobility was also explored. The participants were 104 men and women from a methadone maintenance treatment center. Drug use included 18 persons who injected drugs only in the hands, arms, and above the waist; 70 who injected all over the body including the lower extremities; and 16 who never injected drugs but used illegal substances by other routes. Forty-nine percent of participants had moderate to severe CVD. Participants were classified into 2 groups according to their history of injection drug use: (a) those who injected in the lower extremities (n = 70) and (b) those who injected in the arms plus those who did not inject (n = 34). All measurements were obtained at baseline and again approximately 6.5 weeks later. Structural equation modeling was used to examine the causal effect of CVD on Walking Mobility. The validity of the Balance and Gait scales and the walk time variable as measures of a Walking Mobility factor was examined using a second-order confirmatory factor analysis. Questionnaires included the Demographic and Health History and Drug History. The lower extremities were evaluated with the clinical portion of the Clinical-Etiology-Anatomy-Pathophysiology classification. Participants completed the Tinetti Balance and Gait test. A timed 6-m walk at the person's normal pace was used to calculate walk speed. Test-retest reliability of the Tinetti Balance and Gait test and walk speed ranged from 0.79 to 0.86. Balance and gait scores were skewed toward the high end of the scale. Walking speed was slow. The leg

  19. EFFECTS OF UNSTABLE SHOES ON ENERGY COST DURING TREADMILL WALKING AT VARIOUS SPEEDS

    Directory of Open Access Journals (Sweden)

    Keiji Koyama

    2012-12-01

    Full Text Available In recent years, shoes having rounded soles in the anterior- posterior direction have been commercially introduced, which are commonly known as unstable shoes (US. However, physiological responses during walking in US, particularly at various speeds, have not been extensively studied to date. The purpose of this study was to investigate the effect of wearing unstable shoes while walking at low to high speeds on the rate of perceived exertion (RPE, muscle activation, oxygen consumption (VO2, and optimum speed. Healthy male adults wore US or normal walking shoes (WS, and walked at various speeds on a treadmill with no inclination. In experiment 1, subjects walked at 3, 4, 5, 6, and 7 km·h-1 (duration, 3 min for all speeds and were recorded on video from the right sagittal plane to calculate the step length and cadence. Simultaneously, electromyogram (EMG was recorded from six different thigh and calf muscles, and the integrated EMG (iEMG was calculated. In experiment 2, RPE, heart rate and VO2 were measured with the walking speed being increased from 3.6 to 7.2 km·h-1 incrementally by 0.9 km·h-1 every 6 min. The optimum speed, defined by the least oxygen cost, was calculated from the fitted quadratic relationship between walking speed and oxygen cost. Wearing US resulted in significantly longer step length and lower cadence compared with WS condition at any given speed. For all speeds, iEMG in the medial gastrocnemius and soleus muscles, heart rate, and VO2 were significantly higher in US than WS. However, RPE and optimum speed (US, 4.75 ± 0.32 km·h-1; WS, 4. 79 ± 0.18 km·h-1 did not differ significantly between the two conditions. These results suggest that unstable shoes can increase muscle activity of lower legs and energy cost without influencing RPE and optimum speed during walking at various speeds

  20. Walking speed and subclinical atherosclerosis in healthy older adults: the Whitehall II study.

    Science.gov (United States)

    Hamer, Mark; Kivimaki, Mika; Lahiri, Avijit; Yerramasu, Ajay; Deanfield, John E; Marmot, Michael G; Steptoe, Andrew

    2010-03-01

    Extended walking speed is a predictor of incident cardiovascular disease (CVD) in older individuals, but the ability of an objective short-distance walking speed test to stratify the severity of preclinical conditions remains unclear. This study examined whether performance in an 8-ft walking speed test is associated with metabolic risk factors and subclinical atherosclerosis. Cross-sectional. Setting Epidemiological cohort. 530 adults (aged 63 + or - 6 years, 50.3% male) from the Whitehall II cohort study with no known history or objective signs of CVD. Electron beam computed tomography and ultrasound was used to assess the presence and extent of coronary artery calcification (CAC) and carotid intima-media thickness (IMT), respectively. High levels of CAC (Agatston score >100) were detected in 24% of the sample; the mean IMT was 0.75 mm (SD 0.15). Participants with no detectable CAC completed the walking course 0.16 s (95% CI 0.04 to 0.28) faster than those with CAC > or = 400. Objectively assessed, but not self-reported, faster walking speed was associated with a lower risk of high CAC (odds ratio 0.62, 95% CI 0.40 to 0.96) and lower IMT (beta=-0.04, 95% CI -0.01 to -0.07 mm) in comparison with the slowest walkers (bottom third), after adjusting for conventional risk factors. Faster walking speed was also associated with lower adiposity, C-reactive protein and low-density lipoprotein cholesterol. Short-distance walking speed is associated with metabolic risk and subclinical atherosclerosis in older adults without overt CVD. These data suggest that a non-aerobically challenging walking test reflects the presence of underlying vascular disease.

  1. Short-distance walking speed tests in people with Parkinson disease: reliability, responsiveness, and validity.

    Science.gov (United States)

    Combs, Stephanie A; Diehl, M Dyer; Filip, Jacqueline; Long, Erin

    2014-02-01

    The aims of this study were to determine test-retest reliability and responsiveness of short-distance walking speed tests for persons with Parkinson disease (PD). Discriminant and convergent validity of walking speed tests were also examined. Eighty-eight participants with PD (mean age, 66 years) with mild to moderate severity (stages 1-4 on the Hoehn and Yahr Scale) were tested on medications. Measures of activity included the comfortable and fast 10-m walk tests (CWT, FWT), 6-min walk test (6MWT), mini balance evaluations systems test (mini-BEST Test), fear of falling (FoF), and the Activity-Specific Balance Confidence Scale (ABC). The mobility subsection of the PD quality of life-39 (PDQ39-M) served as a participation-based measure. Test-retest reliability was high for both walking speed measures (CWT, ICC(2,1) = 0.98; FWT, ICC(2,1) = 0.99). Minimal detectable change (MDC(95)) for the CWT and FWT was 0.09 m/s and 0.13 m/s respectively. Participants at Hoehn & Yahr levels 3/4 demonstrated significantly slower walking speed with the CWT and FWT than participants at Hoehn & Yahr levels 1 and 2 (P < .01). The CWT and FWT were both significantly (P ≤ .002) correlated with all activity and participation-based measures. Short-distance walking speed tests are clinically useful measures for persons with PD. The CWT and FWT are highly reliable and responsive to change in persons with PD. Short distance walking speed can be used to discriminate differences in gait function between persons with mild and moderate PD severity. The CWT and FWT had moderate to strong associations with other activity and participation based measures demonstrating convergent validity. Copyright © 2013 Elsevier B.V. All rights reserved.

  2. The Perceived Naturalness of Virtual Walking Speeds during WIP Locomotion

    DEFF Research Database (Denmark)

    Nilsson, Niels Chr.; Serafin, Stefania; Nordahl, Rolf

    2016-01-01

    of the factors contributing to the perceptual distortion have yet to be identified. In this paper we present a summary of seven of our studies investigating what factors that influence self-motion perception during virtual walking and two meta-analyses of the findings of the seven studies. The studies relate...

  3. Walking at speeds close to the preferred transition speed as an approach to obesity treatment

    Directory of Open Access Journals (Sweden)

    Ilić Duško

    2012-01-01

    Full Text Available Introduction. Increasing energy expenditure through certain exercise is an important component of effective interventions to enhance initial weight loss and prevent weight regain. Objective. The purpose of this study was to determine the effect of a 16-week weight loss exercise programme on morpho-functional changes in female adults and to examine the programme effects on two subpopulations with different levels of obesity. Methods. Fifty-six middle-aged women were divided into 2 groups according to their body mass index (BMI: 25-29.9 kg/m2 - overweight (OW and ≥30 kg/m2 - obese (OB. The exercise protocol included a walking technique based on hip rotation at horizontal plane at speeds close to the preferred transition speed (PTS. At the initiation of the study and after 16 weeks of the programme, anthropometric, morphological and cardiovascular parameters of all subjects were assessed. The main effects of Group (OW and OB and Time and the interaction effect of Group by Time were tested by time repeated measures General Linear Model (mixed between-within subjects ANOVA. Results. Mean weight loss during the programme was 10.3 kg and 20.1 kg in OW and OB, respectively. The average fat mass (FM loss was 9.4 kg in OW and 16.9 kg in OB. The Mixed ANOVA revealed a significant Group by Time interaction effects for waist circumference, body weight, body water, fat free mass, FM, %FM and BMI (p<0.05. Conclusion. The applied exercise protocol has proved as beneficial in the treatment of obesity, since it resulted in a significant weight loss and body composition changes. The reduction in body weight was achieved mainly on account of the loss of fat mass.

  4. The influence of step frequency on the range of perceptually natural visual walking speeds during walking-in-place and treadmill locomotion

    DEFF Research Database (Denmark)

    Nilsson, Niels Christian; Serafin, Stefania; Nordahl, Rolf

    2014-01-01

    and virtual walking speeds. This paper details a study investigating the effects of movement type (treadmill walking and WIP) and step frequency (1.4, 1.8 and 2.2 steps per second) on the range of perceptually natural visual walking speeds. The results suggests statistically significant main effects of both...... movement type and step frequency but no significant interaction between the two variables....

  5. An image-processing based technique to obtain instantaneous horizontal walking and running speed.

    Science.gov (United States)

    Nagano, Akinori; Fujimoto, Masahiro; Kudo, Shoma; Akaguma, Ryosuke

    2017-01-01

    Walking and running speed is a fundamental parameter studied in a wide range of areas such as sport biomechanics, rehabilitation, health promotion of the elderly, etc. Given that walking or running speed is not constant even within a stride, instantaneous changes in the body motion need to be evaluated to better understand one's performance. In this study, a new cost- and time- efficient methodology to determine instantaneous horizontal walking and running speed was developed. The newly developed method processes the movies taken with a (high-speed) camera. It consists of five sub-steps, which are performed in a serial order: (1) Subtraction of the background image, (2) filtering, (3) binarization and centroid determination, (4) transformation to the laboratory coordinate system and (5) differentiation. To test the accuracy of the newly developed method, the output (position and speed) was compared with the data obtained using motion capture. The average root mean squared (RMS) error (difference between the outputs of the newly developed method and motion capture) of position-time curves was 0.011m-0.033m. The average RMS error of speed-time curves was 0.054m/s-0.076m/s. It was shown that this new method produces accurate outputs of instantaneous walking and running speed. Copyright © 2016 Elsevier B.V. All rights reserved.

  6. Effects of Door Width and Human Body Size on Walking Speed

    Directory of Open Access Journals (Sweden)

    Jetthumrong Siwalee

    2016-01-01

    Full Text Available Door width is one of the important factors to concern in layout or facilities design because it affects directly to traffic speed and overall traffic time simultaneously. Nowadays, common assessment method is computer simulation which is still not realistic due to the unchanged speed of model while walking through a door. This research aims to study an effect of door width to individual walking speed. Sixty subjects participated in the experiment and performed task by walking through the door that is set the width as 40, 50, 60, 70, 80, 90 and 100 centimetres. The optical motion capture system was used to determine walking speed. The results showed that Fitts’ law was applied to the participants with high weight. Door width below 70 centimetres significantly affected to changing speed at 0-0.5 m. before the door. Additionally, human size also affected changing speed. The factors include shoulder breadth, weight and interaction between shoulder breadth and weight were found to be significant. These factors explained 54.2% of changing speed.

  7. Vitamin D and walking speed in older adults: Systematic review and meta-analysis.

    Science.gov (United States)

    Annweiler, Cedric; Henni, Samir; Walrand, Stéphane; Montero-Odasso, Manuel; Duque, Gustavo; Duval, Guillaume T

    2017-12-01

    Vitamin D is involved in musculoskeletal health. There is no consensus on a possible association between circulating 25-hydroxyvitamin D (25OHD) concentrations and walking speed, a 'vital sign' in older adults. Our objective was to systematically review and quantitatively assess the association of 25OHD concentration with walking speed. A Medline search was conducted on June 2017, with no limit of date, using the MeSH terms "Vitamin D" OR "Vitamin D Deficiency" combined with "Gait" OR "Gait disorders, Neurologic" OR "Walking speed" OR "Gait velocity". Fixed-effect meta-analyses were performed to compute: i) mean differences in usual and fast walking speeds and Timed Up and Go test (TUG) between participants with severe vitamin D deficiency (≤25nmol/L) (SVDD), vitamin D deficiency (≤50nmol/L) (VDD), vitamin D insufficiency (≤75nmol/L) (VDI) and normal vitamin D (>75nmol/L) (NVD); ii) risk of slow walking speed according to vitamin D status. Of the 243 retrieved studies, 22 observational studies (17 cross-sectional, 5 longitudinal) met the selection criteria. The number of participants ranged between 54 and 4100 (0-100% female). Usual walking speed was slower among participants with hypovitaminosis D, with a clinically relevant difference compared with NVD of -0.18m/s for SVDD, -0.08m/s for VDD and -0.12m/s for VDI. We found similar results regarding the fast walking speed (mean differences -0.04m/s for VDD and VDI compared with NVD) and TUG (mean difference 0.48s for SVDD compared with NVD). A slow usual walking speed was positively associated with SVDD (summary OR=2.17[95%CI:1.52-3.10]), VDD (OR=1.38[95%CI:1.01-1.89]) and VDI (OR=1.38[95%CI:1.04-1.83]), using NVD as the reference. In conclusion, this meta-analysis provides robust evidence that 25OHD concentrations are positively associated with walking speed among adults. Copyright © 2017. Published by Elsevier B.V.

  8. Activating and Relaxing Music Entrains the Speed of Beat Synchronized Walking

    Science.gov (United States)

    Leman, Marc; Moelants, Dirk; Varewyck, Matthias; Styns, Frederik; van Noorden, Leon; Martens, Jean-Pierre

    2013-01-01

    Inspired by a theory of embodied music cognition, we investigate whether music can entrain the speed of beat synchronized walking. If human walking is in synchrony with the beat and all musical stimuli have the same duration and the same tempo, then differences in walking speed can only be the result of music-induced differences in stride length, thus reflecting the vigor or physical strength of the movement. Participants walked in an open field in synchrony with the beat of 52 different musical stimuli all having a tempo of 130 beats per minute and a meter of 4 beats. The walking speed was measured as the walked distance during a time interval of 30 seconds. The results reveal that some music is ‘activating’ in the sense that it increases the speed, and some music is ‘relaxing’ in the sense that it decreases the speed, compared to the spontaneous walked speed in response to metronome stimuli. Participants are consistent in their observation of qualitative differences between the relaxing and activating musical stimuli. Using regression analysis, it was possible to set up a predictive model using only four sonic features that explain 60% of the variance. The sonic features capture variation in loudness and pitch patterns at periods of three, four and six beats, suggesting that expressive patterns in music are responsible for the effect. The mechanism may be attributed to an attentional shift, a subliminal audio-motor entrainment mechanism, or an arousal effect, but further study is needed to figure this out. Overall, the study supports the hypothesis that recurrent patterns of fluctuation affecting the binary meter strength of the music may entrain the vigor of the movement. The study opens up new perspectives for understanding the relationship between entrainment and expressiveness, with the possibility to develop applications that can be used in domains such as sports and physical rehabilitation. PMID:23874469

  9. Activating and relaxing music entrains the speed of beat synchronized walking.

    Directory of Open Access Journals (Sweden)

    Marc Leman

    Full Text Available Inspired by a theory of embodied music cognition, we investigate whether music can entrain the speed of beat synchronized walking. If human walking is in synchrony with the beat and all musical stimuli have the same duration and the same tempo, then differences in walking speed can only be the result of music-induced differences in stride length, thus reflecting the vigor or physical strength of the movement. Participants walked in an open field in synchrony with the beat of 52 different musical stimuli all having a tempo of 130 beats per minute and a meter of 4 beats. The walking speed was measured as the walked distance during a time interval of 30 seconds. The results reveal that some music is 'activating' in the sense that it increases the speed, and some music is 'relaxing' in the sense that it decreases the speed, compared to the spontaneous walked speed in response to metronome stimuli. Participants are consistent in their observation of qualitative differences between the relaxing and activating musical stimuli. Using regression analysis, it was possible to set up a predictive model using only four sonic features that explain 60% of the variance. The sonic features capture variation in loudness and pitch patterns at periods of three, four and six beats, suggesting that expressive patterns in music are responsible for the effect. The mechanism may be attributed to an attentional shift, a subliminal audio-motor entrainment mechanism, or an arousal effect, but further study is needed to figure this out. Overall, the study supports the hypothesis that recurrent patterns of fluctuation affecting the binary meter strength of the music may entrain the vigor of the movement. The study opens up new perspectives for understanding the relationship between entrainment and expressiveness, with the possibility to develop applications that can be used in domains such as sports and physical rehabilitation.

  10. Activating and relaxing music entrains the speed of beat synchronized walking.

    Science.gov (United States)

    Leman, Marc; Moelants, Dirk; Varewyck, Matthias; Styns, Frederik; van Noorden, Leon; Martens, Jean-Pierre

    2013-01-01

    Inspired by a theory of embodied music cognition, we investigate whether music can entrain the speed of beat synchronized walking. If human walking is in synchrony with the beat and all musical stimuli have the same duration and the same tempo, then differences in walking speed can only be the result of music-induced differences in stride length, thus reflecting the vigor or physical strength of the movement. Participants walked in an open field in synchrony with the beat of 52 different musical stimuli all having a tempo of 130 beats per minute and a meter of 4 beats. The walking speed was measured as the walked distance during a time interval of 30 seconds. The results reveal that some music is 'activating' in the sense that it increases the speed, and some music is 'relaxing' in the sense that it decreases the speed, compared to the spontaneous walked speed in response to metronome stimuli. Participants are consistent in their observation of qualitative differences between the relaxing and activating musical stimuli. Using regression analysis, it was possible to set up a predictive model using only four sonic features that explain 60% of the variance. The sonic features capture variation in loudness and pitch patterns at periods of three, four and six beats, suggesting that expressive patterns in music are responsible for the effect. The mechanism may be attributed to an attentional shift, a subliminal audio-motor entrainment mechanism, or an arousal effect, but further study is needed to figure this out. Overall, the study supports the hypothesis that recurrent patterns of fluctuation affecting the binary meter strength of the music may entrain the vigor of the movement. The study opens up new perspectives for understanding the relationship between entrainment and expressiveness, with the possibility to develop applications that can be used in domains such as sports and physical rehabilitation.

  11. Genetic Analysis of Daily Maximum Milking Speed by a Random Walk Model in Dairy Cows

    DEFF Research Database (Denmark)

    Karacaören, Burak; Janss, Luc; Kadarmideen, Haja

    Data were obtained from dairy cows stationed at research farm ETH Zurich for maximum milking speed. The main aims of this paper are a) to evaluate if the Wood curve is suitable to model mean lactation curve b) to predict longitudinal breeding values by random regression and random walk models...... of maximum milking speed. Wood curve did not provide a good fit to the data set. Quadratic random regressions gave better predictions compared with the random walk model. However random walk model does not need to be evaluated for different orders of regression coefficients. In addition with the Kalman...... filter applications: random walk model could give online prediction of breeding values. Hence without waiting for whole lactation records, genetic evaluation could be made when the daily or monthly data is available...

  12. How locomotion sub-functions can control walking at different speeds?

    Science.gov (United States)

    Ahmad Sharbafi, Maziar; Seyfarth, Andre

    2017-02-28

    Inspired from template models explaining biological locomotory systems and Raibert׳s pioneering legged robots, locomotion can be realized by basic sub-functions: elastic axial leg function, leg swinging and balancing. Combinations of these three can generate different gaits with diverse properties. In this paper we investigate how locomotion sub-functions contribute to stabilize walking at different speeds. Based on this trilogy, we introduce a conceptual model to quantify human locomotion sub-functions in walking. This model can produce stable walking and also predict human locomotion sub-function control during swing phase of walking. Analyzing experimental data based on this modeling shows different control strategies which are employed to increase speed from slow to moderate and moderate to fast gaits. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Effects of walking speed on asymmetry and bilateral coordination of gait

    Science.gov (United States)

    Plotnik, Meir; Bartsch, Ronny P.; Zeev, Aviva; Giladi, Nir; Hausdorff, Jeffery M.

    2013-01-01

    The mechanisms regulating the bilateral coordination of gait in humans are largely unknown. Our objective was to study how bilateral coordination changes as a result of gait speed modifications during over ground walking. 15 young adults wore force sensitive insoles that measured vertical forces used to determine the timing of the gait cycle events under three walking conditions (i.e., usual-walking, fast and slow). Ground reaction force impact (GRFI) associated with heel-strikes was also quantified, representing the potential contribution of sensory feedback to the regulation of gait. Gait asymmetry (GA) was quantified based on the differences between right and left swing times and the bilateral coordination of gait was assessed using the phase coordination index (PCI), a metric that quantifies the consistency and accuracy of the anti-phase stepping pattern. GA was preserved in the three different gait speeds. PCI was higher (reduced coordination) in the slow gait condition, compared to usual-walking (3.51% vs. 2.47%, respectively, p=0.002), but was not significantly affected in the fast condition. GRFI values were lower in the slow walking as compared to usual-walking and higher in the fast walking condition (pgait related changes in PCI were not associated with the slowed gait related changes in GRFI. The present findings suggest that left-right anti-phase stepping is similar in normal and fast walking, but altered during slowed walking. This behavior might reflect a relative increase in attention resources required to regulate a slow gait speed, consistent with the possibility that cortical function and supraspinal input influences the bilateral coordination of gait. PMID:23680424

  14. Assessing the reliability and validity of a shorter walk test compared with the 10-Meter Walk Test for measurements of gait speed in healthy, older adults.

    Science.gov (United States)

    Peters, Denise M; Fritz, Stacy L; Krotish, Debra E

    2013-01-01

    Walking speed is associated with several health-related outcomes. Research examining how differences in test walking distance affect walking speed reliability and validity is limited. The primary purpose of this study was to examine the reliability and concurrent validity of gait speed measurements obtained from a 4-Meter Walk Test compared with the commonly used 10-Meter Walk Test. A second objective was to similarly examine 2 different timing methods: stopwatch and automatic timers. Forty-three healthy, older adults (mean age = 84.3 ± 6.9 years) performed 3 consecutive walking trials on the 4- and 10-Meter Walk Tests at their self-selected walking speed. Gait speed measurements for both tests were shown to have excellent test-retest reliability (ICC values of 0.96-0.98), with similar results for stopwatch and automatic timer assessments (ICC values of 0.99-1.00). Standard error of the measurement (SEM) values were small (0.004-0.008 m/s) across measurement methods. While the ICC value for gait speed measurements between the 2 walk tests was 0.93, the Bland-Altman analysis revealed a discrepancy of ±0.15 to ±0.17 m/s between measurement methods. Both 4- and 10-m gait speed assessments had excellent test-retest reliability with similar SEM and minimal detectable change values. There was little difference in SEM values between the 2 timing methods. While the mean difference in gait speed between the 4- and 10-Meter Walk Tests was small, the range of the measurement differences was large enough to potentially mask meaningful changes in gait speed over time if both methods were used interchangeably. While the reliability of both walking tests is excellent, the 4-Meter Walk Test does not exhibit a high enough degree of concurrent validity with the 10-Meter Walk Test to be used interchangeably for gait speed assessments in healthy, older adults. We therefore recommend using the 10-Meter Walk Test to obtain the most valid clinical assessment of walking speed when

  15. A novel walking speed estimation scheme and its application to treadmill control for gait rehabilitation

    Directory of Open Access Journals (Sweden)

    Yoon Jungwon

    2012-08-01

    Full Text Available Abstract Background Virtual reality (VR technology along with treadmill training (TT can effectively provide goal-oriented practice and promote improved motor learning in patients with neurological disorders. Moreover, the VR + TT scheme may enhance cognitive engagement for more effective gait rehabilitation and greater transfer to over ground walking. For this purpose, we developed an individualized treadmill controller with a novel speed estimation scheme using swing foot velocity, which can enable user-driven treadmill walking (UDW to more closely simulate over ground walking (OGW during treadmill training. OGW involves a cyclic acceleration-deceleration profile of pelvic velocity that contrasts with typical treadmill-driven walking (TDW, which constrains a person to walk at a preset constant speed. In this study, we investigated the effects of the proposed speed adaptation controller by analyzing the gait kinematics of UDW and TDW, which were compared to those of OGW at three pre-determined velocities. Methods Ten healthy subjects were asked to walk in each mode (TDW, UDW, and OGW at three pre-determined speeds (0.5 m/s, 1.0 m/s, and 1.5 m/s with real time feedback provided through visual displays. Temporal-spatial gait data and 3D pelvic kinematics were analyzed and comparisons were made between UDW on a treadmill, TDW, and OGW. Results The observed step length, cadence, and walk ratio defined as the ratio of stride length to cadence were not significantly different between UDW and TDW. Additionally, the average magnitude of pelvic acceleration peak values along the anterior-posterior direction for each step and the associated standard deviations (variability were not significantly different between the two modalities. The differences between OGW and UDW and TDW were mainly in swing time and cadence, as have been reported previously. Also, step lengths between OGW and TDW were different for 0.5 m/s and 1.5 m/s gait velocities

  16. Timed limb coordination performance is associated with walking speed in healthy older adults: a cross-sectional exploratory study.

    Science.gov (United States)

    Hollman, John H; Conner, Megan N; Goodman, Kelli A; Kremer, Kathryn H; Petkus, Maegan T; Lanzino, Desiree J

    2013-06-01

    Walking speed reflects quality of life, health status and physical function in older adults but interpreting measures of walking speed is affected by several confounders such as gender, age and height. Additionally, walking speed is influenced by neurologic conditions that impair limb coordination. In absence of defined pathology, it is less clear how varying levels of limb coordination influence walking speed. The purpose of this study was to examine the relationship between limb coordination and walking speed in older adults, controlling for effects of gender, age and height. Sixty-nine healthy, community-dwelling individuals over the age of 60 participated in the study. Participants completed a battery of timed upper and lower limb coordination tests. Normal and fast walking speed were measured over the inner six meters of a 10 m walkway. Correlation and regression analyses were used to examine the relationship between limb coordination performance and walking speed. Controlling for gender, age and height, variance in normal walking speed was accounted for by variance in pronation-supination performance (partial r = -0.396, partial r(2) = 0.16) and variance in fast walking speed was accounted for by variance in finger-to-nose performance (partial r = -0.356, partial r(2) = 0.13). The findings support our hypothesis that limb coordination performance would correlate with walking speed in healthy older adults. Moreover, limb coordination performance attenuated the effects of gender, age and height on walking speed. Limb coordination may be a modifiable determinant of walking speed in older adults. Copyright © 2012 Elsevier B.V. All rights reserved.

  17. Obesity does not impair walking economy across a range of speeds and grades

    OpenAIRE

    Browning, Raymond C.; Reynolds, Michelle M.; Board, Wayne J.; Walters, Kellie A.; Reiser, Raoul F.

    2013-01-01

    Despite the popularity of walking as a form of physical activity for obese individuals, relatively little is known about how obesity affects the metabolic rate, economy, and underlying mechanical energetics of walking across a range of speeds and grades. The purpose of this study was to quantify metabolic rate, stride kinematics, and external mechanical work during level and gradient walking in obese and nonobese adults. Thirty-two obese [18 women, mass = 102.1 (15.6) kg, BMI = 33.9 (3.6) kg/...

  18. Energy cost of balance control during walking decreases with external stabilizer stiffness independent of walking speed

    NARCIS (Netherlands)

    Ijmker, T.; Houdijk, J.H.P.; Lamoth, C.J.C.; Beek, P.J.; van der Woude, L.H.V.

    2013-01-01

    Human walking requires active neuromuscular control to ensure stability in the lateral direction, which inflicts a certain metabolic load. The magnitude of this metabolic load has previously been investigated by means of passive external lateral stabilization via spring-like cords. In the present

  19. Effects of Walking with Blood Flow Restriction on Excess Post-exercise Oxygen Consumption.

    Science.gov (United States)

    Mendonca, G V; Vaz, J R; Pezarat-Correia, P; Fernhall, B

    2015-02-09

    This study determined the influence of walking with blood flow restriction (BFR) on the excess post-exercise oxygen consumption (EPOC) of healthy young men. 17 healthy young men (22.1±2.9 years) performed graded treadmill exercise to assess VO2peak. In a randomized fashion, each participant performed 5 sets of 3-min treadmill exercise at their optimal walking speed with 1-min interval either with or without BFR. Participants were then seated in a chair and remained there for 30 min of recovery. Expired gases were continuously monitored during exercise and recovery. BFR increased the O2 cost of walking as well as its relative intensity and cumulative O2 deficit (pEPOC magnitude after walking with BFR was greater than in the non-BFR condition (pEPOC. The EPOC magnitude was no longer different between conditions after controlling for the differences in relative intensity and in the cumulative O2 deficit (p>0.05). These data indicate that walking with BFR increases the magnitude of EPOC. Moreover, they also demonstrate that such increment in EPOC is likely explained by the effects of BFR on walking relative intensity and cumulative O2 deficit. © Georg Thieme Verlag KG Stuttgart · New York.

  20. Effects of Kinesio taping and Mcconnell taping on balance and walking speed of hemiplegia patients.

    Science.gov (United States)

    Choi, Yong-Kyu; Park, Young-Han; Lee, Jung-Ho

    2016-04-01

    [Purpose] The aim of this study was to evaluate the overlap effect of the PNF following the application of Kinesio taping and the McConnell taping, and also the impact of the taping application method on the balance and walking speed of the patients with stroke. [Subjects and Methods] Thirty-six patients who were diagnosed with hemiplegia due to stroke were selected as subjects of this study. They were randomly and evenly divided into experiment group 1 (Kinesio taping group), experiment group 2 (McConnell taping group), and the control group; each group had 12 patients. [Results] The Berg balance scale (BBS) was used to evaluate balance, and the ability in this study. A 10 m walking test (10MWT) was performed to measure the walking speed. Experiment group 1 showed a statistically significant improvement in balance and walking speed compared to experiment group 2, and the control group in week 4 and week 8. [Conclusion] Application of Kinesio taping had a more beneficial effect on the balance and walking speed than joint-fixation taping of the patients with stroke.

  1. Maximum walking speeds obtained using treadmill and overground robot system in persons with post-stroke hemiplegia

    Science.gov (United States)

    2012-01-01

    Background Previous studies demonstrated that stroke survivors have a limited capacity to increase their walking speeds beyond their self-selected maximum walking speed (SMWS). The purpose of this study was to determine the capacity of stroke survivors to reach faster speeds than their SMWS while walking on a treadmill belt or while being pushed by a robotic system (i.e. “push mode”). Methods Eighteen chronic stroke survivors with hemiplegia were involved in the study. We calculated their self-selected comfortable walking speed (SCWS) and SMWS overground using a 5-meter walk test (5-MWT). Then, they were exposed to walking at increased speeds, on a treadmill and while in “push mode” in an overground robotic device, the KineAssist, until they were tested at a speed that they could not sustain without losing balance. We recorded the time and number of steps during each trial and calculated gait speed, average cadence and average step length. Results Maximum walking speed in the “push mode” was 13% higher than the maximum walking speed on the treadmill and both were higher (“push mode”: 61%; treadmill: 40%) than the maximum walking speed overground. Subjects achieved these faster speeds by initially increasing both step length and cadence and, once individuals stopped increasing their step length, by only increasing cadence. Conclusions With post-stroke hemiplegia, individuals are able to walk at faster speeds than their SMWS overground, when provided with a safe environment that provides external forces that requires them to attempt dynamic stability maintenance at higher gait speeds. Therefore, this study suggests the possibility that, given the appropriate conditions, people post-stroke can be trained at higher speeds than previously attempted. PMID:23057500

  2. Obesity does not impair walking economy across a range of speeds and grades.

    Science.gov (United States)

    Browning, Raymond C; Reynolds, Michelle M; Board, Wayne J; Walters, Kellie A; Reiser, Raoul F

    2013-05-01

    Despite the popularity of walking as a form of physical activity for obese individuals, relatively little is known about how obesity affects the metabolic rate, economy, and underlying mechanical energetics of walking across a range of speeds and grades. The purpose of this study was to quantify metabolic rate, stride kinematics, and external mechanical work during level and gradient walking in obese and nonobese adults. Thirty-two obese [18 women, mass = 102.1 (15.6) kg, BMI = 33.9 (3.6) kg/m(2); mean (SD)] and 19 nonobese [10 women, mass = 64.4 (10.6) kg, BMI = 21.6 (2.0) kg/m(2)] volunteers participated in this study. We measured oxygen consumption, ground reaction forces, and lower extremity kinematics while subjects walked on a dual-belt force-measuring treadmill at 11 speeds/grades (0.50-1.75 m/s, -3° to +9°). We calculated metabolic rate, stride kinematics, and external work. Net metabolic rate (Ė net/kg, W/kg) increased with speed or grade across all individuals. Surprisingly and in contrast with previous studies, Ė net/kg was 0-6% less in obese compared with nonobese adults (P = 0.013). External work, although a primary determinant of Ė net/kg, was not affected by obesity across the range of speeds/grades used in this study. We also developed new prediction equations to estimate oxygen consumption and Ė net/kg and found that Ė net/kg was positively related to relative leg mass and step width and negatively related to double support duration. These results suggest that obesity does not impair walking economy across a range of walking speeds and grades.

  3. Evaluation of a Viscoelastic Ankle-Foot Prosthesis at Slow and Normal Walking Speeds on an Able-Bodied Subject

    Directory of Open Access Journals (Sweden)

    Zahra Safaeepour

    2015-12-01

    Full Text Available Objectives: This paper describes further improvement and preliminarily evaluation of a novel viscoelastic ankle-foot prosthesis prototype. The objective was to control the ankle hysteresis at slow and normal walking speeds. Methods: Inspired by the ankle biomechanics, in which the hysteresis differs based on the gait speeds, a manually damping control mechanism imbedded in the prosthesis for adjusting the ankle damping at slow and normal walking speeds. The prototype was then preliminarily tested on an able-bodied subject wearing an adaptor which simulates the amputee walking. The ankle joint kinetics and kinematics were measured in a gait analysis lab at different walking speeds. Results: The results suggest that the viscoelastic ankle foot prosthesis prototype could provide a smooth normal-like walking for most of the measured gait characteristics in slow and normal speeds. Discussion: Therefore, it is suggested to apply a controllable damping mechanism based on the gait speeds in the design of new prosthetic feet.

  4. The Effect of Head Mounted Display Weight and Locomotion Method on the Perceived Naturalness of Virtual Walking Speeds

    DEFF Research Database (Denmark)

    Nilsson, Niels Chr.; Serafin, Stefania; Nordahl, Rolf

    This poster details a study investigating the effect of Head Mounted Display (HMD) weight and locomotion method (Walking-In-Place and treadmill walking) on the perceived naturalness of virtual walking speeds. The results revealed significant main effects of movement type, but no significant effects...

  5. 3D intersegmental knee loading in below-knee amputees across steady-state walking speeds.

    Science.gov (United States)

    Fey, Nicholas P; Neptune, Richard R

    2012-05-01

    Unilateral below-knee amputees often develop comorbidities that include knee joint disorders (e.g., intact leg knee osteoarthritis), with the mechanisms leading to these comorbidities being poorly understood. Mechanical knee loading of non-amputees has been associated with joint disorders and shown to be influenced by walking speed. However, the relationships between amputee knee loading and speed have not been identified. This study examined three-dimensional mechanical knee loading of amputees across a wide range of steady-state walking speeds. Fourteen amputees and 10 non-amputee control subjects were analyzed at four overground walking speeds. At each speed, intersegmental joint moment and force impulses (i.e., time-integrals over the stance phase) were compared between the control, intact and residual knees using repeated-measures ANOVAs. There were no differences in joint force impulses between the intact and control knees. The intact knee abduction moment impulse was lower than the non-amputees at 0.6 and 0.9 m/s. The intact knee flexion moment impulses at 0.6, 1.2 and 1.5m/s and knee external rotation moment impulses at all speeds were greater than the residual knee. The residual knee extension moment and posterior force impulses were insensitive to speed increases, while these quantities increased in intact and control knees. These results suggest the intact knees of asymptomatic and relatively new amputees are not overloaded during walking compared to non-amputees. Increased knee loads may develop in response to prolonged prosthesis usage or joint disorder onset. Further study is needed to determine if the identified bilateral loading asymmetries across speeds lead to diminished knee joint health. Copyright © 2011 Elsevier Ltd. All rights reserved.

  6. Gait parameters database for young children: The influences of age and walking speed

    OpenAIRE

    Van Hamme, Angèle; El Habachi, Aimad; SAMSON, William; Dumas, Raphaël; Cheze, Laurence; DOHIN, Bruno

    2015-01-01

    Background. Reference databases are mandatory in orthopaedics because they enable the detection of gait abnormalities in patients. Such databases rarely include data on children under seven years of age. In young children, gait is principally influenced by age and walking speed. The influence of the age-speed interaction has not been well established. Therefore, the objective of the present study is to propose normative values for biomechanical gait parameters in children taking into account ...

  7. Skeletal muscle mitochondrial energetics are associated with maximal aerobic capacity and walking speed in older adults.

    Science.gov (United States)

    Coen, Paul M; Jubrias, Sharon A; Distefano, Giovanna; Amati, Francesca; Mackey, Dawn C; Glynn, Nancy W; Manini, Todd M; Wohlgemuth, Stephanie E; Leeuwenburgh, Christiaan; Cummings, Steven R; Newman, Anne B; Ferrucci, Luigi; Toledo, Frederico G S; Shankland, Eric; Conley, Kevin E; Goodpaster, Bret H

    2013-04-01

    Lower ambulatory performance with aging may be related to a reduced oxidative capacity within skeletal muscle. This study examined the associations between skeletal muscle mitochondrial capacity and efficiency with walking performance in a group of older adults. Thirty-seven older adults (mean age 78 years; 21 men and 16 women) completed an aerobic capacity (VO2 peak) test and measurement of preferred walking speed over 400 m. Maximal coupled (State 3; St3) mitochondrial respiration was determined by high-resolution respirometry in saponin-permeabilized myofibers obtained from percutanous biopsies of vastus lateralis (n = 22). Maximal phosphorylation capacity (ATPmax) of vastus lateralis was determined in vivo by (31)P magnetic resonance spectroscopy (n = 30). Quadriceps contractile volume was determined by magnetic resonance imaging. Mitochondrial efficiency (max ATP production/max O2 consumption) was characterized using ATPmax per St3 respiration (ATPmax/St3). In vitro St3 respiration was significantly correlated with in vivo ATPmax (r (2) = .47, p = .004). Total oxidative capacity of the quadriceps (St3*quadriceps contractile volume) was a determinant of VO2 peak (r (2) = .33, p = .006). ATPmax (r (2) = .158, p = .03) and VO2 peak (r (2) = .475, p efficiency is an important determinant for preferred walking speed. Lower mitochondrial capacity and efficiency were both associated with slower walking speed within a group of older participants with a wide range of function. In addition to aerobic capacity, lower mitochondrial capacity and efficiency likely play roles in slowing gait speed with age.

  8. Mobility-Related Fatigue, Walking Speed, and Muscle Strength in Older People

    DEFF Research Database (Denmark)

    Mänty, Minna; Mendes de Leon, Carlos F.; Rantanen, Taina

    2012-01-01

    Background. Fatigue is an important early marker of functional decline among older people, but the mechanisms underlying this association are not fully understood. The purpose of the present study was to examine the association between mobility-related fatigue and walking speed and to test...... among men (b = −.04, p older adults...

  9. Does training have consequences for the walk-run transition speed?

    Science.gov (United States)

    Beaupied, Hélène; Multon, Franck; Delamarche, Paul

    2003-02-01

    A number of authors when studying the walk-run transition phenomenon focused either on the mechanical or energy expenditure whilst only a few used both parameters concurrently. Moreover the literature demonstrates that the contribution of these variables changes along with the level and method of training. Consequently the purpose of this study is to find, by analyzing concurrently these two variables, if the walk-run transition speed is linked to the type of training. To this end we calculated two theoretical transition speeds: one based on the metabolic energy expenditure St(1) and the second one based on the internal work St(2). Subjects were divided into three groups (untrained, sprint and endurance-trained men) who were required to walk and run on a treadmill at increasing speeds. Firstly we show that the relationship between St(1) and St(2) differs depending on the groups. Sprinters have a significantly lower St(2) than St(1) whereas the opposite is found for untrained subjects. We also show that the transition speed is linked to the subject's type of training. To conclude it seems that acquiring running techniques through specific training has consequences for the walk-run transition phenomenon.

  10. Using perceptive computing in multiple sclerosis - the Short Maximum Speed Walk test

    Science.gov (United States)

    2014-01-01

    Background We investigated the applicability and feasibility of perceptive computing assisted gait analysis in multiple sclerosis (MS) patients using Microsoft Kinect™. To detect the maximum walking speed and the degree of spatial sway, we established a computerized and observer-independent measure, which we named Short Maximum Speed Walk (SMSW), and compared it to established clinical measures of gait disability in MS, namely the Expanded Disability Status Scale (EDSS) and the Timed 25-Foot Walk (T25FW). Methods Cross-sectional study of 22 MS patients (age mean ± SD 43 ± 9 years, 13 female) and 22 age and gender matched healthy control subjects (HC) (age 37 ± 11 years, 13 female). The disability level of each MS patient was graded using the EDSS (median 3.0, range 0.0-6.0). All subjects then performed the SMSW and the Timed 25-Foot Walk (T25FW). The SMSW comprised five gait parameters, which together assessed average walking speed and gait stability in different dimensions (left/right, up/down and 3D deviation). Results SMSW average walking speed was slower in MS patients (1.6 ± 0.3 m/sec) than in HC (1.8 ± 0.4 m/sec) (p = 0.005) and correlated well with EDSS (Spearman’s Rho 0.676, p Kinect™ are feasible, well tolerated and can detect clinical gait disturbances in patients with MS. The retest-reliability was on par with the T25FW. PMID:24886525

  11. Cardiovascular Risk Burden and Future Risk of Walking Speed Limitation in Older Adults.

    Science.gov (United States)

    Heiland, Emerald G; Qiu, Chengxuan; Wang, Rui; Santoni, Giola; Liang, Yajun; Fratiglioni, Laura; Welmer, Anna-Karin

    2017-11-01

    To explore the association between cardiovascular risk factor (CRF) burden and limitation in walking speed, balance, and chair stand and to verify whether these associations vary according to age and cognitive status. Longitudinal population-based study. Urban area of Stockholm, Sweden. Individuals aged 60 and older who participated in the Swedish National Study on Aging and Care in Kungsholmen and were free of limitations in walking speed (n = 1,441), balance (n = 1,154), or chair stands (n = 1,496) at baseline (2001-04). At baseline, data on demographic characteristics, CRFs, other lifestyle factors, C-reactive protein, and cognitive function were collected. CRF burden was measured using the Framingham general cardiovascular risk score (FRS). Limitations in walking speed (<0.8 m/s), balance (<5 seconds), and chair stand (inability to rise 5 times) were determined at 3-, 6-, and 9-year follow-up. Data were analyzed using Cox proportional hazards models stratified according to age (<78, ≥78). During follow-up, 326 persons developed limitations in walking speed, 303 in balance, and 374 in chair stands. An association between the FRS and walking speed limitation was evident only in adults younger than 78 (for each 1-point increase in FRS: hazard ratio (HR) = 1.09, 95% confidence interval (CI) = 1.02-1.17) after controlling for potential confounders including cognitive function (correspondingly, in adults aged ≥78: HR = 0.98, 95% CI = 0.92-1.03). Also, higher FRS was significantly associated with faster decline in walking speed (P < .001). A higher FRS is associated with greater risk of subsequent development of walking speed limitation in adults younger than 78, independent of cognitive function. Interventions targeting multiple CRFs in younger-old people may help in maintaining mobility function. © 2017, Copyright the Authors Journal compilation © 2017, The American Geriatrics Society.

  12. Changes in Energy Cost and Total External Work of Muscles in Elite Race Walkers Walking at Different Speeds

    Directory of Open Access Journals (Sweden)

    Chwała Wiesław

    2014-12-01

    Full Text Available The aim of the study was to assess energy cost and total external work (total energy depending on the speed of race walking. Another objective was to determine the contribution of external work to total energy cost of walking at technical, threshold and racing speed in elite competitive race walkers.

  13. The Combined Effects of Body Weight Support and Gait Speed on Gait Related Muscle Activity: A Comparison between Walking in the Lokomat Exoskeleton and Regular Treadmill Walking

    Science.gov (United States)

    Van Kammen, Klaske; Boonstra, Annemarijke; Reinders-Messelink, Heleen; den Otter, Rob

    2014-01-01

    Background For the development of specialized training protocols for robot assisted gait training, it is important to understand how the use of exoskeletons alters locomotor task demands, and how the nature and magnitude of these changes depend on training parameters. Therefore, the present study assessed the combined effects of gait speed and body weight support (BWS) on muscle activity, and compared these between treadmill walking and walking in the Lokomat exoskeleton. Methods Ten healthy participants walked on a treadmill and in the Lokomat, with varying levels of BWS (0% and 50% of the participants’ body weight) and gait speed (0.8, 1.8, and 2.8 km/h), while temporal step characteristics and muscle activity from Erector Spinae, Gluteus Medius, Vastus Lateralis, Biceps Femoris, Gastrocnemius Medialis, and Tibialis Anterior muscles were recorded. Results The temporal structure of the stepping pattern was altered when participants walked in the Lokomat or when BWS was provided (i.e. the relative duration of the double support phase was reduced, and the single support phase prolonged), but these differences normalized as gait speed increased. Alternations in muscle activity were characterized by complex interactions between walking conditions and training parameters: Differences between treadmill walking and walking in the exoskeleton were most prominent at low gait speeds, and speed effects were attenuated when BWS was provided. Conclusion Walking in the Lokomat exoskeleton without movement guidance alters the temporal step regulation and the neuromuscular control of walking, although the nature and magnitude of these effects depend on complex interactions with gait speed and BWS. If normative neuromuscular control of gait is targeted during training, it is recommended that very low speeds and high levels of BWS should be avoided when possible. PMID:25226302

  14. Restricted Arm Swing Affects Gait Stability and Increased Walking Speed Alters Trunk Movements in Children with Cerebral Palsy

    Science.gov (United States)

    Delabastita, Tijs; Desloovere, Kaat; Meyns, Pieter

    2016-01-01

    Observational research suggests that in children with cerebral palsy, the altered arm swing is linked to instability during walking. Therefore, the current study investigates whether children with cerebral palsy use their arms more than typically developing children, to enhance gait stability. Evidence also suggests an influence of walking speed on gait stability. Moreover, previous research highlighted a link between walking speed and arm swing. Hence, the experiment aimed to explore differences between typically developing children and children with cerebral palsy taking into account the combined influence of restricting arm swing and increasing walking speed on gait stability. Spatiotemporal gait characteristics, trunk movement parameters and margins of stability were obtained using three dimensional gait analysis to assess gait stability of 26 children with cerebral palsy and 24 typically developing children. Four walking conditions were evaluated: (i) free arm swing and preferred walking speed; (ii) restricted arm swing and preferred walking speed; (iii) free arm swing and high walking speed; and (iv) restricted arm swing and high walking speed. Double support time and trunk acceleration variability increased more when arm swing was restricted in children with bilateral cerebral palsy compared to typically developing children and children with unilateral cerebral palsy. Trunk sway velocity increased more when walking speed was increased in children with unilateral cerebral palsy compared to children with bilateral cerebral palsy and typically developing children and in children with bilateral cerebral palsy compared to typically developing children. Trunk sway velocity increased more when both arm swing was restricted and walking speed was increased in children with bilateral cerebral palsy compared to typically developing children. It is proposed that facilitating arm swing during gait rehabilitation can improve gait stability and decrease trunk movements in

  15. IMPACT OF BODY WEIGHT SUPPORTED BACKWARD TREADMILL TRAINING ON WALKING SPEED IN CHILDREN WITH SPASTIC DIPLEGIA

    Directory of Open Access Journals (Sweden)

    Hamada El Sayed Abd Allah Ayoub

    2016-10-01

    Full Text Available Background: A lot of the ambulating children with spastic diplegia were able to walk with flexed hips, knees and ankles this gait pattern is known as crouch gait. The most needed functional achievement of diplegic children habilitation is to be able to walk appropriately. The development of an independent and efficient walking is one of the main objectives for children with cerebral palsy especially those with spastic diplegia. Method: Twenty children with spastic diplegia enrolled in this study, they were classified into two groups of equal number, eligibility to our study were ages ranged from seven to ten years, were able to ambulate, They had gait problems and abnormal gait kinematics. The control group (A received selected physical therapy program based on neurodevelopmental approach for such cases, while the study group (B received partial body weight supported backward treadmill training in addition to regular exercise program. Gait pattern was assessed using the Biodex Gait Trainer II for each group pre and post three months of the treatment program. Results: There was statistically significant improvement in walking speed in the study group (P<0.05 with significant difference when comparing post treatment results between groups (p<0.05. Conclusion: These findings suggested that partial body weight supported backward treadmill training can be included as a supplementary therapeutic modality to improve walking speed and functional abilities of children with diplegic cerebral palsy.

  16. Impact of tooth loss on walking speed decline over time in older adults: a population-based cohort study.

    Science.gov (United States)

    Welmer, Anna-Karin; Rizzuto, Debora; Parker, Marti G; Xu, Weili

    2017-08-01

    Tooth loss has been linked to poor health such as chronic diseases and mobility limitations. Prospective evidence on the association between tooth loss and walking speed decline is however lacking. To examine the impact of tooth loss on walking speed over time and explore whether inflammation may account for this association. This study included 2695 persons aged 60 years and older, who were free from severe mobility limitation at baseline. Information on dental status was assessed through self-report during the nurse interview at baseline. Walking speed baseline and at 3- and 6-year follow-ups was assessed when participants walked at their usual pace. Covariates included age, sex, education, lifestyle-related factors, and chronic diseases. Blood samples were taken, and C-reactive protein (CRP) was tested. At baseline, 389 (13.1 %) participants had partial tooth loss and 204 (6.9 %) had complete tooth loss. Mixed-effects models showed that tooth loss was associated with a greater decline in walking speed over time after adjustment for lifestyle-related factors and chronic diseases (p = 0.001 for interaction between time and tooth loss on walking speed decline); however, when further adjusting for inflammation (CRP), the association was attenuated and no longer significant. Tooth loss was associated with an accelerated decline in walking speed in older adults. Inflammation may play a role in the association between tooth loss and walking speed decline.

  17. Gait parameters database for young children: The influences of age and walking speed.

    Science.gov (United States)

    Van Hamme, A; El Habachi, A; Samson, W; Dumas, R; Chèze, L; Dohin, B

    2015-07-01

    Reference databases are mandatory in orthopaedics because they enable the detection of gait abnormalities in patients. Such databases rarely include data on children under seven years of age. In young children, gait is principally influenced by age and walking speed. The influence of the age-speed interaction has not been well established. Therefore, the objective of the present study is to propose normative values for biomechanical gait parameters in children taking into account age, walking speed, and the age-speed interaction. Gait analyses were performed on 106 healthy children over a large age range (between one and seven years of age) during gait trials at a self-selected speed. From these gait cycles, biomechanical parameters, such as the joint angles and joint power of the lower limbs, were computed. Specific peak values and the times of occurrence of each biomechanical gait parameter were identified. Linear regressions are proposed for studying the influence of age, walking speed and the age-speed interaction. Most of the regressions achieved good accuracy in fitting the curve peaks and times of occurrence, and the normal reference targets of biomechanical parameters could be deduced from these regressions. The biomechanical gait parameters of a pathological case were plotted against the normal reference targets to illustrate the relevance of the proposed targeting method. The normal reference targets for biomechanical gait parameters based on age-speed regressions in a large database might help clinicians detect gait abnormalities in children from one to seven years of age. Copyright © 2015 Elsevier Ltd. All rights reserved.

  18. The Effect of Visual Display Properties and Gain Presentation Mode on the Perceived Naturalness of Virtual Walking Speeds

    DEFF Research Database (Denmark)

    Nilsson, Niels Chr.; Serafin, Stefania; Nordahl, Rolf

    2015-01-01

    Individuals tend to find realistic walking speeds too slow when relying on treadmill walking or Walking-In-Place (WIP) techniques for virtual travel. This paper details three studies investigating the effects of visual display properties and gain presentation mode on the perceived naturalness...... of virtual walking speeds: The first study compared three different degrees of peripheral occlusion; the second study compared three different degrees of perceptual distortion produced by varying the geometric field of view (GFOV); and the third study compared three different ways of presenting visual gains...

  19. Hip flexor muscle dysfunction during walking at self-selected and fast speed in patients with aortoiliac peripheral arterial disease.

    Science.gov (United States)

    Kakihana, Takaaki; Ito, Osamu; Sekiguchi, Yusuke; Ito, Daisuke; Goto, Hitoshi; Akamatsu, Daijirou; Matsumoto, Yasuharu; Kohzuki, Masahiro

    2017-08-01

    Intermittent claudication aggravates physical function and is associated with an increased risk of death in patients with peripheral arterial disease (PAD). Previous studies on kinetic parameters (joint moment and power) of lower limbs in these patients have largely focused on the decline in the ankle plantar flexor moment and power at self-selected (SS) walking speed, which may not be an optimal condition to induce claudication pain. In the present study, we investigated the abnormalities in joint kinetic parameters in patients with PAD at both SS and at fast walking speeds. We recruited 16 patients with aortoiliac PAD (4 unilateral and 12 bilateral) and 10 healthy controls. The participants were instructed to walk at SS and fast speeds along a 7-meter walkway embedded with a force plate. Spatiotemporal parameters and joint kinetic parameters of the lower limbs during the stance phase were recorded using a three-dimensional motion analysis device. Compared with the controls, patients with PAD showed a significant reduction in their walking speed, step length, stride length, and cadence. Further, a reduction in peak hip flexor moment at fast walking speed and in peak hip flexor generation power was observed in both modes of walking. However, no significant between-group differences were observed for the peak ankle plantar flexor moment or power at either walking speed. Multiple regression analysis showed peak hip flexor generation power was a strong contributor to reduction at both SS and fast walking speeds in patients with PAD. Patients with aortoiliac PAD walk slowly and show reduced kinetic parameters of the hip joint at both SS and fast walking speeds. Our results suggest that hip flexor muscles may be a useful target for exercise training in patients with aortoiliac PAD. Copyright © 2017 Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.

  20. The effect of waist twisting on walking speed of an amphibious salamander like robot

    Science.gov (United States)

    Yin, Xin-Yan; Jia, Li-Chao; Wang, Chen; Xie, Guang-Ming

    2016-06-01

    Amphibious salamanders often swing their waist to coordinate quadruped walking in order to improve their crawling speed. A robot with a swing waist joint, like an amphibious salamander, is used to mimic this locomotion. A control method is designed to allow the robot to maintain the rotational speed of its legs continuous and avoid impact between its legs and the ground. An analytical expression is established between the amplitude of the waist joint and the step length. Further, an optimization amplitude is obtained corresponding to the maximum stride. The simulation results based on automatic dynamic analysis of mechanical systems (ADAMS) and physical experiments verify the rationality and validity of this expression.

  1. Hexapod Walking Robot Energy Consumption Dependence On Different Gaits And Speed While Moving On Even Terrain

    Directory of Open Access Journals (Sweden)

    Mindaugas Luneckas

    2014-05-01

    Full Text Available Evaluation of robotic energetics while moving on rough terrain becomes a difficult task without having the information about the movement on even terrain. The problem appears in selection of gaits depending on how much power robot consumes. In this paper, energy consumption of a hexapod walking robot dependence on different gaits and speed is observed. Three most common gaits were used in this experiment: tripod gait, bipod gait and wave gait. Results clearly show that while moving at slow speed, the least energy is consumed by wave gait. As the speed increases, bipod gait selection is required to lower energy consumption. Finally, tripod gait must be selected at even higher speed.

  2. Effect of walking speed on the gait of king penguins: An accelerometric approach.

    Science.gov (United States)

    Willener, Astrid S T; Handrich, Yves; Halsey, Lewis G; Strike, Siobhán

    2015-12-21

    Little is known about non-human bipedal gaits. This is probably due to the fact that most large animals are quadrupedal and that non-human bipedal animals are mostly birds, whose primary form of locomotion is flight. Very little research has been conducted on penguin pedestrian locomotion with the focus instead on their associated high energy expenditure. In animals, tri-axial accelerometers are frequently used to estimate physiological energy cost, as well as to define the behaviour pattern of a species, or the kinematics of swimming. In this study, we showed how an accelerometer-based technique could be used to determine the biomechanical characteristics of pedestrian locomotion. Eight king penguins, which represent the only family of birds to have an upright bipedal gait, were trained to walk on a treadmill. The trunk tri-axial accelerations were recorded while the bird was walking at four different speeds (1.0, 1.2, 1.4 and 1.6km/h), enabling the amplitude of dynamic body acceleration along the three axes (amplitude of DBAx, DBAy and DBAz), stride frequency, waddling and leaning amplitude, as well as the leaning angle to be defined. The magnitude of the measured variables showed a significant increase with increasing speed, apart from the backwards angle of lean, which decreased with increasing speed. The variability of the measured variables also showed a significant increase with speed apart from the DBAz amplitude, the waddling amplitude, and the leaning angle, where no significant effect of the walking speed was found. This paper is the first approach to describe 3D biomechanics with an accelerometer on wild animals, demonstrating the potential of this technique. Copyright © 2015 Elsevier Ltd. All rights reserved.

  3. Walking economy is predictably determined by speed, grade and gravitational load.

    Science.gov (United States)

    Ludlow, Lindsay W; Weyand, Peter G

    2017-07-20

    The metabolic energy human walking requires can vary by more than 10-fold depending on the speed, surface gradient and load carried. Although the mechanical factors determining economy are generally considered to be numerous and complex, we tested a minimum-mechanics hypothesis that only three variables are needed for broad, accurate prediction: speed, surface grade, and total gravitational load. We first measured steady-state rates of oxygen uptake in 20 healthy adult subjects during unloaded treadmill trials from 0.4-1.6 m•s(-1) on six gradients: -6º, -3º, 0º, 3º, 6º, and 9º. Next, we tested a second set of 20 subjects under three torso-loading conditions (no-load, +18, and +31% body weight) at speeds from 0.6-1.4 m•s(-1) on the same six gradients. Metabolic rates spanned a 14-fold range from supine rest to the greatest single-trial, walking mean (3.1±0.1 to 43.3±0.5 mls O2•kg-body(-1)•min(-1), respectively). As theorized, the walking portion (VO2-walk=VO2-gross-VO2-supine-rest) of the body's gross metabolic rate increased in direct proportion to load and largely in accordance with support force requirements across both speed and grade. Consequently, a single minimum-mechanics equation was derived from the data of 10 unloaded-condition subjects to predict the pooled mass-specific economy (VO2-gross, mls O2•kg-body+load(-1)•min(-1)) of all the remaining loaded and unloaded trials combined (n=1412 trials from 90 speed-grade-load conditions). The accuracy of prediction achieved (R(2)=0.99, SEE=1.06 mls O2•kg(-1)•min(-1)) leads us to conclude that human walking economy is predictably determined by the minimum mechanical requirements present across a broad range of conditions. Copyright © 2017, Journal of Applied Physiology.

  4. Pendular energy transduction within the step during human walking on slopes at different speeds.

    Directory of Open Access Journals (Sweden)

    Arthur H Dewolf

    Full Text Available When ascending (descending a slope, positive (negative work must be performed to overcome changes in gravitational potential energy at the center of body mass (COM. This modifies the pendulum-like behavior of walking. The aim of this study is to analyze how energy exchange and mechanical work done vary within a step across slopes and speeds. Ten subjects walked on an instrumented treadmill at different slopes (from -9° to 9°, and speeds (between 0.56 and 2.22 m s-1. From the ground reaction forces, we evaluated energy of the COM, recovery (i.e. the potential-kinetic energy transduction and pendular energy savings (i.e. the theoretical reduction in work due to this recovered energy throughout the step. When walking uphill as compared to level, pendular energy savings increase during the first part of stance (when the COM is lifted and decreases during the second part. Conversely in downhill walking, pendular energy savings decrease during the first part of stance and increase during the second part (when the COM is lowered. In uphill and downhill walking, the main phase of external work occurs around double support. Uphill, the positive work phase is extended during the beginning of single support to raise the body. Downhill, the negative work phase starts before double support, slowing the downward velocity of the body. Changes of the pendulum-like behavior as a function of slope can be illustrated by tilting the 'classical compass model' backwards (uphill or forwards (downhill.

  5. Prefrontal, posterior parietal and sensorimotor network activity underlying speed control during walking

    Directory of Open Access Journals (Sweden)

    Thomas C Bulea

    2015-05-01

    Full Text Available Accumulating evidence suggests cortical circuits may contribute to control of human locomotion. Here, noninvasive electroencephalography (EEG recorded from able-bodied volunteers during a novel treadmill walking paradigm was used to assess neural correlates of walking. A systematic processing method, including a recently developed subspace reconstruction algorithm, reduced movement-related EEG artifact prior to independent component analysis and dipole source localization. We quantified cortical activity while participants tracked slow and fast target speeds across two treadmill conditions: an active mode that adjusted belt speed based on user movements and a passive mode reflecting a typical treadmill. Our results reveal frequency specific, multi-focal task related changes in cortical oscillations elicited by active walking. Low γ band power, localized to the prefrontal and posterior parietal cortices, was significantly increased during double support and early swing phases, critical points in the gait cycle since the active controller adjusted speed based on pelvis position and swing foot velocity. These phasic γ band synchronizations provide evidence that prefrontal and posterior parietal networks, previously implicated in visuo-spatial and somotosensory integration, are engaged to enhance lower limb control during gait. Sustained μ and β band desynchronization within sensorimotor cortex, a neural correlate for movement, was observed during walking thereby validating our methods for isolating cortical activity. Our results also demonstrate the utility of EEG recorded during locomotion for probing the multi-regional cortical networks which underpin its execution. For example, the cortical network engagement elicited by the active treadmill suggests that it may enhance neuroplasticity for more effective motor training.

  6. Age-associated effects of a concurrent cognitive task on gait speed and stability during narrow-base walking.

    Science.gov (United States)

    Kelly, Valerie E; Schrager, Matthew A; Price, Robert; Ferrucci, Luigi; Shumway-Cook, Anne

    2008-12-01

    In older adults, changes in speed and stability during walking are associated with impaired balance and increased fall risk. Narrow-base walking requires increased frontal plane stability and can be used to assess postural control while walking. Performance of a concurrent cognitive task (dual task) may further increase the complexity of walking, potentially allowing identification of individuals with instability that is not detected under single-task conditions. The purpose of this study was to examine age-associated effects of a cognitive task on speed and frontal plane stability during narrow-base walking. Thirty-four healthy adults participated, categorized by age: or =75 years. Participants walked at a comfortable pace within a narrow path under both single- and dual-task conditions. We examined spatiotemporal variables and frontal plane center of mass (CoM) parameters using a 13-segment biomechanical model. Increasing age (p task (p dual-task performance had no effect on these variables (both p >.450). Age-associated changes in both speed and stability are observed during narrow-base walking. Among this sample of healthy older adults, the addition of a concurrent cognitive task resulted in reduced speed, with no effect on frontal plane stability. Further research is needed to determine if dual-task, narrow-base walking is a sensitive and specific approach to identifying older adults at risk for falls.

  7. A prediction model for determining over ground walking speed after locomotor training in persons with motor incomplete spinal cord injury.

    Science.gov (United States)

    Winchester, Patricia; Smith, Patricia; Foreman, Nathan; Mosby, James M; Pacheco, Fides; Querry, Ross; Tansey, Keith

    2009-01-01

    To develop and test a clinically relevant model for predicting the recovery of over ground walking speed after 36 sessions of progressive body weight-supported treadmill training (BWSTT) in individuals with motor incomplete spinal cord injury (SCI). A retrospective review and stepwise regression analysis of a SCI clinical outcomes data set. Outpatient SCI laboratory. Thirty individuals with a motor incomplete SCI who had participated in locomotor training with BWSTT. Eight individuals with similar diagnoses were used to prospectively test the prediction model. Over ground walking speed was assessed using the 10-m walking test. The locomotor training program consisted of 36 sessions of sequential comprehensive training comprised of robotic assisted BWSTT, followed by manual assisted BWSTT, and over ground walking. The dose of locomotor training was standardized throughout the protocol. Clinical characteristics with predictive value for walking speed were time from injury onset, the presence or absence of voluntary bowel and bladder voiding, a functional spasticity assessment, and over ground walking speed before locomotor training. The model identified that these characteristics accounted for 78.3% of the variability in the actual final over ground walking speed after 36 sessions of locomotor training. The model was successful in prospectively predicting over ground walking speed in the 8 test participants within 4.15 +/- 2.22 cm/s in their recovered walking speed. This prediction model can identify individuals who are most likely to experience success using locomotor training by determining an expected magnitude of training effect, thereby allowing individualized decisions regarding the use of this intensive approach to rehabilitation.

  8. EEG Single-Trial Detection of Gait Speed Changes during Treadmill Walk.

    Directory of Open Access Journals (Sweden)

    Giuseppe Lisi

    Full Text Available In this study, we analyse the electroencephalography (EEG signal associated with gait speed changes (i.e. acceleration or deceleration. For data acquisition, healthy subjects were asked to perform volitional speed changes between 0, 1, and 2 Km/h, during treadmill walk. Simultaneously, the treadmill controller modified the speed of the belt according to the subject's linear speed. A classifier is trained to distinguish between the EEG signal associated with constant speed gait and with gait speed changes, respectively. Results indicate that the classification performance is fair to good for the majority of the subjects, with accuracies always above chance level, in both batch and pseudo-online approaches. Feature visualisation and equivalent dipole localisation suggest that the information used by the classifier is associated with increased activity in parietal areas, where mu and beta rhythms are suppressed during gait speed changes. Specifically, the parietal cortex may be involved in motor planning and visuomotor transformations throughout the online gait adaptation, which is in agreement with previous research. The findings of this study may help to shed light on the cortical involvement in human gait control, and represent a step towards a BMI for applications in post-stroke gait rehabilitation.

  9. Gait characteristics associated with walking speed decline in older adults: results from the Baltimore Longitudinal Study of Aging.

    Science.gov (United States)

    Jerome, Gerald J; Ko, Seung-uk; Kauffman, Danielle; Studenski, Stephanie A; Ferrucci, Luigi; Simonsick, Eleanor M

    2015-01-01

    Understanding the mechanisms that contribute to walking speed decline can provide needed insight for developing targeted interventions to reduce the rate and likelihood of decline. Examine the association between gait characteristics and walking speed decline in older adults. Participants in the Baltimore Longitudinal Study of Aging aged 60 to 89 were evaluated in the gait laboratory which used a three dimensional motion capture system and force platforms to assess cadence, stride length, stride width, percent of gait cycle in double stance, anterior-posterior mechanical work expenditure (MWE), and medial-lateral MWE. Usual walking speed was assessed over 6 m at baseline and follow-up. Gait characteristics associated with meaningful decline (decline≥0.05 m/s/y) in walking speed were evaluated by logistic regression adjusted for age, sex, race, height, weight, initial walking speed and follow-up time. Among 362 participants, the average age was 72.4 (SD=8.1) years, 51% were female, 27% were black and 23% were identified has having meaningful decline in usual walking speed with an average follow-up time of 3.2 (1.1) years. In the fully adjusted model, faster cadence [ORadj=0.65, 95% CI (0.43,0.97)] and longer strides [ORadj=0.87, 95% CI (0.83,0.91)] were associated with lower odds of decline. However age [ORadj=1.04, 95% CI (0.99,1.10)] was not associated with decline when controlling for gait characteristics and other demographics. A sizable proportion of healthy older adults experienced walking speed decline over an average of 3 years. Longer stride and faster cadence were protective against meaningful decline in usual walking speed. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  10. Human Skeleton Model Based Dynamic Features for Walking Speed Invariant Gait Recognition

    Directory of Open Access Journals (Sweden)

    Jure Kovač

    2014-01-01

    Full Text Available Humans are able to recognize small number of people they know well by the way they walk. This ability represents basic motivation for using human gait as the means for biometric identification. Such biometrics can be captured at public places from a distance without subject's collaboration, awareness, and even consent. Although current approaches give encouraging results, we are still far from effective use in real-life applications. In general, methods set various constraints to circumvent the influence of covariate factors like changes of walking speed, view, clothing, footwear, and object carrying, that have negative impact on recognition performance. In this paper we propose a skeleton model based gait recognition system focusing on modelling gait dynamics and eliminating the influence of subjects appearance on recognition. Furthermore, we tackle the problem of walking speed variation and propose space transformation and feature fusion that mitigates its influence on recognition performance. With the evaluation on OU-ISIR gait dataset, we demonstrate state of the art performance of proposed methods.

  11. Reduced walking speed and distance as harbingers of the approaching grim reaper.

    Science.gov (United States)

    Franklin, Barry A; Brinks, Jenna; Sacks, Roger; Trivax, Justin; Friedman, Harold

    2015-07-15

    Although treadmill exercise testing can provide an assessment of cardiorespiratory fitness, which serves as an independent prognostic indicator, numerous studies now suggest that usual gait speed, time, or distance covered during walk performance tests and weekly walking distance/time are powerful predictors of mortality and future cardiovascular events in selected patients. This review summarizes the relation between these variables and their association with cardiovascular and all-cause mortality, with specific reference to potential underlying mechanisms and implications for the clinician. Contemporary health care providers have escalating opportunities to promote lifestyle physical activity using pedometers, accelerometers, and smartphone-based health and wellness applications. In conclusion, fitness and/or ambulatory indexes should be considered a "vital sign" in middle-aged and older adults. Copyright © 2015 Elsevier Inc. All rights reserved.

  12. Experimental evaluation of regression model-based walking speed estimation using lower body-mounted IMU.

    Science.gov (United States)

    Zihajehzadeh, Shaghayegh; Park, Edward J

    2016-08-01

    This study provides a concurrent comparison of regression model-based walking speed estimation accuracy using lower body mounted inertial sensors. The comparison is based on different sets of variables, features, mounting locations and regression methods. An experimental evaluation was performed on 15 healthy subjects during free walking trials. Our results show better accuracy of Gaussian process regression compared to least square regression using Lasso. Among the variables, external acceleration tends to provide improved accuracy. By using both time-domain and frequency-domain features, waist and ankle-mounted sensors result in similar accuracies: 4.5% for the waist and 4.9% for the ankle. When using only frequency-domain features, estimation accuracy based on a waist-mounted sensor suffers more compared to the one from ankle.

  13. The biomechanical mechanism of how strength and power training improves walking speed in old adults remains unknown

    NARCIS (Netherlands)

    Beijersbergen, C. M. I.; Granacher, U.; Vandervoort, A. A.; DeVita, P.; Hortobagyi, T.

    Maintaining and increasing walking speed in old age is clinically important because this activity of daily living predicts functional and clinical state. We reviewed evidence for the biomechanical mechanisms of how strength and power training increase gait speed in old adults. A systematic search

  14. High speed flow cytometric separation of viable cells

    Science.gov (United States)

    Sasaki, Dennis T.; Van den Engh, Gerrit J.; Buckie, Anne-Marie

    1995-01-01

    Hematopoietic cell populations are separated to provide cell sets and subsets as viable cells with high purity and high yields, based on the number of original cells present in the mixture. High-speed flow cytometry is employed using light characteristics of the cells to separate the cells, where high flow speeds are used to reduce the sorting time.

  15. Walking speed affects instrumental activities of daily living in patients with hip osteoarthritis.

    Science.gov (United States)

    Tanaka, Shigeharu; Matsumoto, Shinsuke; Kawashima, Takaki; Mitani, Shigeru; Miura, Yasushi

    2017-01-01

    The symptoms of hip osteoarthritis (OA) influence instrumental activities of daily living (IADL). Evidence form previous studies suggest that body functions and walking speed are important etiological factors for IADL. However, no studies have investigated which factors that have the greatest influence on IADL. The aims of this study were (1) to analyze factors related to IADL in patients with hip OA, including 10 m walking speed (10 mWS), and (2) to establish cut-off values for factors that predict maintenance of IADL. Forty-eight patients participated in this study. IADL was treated as dependent variable. Range of motion (ROM), muscle strength of the hips and knees, and 10 mWS were measured as independent variables. Other potential confounding factors were also measured. Data were analyzed using hierarchical multiple regression and Receiver Operating Characteristic curve analysis. The hip flexion ROM on the affected side and 10 mWS were selected as significant variables in this study. The cut-off values obtained were 92.5 degrees for the hip flexion ROM on the affected side and 42.3 m/min for 10 mWS. The suggested target associated with maintaining IADL in patients with hip OA is the cut-off value of 42.3 m/min for 10 mWS found in this study.

  16. Differences in physical aging measured by walking speed: evidence from the English Longitudinal Study of Ageing.

    Science.gov (United States)

    Weber, Daniela

    2016-01-28

    Physical functioning and mobility of older populations are of increasing interest when populations are aging. Lower body functioning such as walking is a fundamental part of many actions in daily life. Limitations in mobility threaten independent living as well as quality of life in old age. In this study we examine differences in physical aging and convert those differences into the everyday measure of single years of age. We use the English Longitudinal Study of Ageing, which was collected biennially between 2002 and 2012. Data on physical performance, health as well as information on economics and demographics of participants were collected. Lower body performance was assessed with two timed walks at normal pace each of 8 ft (2.4 m) of survey participants aged at least 60 years. We employed growth curve models to study differences in physical aging and followed the characteristic-based age approach to illustrate those differences in single years of age. First, we examined walking speed of about 11,700 English individuals, and identified differences in aging trajectories by sex and other characteristics (e.g. education, occupation, regional wealth). Interestingly, higher educated and non-manual workers outperformed their counterparts for both men and women. Moreover, we transformed the differences between subpopulations into single years of age to demonstrate the magnitude of those gaps, which appear particularly high at early older ages. This paper expands research on aging and physical performance. In conclusion, higher education provides an advantage in walking of up to 15 years for men and 10 years for women. Thus, enhancements in higher education have the potential to ensure better mobility and independent living in old age for a longer period.

  17. Transient response of sap flow to wind speed.

    Science.gov (United States)

    Chu, Chia R; Hsieh, Cheng-I; Wu, Shen-Yuang; Phillips, Nathan G

    2009-01-01

    Transient responses of sap flow to step changes in wind speed were experimentally investigated in a wind tunnel. A Granier-type sap flow sensor was calibrated and tested in a cylindrical tube for analysis of its transient time response. Then the sensor was used to measure the transient response of a well-watered Pachira macrocarpa plant to wind speed variations. The transient response of sap flow was described using the resistance-capacitance model. The steady sap flow rate increased as the wind speed increased at low wind speeds. Once the wind speed exceeded 8.0 m s(-1), the steady sap flow rate did not increase further. The transpiration rate, measured gravimetrically, showed a similar trend. The response of nocturnal sap flow to wind speed variation was also measured and compared with the results in the daytime. Under the same wind speed, the steady sap flow rate was smaller than that in the daytime, indicating differences between diurnal and nocturnal hydraulic function, and incomplete stomatal closure at night. In addition, it was found that the temporal response of the Granier sensor is fast enough to resolve the transient behaviour of water flux in plant tissue.

  18. Does public transport use prevent declines in walking speed among older adults living in England? A prospective cohort study.

    Science.gov (United States)

    Rouxel, Patrick; Webb, Elizabeth; Chandola, Tarani

    2017-09-28

    Although there is some evidence that public transport use confers public health benefits, the evidence is limited by cross-sectional study designs and health-related confounding factors. This study examines the effect of public transport use on changes in walking speed among older adults living in England, comparing frequent users of public transport to their peers who did not use public transport because of structural barriers (poor public transport infrastructure) or through choice. Prospective cohort study. England, UK. Older adults aged ≥60 years eligible for the walking speed test. 6246 individuals at wave 2 (2004-2005); 5909 individuals at wave 3 (2006-2007); 7321 individuals at wave 4 (2008-2009); 7535 individuals at wave 5 (2010-2011) and 7664 individuals at wave 6 (2012-2013) of the English Longitudinal Study of Ageing. The walking speed was estimated from the time taken to walk 2.4 m. Fixed effects models and growth curve models were used to examine the associations between public transport use and walking speed. Older adults who did not use public transport through choice or because of structural reasons had slower walking speeds (-0.02 m/s (95% CI -0.03 to -0.003) and -0.02 m/s (95% CI -0.03 to -0.01), respectively) and took an extra 0.07 s to walk 2.4 m compared with their peers who used public transport frequently. The age-related trajectories of decline in walking speed were slower for frequent users of public transport compared with non-users. Frequent use of public transport may prevent age-related decline in physical capability by promoting physical activity and lower limb muscle strength among older adults. The association between public transport use and slower decline in walking speed among older adults is unlikely to be confounded by health-related selection factors. Improving access to good quality public transport could improve the health of older adults. © Article author(s) (or their employer(s) unless otherwise stated in the text

  19. Biomechanical analysis of gait termination in 11-17year old youth at preferred and fast walking speeds.

    Science.gov (United States)

    Ridge, Sarah Trager; Henley, John; Manal, Kurt; Miller, Freeman; Richards, James G

    2016-10-01

    In populations where walking and/or stopping can be difficult, such as in children with cerebral palsy, the ability to quickly stop walking may be beyond the child's capabilities. Gait termination may be improved with physical therapy. However, without a greater understanding of the mechanical requirements of this skill, treatment planning is difficult. The purpose of this study was to understand how healthy children successfully terminate gait in one step when walking quickly, which can be challenging even for healthy children. Lower extremity kinematic and kinetic data were collected from 15 youth as they performed walking, planned, and unplanned stopping tasks. Each stopping task was performed as the subject walked at his/her preferred speed and a fast speed. The most significant changes in mechanics between speed conditions (preferred and fast) of the same stopping task were greater knee flexion angles (unplanned: +16.49±0.54°, p=0.00; planned: +15.75±1.1°, p=0.00) and knee extension moments (unplanned: +0.67±0.02N/kgm, p=0.00; planned: +0.57±0.23N/kgm, p=0.00) at faster speeds. The extra range of motion in the joints and extra muscle strength required to maintain the stopping position suggests that stretching and strengthening the muscles surrounding the joints of the lower extremity, particularly the knee, may be a useful intervention. Copyright © 2016. Published by Elsevier B.V.

  20. Start-up time and walking speed in older adults under loaded conditions during simulated road crossing.

    Science.gov (United States)

    Kong, Pui W; Chua, YaoHui K

    2014-01-01

    BACKGROUND/STUDY CONTEXT: The safety of older pedestrians in road crossing has received considerable attention but previous studies measure gait characteristics only under unloaded conditions. The aim of this study was to investigate the start-up time and walking speed under loaded conditions that reflect daily activities of older adults in Singapore. Thirty-two older adults (age (SD) = 69.4 (7.0) years) and 20 young controls (age (SD) = 23.1 (2.0) years) walked under four conditions: (1) unloaded, (2) pushing a stroller loaded with 10 kg, (3) pulling a shopping cart loaded with 15 kg, and (4) carrying two shopping bags each loaded with 2 kg. Start-up time was determined from video recordings and walking speed measured using timing gates. A mixed-model analysis of variance (ANOVA; age by walking condition) with repeated measures was applied. Start-up times were slower in the stroller and shopping cart conditions compared with the unloaded and shopping bags conditions. Loading reduced walking speed, with the shopping cart being the slowest, followed by the stroller and then the shopping bags. A significant interaction was found, with young controls reducing their speeds more substantially while handling the stroller/cart than older participants. Loading caused a compromise in start-up time and walking speed. The start-up time was slower when pushing a stroller or pulling a shopping cart but remained unaffected by carrying shopping bags. Speed was reduced under all loaded conditions, with a greater effect in young than older participants when handling a stroller or shopping cart.

  1. Determination of the optimal walking speed for neural relaxation in healthy elderly women using electromyogram and electroencephalogram analyses.

    Science.gov (United States)

    Shibata, M; Shimura, M; Shibata, S; Wakamura, T; Moritani, T

    1997-01-01

    The purpose of this study was to determine the walking speed which has the greatest influence on neural relaxation in healthy elderly women as determined by electromyogram (EMG) and electroencephalogram (EEG) analyses. Seven elderly female volunteers [mean age 68.5 (SD 3.95) years] served as subjects for this study. The EMG signals were recorded from the gastrocnemius (MG), soleus (SL) and tibialis anterior (TA) muscles while walking on a treadmill, starting at 40 m.min-1 and increasing 6 m.min-1 incrementally for 10 min. The turning point of muscle activities (by integrated EMG. iEMGtp) was determined as the walking speed at the point at which the mean rate of change of iEMG (MG + SL + TA) abruptly increased. After the determination of iEMGtp. the treadmill was set at three constant speeds, one corresponding to the speed for the iEMGtp and two others 20% higher or lower than that for the iEMGtp. The subjects then walked for 20 min at each of these speeds on 3 separate days and their EEG power spectrum data were obtained for frequencies from the 8 to 13 Hz (z-wave component, AWC). The mean of iEMGtp for our subjects was at a mean walking speed of 64.7 (SD 7.9) m.min-1. Considering the subjects' age and height, iEMGtp was somewhat faster than their expected self-paced normal walking speed. There were no differences between the mean AWC values of the subjects prior to exercising at each of the three speeds. The mean AWC values after exercise were significantly (P < 0.01) greater than before. The extent of the increase in AWC at iEMGtp was greater than those at slower speeds. Our data would suggest that walking exercise at the speed which corresponds with EMG evidence of iEMGtp may induce the most significant relaxing effects in elderly women.

  2. Walking, running, and resting under time, distance, and average speed constraints: optimality of walk–run–rest mixtures

    Science.gov (United States)

    Long, Leroy L.; Srinivasan, Manoj

    2013-01-01

    On a treadmill, humans switch from walking to running beyond a characteristic transition speed. Here, we study human choice between walking and running in a more ecological (non-treadmill) setting. We asked subjects to travel a given distance overground in a given allowed time duration. During this task, the subjects carried, and could look at, a stopwatch that counted down to zero. As expected, if the total time available were large, humans walk the whole distance. If the time available were small, humans mostly run. For an intermediate total time, humans often use a mixture of walking at a slow speed and running at a higher speed. With analytical and computational optimization, we show that using a walk–run mixture at intermediate speeds and a walk–rest mixture at the lowest average speeds is predicted by metabolic energy minimization, even with costs for transients—a consequence of non-convex energy curves. Thus, sometimes, steady locomotion may not be energy optimal, and not preferred, even in the absence of fatigue. Assuming similar non-convex energy curves, we conjecture that similar walk–run mixtures may be energetically beneficial to children following a parent and animals on long leashes. Humans and other animals might also benefit energetically from alternating between moving forward and standing still on a slow and sufficiently long treadmill. PMID:23365192

  3. Speed and efficiency in walking and wheeling with novel stimulation and bracing systems after spinal cord injury: a case study.

    Science.gov (United States)

    Stein, Richard B; Hayday, Frank; Chong, Suling; Thompson, Aiko K; Rolf, Robert; James, Kelvin B; Bell, Gordon

    2005-10-01

    To compare various novel and conventional systems for locomotion, a 25-year-old man was studied with motor complete spinal cord injury at the T4/5 level. He used various devices in the community, and changes in speed, physiological cost index (PCI), and oxygen consumption were measured periodically. Speed was fastest with a conventional manual wheelchair (nearly 120 m/min in a 4-min test). Speed was about 30% less, but the PCI was lowest (highest efficiency) using functional electrical stimulation (FES) of the quadriceps and hamstring muscles to propel a novel wheelchair. He walked with knee-ankle-foot orthoses (KAFO) at much lower speed (8.8 m/min) and higher PCI. He walked with an alternating gait using a new stance-control KAFO with FES. The speed was still slow (5 m/min), but he prefers the more normal-looking gait and uses it daily. Walking with FES and ankle-foot orthoses (AFO) was slowest (3.5 m/min) and had the highest PCI. In conclusion, the leg-propelled wheelchair provides a more efficient method of locomotion. A new stance-controlled KAFO with FES may provide a more acceptable walking system, but must be tested on other subjects.

  4. Unsteady Flow Simulation of High-speed Turbopumps

    Science.gov (United States)

    Kiris, Cetin C.; Kwak, dochan; Chan, William; Housman, Jeffrey A.

    2006-01-01

    Computation of high-speed hydrodynamics requires high-fidelity simulation to resolve flow features involving transient flow, cavitation, tip vortex and multiple scales of unsteady fluctuations. One example of this type in aerospace is related to liquid-fueled rocket turbopump. Rocket turbopumps operate under severe conditions at very high rotational speeds typically at thousands of rpm. For example, the Shuttle orbiter low-pressure-fuel-turbopump creates transient flow features associated with reverse flows, tip clearance effects, secondary flows, vortex shedding, junction flows, and cavitation effects. Flow unsteadiness originating from the orbiter Low-Pressure-Fuel-Turbopump (LPFTP) inducer is one of the major contributors to the high frequency cyclic loading that results in high cycle fatigue damage to the flow liners just upstream of the LPFTP. The reverse flow generated at the tip of the inducer blades travels upstream and interacts with the bellows cavity. Simulation procedure for this type high-speed hydrodynamic problems requires a method for quantifying multi-scale and multi-phase flow as well as an efficient high-end computing strategy. The current paper presents a high-fidelity computational procedure for unsteady hydrodynamic problems using a high-speed liquid-fueled rocket turbopump.

  5. Validity of treadmill- and track-based individual calibration methods for estimating free-living walking speed and VO2 using the Actigraph accelerometer.

    Science.gov (United States)

    Barnett, Anthony; Cerin, Ester; Vandelanotte, Corneel; Matsumoto, Aya; Jenkins, David

    2015-01-01

    For many patients clinical prescription of walking will be beneficial to health and accelerometers can be used to monitor their walking intensity, frequency and duration over many days. Walking intensity should include establishment of individual specific accelerometer count, walking speed and energy expenditure (VO2) relationships and this can be achieved using a walking protocol on a treadmill or overground. However, differences in gait mechanics during treadmill compared to overground walking may result in inaccurate estimations of free-living walking speed and VO2. The aims of this study were to compare the validity of track- and treadmill-based calibration methods for estimating free-living level walking speed and VO2 and to explain between-method differences in accuracy of estimation. Fifty healthy adults [32 women and 18 men; mean (SD): 40 (13) years] walked at four pre-determined speeds on an outdoor track and a treadmill, and completed three 1-km self-paced level walks while wearing an Actigraph monitor and a mobile oxygen analyser. Speed- and VO2-to-Actigraph count individual calibration equations were computed for each calibration method. Between-method differences in calibration equation parameters, prediction errors, and relationships of walking speed with VO2 and Actigraph counts were assessed. The treadmill-calibration equation overestimated free-living walking speed (on average, by 0.7 km · h(-1)) and VO2 (by 4.99 ml · kg(-1) · min(-1)), while the track-calibration equation did not. This was because treadmill walking, from which the calibration equation was derived, produced lower Actigraph counts and higher VO2 for a given walking speed compared to walking on a track. The prediction error associated with the use of the treadmill-calibration method increased with free-living walking speed. This issue was not observed when using the track-calibration method. The proposed track-based individual accelerometer calibration method can

  6. Assessing gait variability in transtibial amputee fallers based on spatial-temporal gait parameters normalized for walking speed.

    Science.gov (United States)

    Hordacre, Brenton G; Barr, Christopher; Patritti, Benjamin L; Crotty, Maria

    2015-06-01

    To determine whether normalizing spatial-temporal gait data for walking speed obtained from multiple walking trials leads to differences in gait variability parameters associated with a history of falling in people with transtibial amputations. Cross-sectional study. Rehabilitation center. People with unilateral transtibial amputations (N=45; mean age ± SD, 60.5±13.7y; 35 men [78%]) were recruited. Not applicable. Participants completed 10 consecutive walking trials using an instrumented walkway system. Primary gait parameters were walking speed and step-length, step-width, step-time, and swing-time variability. A retrospective 12-month fall history was obtained from participants. Sixteen amputees (36%) were classified as fallers. Variation in gait speed across the 10 walking trials was 2.9% (range, 1.1%-12.1%). Variability parameters of normalized gait data were significantly different from variability parameters of nonnormalized data (all Pamputees with a fall history. Copyright © 2015 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

  7. Is Trunk Posture in Walking a Better Marker than Gait Speed in Predicting Decline in Function and Subsequent Frailty?

    Science.gov (United States)

    Merchant, Reshma A; Banerji, Subhasis; Singh, Gautam; Chew, Effie; Poh, Chueh L; Tapawan, Sarah C; Guo, Yan R; Pang, Yu W; Sharma, Mridula; Kambadur, Ravi; Tay, Stacey

    2016-01-01

    Many recent guidelines and consensus on sarcopenia have incorporated gait speed and grip strength as diagnostic criteria without addressing early posture changes adopted to maintain gait speed before weakness is clinically evident. Older adults are known to compensate well for declining physiological reserve through environmental modification and posture adaptation. This study aimed to analyze and identify significant posture adaptation in older adults that is required to maintain gait speed in the face of increasing vulnerability. This would be a useful guide for early posture correction exercise interventions to prevent further decline, in addition to traditional gait, balance, and strength training. A community-based cross-sectional study. The participants comprised 90 healthy community-dwelling Chinese men between the ages of 60 and 80 years and 20 Chinese adults between the ages of 21 and 50 years within the normal BMI range as a comparison group. All the participants underwent handgrip strength testing, 6-minute walk, timed up-and-go (TUG), and motion analysis for gait characteristics. Low function was characterized by slow walking speed (10 seconds), whereas low strength was determined by hand grip dynamometer testing (healthy and vulnerable older adults. As expected, the vulnerable older adults had lower functional performance and strength compared with the healthy older adults group. However, a significant number demonstrated posture adaptations in walking in all 3 groups, including those who maintained a good walking speed (>1.0 m/s). The extent of such adaptation was larger in the vulnerable group as compared with the healthy group. Although gait speed is a robust parameter for screening older adults for sarcopenia and frailty, our data suggest that identifying trunk posture adaptation before the onset of decline in gait speed will help in planning interventions in the at-risk community-dwelling older adults even before gait speed declines. Copyright

  8. Adaptive locomotor network activation during randomized walking speeds using functional near-infrared spectroscopy.

    Science.gov (United States)

    Kim, Ha Yeon; Kim, Eun Joo; You, Joshua Sung H

    2017-07-20

    An improved understanding of the mechanisms underlying locomotor networks has the potential to benefit the neurorehabilitation of patients with neurological locomotor deficits. However, the specific locomotor networks that mediate adaptive locomotor performance and changes in gait speed remain unknown. The aim of the present study was to examine patterns of cortical activation associated with the walking speeds of 1.5, 2.0, 2.5, and 3.0 km/h on a treadmill. Functional near-infrared spectroscopy (fNIRS) was performed on a 30-year-old right-handed healthy female subject, and cerebral hemodynamic changes were observed in cortical locomotor network areas including the primary sensorimotor cortex (SMC), premotor cortex (PMC), supplementary motor area (SMA), prefrontal cortex (PFC), and sensory association cortex (SAC). The software package NIRS-statistical parametric mapping (NIRS-SPM) was utilized to analyze fNIRS data in the MATLAB environment. SPM t-statistic maps were computed at an uncorrected threshold of pglobalized locomotor network activation of the SMC, PMC, SMA, and PMC; additionally, the site with the highest cortical activation ratio shifted from the SMC to the SMA. Global locomotor network recruitment, in particular PFC activation indicated by OxyHb in our study, may indicate a response to increased cognitive-locomotor demand due to simultaneous postural maintenance and leg movement coordination.

  9. Reference values of maximum walking speed among independent community-dwelling Danish adults aged 60 to 79 years

    DEFF Research Database (Denmark)

    Tibaek, S; Holmestad-Bechmann, N; Pedersen, Trine B

    2015-01-01

    OBJECTIVES: To establish reference values for maximum walking speed over 10m for independent community-dwelling Danish adults, aged 60 to 79 years, and to evaluate the effects of gender and age. DESIGN: Cross-sectional study. SETTING: Danish companies and senior citizens clubs. PARTICIPANTS: Two ...

  10. The relationship between joint kinetic factors and the walk-run gait transition speed during human locomotion.

    Science.gov (United States)

    Hreljac, Alan; Imamura, Rodney T; Escamilla, Rafael F; Edwards, W Brent; MacLeod, Toran

    2008-05-01

    The primary purpose of this project was to examine whether lower extremity joint kinetic factors are related to the walk-run gait transition during human locomotion. Following determination of the preferred transition speed (PTS), each of the 16 subjects walked down a 25-m runway, and over a floor-mounted force platform at five speeds (70, 80, 90, 100, and 110% of the PTS), and ran over the force platform at three speeds (80, 100, and 120% of the PTS) while being videotaped (240 Hz) from the right sagittal plane. Two-dimensional kinematic data were synchronized with ground reaction force data (960 Hz). After smoothing, ankle and knee joint moments and powers were calculated using standard inverse dynamics calculations. The maximum dorsiflexor moment was the only variable tested that increased as walking speed increased and then decreased when gait changed to a run at the PTS, meeting the criteria set to indicate that this variable influences the walk-run gait transition during human locomotion. This supports previous research suggesting that an important factor in changing gaits at the PTS is the prevention of undue stress in the dorsiflexor muscles.

  11. The effect of walking speed on hamstrings length and lengthening velocity in children with spastic cerebral palsy

    NARCIS (Netherlands)

    Krogt, van der M.M.; Doorenbosch, C.A.M.; Harlaar, J.

    2009-01-01

    0.001). These data are important as a reference for valid interpretation of hamstrings length and velocity data in gait analyses at different walking speeds. The results indicate that the presence of spasticity is associated with reduced hamstrings length and lengthening velocity during gait, even

  12. Walking beyond preferred transition speed increases muscle activations with a shift from inverted pendulum to spring mass model in lower extremity.

    Science.gov (United States)

    Shih, Yo; Chen, Yi-Chun; Lee, Yin-Shin; Chan, Ming-Sheng; Shiang, Tzyy-Yuang

    2016-05-01

    The triggers for the transition of gait from walking to running during increasing speed locomotion have been attributed to an energy conservation strategy or a relief of excessive muscle activation. Walking beyond the preferred transition speed (PTS) has been proposed as an exercise protocol for boosting energy consumption. However, the biomechanical factors involved while this protocol is used have not been investigated. Thus, this study investigated the difference between walking and running below, during, and beyond the PTS from a biomechanical perspective. Sixteen healthy male participants were recruited. After determination of their PTS, five speeds of walking and running were defined. Kinematic data, including center-of-mass (COM) displacement, COM acceleration, and electromyography (EMG) data of rectus femoris (RF), biceps femoris, gastrocnemius (GAS), and tibialis anterior were collected at the five speeds for both walking and running. The vertical COM displacement and acceleration in running were significantly larger than those in walking at all five speeds (pantigravity muscles, RF and GAS, demonstrated a significant higher activation in walking than that in running at the speed beyond PTS (pmuscles. The smaller vertical COM displacements and accelerations exhibited when participants walked beyond the PTS rather than ran did not indicate adverse effects of using walking beyond the PTS as an exercise prescription for boosting energy consumption. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. Speed and Duration of Walking and Other Leisure Time Physical Activity and the Risk of Heart Failure

    DEFF Research Database (Denmark)

    Sævereid, Hans Askelund; Schnohr, Peter; Prescott, Eva

    2014-01-01

    in 1976-2003, we studied the association between updated self-assessed leisure-time PA, speed and duration of walking and subsequent hospitalization or death from HF. Light and moderate/high level of leisure-time PA and brisk walking were associated with reduced risk of HF in both genders whereas...... no consistent association with duration of walking was seen. In 18,209 subjects age 20-80 with 1580 cases of HF, using the lowest activity level as reference, the confounder-adjusted hazard ratios (HR) for light and moderate/high leisure-time physical activity were 0.75 (0.66-0.86) and 0.80 (0.......96 (0.73-1.27), respectively. Results were similar for both genders and remained robust after exclusion of HF related to coronary heart disease and after a series of sensitivity analyses. CONCLUSIONS: Speed rather than duration of walking was associated with reduced risk of HF. Walking is the most wide...

  14. Exploring the Metabolic and Perceptual Correlates of Self-Selected Walking Speed under Constrained and Un-Constrained Conditions

    Directory of Open Access Journals (Sweden)

    David T Godsiff, Shelly Coe, Charlotte Elsworth-Edelsten, Johnny Collett, Ken Howells, Martyn Morris, Helen Dawes

    2018-03-01

    Full Text Available Mechanisms underpinning self-selected walking speed (SSWS are poorly understood. The present study investigated the extent to which SSWS is related to metabolism, energy cost, and/or perceptual parameters during both normal and artificially constrained walking. Fourteen participants with no pathology affecting gait were tested under standard conditions. Subjects walked on a motorized treadmill at speeds derived from their SSWS as a continuous protocol. RPE scores (CR10 and expired air to calculate energy cost (J.kg-1.m-1 and carbohydrate (CHO oxidation rate (J.kg-1.min-1 were collected during minutes 3-4 at each speed. Eight individuals were re-tested under the same conditions within one week with a hip and knee-brace to immobilize their right leg. Deflection in RPE scores (CR10 and CHO oxidation rate (J.kg-1.min-1 were not related to SSWS (five and three people had deflections in the defined range of SSWS in constrained and unconstrained conditions, respectively (p > 0.05. Constrained walking elicited a higher energy cost (J.kg-1.m-1 and slower SSWS (p 0.05. SSWS did not occur at a minimum energy cost (J.kg-1.m-1 in either condition, however, the size of the minimum energy cost to SSWS disparity was the same (Froude {Fr} = 0.09 in both conditions (p = 0.36. Perceptions of exertion can modify walking patterns and therefore SSWS and metabolism/ energy cost are not directly related. Strategies which minimize perceived exertion may enable faster walking in people with altered gait as our findings indicate they should self-optimize to the same extent under different conditions.

  15. Development and validation of a new method to measure walking speed in free-living environments using the actibelt® platform.

    Directory of Open Access Journals (Sweden)

    Michaela Schimpl

    Full Text Available Walking speed is a fundamental indicator for human well-being. In a clinical setting, walking speed is typically measured by means of walking tests using different protocols. However, walking speed obtained in this way is unlikely to be representative of the conditions in a free-living environment. Recently, mobile accelerometry has opened up the possibility to extract walking speed from long-time observations in free-living individuals, but the validity of these measurements needs to be determined. In this investigation, we have developed algorithms for walking speed prediction based on 3D accelerometry data (actibelt® and created a framework using a standardized data set with gold standard annotations to facilitate the validation and comparison of these algorithms. For this purpose 17 healthy subjects operated a newly developed mobile gold standard while walking/running on an indoor track. Subsequently, the validity of 12 candidate algorithms for walking speed prediction ranging from well-known simple approaches like combining step length with frequency to more sophisticated algorithms such as linear and non-linear models was assessed using statistical measures. As a result, a novel algorithm employing support vector regression was found to perform best with a concordance correlation coefficient of 0.93 (95%CI 0.92-0.94 and a coverage probability CP1 of 0.46 (95%CI 0.12-0.70 for a deviation of 0.1 m/s (CP2 0.78, CP3 0.94 when compared to the mobile gold standard while walking indoors. A smaller outdoor experiment confirmed those results with even better coverage probability. We conclude that walking speed thus obtained has the potential to help establish walking speed in free-living environments as a patient-oriented outcome measure.

  16. Are there different factors affecting walking speed and gait cycle variability between men and women in community-dwelling older adults?

    Science.gov (United States)

    Inoue, Wakako; Ikezoe, Tome; Tsuboyama, Tadao; Sato, Ikuya; Malinowska, Katarzyna Bronislawa; Kawaguchi, Takahisa; Tabara, Yasuharu; Nakayama, Takeo; Matsuda, Fumihiko; Ichihashi, Noriaki

    2017-04-01

    Few studies have examined the relationships between walking speed and gait cycle variability, and muscle strength and postural stability, with a focus on gender differences. The aim of this study was to examine whether there are different factors affecting walking speed and gait cycle variability between men and women in community-dwelling older adults. The subjects comprised 712 community-dwelling older adults (252 men, 460 women, aged 68.7 ± 4.8 years). Walking speed and coefficient of variation (CV) of step time at a comfortable walking pace were measured. The maximal isometric strength of six lower limb muscles and postural stability were evaluated. Stepwise regression analysis was performed, using lower limb muscle strength and postural stability as independent variables, to investigate the association with walking speed or CV. For older men, age, body mass index (BMI) and quadriceps setting (QS) strength were significant and independent determinants of walking speed. No variables were identified as significant determinants of CV. For older women, BMI and hip flexion, hip abduction, QS muscle strength were significant determinants of walking speed. Only hip abduction strength was a significant determinant of CV. The results of this study suggest that QS strength is related to walking speed in both men and women, whereas hip flexion and abduction muscle strength are related to walking speed, and hip abduction muscle strength is related to gait cycle variability in older women. Gender differences exist in factors affecting walking speed and gait cycle variability in community-dwelling older adults.

  17. Differences in whole-body angular momentum between below-knee amputees and non-amputees across walking speeds.

    Science.gov (United States)

    Silverman, A K; Neptune, R R

    2011-02-03

    Unilateral, below-knee amputees have an increased risk of falling compared to non-amputees. The regulation of whole-body angular momentum is important for preventing falls, but little is known about how amputees regulate angular momentum during walking. This study analyzed three-dimensional, whole-body angular momentum at four walking speeds in 12 amputees and 10 non-amputees. The range of angular momentum in all planes significantly decreased with increasing walking speed for both groups. However, the range of frontal-plane angular momentum was greater in amputees compared to non-amputees at the first three walking speeds. This range was correlated with a reduced second vertical ground reaction force peak in both the intact and residual legs. In the sagittal plane, the amputee range of angular momentum in the first half of the residual leg gait cycle was significantly larger than in the non-amputees at the three highest speeds. In the second half of the gait cycle, the range of sagittal-plane angular momentum was significantly smaller in amputees compared to the non-amputees at all speeds. Correlation analyses suggested that the greater range of angular momentum in the first half of the amputee gait cycle is associated with reduced residual leg braking and that the smaller range of angular momentum in the second half of the gait cycle is associated with reduced residual leg propulsion. Thus, reducing residual leg braking appears to be a compensatory mechanism to help regulate sagittal-plane angular momentum over the gait cycle, but may lead to an increased risk of falling. Copyright © 2010 Elsevier Ltd. All rights reserved.

  18. Load flow analysis for variable speed offshore wind farms

    DEFF Research Database (Denmark)

    Chen, Zhe; Zhao, Menghua; Blaabjerg, Frede

    2009-01-01

    A serial AC-DC integrated load flow algorithm for variable speed offshore wind farms is proposed. It divides the electrical system of a wind farm into several local networks, and different load flow methods are used for these local networks sequentially. This method is fast, more accurate, and many...... factors such as the different wind farm configurations, the control of wind turbines and the power losses of pulse width modulation converters are considered. The DC/DC converter model is proposed and integrated into load flow algorithm by modifying the Jacobian matrix. Two iterative methods are proposed...... and integrated into the load flow algorithm: one takes into account the control strategy of converters and the other considers the power losses of converters. In addition, different types of variable speed wind turbine systems with different control methods are investigated. Finally, the method is demonstrated...

  19. Device for Measuring Low Flow Speed in a Duct

    Science.gov (United States)

    Quinn, Frank; Magee, Kevin

    2009-01-01

    A multiple-throat venturi system has been invented for measuring laminar flow of air or other gas at low speed (1 to 30 cm/s) in a duct while preserving the laminar nature of the flow and keeping the velocity profile across the duct as nearly flat as possible. While means for measuring flows at higher speeds are well established, heretofore, there have been no reliable means for making consistent, accurate measurements in this speed range. In the original application for which this system was invented, the duct leads into the test section of a low-speed wind tunnel wherein uniform, low-speed, laminar flow is required for scientific experiments. The system could also be used to monitor a slow flow of gas in an industrial process like chemical vapor deposition. In the original application, the multiple- throat venturi system is mounted at the inlet end of the duct having a rectangular cross section of 19 by 14 cm, just upstream of an assembly of inlet screens and flow straighteners that help to suppress undesired flow fluctuations (see Figure 1). The basic venturi measurement principle is well established: One measures the difference in pressure between (1) a point just outside the inlet, where the pressure is highest and the kinetic energy lowest; and (2) the narrowest part (the throat) of the venturi passage, where the kinetic energy is highest and the pressure is lowest. Then by use of Bernoulli s equation for the relationship between pressure and kinetic energy, the volumetric flow speed in the duct can be calculated from the pressure difference and the inlet and throat widths. The design of this system represents a compromise among length, pressure recovery, uniformity of flow, and complexity of assembly. Traditionally, venturis are used to measure faster flows in narrower cross sections, with longer upstream and downstream passages to maintain accuracy. The dimensions of the passages of the present venturi system are sized to provide a readily measurable

  20. Validity of a Wireless Gait Analysis Tool (Wi-GAT) in assessing spatio-temporal gait parameters at slow, preferred and fast walking speeds.

    Science.gov (United States)

    DesJardins, Ashley M; Schiller, Martha; Eraqi, Enas; Samuels, Amanda Nicole; Galen, Sujay S

    2016-11-14

    The wireless gait assessment tool (Wi-GAT) measures have been shown to have good to excellent concurrent validity with preferred walking speeds, however, the validity of the Wi-GAT measures at slow and fast walking speeds is unknown. To establish validity of the Wi-GAT spatio-temporal gait measures at slow, fast, and preferred walking speeds. Twenty two healthy adult volunteers, with a mean age of 25.7 (± 5.3) participated in this study. The spatio-temporal gait variables of each participant were concurrently recorded using the GAITrite and the Wi-GAT system, while the participants performed 3 trials for each walking speed in a randomized order. Intraclass correlation analyses were performed to establish the agreement between the measures recorded by the GAITrite and Wi-GAT systems. Walking speed measured both by the Wi-GAT and the GAITrite systems showed excellent agreement for preferred (ICC = 0.979 pgait parameters recorded at slow walking speed showed good (ICC > 0.70) to excellent (ICC > 0.85) agreement. Gait parameters recorded by the Wi-GAT system showed fair to excellent validity for preferred and slow walking speeds.

  1. Does walking speed mediate the association between visual impairment and self-report of mobility disability? The Salisbury Eye Evaluation Study.

    Science.gov (United States)

    Swenor, Bonnielin K; Bandeen-Roche, Karen; Muñoz, Beatriz; West, Sheila K

    2014-08-01

    To determine whether performance speeds mediate the association between visual impairment and self-reported mobility disability over an 8-year period. Longitudinal analysis. Salisbury, Maryland. Salisbury Eye Evaluation Study participants aged 65 and older (N=2,520). Visual impairment was defined as best-corrected visual acuity worse than 20/40 in the better-seeing eye or visual field less than 20°. Self-reported mobility disability on three tasks was assessed: walking up stairs, walking down stairs, and walking 150 feet. Performance speed on three similar tasks was measured: walking up steps (steps/s), walking down steps (steps/s), and walking 4 m (m/s). For each year of observation, the odds of reporting mobility disability was significantly greater for participants who were visually impaired (VI) than for those who were not (NVI) (odds ratio (OR) difficulty walking up steps=1.58, 95% confidence interval (CI)=1.32-1.89; OR difficulty walking down steps=1.90, 95% CI=1.59-2.28; OR difficulty walking 150 feet=2.11, 95% CI=1.77-2.51). Once performance speed on a similar mobility task was included in the models, VI participants were no longer more likely to report mobility disability than those who were NVI (OR difficulty walking up steps=0.84, 95% CI=0.65-1.11; OR difficulty walking down steps=0.96, 95% CI=0.74-1.24; OR difficulty walking 150 feet=1.22, 95% CI=0.98-1.50). Slower performance speed in VI individuals largely accounted for the difference in the odds of reporting mobility disability, suggesting that VI older adults walk slower and are therefore more likely to report mobility disability than those who are NVI. Improving mobility performance in older adults with visual impairment may minimize the perception of mobility disability. © 2014, Copyright the Authors Journal compilation © 2014, The American Geriatrics Society.

  2. An adaptive finite element method for high speed flows

    Science.gov (United States)

    Peraire, J.; Morgan, K.; Peiro, J.; Zienkiewicz, O. C.

    1987-01-01

    The solution of the equations of compressible high speed flow, on unstructured triangular grids in 2D and tetrahedral grids in 3D, is considered. Solution methods based upon both Taylor-Galerkin and Runge-Kutta time-stepping techniques are presented and the incorporation of the ideas of flux corrected transport (FCT) is discussed. These methods are combined with an adaptive mesh regeneration procedure and are employed in the solution of several examples, consisting of Euler flows in both 2D and 3D and Navier-Stokes flows in 2D.

  3. Direct Numerical Simulation of Disperse Multiphase High-Speed Flows

    Energy Technology Data Exchange (ETDEWEB)

    Nourgaliev, R R; Dinh, T N; Theofanous, T G; Koning, J M; Greenman, R M; Nakafuji, G T

    2004-02-17

    A recently introduced Level-Set-based Cartesian Grid (LSCG) Characteristics-Based Matching (CBM) method is applied for direct numerical simulation of shock-induced dispersal of solid material. The method incorporates the latest advancements in the level set technology and characteristics-based numerical methods for solution of hyperbolic conservation laws and boundary treatment. The LSCG/CBM provides unique capabilities to simulate complex fluid-solid (particulate) multiphase flows under high-speed flow conditions and taking into account particle-particle elastic and viscoelastic collisions. The particular emphasis of the present study is placed on importance of appropriate modeling of particle-particle collisions, which are demonstrated to crucially influence the global behavior of high-speed multiphase particulate flows. The results of computations reveal the richness and complexity of flow structures in compressible disperse systems, due to dynamic formation of shocks and contact discontinuities, which provide an additional long-range interaction mechanism in dispersed high-speed multiphase flows.

  4. Unsteady flow simulations of Pelton turbine at different rotational speeds

    Directory of Open Access Journals (Sweden)

    Minsuk Choi

    2015-11-01

    Full Text Available This article presents numerical simulations of a small Pelton turbine suitable for desalination system. A commercial flow solver was adopted to resolve difficulties in the numerical simulation for Pelton turbine such as the relative motion of the turbine runner to the injector and two-phase flow of water and air. To decrease the numerical diffusion of the water jet, a new topology with only hexagonal mesh was suggested for the computational mesh around the complex geometry of a bucket. The predicted flow coefficient, net head coefficient, and overall efficiency showed a good agreement with the experimental data. Based on the validation of the numerical results, the pattern of wet area on the bucket inner surface has been analyzed at different rotational speeds, and an attempt to find the connection between rotational speeds, torque, and efficiency has been made.

  5. Association between walking speed and age in healthy, free-living individuals using mobile accelerometry--a cross-sectional study.

    Directory of Open Access Journals (Sweden)

    Michaela Schimpl

    Full Text Available CONTEXT: Walking speed is a fundamental parameter of human motion and is increasingly considered as an important indicator of individuals' health status. OBJECTIVE: To evaluate the relationship of gait parameters, and demographic and physical characteristics in healthy men and women. DESIGN, SETTING, AND PARTICIPANTS: Recruitment of a subsample (n = 358 of male and female blood donors taking part in the Cambridge CardioResource study. Collection of demographic data, measurement of physical characteristics (height, weight and blood pressure and assessment of 7-day, free-living activity parameters using accelerometry and a novel algorithm to measure walking speed. Participants were a median (interquartile range[IQR] age of 49 (16 years; 45% women; and had a median (IQR BMI of 26 (5.4. MAIN OUTCOME MEASURE: Walking speed. RESULTS: In this study, the hypothesis that walking speed declines with age was generated using an initial 'open' dataset. This was subsequently validated in a separate 'closed' dataset that showed a decrease of walking speed of -0.0037 m/s per year. This is equivalent to a difference of 1.2 minutes, when walking a distance of 1 km aged 20 compared to 60 years. Associations between walking speed and other participant characteristics (i.e. gender, BMI and blood pressure were non-significant. BMI was negatively correlated with the number of walking and running steps and longest non-stop distance. CONCLUSION: This is the first study using accelerometry which shows an association between walking speed and age in free-living, healthy individuals. Absolute values of gait speed are comparable to published normal ranges in clinical settings. This study highlights the potential use of mobile accelerometry to assess gait parameters which may be indicative of future health outcomes in healthy individuals.

  6. Risk of Knee Osteoarthritis Over 24 Months in Individuals Who Decrease Walking Speed During a 12-Month Period: Data from the Osteoarthritis Initiative.

    Science.gov (United States)

    Herzog, Mackenzie M; Driban, Jeffrey B; Cattano, Nicole M; Cameron, Kenneth L; Tourville, Timothy W; Marshall, Stephen W; Pietrosimone, Brian

    2017-08-01

    To assess the association between change in walking speed over a 12-month period and risk of developing radiographic knee osteoarthritis (rKOA) over a 24-month period. We included participants without rKOA from the Osteoarthritis Initiative. Change in walking speed was determined from a 20-m walk assessment, calculated using walking speed at 12-month followup minus baseline speed and/or 24-month followup walking speed minus 12-month speed. Incident rKOA was defined as progressing to Kellgren-Lawrence arthritis grading scale ≥ 2 within 24 months (i.e., incidence between 12 and 36 mos or 24 and 48 mos). Self-reported significant knee injury during the exposure period, age, body mass index (BMI), and Physical Activity Scale for the Elderly (PASE) score were adjusted for analytically. We included 2638 observations among 1460 unique participants (58% women; aged 59 ± 9 yrs, range 45-79). The mean change in walking speed over 12 months was 0.001 ± 0.13 m/s (range -0.6271 to 1.4968). About 5% of the sample (n = 122) developed rKOA over a 24-month period. After controlling for significant knee injury, age, BMI, and PASE score, we found an 8% relative increase in risk of developing rKOA for every 0.1 m/s decrease in walking speed over a 12-month period (risk ratio 1.08, 95% CI 1.00-1.15, p = 0.05). Evaluating change in speed over a 12-month period using a 20-m walk test may be useful in identifying individuals at increased risk of developing rKOA over the subsequent 24 months. Identification of patients at high risk for developing rKOA would allow medical providers to implement early interventions to maximize joint health.

  7. Fluctuations around mean walking behaviours in diluted pedestrian flows

    CERN Document Server

    Corbetta, Alessandro; Benzi, Roberto; Muntean, Adrian; Toschi, Federico

    2016-01-01

    Understanding and modeling the dynamics of pedestrian crowds can help with designing and increasing the safety of civil facilities. A key feature of crowds is its intrinsic stochasticity, appearing even under very diluted conditions, due to the variability in individual behaviours. Individual stochasticity becomes even more important under densely crowded conditions, since it can be nonlinearly magnified and may lead to potentially dangerous collective behaviours. To understand quantitatively crowd stochasticity, we study the real-life dynamics of a large ensemble of pedestrians walking undisturbed, and we perform a statistical analysis of the fully-resolved pedestrian trajectories obtained by a year-long high-resolution measurement campaign. Our measurements have been carried out in a corridor of the Eindhoven University of Technology via a combination of Microsoft Kinect 3D-range sensor and automatic head-tracking algorithms. The temporal homogeneity of our large database of trajectories allows us to robust...

  8. Fatigue and Muscle Strength Involving Walking Speed in Parkinson’s Disease: Insights for Developing Rehabilitation Strategy for PD

    Directory of Open Access Journals (Sweden)

    Ying-Zu Huang

    2017-01-01

    Full Text Available Background. Problems with gait in Parkinson’s disease (PD are a challenge in neurorehabilitation, partly because the mechanisms causing the walking disability are unclear. Weakness and fatigue, which may significantly influence gait, are commonly reported by patients with PD. Hence, the aim of this study was to investigate the association between weakness and fatigue and walking ability in patients with PD. Methods. We recruited 25 patients with idiopathic PD and 25 age-matched healthy adults. The maximum voluntary contraction (MVC, twitch force, and voluntary activation levels were measured before and after a knee fatigue exercise. General fatigue, central fatigue, and peripheral fatigue were quantified by exercise-induced changes in MVC, twitch force, and activation level. In addition, subjective fatigue was measured using the Multidimensional Fatigue Inventory (MFI and Fatigue Severity Scale (FSS. Results. The patients with PD had lower activation levels, more central fatigue, and more subjective fatigue than the healthy controls. There were no significant differences in twitch force or peripheral fatigue index between the two groups. The reduction in walking speed was related to the loss of peripheral strength and PD itself. Conclusion. Fatigue and weakness of central origin were related to PD, while peripheral strength was important for walking ability. The results suggest that rehabilitation programs for PD should focus on improving both central and peripheral components of force.

  9. Fatigue and Muscle Strength Involving Walking Speed in Parkinson's Disease: Insights for Developing Rehabilitation Strategy for PD.

    Science.gov (United States)

    Huang, Ying-Zu; Chang, Fang-Yu; Liu, Wei-Chia; Chuang, Yu-Fen; Chuang, Li-Ling; Chang, Ya-Ju

    2017-01-01

    Background . Problems with gait in Parkinson's disease (PD) are a challenge in neurorehabilitation, partly because the mechanisms causing the walking disability are unclear. Weakness and fatigue, which may significantly influence gait, are commonly reported by patients with PD. Hence, the aim of this study was to investigate the association between weakness and fatigue and walking ability in patients with PD. Methods . We recruited 25 patients with idiopathic PD and 25 age-matched healthy adults. The maximum voluntary contraction (MVC), twitch force, and voluntary activation levels were measured before and after a knee fatigue exercise. General fatigue, central fatigue, and peripheral fatigue were quantified by exercise-induced changes in MVC, twitch force, and activation level. In addition, subjective fatigue was measured using the Multidimensional Fatigue Inventory (MFI) and Fatigue Severity Scale (FSS). Results . The patients with PD had lower activation levels, more central fatigue, and more subjective fatigue than the healthy controls. There were no significant differences in twitch force or peripheral fatigue index between the two groups. The reduction in walking speed was related to the loss of peripheral strength and PD itself. Conclusion . Fatigue and weakness of central origin were related to PD, while peripheral strength was important for walking ability. The results suggest that rehabilitation programs for PD should focus on improving both central and peripheral components of force.

  10. Modeling Compressibility Effects in High-Speed Turbulent Flows

    Science.gov (United States)

    Sarkar, S.

    2004-01-01

    Man has strived to make objects fly faster, first from subsonic to supersonic and then to hypersonic speeds. Spacecraft and high-speed missiles routinely fly at hypersonic Mach numbers, M greater than 5. In defense applications, aircraft reach hypersonic speeds at high altitude and so may civilian aircraft in the future. Hypersonic flight, while presenting opportunities, has formidable challenges that have spurred vigorous research and development, mainly by NASA and the Air Force in the USA. Although NASP, the premier hypersonic concept of the eighties and early nineties, did not lead to flight demonstration, much basic research and technology development was possible. There is renewed interest in supersonic and hypersonic flight with the HyTech program of the Air Force and the Hyper-X program at NASA being examples of current thrusts in the field. At high-subsonic to supersonic speeds, fluid compressibility becomes increasingly important in the turbulent boundary layers and shear layers associated with the flow around aerospace vehicles. Changes in thermodynamic variables: density, temperature and pressure, interact strongly with the underlying vortical, turbulent flow. The ensuing changes to the flow may be qualitative such as shocks which have no incompressible counterpart, or quantitative such as the reduction of skin friction with Mach number, large heat transfer rates due to viscous heating, and the dramatic reduction of fuel/oxidant mixing at high convective Mach number. The peculiarities of compressible turbulence, so-called compressibility effects, have been reviewed by Fernholz and Finley. Predictions of aerodynamic performance in high-speed applications require accurate computational modeling of these "compressibility effects" on turbulence. During the course of the project we have made fundamental advances in modeling the pressure-strain correlation and developed a code to evaluate alternate turbulence models in the compressible shear layer.

  11. Embedded function methods for compressible high speed turbulent flow

    Science.gov (United States)

    Walker, J. D. A.

    1994-09-01

    This is the final report on the work performed on the grant 'Embedded Function Methods for Compressible High Speed Turbulent Flow' carried out at Lehigh University during the contract period from September, 1987, to October of 1991. Work has continued at Lehigh on this project on an unfunded basis to the present. The original proposed work had two separate thrusts which were associated with developing embedded function methods in order to obviate the need to expend computational resources on turbulent wall layers in Navier Stokes and boundary-layer calculations. Previous work on the incompressible problem had indicated that this could be done successfully for two-dimensional and three-dimensional incompressible flows. The central objective here was to extend the basic approach to the high speed compressible problem.

  12. Cardiovascular conditioning for comfortable gait speed and total distance walked during the chronic stage of stroke: a meta-analysis.

    Science.gov (United States)

    Mehta, Swati; Pereira, Shelialah; Janzen, Shannon; Mays, Rachel; Viana, Ricardo; Lobo, Liane; Teasell, Robert W

    2012-01-01

    To examine the effectiveness of cardiovascular conditioning on comfortable gait speed and total distance walked when initiated in the chronic stage of stroke through a meta-analysis. MEDLINE, CINAHL, EMBASE, and Scopus databases were searched from 1980 to June 2012. A study was selected if (1) it was a randomized controlled trial; (2) individuals in the study were entered into the study at or over 6 months post stroke; (3) cardiorespiratory training was initiated during the chronic stage of stroke; and (4) study participants were ≥18 years of age. A standardized mean difference (SMD ± SE and 95% confidence interval [CI]) was calculated for comfortable gait speed and/or 6-minute walk test (6MWT). results from all studies were then pooled using a random effects model. Treatment effect sizes were interpreted as small, ≯0.2; moderate, ≯0.5; or large, ≯0.8. Methodological quality of studies was assessed using the Physiotherapy Evidence Database (PEDro) tool. Seven studies met inclusion criteria. The analysis demonstrated a moderate and significant effect on 6MWT post treatment (SMD = 0.581 ± 0.277; 95% CI, -0.037 to 1.125; P = .036) with an improvement of 111.4 m to a pooled average of 357.7 m. No significant improvement in comfortable gait speed was noted post treatment (SMD = 0.159 ± 0.124; 95% CI, -0.085 to 0.402; P = .202) or at follow-up (SMD = 0.248 ± 0.256; 95% CI, -0.253 to 0.750; P = .332). Cardiovascular conditioning resulted in clinically relevant gains in walking distance of over 100 m post treatment on the 6MWT when initiated during the chronic stage of stroke. These results demonstrate that individuals in the chronic stage of stroke can still benefit from interventions to improve gait and mobility. This has important implications for outpatient and community-based programs.

  13. Step-Detection and Adaptive Step-Length Estimation for Pedestrian Dead-Reckoning at Various Walking Speeds Using a Smartphone.

    Science.gov (United States)

    Ho, Ngoc-Huynh; Truong, Phuc Huu; Jeong, Gu-Min

    2016-09-02

    We propose a walking distance estimation method based on an adaptive step-length estimator at various walking speeds using a smartphone. First, we apply a fast Fourier transform (FFT)-based smoother on the acceleration data collected by the smartphone to remove the interference signals. Then, we analyze these data using a set of step-detection rules in order to detect walking steps. Using an adaptive estimator, which is based on a model of average step speed, we accurately obtain the walking step length. To evaluate the accuracy of the proposed method, we examine the distance estimation for four different distances and three speed levels. The experimental results show that the proposed method significantly outperforms conventional estimation methods in terms of accuracy.

  14. Best facilitated cortical activation during different stepping, treadmill, and robot-assisted walking training paradigms and speeds: A functional near-infrared spectroscopy neuroimaging study.

    Science.gov (United States)

    Kim, Ha Yeon; Yang, Sung Phil; Park, Gyu Lee; Kim, Eun Joo; You, Joshua Sung Hyun

    2016-01-01

    Robot-assisted and treadmill-gait training are promising neurorehabilitation techniques, with advantages over conventional gait training, but the neural substrates underpinning locomotor control remain unknown particularly during different gait training modes and speeds. The present optical imaging study compared cortical activities during conventional stepping walking (SW), treadmill walking (TW), and robot-assisted walking (RW) at different speeds. Fourteen healthy subjects (6 women, mean age 30.06, years ± 4.53) completed three walking training modes (SW, TW, and RW) at various speeds (self-selected, 1.5, 2.0, 2.5, and 3.0  km/h). A functional near-infrared spectroscopy (fNIRS) system determined cerebral hemodynamic changes associated with cortical locomotor network areas in the primary sensorimotor cortex (SMC), premotor cortex (PMC), supplementary motor area (SMA), prefrontal cortex (PFC), and sensory association cortex (SAC). There was increased cortical activation in the SMC, PMC, and SMA during different walking training modes. More global locomotor network activation was observed during RW than TW or SW. As walking speed increased, multiple locomotor network activations were observed, and increased activation power spectrum. This is the first empirical evidence highlighting the neural substrates mediating dynamic locomotion for different gait training modes and speeds. Fast, robot-assisted gait training best facilitated cortical activation associated with locomotor control.

  15. Measurements of granular flow dynamics with high speed digital images

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jingeol [Univ. of Florida, Gainesville, FL (United States)

    1994-01-01

    The flow of granular materials is common to many industrial processes. This dissertation suggests and validates image processing algorithms applied to high speed digital images to measure the dynamics (velocity, temperature and volume fraction) of dry granular solids flowing down an inclined chute under the action of gravity. Glass and acrylic particles have been used as granular solids in the experiment. One technique utilizes block matching for spatially averaged velocity measurements of the glass particles. This technique is compared with the velocity measurement using an optic probe which is a conventional granular flow velocity measurement device. The other technique for measuring the velocities of individual acrylic particles is developed with correspondence using a Hopfield network. This technique first locates the positions of particles with pattern recognition techniques, followed by a clustering technique, which produces point patterns. Also, several techniques are compared for particle recognition: synthetic discriminant function (SDF), minimum average correlation energy (MACE) filter, modified minimum average correlation energy (MMACE) filter and variance normalized correlation. The author proposes an MMACE filter which improves generalization of the MACE filter by adjusting the amount of averaged spectrum of training images in the spectrum whitening stages of the MACE filter. Variance normalized correlation is applied to measure the velocity and temperature of flowing glass particles down the inclined chute. The measurements are taken for the steady and wavy flow and qualitatively compared with a theoretical model of granular flow.

  16. The adaptation of limb kinematics to increasing walking speeds in freely moving mice 129/Sv and C57BL/6.

    Science.gov (United States)

    Serradj, Nadjet; Jamon, Marc

    2009-07-19

    The kinematics of locomotion was analyzed in two strains of great importance for the creation of mutated mice (C56BL/6 and 129/Sv). Different behavioral situations were used to trigger sequences of movement covering the whole range of velocities in the mice, and the variations of kinematic parameters were analyzed in relation with velocity. Both stride frequency and stride length contributed to the moving speed, but stride frequency was found to be the main contributor to the speed increase. A trot-gallop transition was detected at speed about 70 cm/s, in relation with a sharp shift in limb coordination. The results of this study were consistent with pieces of information previously published concerning the gait analyses of other strains, and provided an integrative view of the basic motor pattern of mice. On the other hand some qualitative differences were found in the movement characteristics of the two strains. The stride frequency showed a higher contribution to speed in 129/Sv than in C57BL/6. In addition, 129/Sv showed a phase shift in the forelimb and hindlimb, and a different position of the foot during the stance time that revealed a different gait and body position during walking. Overall, 129/Sv moved at a slower speed than C57BL/6 in any behavioral situation. This difference was related to a basal lower level of motor activity. The possibility that an alteration in the dopamine circuit was responsible for the different movement pattern in 129/Sv is discussed.

  17. The Hidden Flow Structure and Metric Space of Network Embedding Algorithms Based on Random Walks.

    Science.gov (United States)

    Gu, Weiwei; Gong, Li; Lou, Xiaodan; Zhang, Jiang

    2017-10-13

    Network embedding which encodes all vertices in a network as a set of numerical vectors in accordance with it's local and global structures, has drawn widespread attention. Network embedding not only learns significant features of a network, such as the clustering and linking prediction but also learns the latent vector representation of the nodes which provides theoretical support for a variety of applications, such as visualization, link prediction, node classification, and recommendation. As the latest progress of the research, several algorithms based on random walks have been devised. Although those algorithms have drawn much attention for their high scores in learning efficiency and accuracy, there is still a lack of theoretical explanation, and the transparency of those algorithms has been doubted. Here, we propose an approach based on the open-flow network model to reveal the underlying flow structure and its hidden metric space of different random walk strategies on networks. We show that the essence of embedding based on random walks is the latent metric structure defined on the open-flow network. This not only deepens our understanding of random- walk-based embedding algorithms but also helps in finding new potential applications in network embedding.

  18. Control entropy identifies differential changes in complexity of walking and running gait patterns with increasing speed in highly trained runners

    Science.gov (United States)

    McGregor, Stephen J.; Busa, Michael A.; Skufca, Joseph; Yaggie, James A.; Bollt, Erik M.

    2009-06-01

    Regularity statistics have been previously applied to walking gait measures in the hope of gaining insight into the complexity of gait under different conditions and in different populations. Traditional regularity statistics are subject to the requirement of stationarity, a limitation for examining changes in complexity under dynamic conditions such as exhaustive exercise. Using a novel measure, control entropy (CE), applied to triaxial continuous accelerometry, we report changes in complexity of walking and running during increasing speeds up to exhaustion in highly trained runners. We further apply Karhunen-Loeve analysis in a new and novel way to the patterns of CE responses in each of the three axes to identify dominant modes of CE responses in the vertical, mediolateral, and anterior/posterior planes. The differential CE responses observed between the different axes in this select population provide insight into the constraints of walking and running in those who may have optimized locomotion. Future comparisons between athletes, healthy untrained, and clinical populations using this approach may help elucidate differences between optimized and diseased locomotor control.

  19. Age differences in the required coefficient of friction during level walking do not exist when experimentally-controlling speed and step length

    Science.gov (United States)

    Anderson, Dennis E.; Franck, Christopher T.; Madigan, Michael L.

    2015-01-01

    The effects of gait speed and step length on the required coefficient of friction (COF) confounds the investigation of age-related differences in required COF. The goals of this study were to investigate whether age differences in required COF during self-selected gait persist when experimentally-controlling speed and step length, and to determine the independent effects of speed and step length on required COF. Ten young and ten older healthy adults performed gait trials under five gait conditions: self-selected, slow and fast speeds without controlling step length, and slow and fast speeds while controlling step length. During self-selected gait, older adults walked with shorter step lengths and exhibited a lower required COF. Older adults also exhibited a lower required COF when walking at a controlled speed without controlling step length. When both age groups walked with the same speed and step length, no age difference in required COF was found. Thus, speed and step length can have a large influence on studies investigating age-related differences in required COF. It was also found that speed and step length have independent and opposite effects on required COF, with step length having a strong positive effect on required COF, and speed a weaker negative effect. PMID:24979811

  20. Older adults must hurry at pedestrian lights! A cross-sectional analysis of preferred and fast walking speed under single- and dual-task conditions.

    Directory of Open Access Journals (Sweden)

    Patrick Eggenberger

    Full Text Available Slow walking speed is strongly associated with adverse health outcomes, including cognitive impairment, in the older population. Moreover, adequate walking speed is crucial to maintain older pedestrians' mobility and safety in urban areas. This study aimed to identify the proportion of Swiss older adults that didn't reach 1.2 m/s, which reflects the requirements to cross streets within the green-yellow phase of pedestrian lights, when walking fast under cognitive challenge. A convenience sample, including 120 older women (65% and men, was recruited from the community (88% and from senior residences and divided into groups of 70-79 years (n = 59, 74.8 ± 0.4 y; mean ± SD and ≥80 years (n = 61, 85.5 ± 0.5 y. Steady state walking speed was assessed under single- and dual-task conditions at preferred and fast walking speed. Additionally, functional lower extremity strength (5-chair-rises test, subjective health rating, and retrospective estimates of fall frequency were recorded. Results showed that 35.6% of the younger and 73.8% of the older participants were not able to walk faster than 1.2 m/s under the fast dual-task walking condition. Fast dual-task walking speed was higher compared to the preferred speed single- and dual-task conditions (all p < .05, r = .31 to .48. Average preferred single-task walking speed was 1.19 ± 0.24 m/s (70-79 y and 0.94 ± 0.27 m/s (≥80 y, respectively, and correlated with performance in the 5-chair-rises test (rs = -.49, p < .001, subjective health (τ = .27, p < .001, and fall frequency (τ = -.23, p = .002. We conclude that the fitness status of many older people is inadequate to safely cross streets at pedestrian lights and maintain mobility in the community's daily life in urban areas. Consequently, training measures to improve the older population's cognitive and physical fitness should be promoted to enhance walking speed and safety of older pedestrians.

  1. Maximum speeds and alpha angles of flowing avalanches

    Science.gov (United States)

    McClung, David; Gauer, Peter

    2016-04-01

    A flowing avalanche is one which initiates as a slab and, if consisting of dry snow, will be enveloped in a turbulent snow dust cloud once the speed reaches about 10 m/s. A flowing avalanche has a dense core of flowing material which dominates the dynamics by serving as the driving force for downslope motion. The flow thickness typically on the order of 1 -10 m which is on the order of about 1% of the length of the flowing mass. We have collected estimates of maximum frontal speed um (m/s) from 118 avalanche events. The analysis is given here with the aim of using the maximum speed scaled with some measure of the terrain scale over which the avalanches ran. We have chosen two measures for scaling, from McClung (1990), McClung and Schaerer (2006) and Gauer (2012). The two measures are the √H0-;√S0-- (total vertical drop; total path length traversed). Our data consist of 118 avalanches with H0 (m)estimated and 106 with S0 (m)estimated. Of these, we have 29 values with H0 (m),S0 (m)and um (m/s)estimated accurately with the avalanche speeds measured all or nearly all along the path. The remainder of the data set includes approximate estimates of um (m/s)from timing the avalanche motion over a known section of the path where approximate maximum speed is expected and with either H0or S0or both estimated. Our analysis consists of fitting the values of um/√H0--; um/√S0- to probability density functions (pdf) to estimate the exceedance probability for the scaled ratios. In general, we found the best fits for the larger data sets to fit a beta pdf and for the subset of 29, we found a shifted log-logistic (s l-l) pdf was best. Our determinations were as a result of fitting the values to 60 different pdfs considering five goodness-of-fit criteria: three goodness-of-fit statistics :K-S (Kolmogorov-Smirnov); A-D (Anderson-Darling) and C-S (Chi-squared) plus probability plots (P-P) and quantile plots (Q-Q). For less than 10% probability of exceedance the results show that

  2. Wave-speed-determined flow limitation at peak flow in normal and asthmatic subjects.

    Science.gov (United States)

    Pedersen, O F; Brackel, H J; Bogaard, J M; Kerrebijn, K F

    1997-11-01

    The purpose of this study was to examine whether peak expiratory flow is determined by the wave-speed flow-limiting mechanism. We examined 17 healthy subjects and 11 subjects with stable asthma, the latter treated with inhaled bronchodilators and corticosteroids. We used an esophageal balloon and a Pitot-static probe positioned at five locations between the right lower lobe and midtrachea to obtain dynamic area-transmural pressure (A-Ptm) curves as described (O. F. Pedersen, B. Thiessen, and S. Lyager. J. Appl. Physiol. 52: 357-369, 1982). From these curves we obtained cross-sectional area (A) and airway compliance (Caw = dA/dPtm) at PEF, calculated flow at wave speed (Vws = A[A/(Caw*rho)0.5], where rho is density) and speed index is (SI = V/Vws). In 13 of 15 healthy and in 4 of 10 asthmatic subjects, who could produce satisfactory curves, SI at PEF was > 0.9 at one or more measured positions. Alveolar pressure continued to increase after PEF was achieved, suggesting flow limitation somewhere in the airway in all of these subjects. We conclude that wave speed is reached in central airways at PEF in most subjects, but it cannot be excluded that wave speed is also reached in more peripheral airways.

  3. Concurrent validity of walking speed values calculated via the GAITRite electronic walkway and 3 meter walk test in the chronic stroke population.

    Science.gov (United States)

    Peters, Denise M; Middleton, Addie; Donley, Jonathan W; Blanck, Erika L; Fritz, Stacy L

    2014-04-01

    The purpose of this study was to provide novel information regarding the concurrent validity (primary aim) and reliability (secondary aim) of walking speed (WS) calculated via the GAITRite electronic walkway system and 3 meter walk test (3MWT) in the chronic stroke population. The 3MWT is a feasible option for clinicians working in environments where space is limited. Psychometric properties of the test have not been established. Participants with chronic stroke were stratified into three groups: (1) household ambulators (HA) (self-selected WS  0.8 m/s, 26 participants, 71 observations). Three consecutive trials of GAITRite and 3MWT were performed at participant's self-selected WS. Average WS measurements differed significantly (p < 0.05) between GAITRite and 3MWT for all three groups. HA group: GAITRite 0.25 (0.11) m/s, 3MWT 0.27 (0.11) m/s; LCA group: GAITRite 0.56 (0.11) m/s, 3MWT 0.52 (0.10) m/s; CA group: GAITRite 1.03 (0.16) m/s, 3MWT 0.89 (0.15) m/s. Both WS measures had excellent within-session reliability (ICC's ranging from 0.85 to 0.97, SEM95 from 0.04 to 0.12 m/s and MDC95 from 0.05 to 0.16 m/s). Reliability was highest for HA on both measures. Although both the 3MWT and the GAITRite are reliable measures of WS for individuals with chronic stroke, the two measures do not demonstrate concurrent validity.

  4. Flow in a Low Specific Speed Centrifugal Pump Using PIV

    Directory of Open Access Journals (Sweden)

    Cui Dai

    2013-01-01

    Full Text Available The interflow plays important roles in centrifugal pump design. In order to study the effect of rotation and z-axis on internal flow, two-dimensional particle image velocimetry (PIV measurements have been performed to measure the steady velocity field on three planes in all impeller passages of a low specific-speed centrifugal pump. The results show that the relative velocity flows in blade passages are obviously different in terms of the positions of the blade relative to the tongue. The interaction between the impeller and tongue changes the occurrence and development of low velocity region with time. From shroud to hub, the relative velocity gradually increases, and the minimum value moves toward the suction surface. On the midplane, the magnitude increases with increased flow rate from pressure surface to suction surface, while at the shroud and hub, the measured velocity first increases with decreased flow rate from the blade pressure surface to nearly ζ = 0.5 to 0.6.

  5. Preconditioned Conjugate Gradient methods for low speed flow calculations

    Science.gov (United States)

    Ajmani, Kumud; Ng, Wing-Fai; Liou, Meng-Sing

    1993-01-01

    An investigation is conducted into the viability of using a generalized Conjugate Gradient-like method as an iterative solver to obtain steady-state solutions of very low-speed fluid flow problems. Low-speed flow at Mach 0.1 over a backward-facing step is chosen as a representative test problem. The unsteady form of the two dimensional, compressible Navier-Stokes equations are integrated in time using discrete time-steps. The Navier-Stokes equations are cast in an implicit, upwind finite-volume, flux split formulation. The new iterative solver is used to solve a linear system of equations at each step of the time-integration. Preconditioning techniques are used with the new solver to enhance the stability and the convergence rate of the solver and are found to be critical to the overall success of the solver. A study of various preconditioners reveals that a preconditioner based on the lower-upper (L-U)-successive symmetric over-relaxation iterative scheme is more efficient than a preconditioner based on incomplete L-U factorizations of the iteration matrix. The performance of the new preconditioned solver is compared with a conventional line Gauss-Seidel relaxation (LGSR) solver. Overall speed-up factors of 28 (in terms of global time-steps required to converge to a steady-state solution) and 20 (in terms of total CPU time on one processor of a CRAY-YMP) are found in favor of the new preconditioned solver, when compared with the LGSR solver.

  6. Lagrangian transported MDF methods for compressible high speed flows

    Science.gov (United States)

    Gerlinger, Peter

    2017-06-01

    This paper deals with the application of thermochemical Lagrangian MDF (mass density function) methods for compressible sub- and supersonic RANS (Reynolds Averaged Navier-Stokes) simulations. A new approach to treat molecular transport is presented. This technique on the one hand ensures numerical stability of the particle solver in laminar regions of the flow field (e.g. in the viscous sublayer) and on the other hand takes differential diffusion into account. It is shown in a detailed analysis, that the new method correctly predicts first and second-order moments on the basis of conventional modeling approaches. Moreover, a number of challenges for MDF particle methods in high speed flows is discussed, e.g. high cell aspect ratio grids close to solid walls, wall heat transfer, shock resolution, and problems from statistical noise which may cause artificial shock systems in supersonic flows. A Mach 2 supersonic mixing channel with multiple shock reflection and a model rocket combustor simulation demonstrate the eligibility of this technique to practical applications. Both test cases are simulated successfully for the first time with a hybrid finite-volume (FV)/Lagrangian particle solver (PS).

  7. Accurate measurement of streamwise vortices in low speed aerodynamic flows

    Science.gov (United States)

    Waldman, Rye M.; Kudo, Jun; Breuer, Kenneth S.

    2010-11-01

    Low Reynolds number experiments with flapping animals (such as bats and small birds) are of current interest in understanding biological flight mechanics, and due to their application to Micro Air Vehicles (MAVs) which operate in a similar parameter space. Previous PIV wake measurements have described the structures left by bats and birds, and provided insight to the time history of their aerodynamic force generation; however, these studies have faced difficulty drawing quantitative conclusions due to significant experimental challenges associated with the highly three-dimensional and unsteady nature of the flows, and the low wake velocities associated with lifting bodies that only weigh a few grams. This requires the high-speed resolution of small flow features in a large field of view using limited laser energy and finite camera resolution. Cross-stream measurements are further complicated by the high out-of-plane flow which requires thick laser sheets and short interframe times. To quantify and address these challenges we present data from a model study on the wake behind a fixed wing at conditions comparable to those found in biological flight. We present a detailed analysis of the PIV wake measurements, discuss the criteria necessary for accurate measurements, and present a new dual-plane PIV configuration to resolve these issues.

  8. Volitional Muscle Strength in the Legs Predicts Changes in Walking Speed Following Locomotor Training in People With Chronic Spinal Cord Injury

    Science.gov (United States)

    Norton, Jonathan; Nevett-Duchcherer, Jennifer; Roy, Francois D.; Gross, Douglas P.; Gorassini, Monica A.

    2011-01-01

    Background It is unclear which individuals with incomplete spinal cord injury best respond to body-weight–supported treadmill training. Objective The purpose of this study was to determine the factors that predict whether a person with motor incomplete spinal cord injury will respond to body-weight–supported treadmill training. Design This was a prognostic study with a one-group pretest-posttest design. Methods Demographic, clinical, and electrophysiological measurements taken prior to training were examined to determine which measures best predicted improvements in walking speed in 19 individuals with chronic (>7 months postinjury), motor-incomplete spinal cord injuries (ASIA Impairment Scale categories C and D, levels C1–L1). Results Two initial measures correlated significantly with improvements in walking speed: (1) the ability to volitionally contract a muscle, as measured by the lower-extremity manual muscle test (LE MMT) (r=.72), and (2) the peak locomotor electromyographic (EMG) amplitude in the legs (r=.56). None of the demographics (time since injury, age, body mass index) were significantly related to improvements in walking speed, nor was the clinical measure of balance (Berg Balance Scale). Further analysis of LE MMT scores showed 4 key muscle groups were significantly related to improvements in walking speed: knee extensors, knee flexors, ankle plantar flexors, and hip abductors (r=.82). Prediction using the summed MMT scores from those muscles and peak EMG amplitude in a multivariable regression indicated that peak locomotor EMG amplitude did not add significantly to the prediction provided by the LE MMT alone. Change in total LE MMT scores from the beginning to the end of training was not correlated with a change in walking speed over the same period. Limitations The sample size was limited, so the results should be considered exploratory. Conclusions The results suggest that preserved muscle strength in the legs after incomplete spinal cord

  9. Transient flow characteristics of a high speed rotary valve

    Science.gov (United States)

    Browning, Patrick H.

    were experimentally mapped as a function of valve speed, inter-cylinder pressure ratios and volume ratios and the results were compared to compressible flow theoretical models. Specifically, the transient behavior suggested a short-lived loss-mode initiation closely resembled by shock tube theory followed by a quasi-steady flow regime resembling choked flow behavior. An empirical model was then employed to determine the useful range of the CCV design as applied to a four-stroke CIBAI engine cycle modeled using a 1-D quasi-steady numerical method, with particular emphasis on the cyclic timing of the CCV opening. Finally, a brief discussion of a high-temperature version of the CCV design is presented.

  10. Trunk and pelvic coordination at various walking speeds during an anterior load carriage task in subjects with and without chronic low back pain

    OpenAIRE

    Kim, Tackhoon; Chai, Eunsu

    2015-01-01

    [Purpose] This study compared the coordination patterns of the trunk and pelvis in the transverse plane between healthy subjects and patients with chronic low back pain during an anterior load carriage task at various walking speeds. [Subjects] Ten healthy subjects and 10 patients with chronic low back pain performed an anterior carriage task with a load of 10% body weight at walking speeds of 3.5, 4.5, or 5.5?km/h. [Methods] The trunk and pelvic kinematics were measured by using a motion ana...

  11. Internal Flow of a High Specific-Speed Diagonal-Flow Fan (Rotor Outlet Flow Fields with Rotating Stall

    Directory of Open Access Journals (Sweden)

    Norimasa Shiomi

    2003-01-01

    Full Text Available We carried out investigations for the purpose of clarifying the rotor outlet flow fields with rotating stall cell in a diagonal-flow fan. The test fan was a high–specific-speed (ns=1620 type of diagonal-flow fan that had 6 rotor blades and 11 stator blades. It has been shown that the number of the stall cell is 1, and its propagating speed is approximately 80% of its rotor speed, although little has been known about the behavior of the stall cell because a flow field with a rotating stall cell is essentially unsteady. In order to capture the behavior of the stall cell at the rotor outlet flow fields, hot-wire surveys were performed using a single-slant hotwire probe. The data obtained by these surveys were processed by means of a double phase-locked averaging technique, which enabled us to capture the flow field with the rotating stall cell in the reference coordinate system fixed to the rotor. As a result, time-dependent ensemble averages of the three-dimensional velocity components at the rotor outlet flow fields were obtained. The behavior of the stall cell was shown for each velocity component, and the flow patterns on the meridional planes were illustrated.

  12. Speed and duration of walking and other leisure time physical activity and the risk of heart failure: a prospective cohort study from the Copenhagen City Heart Study.

    Directory of Open Access Journals (Sweden)

    Hans Askelund Saevereid

    Full Text Available AIM: Physical activity (PA confers some protection against development of heart failure (HF but little is known of the role of intensity and duration of exercise. METHODS AND RESULTS: In a prospective cohort study of men and women free of previous MI, stroke or HF with one or more examinations in 1976-2003, we studied the association between updated self-assessed leisure-time PA, speed and duration of walking and subsequent hospitalization or death from HF. Light and moderate/high level of leisure-time PA and brisk walking were associated with reduced risk of HF in both genders whereas no consistent association with duration of walking was seen. In 18,209 subjects age 20-80 with 1580 cases of HF, using the lowest activity level as reference, the confounder-adjusted hazard ratios (HR for light and moderate/high leisure-time physical activity were 0.75 (0.66-0.86 and 0.80 (0.69-0.93, respectively. In 9,937 subjects with information on walking available and 542 cases of HF, moderate and high walking speed were associated with adjusted HRs of 0.53 (0.43-0.66 and 0.30 (0.21-0.44, respectively, and daily walking of ½-1 hrs, 1-2 and >2 hrs with HR of 0.80 (0.61-1.06, 0.82 (0.62-1.06, and 0.96 (0.73-1.27, respectively. Results were similar for both genders and remained robust after exclusion of HF related to coronary heart disease and after a series of sensitivity analyses. CONCLUSIONS: Speed rather than duration of walking was associated with reduced risk of HF. Walking is the most wide-spread PA and public health measures to curb the increase in HF may benefit from this information.

  13. Speed and duration of walking and other leisure time physical activity and the risk of heart failure: a prospective cohort study from the Copenhagen City Heart Study.

    Science.gov (United States)

    Saevereid, Hans Askelund; Schnohr, Peter; Prescott, Eva

    2014-01-01

    Physical activity (PA) confers some protection against development of heart failure (HF) but little is known of the role of intensity and duration of exercise. In a prospective cohort study of men and women free of previous MI, stroke or HF with one or more examinations in 1976-2003, we studied the association between updated self-assessed leisure-time PA, speed and duration of walking and subsequent hospitalization or death from HF. Light and moderate/high level of leisure-time PA and brisk walking were associated with reduced risk of HF in both genders whereas no consistent association with duration of walking was seen. In 18,209 subjects age 20-80 with 1580 cases of HF, using the lowest activity level as reference, the confounder-adjusted hazard ratios (HR) for light and moderate/high leisure-time physical activity were 0.75 (0.66-0.86) and 0.80 (0.69-0.93), respectively. In 9,937 subjects with information on walking available and 542 cases of HF, moderate and high walking speed were associated with adjusted HRs of 0.53 (0.43-0.66) and 0.30 (0.21-0.44), respectively, and daily walking of ½-1 hrs, 1-2 and >2 hrs with HR of 0.80 (0.61-1.06), 0.82 (0.62-1.06), and 0.96 (0.73-1.27), respectively. Results were similar for both genders and remained robust after exclusion of HF related to coronary heart disease and after a series of sensitivity analyses. Speed rather than duration of walking was associated with reduced risk of HF. Walking is the most wide-spread PA and public health measures to curb the increase in HF may benefit from this information.

  14. [Effect of walking speed on pressure distribution of orthopedic shoe technology].

    Science.gov (United States)

    Drerup, B; Hafkemeyer, U; Möller, M; Wetz, H H

    2001-03-01

    Lesions to the diabetic foot have various causes. However, there is broad consensus that excessive plantar pressure plays a major role in the chain of events leading to ulcerations and gangrenes. During walking, on the other hand, peak values of plantar pressure are likely to increase with velocity even in therapeutic shoes. Therefore, the question arises whether a moderate velocity should be recommended to diabetic patients to reduce the risk of foot lesions. In this study, two velocities were compared for different types of therapeutic footwear. The velocities selected were considered moderate (0.7 m/s) and normal (1.3 m/s) for diabetic patients. A specially designed mathematical algorithm (velocity normalization) provided the pressure distributions from a common set of measurements: seven trials at different velocities for each subject and each type of footwear. Ten test subjects with healthy feet were studied. The shoes were ready-made and all had a midfoot rocker. The following four conditions were tested: flexible or rigid outsole respectively in combination with a flat insole or molded foot bed respectively. Pressure distribution measurements were performed with the Pedar in-shoe system, and the Pedar software package was used for analysis. The foot was divided into six regions: first toe, second to fifth toes, metatarsal region, medial midfoot, lateral midfoot, and heel. Only peak pressures were taken into account. Gait velocity was found to have an effect on plantar pressure distribution, mainly in the toes and heel region. Peak pressure in the heels increased significantly by about 20%. In the toe region, the increase was about the same, but was not statistically significant. At a higher velocity, pressure even slightly decreased in the midfoot region. The percentage variation was similar for all four conditions. Thus, walking slowly prevented the foot from high peak pressures, and the combination of rigid outsole and molded foot bed was best suited for

  15. Flow speed measurement using two-point collective light scattering

    Energy Technology Data Exchange (ETDEWEB)

    Heinemeier, N.P

    1998-09-01

    Measurements of turbulence in plasmas and fluids using the technique of collective light scattering have always been plagued by very poor spatial resolution. In 1994, a novel two-point collective light scattering system for the measurement of transport in a fusion plasma was proposed. This diagnostic method was design for a great improvement of the spatial resolution, without sacrificing accuracy in the velocity measurement. The system was installed at the W7-AS steallartor in Garching, Germany, in 1996, and has been operating since. This master thesis is an investigation of the possible application of this new method to the measurement of flow speeds in normal fluids, in particular air, although the results presented in this work have significance for the plasma measurements as well. The main goal of the project was the experimental verification of previous theoretical predictions. However, the theoretical considerations presented in the thesis show that the method can only be hoped to work for flows that are almost laminar and shearless, which makes it of very small practical interest. Furthermore, this result also implies that the diagnostic at W7-AS cannot be expected to give the results originally hoped for. (au) 1 tab., 51 ills., 29 refs.

  16. AC-DC integrated load flow calculation for variable speed offshore wind farms

    DEFF Research Database (Denmark)

    Zhao, Menghua; Chen, Zhe; Blaabjerg, Frede

    2005-01-01

    This paper proposes a sequential AC-DC integrated load flow algorithm for variable speed offshore wind farms. In this algorithm, the variable frequency and the control strategy of variable speed wind turbine systems are considered. In addition, the losses of wind turbine systems and the losses...... of converters are also integrated into the load flow algorithm. As a general algorithm, it can be applied to different types of wind farm configurations, and the load flow is related to the wind speed....

  17. The Steady Flow Resistance of Perforated Sheet Materials in High Speed Grazing Flows

    Science.gov (United States)

    Syed, Asif A.; Yu, Jia; Kwan, H. W.; Chien, E.; Jones, Michael G. (Technical Monitor)

    2002-01-01

    A study was conducted to determine the effects of high speed grazing air flow on the acoustic resistance of perforated sheet materials used in the construction of acoustically absorptive liners placed in commercial aircraft engine nacelles. Since DC flow resistance of porous sheet materials is known to be a major component of the acoustic resistance of sound suppression liners, the DC flow resistance of a set of perforated face-sheets and linear 'wiremesh' face-sheets was measured in a flow duct apparatus (up to Mach 0.8). Samples were fabricated to cover typical variations in perforated face-sheet parameters, such as hole diameter, porosity and sheet thickness, as well as those due to different manufacturing processes. The DC flow resistance data from perforated sheets were found to correlate strongly with the grazing flow Mach number and the face-sheet porosity. The data also show correlation against the boundary layer displacement thickness to hole-diameter ratio. The increase in resistance with grazing flow for punched aluminum sheets is in good agreement with published results up to Mach 0.4, but is significantly larger than expected above Mach 0.4. Finally, the tests demonstrated that there is a significant increase in the resistance of linear 'wiremesh' type face-sheet materials.

  18. Rehabilitation that incorporates virtual reality is more effective than standard rehabilitation for improving walking speed, balance and mobility after stroke: a systematic review.

    Science.gov (United States)

    Corbetta, Davide; Imeri, Federico; Gatti, Roberto

    2015-07-01

    In people after stroke, does virtual reality based rehabilitation (VRBR) improve walking speed, balance and mobility more than the same duration of standard rehabilitation? In people after stroke, does adding extra VRBR to standard rehabilitation improve the effects on gait, balance and mobility? Systematic review with meta-analysis of randomised trials. Adults with a clinical diagnosis of stroke. Eligible trials had to include one these comparisons: VRBR replacing some or all of standard rehabilitation or VRBR used as extra rehabilitation time added to a standard rehabilitation regimen. Walking speed, balance, mobility and adverse events. In total, 15 trials involving 341 participants were included. When VRBR replaced some or all of the standard rehabilitation, there were statistically significant benefits in walking speed (MD 0.15 m/s, 95% CI 0.10 to 0.19), balance (MD 2.1 points on the Berg Balance Scale, 95% CI 1.8 to 2.5) and mobility (MD 2.3 seconds on the Timed Up and Go test, 95% CI 1.2 to 3.4). When VRBR was added to standard rehabilitation, mobility showed a significant benefit (0.7 seconds on the Timed Up and Go test, 95% CI 0.4 to 1.1), but insufficient evidence was found to comment about walking speed (one trial) and balance (high heterogeneity). Substituting some or all of a standard rehabilitation regimen with VRBR elicits greater benefits in walking speed, balance and mobility in people with stroke. Although the benefits are small, the extra cost of applying virtual reality to standard rehabilitation is also small, especially when spread over many patients in a clinic. Adding extra VRBR time to standard rehabilitation also has some benefits; further research is needed to determine if these benefits are clinically worthwhile. Copyright © 2015 Australian Physiotherapy Association. Published by Elsevier B.V. All rights reserved.

  19. Experimental Comparison of Speed : Fuel-flow and Speed-area Controls on a Turbojet Engine for Small Step Disturbances

    Science.gov (United States)

    Wenzel, L M; Hart, C E; Craig, R T

    1957-01-01

    Optimum proportional-plus-integral control settings for speed - fuel-flow control, determined by minimization of integral criteria, correlated well with analytically predicted optimum settings. Engine response data are given for a range of control settings around the optimum. An inherent nonlinearity in the speed-area loop necessitated the use of nonlinear controls. Response data for two such nonlinear control schemes are presented.

  20. Normative pedestrian flow behavior theory and applications

    NARCIS (Netherlands)

    Hoogendoorn, S.P.

    2001-01-01

    Gaining insights into pedestrian flow operations and assessment tools for pedestrian walking speeds and comfort is important in for instance planning and geometric design of infrastructural facilities. Additionally, management of pedestrian flows requires knowledge of pedestrian flow behavior.

  1. Rehabilitation that incorporates virtual reality is more effective than standard rehabilitation for improving walking speed, balance and mobility after stroke: a systematic review

    Directory of Open Access Journals (Sweden)

    Davide Corbetta

    2015-07-01

    Full Text Available Question: In people after stroke, does virtual reality based rehabilitation (VRBR improve walking speed, balance and mobility more than the same duration of standard rehabilitation? In people after stroke, does adding extra VRBR to standard rehabilitation improve the effects on gait, balance and mobility? Design: Systematic review with meta-analysis of randomised trials. Participants: Adults with a clinical diagnosis of stroke. Intervention: Eligible trials had to include one these comparisons: VRBR replacing some or all of standard rehabilitation or VRBR used as extra rehabilitation time added to a standard rehabilitation regimen. Outcome measures: Walking speed, balance, mobility and adverse events. Results: In total, 15 trials involving 341 participants were included. When VRBR replaced some or all of the standard rehabilitation, there were statistically significant benefits in walking speed (MD 0.15 m/s, 95% CI 0.10 to 0.19, balance (MD 2.1 points on the Berg Balance Scale, 95% CI 1.8 to 2.5 and mobility (MD 2.3 seconds on the Timed Up and Go test, 95% CI 1.2 to 3.4. When VRBR was added to standard rehabilitation, mobility showed a significant benefit (0.7 seconds on the Timed Up and Go test, 95% CI 0.4 to 1.1, but insufficient evidence was found to comment about walking speed (one trial and balance (high heterogeneity. Conclusion: Substituting some or all of a standard rehabilitation regimen with VRBR elicits greater benefits in walking speed, balance and mobility in people with stroke. Although the benefits are small, the extra cost of applying virtual reality to standard rehabilitation is also small, especially when spread over many patients in a clinic. Adding extra VRBR time to standard rehabilitation also has some benefits; further research is needed to determine if these benefits are clinically worthwhile. [Corbetta D, Imeri F, Gatti R (2015 Rehabilitation that incorporates virtual reality is more effective than standard

  2. Dynamic visual acuity (DVA) during locomotion for targets at near and far distances: effects of aging, walking speed and head-trunk coupling.

    Science.gov (United States)

    Deshpande, Nandini; Tourtillott, Brandon M; Peters, Brian T; Bloomberg, Jacob J

    2013-01-01

    This study examined effects of aging, head-trunk coupling (HTcoupling) and walking speed on dynamic visual acuity (DVA) at near and far viewing distances. Ten healthy participants were recruited in 3 groups; young: 20-33 years, Older1: 65-74 years, Older2: 75-85 years. The binocular DVA was measured while walking on a treadmill at 0.75 and 1.5 m/s speeds. The optotype display was placed at 0.5 m for NearDVA and at 3.0 m for FarDVA. On randomly selected trials, HTcoupling was achieved by using a collar. A mix-factor ANOVA (age-group x HTcoupling x speed) was performed separately for the Near and FarDVA. NearDVA declined with HTcoupling (p=0.021). Additionally, NearDVA worsened at the faster speed (p< 0.001). At 1.5 m/s speed the differences between Young and Older2 groups were significant (p=0.012) and those between Older1 and Older2 were marginal (p=0.085). FarDVA declined at the faster speed (p< 0.001) with no effect of HTcoupling or age-group. NearDVA is more sensitive to normal aging process. These age-related deficits become more apparent at higher walking speeds. Effect of HTcoupling on NearDVA suggests a possible additive effect of insufficient dampening of the vertical movement of the overall head-trunk complex and inability of the linear vestibulo-ocular reflex to compensate for the consequent high discrepancy.

  3. Flow Characteristics at the Pump-Turbine Interface of a Torque Converter at Extreme Speed Ratios

    Directory of Open Access Journals (Sweden)

    A. Habsieger

    2003-01-01

    Full Text Available The average velocity field at the pump–turbine interface in a scaled version of a truck torque converter was studied. Seven different turbine-to-pump rotational-speed ratios were examined, ranging from near stall (0.065 to overspeed (1.050 so as to determine the effect of the speed ratio on the flow field and on the mass flow rate. Laser velocimetry was used to measure the flow velocity through the pump's exit and the turbine's inlet plane. At the pump's exit, as the speed ratio increases, the high velocities move to the pressure-shell corner and then to both the core-suction and the pressureshell corners. Concentrated velocity gradients are largest at the lowest speed ratio, but areas of velocity gradients are largest near the coupling point. Near the coupling point, the flow field is most nonuniform, which yields a highly periodic flow into the turbine inlet. Above the coupling point, the high velocity remains in the pressure-shell corner but separation is seen to develop at the highest speed ratio. At the turbine's inlet, reverse flow is seen at low speed ratios and is an indicator of flow leakage through the core. Velocity gradients are very large at low speed ratios. As the speed ratio increases to the coupling point, the high velocities remain on the shell side. Above the coupling point, the high-velocity flow migrates from the shell side to the core side. The mass flow rate decreases significantly and nonlinearly with the increase of the speed ratio, but for speed ratios greater than 1.000, the negative slope decreases.

  4. Stability Analysis of High-Speed Boundary-Layer Flow with Gas Injection

    Science.gov (United States)

    2014-06-01

    boundary-layer flow with gas injection 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER Alexander V. Fedorov ...distribution unlimited Stability analysis of high-speed boundary-layer flow with gas injection Alexander V. Fedorov * and Vitaly G. Soudakov...Laminar Flow, AGARD Report Number 709, 1984. 2. Fedorov , A., “Transition and Stability of High-Speed Boundary Layers,” Annu. Rev. Fluid Mech., Vol

  5. High-Speed Thermal Characterization of Cryogenic Flows Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Luna proposes to continue development on a high-speed fiber optic sensor and readout system for cryogenic temperature measurements in liquid oxygen (LOX) and liquid...

  6. Rehabilitation that incorporates virtual reality is more effective than standard rehabilitation for improving walking speed, balance and mobility after stroke: a systematic review

    OpenAIRE

    Corbetta, Davide; Imeri, Federico; Gatti, Roberto

    2015-01-01

    Question: In people after stroke, does virtual reality based rehabilitation (VRBR) improve walking speed, balance and mobility more than the same duration of standard rehabilitation? In people after stroke, does adding extra VRBR to standard rehabilitation improve the effects on gait, balance and mobility? Design: Systematic review with meta-analysis of randomised trials. Participants: Adults with a clinical diagnosis of stroke. Intervention: Eligible trials had to include one these compariso...

  7. Comparison between Mother, ActiGraph wGT3X-BT, and a hand tally for measuring steps at various walking speeds under controlled conditions

    Directory of Open Access Journals (Sweden)

    Henrik Riel

    2016-12-01

    Full Text Available Introduction Walking is endorsed as health enhancing and is the most common type of physical activity among older adults. Accelerometers are superior to self-reports when measuring steps, however, if they are to be used by clinicians the validity is of great importance. The aim of this study was to investigate the criterion validity of Mother and ActiGraph wGT3X-BT in measuring steps by comparing the devices to a hand tally under controlled conditions in healthy participants. Methods Thirty healthy participants were fitted with a belt containing the sensor of Mother (Motion Cookie and ActiGraph. Participants walked on a treadmill for two minutes at each of the following speeds; 3.2, 4.8, and 6.4 km/h. The treadmill walking was video recorded and actual steps were subsequently determined by using a hand tally. Wilcoxon’s signed ranks test was used to determine whether Mother and ActiGraph measured an identical number of steps compared to the hand tally. Intraclass correlation coefficients were calculated to determine the relationship and Root Mean Square error was calculated to investigate the average error between the devices and the hand tally. Percent differences (PD were calculated for between-instrument agreement (Mother vs. the hand tally and ActiGraph vs. the hand tally and PDs below 3% were interpreted as acceptable and clinically irrelevant. Results Mother and ActiGraph under-counted steps significantly compared to the hand tally at all walking speeds (p < 0.001. Mother had a median of total differences of 9.5 steps (IQR = 10 and ActiGraph 59 steps (IQR = 77. Mother had smaller PDs at all speeds especially at 3.2 km/h (2.5% compared to 26.7%. Mother showed excellent ICC values ≥0.88 (0.51–0.96 at all speeds whilst ActiGraph had poor and fair to good ICC values ranging from 0.03 (−0.09–0.21 at a speed of 3.2 km/h to 0.64 (0.16–0.84 at a speed of 6.4 km/h. Conclusion Mother provides valid measures of steps at walking speeds

  8. Effect of Transcutaneous Electrical Nerve Stimulation on Plantar Flexor Muscle Spasticity and Walking Speed in Stroke Patients.

    Science.gov (United States)

    Laddha, Darshan; Ganesh, G Shankar; Pattnaik, Monalisa; Mohanty, Patitapaban; Mishra, Chittaranjan

    2016-12-01

    Spasticity is a major disabling symptom in patients post stroke. Although studies have demonstrated that transcutaneous electrical nerve stimulation (TENS) can reduce spasticity, the duration of single session TENS is a subject of debate. The purpose of this study was to determine the sustainability of the effects of TENS applied over common peroneal nerve in the reduction of ankle plantar-flexor spasticity and improving gait speed in patients post stroke. Thirty patients (11 women and 19 men) (mean age of 46.46 years) were randomly assigned to group 1 (task oriented exercises), group 2 (TENS for 30 min and task oriented exercises) and group 3 (TENS for 60 min and task oriented exercises) for a period of five sessions per week for 6 weeks. All patients were assessed for ankle plantar-flexor spasticity, passive ankle dorsi-flexion range of motion, clonus and timed up and go test at the time of recruitment to study, at 3 and 6 weeks of therapeutic intervention. The overall results of the study suggest that there was a decrease in ankle plantar flexor spasticity, ankle clonus and timed up and go score in all the groups. A greater reduction of spasticity was seen in TENS groups (groups 2 and 3) when compared to control. No significant improvement was found in timed up and go test (TUG) scores between groups. Both 30 min and 60 min of application of TENS are effective in reducing spasticity of ankle plantar flexors, improving walking ability and increase the effectiveness of task related training. Based on the effect size, we would recommend a longer duration application for the reduction of spasticity. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

  9. Multicomponent Exercise Improves Hemodynamic Parameters and Mobility, but Not Maximal Walking Speed, Transfer Capacity, and Executive Function of Older Type II Diabetic Patients

    Directory of Open Access Journals (Sweden)

    Hélio José Coelho Junior

    2018-01-01

    Full Text Available The present study aimed to investigate the effects of a 6-month multicomponent exercise program (MCEP on functional, cognitive, and hemodynamic parameters of older Type 2 diabetes mellitus (T2DM patients. Moreover, additional analyses were performed to evaluate if T2DM patients present impaired adaptability in response to physical exercise when compared to nondiabetic volunteers. A total of 72 T2DM patients and 72 age-matched healthy volunteers (CG were recruited and submitted to functional, cognitive, and hemodynamic evaluations before and after six months of a MCEP. The program of exercise was performed twice a week at moderate intensity. Results indicate T2DM and nondiabetic patients present an increase in mobility (i.e., usual walking speed after the MCEP. However, improvements in maximal walking speed, transfer capacity, and executive function were only observed in the CG. On the other hand, only T2DM group reveals a marked decline in blood pressure. In conclusion, data of the current study indicate that a 6-month MCEP improves mobility and reduce blood pressure in T2DM patients. However, maximal walking speed, transfer capacity, and executive function were only improved in CG, indicating that T2DM may present impaired adaptability in response to physical stimulus.

  10. Effects of geometry and tip speed ratio on the HAWT blade's root flow

    NARCIS (Netherlands)

    Akay, B.; Micallef, D.; Simao Ferreira, C.J.; Van Bussel, G.J.W.

    2014-01-01

    In this study, the effect of the parameters playing a role in the root flow behavior of HAWT are only partly understood. To better reveal the root flow properties, this study presents the progression of HAWT blade root flow at two different blade geometries and at two different tip speed ratios. The

  11. PDF methods for combustion in high-speed turbulent flows

    Science.gov (United States)

    Pope, Stephen B.

    1995-01-01

    This report describes the research performed during the second year of this three-year project. The ultimate objective of the project is extend the applicability of probability density function (pdf) methods from incompressible to compressible turbulent reactive flows. As described in subsequent sections, progress has been made on: (1) formulation and modelling of pdf equations for compressible turbulence, in both homogeneous and inhomogeneous inert flows; and (2) implementation of the compressible model in various flow configurations, namely decaying isotropic turbulence, homogeneous shear flow and plane mixing layer.

  12. A new approach to speed-flow curves

    DEFF Research Database (Denmark)

    Fosgerau, Mogens; Hjorth, Katrine; Jensen, Thomas Christian

    We develop a simple model of travel time as a function of travel demand, using loop detector data of travel times and traffic flows on a Danish motorway. Our goal is a model that avoids the potential endogeneity problems related to modelling travel time as a function of observed traffic flow. Ins...

  13. Technical report on prototype intelligent network flow optimization (INFLO) dynamic speed harmonization and queue warning.

    Science.gov (United States)

    2015-06-01

    This Technical Report on Prototype Intelligent Network Flow Optimization (INFLO) Dynamic Speed Harmonization and : Queue Warning is the final report for the project. It describes the prototyping, acceptance testing and small-scale : demonstration of ...

  14. Turbulent Scalar Transport Model Validation for High Speed Propulsive Flows Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This effort entails the validation of a RANS turbulent scalar transport model (SFM) for high speed propulsive flows, using new experimental data sets and...

  15. [Influence of manipulation on arteria vertebralis morphology and blood flow speed of cervical vertigo].

    Science.gov (United States)

    Fan, Bing-Hua; Wang, Peng; Xu, Quan-Zhen

    2009-05-01

    To discuss the influence of manipulation on cervical vertigo arteria vertebralis morphology and blood flow speed. Forty-five patients with cervical vertigo included 27 males and 18 females with an average age of 41.6 years old ranging from 25 to 60. The course of disease was from 2 weeks to 5 years. TCD were applied to test arteria vertebralis blood flow speed and 3D-CTA applied to inspect arteria vertebralis morphology as the observation targets. According to the morphology change different stage localization, the 3-step manipulation were adopt to observe the arteria vertebralis blood flow speed and the morphology influence. After cervical manipulation, the scoring of vertigo symptoms were improved remarkable (Pmanipulation exceptionally has the bidirectional control action to arteria vertebralis morphology change and blood flow speed in the cervical vertigo, and can cause the partial blood tubular-shaped condition to have the reversal changed.

  16. Flow-Visualization Techniques Used at High Speed by Configuration Aerodynamics Wind-Tunnel-Test Team

    Science.gov (United States)

    Lamar, John E. (Editor)

    2001-01-01

    This paper summarizes a variety of optically based flow-visualization techniques used for high-speed research by the Configuration Aerodynamics Wind-Tunnel Test Team of the High-Speed Research Program during its tenure. The work of other national experts is included for completeness. Details of each technique with applications and status in various national wind tunnels are given.

  17. Online Speed Scaling Based on Active Job Count to Minimize Flow Plus Energy

    DEFF Research Database (Denmark)

    Lam, Tak-Wah; Lee, Lap Kei; To, Isaac K. K.

    2013-01-01

    This paper is concerned with online scheduling algorithms that aim at minimizing the total flow time plus energy usage. The results are divided into two parts. First, we consider the well-studied “simple” speed scaling model and show how to analyze a speed scaling algorithm (called AJC) that chan...

  18. Assessment of modern methods in numerical simulations of high speed flows

    Science.gov (United States)

    Pindera, M. Z.; Yang, H. Q.; Przekwas, A. J.; Tucker, K.

    1992-01-01

    Results of extensive studies on CFD algorithms for 2D inviscid flows in Cartesian and body fitted coordinates geometries are reviewed. These studies represent part of an ongoing investigation of combustion instabilities involving the interactions of high-speed nonlinear acoustic waves. Four numerical methods for the treatment of high speed flows are compared, namely, Roe-Sweby TVD, Yee symmetric TVD; Osher-Chakravarthy TVD; and the Colella's multi-dimensional Godunov method.

  19. Fundamental Structure of High-Speed Reacting Flows: Supersonic Combustion and Detonation

    Science.gov (United States)

    2016-04-30

    liquid rocket engines, studied the concept of rotating detonation rocket engine in both gaseous and two-phase propellants . Recently, there have been...AFRL-AFOSR-VA-TR-2016-0195 Fundamental Structure of High-Speed Reacting Flows: Supersonic Combustion and Detonation Kenneth Yu MARYLAND UNIV COLLEGE...MARCH 2016 4. TITLE AND SUBTITLE FUNDAMENTAL STRUCTURE OF HIGH-SPEED REACTING FLOWS: SUPERSONIC COMBUSTION AND DETONATION 5a. CONTRACT NUMBER

  20. Children's Brain Responses to Optic Flow Vary by Pattern Type and Motion Speed.

    Directory of Open Access Journals (Sweden)

    Rick O Gilmore

    Full Text Available Structured patterns of global visual motion called optic flow provide crucial information about an observer's speed and direction of self-motion and about the geometry of the environment. Brain and behavioral responses to optic flow undergo considerable postnatal maturation, but relatively little brain imaging evidence describes the time course of development in motion processing systems in early to middle childhood, a time when psychophysical data suggest that there are changes in sensitivity. To fill this gap, electroencephalographic (EEG responses were recorded in 4- to 8-year-old children who viewed three time-varying optic flow patterns (translation, rotation, and radial expansion/contraction at three different speeds (2, 4, and 8 deg/s. Modulations of global motion coherence evoked coherent EEG responses at the first harmonic that differed by flow pattern and responses at the third harmonic and dot update rate that varied by speed. Pattern-related responses clustered over right lateral channels while speed-related responses clustered over midline channels. Both children and adults show widespread responses to modulations of motion coherence at the second harmonic that are not selective for pattern or speed. The results suggest that the developing brain segregates the processing of optic flow pattern from speed and that an adult-like pattern of neural responses to optic flow has begun to emerge by early to middle childhood.

  1. Perceived enjoyment, concentration, intention, and speed violation behavior: Using flow theory and theory of planned behavior.

    Science.gov (United States)

    Atombo, Charles; Wu, Chaozhong; Zhang, Hui; Wemegah, Tina D

    2017-10-03

    Road accidents are an important public health concern, and speeding is a major contributor. Although flow theory (FLT) is a valid model for understanding behavior, currently the nature of the roles and interplay of FLT constructs within the theory of planned behavior (TPB) framework when attempting to explain the determinants of motivations for intention to speed and speeding behavior of car drivers is not yet known. The study aims to synthesize TPB and FLT in explaining drivers of advanced vehicles intentions to speed and speed violation behaviors and evaluate factors that are critical for explaining intention and behavior. The hypothesized model was validated using a sample collected from 354 fully licensed drivers of advanced vehicles, involving 278 males and 76 females on 2 occasions separated by a 3-month interval. During the first of the 2 occasions, participants completed questionnaire measures of TPB and FLT variables. Three months later, participants' speed violation behaviors were assessed. The study observed a significant positive relationship between the constructs. The proposed model accounted for 51 and 45% of the variance in intention to speed and speed violation behavior, respectively. The independent predictors of intention were enjoyment, attitude, and subjective norm. The independent predictors of speed violation behavior were enjoyment, concentration, intention, and perceived behavioral control. The findings suggest that safety interventions for preventing speed violation behaviors should be aimed at underlying beliefs influencing the speeding behaviors of drivers of advanced vehicles. Furthermore, perceived enjoyment is of equal importance to driver's intention, influencing speed violation behavior.

  2. assessment of traffic flow on enugu highways using speed density

    African Journals Online (AJOL)

    HOD

    effectively if traffic behaviours under all conditions are modeled accurately [2]. Traffic flow in engineering is the study of interaction between vehicles, commuters and infrastructure. (including the highways, signage and traffic control devices) with the aim of understanding and developing an optimal road network with efficient ...

  3. Study on transient hydrodynamic performance and cavitation characteristic of high-speed mixed-flow pump

    Science.gov (United States)

    Chen, T.; Sun, Y. B.; Liu, Y. L.; Wu, D. Z.; Wang, L. Q.

    2013-12-01

    In order to analyse the hydrodynamic performance and cavitation characteristic of a high-speed mixed-flow pump during transient operations, experimental studies were carried out. The transient hydrodynamic performance and cavitation characteristics of the mixed-flow pump with guide vane during start-up operation processes were tested on the pump performance test-bed. Performance tests of the pump were carried out under various inlet pressures and speed-changing operations. The real-time instantaneous external characteristics such as rotational speed, hydraulic head, flow rate, suction pressure and discharge pressure of the pump were measured. Based on the experimental results, the effect of fluid acceleration on the hydrodynamic performances and cavitation characteristics of the mixed-flow pump were analysed and evaluated.

  4. Local scattering property scales flow speed estimation in laser speckle contrast imaging

    Science.gov (United States)

    Miao, Peng; Chao, Zhen; Feng, Shihan; Yu, Hang; Ji, Yuanyuan; Li, Nan; Thakor, Nitish V.

    2015-07-01

    Laser speckle contrast imaging (LSCI) has been widely used in in vivo blood flow imaging. However, the effect of local scattering property (scattering coefficient µ s ) on blood flow speed estimation has not been well investigated. In this study, such an effect was quantified and involved in relation between speckle autocorrelation time τ c and flow speed v based on simulation flow experiments. For in vivo blood flow imaging, an improved estimation strategy was developed to eliminate the estimation bias due to the inhomogeneous distribution of the scattering property. Compared to traditional LSCI, a new estimation method significantly suppressed the imaging noise and improves the imaging contrast of vasculatures. Furthermore, the new method successfully captured the blood flow changes and vascular constriction patterns in rats’ cerebral cortex from normothermia to mild and moderate hypothermia.

  5. Comparison of the Mini-Balance Evaluations Systems Test with the Berg Balance Scale in relationship to walking speed and motor recovery post stroke.

    Science.gov (United States)

    Madhavan, Sangeetha; Bishnoi, Alka

    2017-12-01

    The Mini-BESTest is a recently developed balance assessment tool that incorporates challenging dynamic balance tasks. Few studies have compared the psychometric properties of the Mini-BESTest to the commonly used Berg Balance Scale (BBS). However, the utility of these scales in relationship to post stroke walking speeds has not been explored. The purpose of this study was to compare the sensitivity and specificity of the Mini-BESTest and BBS to evaluate walking speeds in individuals with stroke. A retrospective exploratory design. Forty-one individuals with chronic stroke were evaluated with the Mini-BESTest, BBS, and 10-meter self-selected walk test (10MWT). Based on their self-selected gait speeds (below or above 0.8 m/s), participants were classified as slow and fast walkers. Significant linear correlations were observed between the Mini-BESTest vs. BBS (r = 0.72, p ≤ 0.001), Mini-BESTest vs. 10MWT (r = 0.58, p ≤ 0.001), and BBS vs. 10MWT (r = 0.30, p = 0.05). Independent t-tests comparing the balance scores for the slow and fast walkers revealed significant group differences for the Mini-BESTest (p = 0.003), but not for the BBS (p = 0.09). The Mini-BESTest demonstrated higher sensitivity (93%) and specificity (64%) compared to the BBS (sensitivity 81%, specificity 56%) for discriminating participants into slow and fast walkers. The Mini-BESTest has a greater discriminative ability than the BBS to categorize individuals with stroke into slow and fast walkers.

  6. Honeybees' speed depends on dorsal as well as lateral, ventral and frontal optic flows.

    Directory of Open Access Journals (Sweden)

    Geoffrey Portelli

    Full Text Available Flying insects use the optic flow to navigate safely in unfamiliar environments, especially by adjusting their speed and their clearance from surrounding objects. It has not yet been established, however, which specific parts of the optical flow field insects use to control their speed. With a view to answering this question, freely flying honeybees were trained to fly along a specially designed tunnel including two successive tapering parts: the first part was tapered in the vertical plane and the second one, in the horizontal plane. The honeybees were found to adjust their speed on the basis of the optic flow they perceived not only in the lateral and ventral parts of their visual field, but also in the dorsal part. More specifically, the honeybees' speed varied monotonically, depending on the minimum cross-section of the tunnel, regardless of whether the narrowing occurred in the horizontal or vertical plane. The honeybees' speed decreased or increased whenever the minimum cross-section decreased or increased. In other words, the larger sum of the two opposite optic flows in the horizontal and vertical planes was kept practically constant thanks to the speed control performed by the honeybees upon encountering a narrowing of the tunnel. The previously described ALIS ("AutopiLot using an Insect-based vision System" model nicely matches the present behavioral findings. The ALIS model is based on a feedback control scheme that explains how honeybees may keep their speed proportional to the minimum local cross-section of a tunnel, based solely on optic flow processing, without any need for speedometers or rangefinders. The present behavioral findings suggest how flying insects may succeed in adjusting their speed in their complex foraging environments, while at the same time adjusting their distance not only from lateral and ventral objects but also from those located in their dorsal visual field.

  7. Reconstructing meridional flow speed variation from synthetic magnetic observations by using EnKF data assimilation

    Science.gov (United States)

    Dikpati, M.; Anderson, J. L.

    2014-12-01

    Meridional circulation plays an important role ingoverning cycle period and memory of solar dynamo models.Accurate knowledge of time variation in flow speed andprofile is crucial for estimating a solar cycle's amplitude,timing, rise and fall patterns and north-south asymmetry,which are ultimately responsible for causing space climatevariation. However, no consensus has been reached yet aboutthe Sun's meridional circulation pattern from observationsand theories. Therefore, it is necessary to implement dataassimilation approaches, in addition to observations andmodels, to investigate solar interior flow properties. Wepresent here first results from a sequential dataassimilation into a Babcock-Leighton flux-transport solardynamo model to reconstruct time-varying meridionalcirculation speed. We perform several observation systemsimulation experiments (OSSE) by implementing an EnsembleKalman Filter (EnKF) in the framework of the Data AssimilationResearch Testbed (DART). We find that the best reconstructionof time-variation in meridional flow-speed can be obtainedwhen ten or more observations are used with an updatingtime of 15 days and a 10% observational error. Increasingensemble-size from 16 to 160 improves reconstruction, buteven larger ensembles do not lead to further improvement.Comparison of reconstructed flow-speed with "true-state"reveals that EnKF data assimilation is very powerful forreconstructing meridional flow-speeds and suggests that it can be implemented for reconstructing spatio-temporal patterns of meridional circulation. This work is partially supported by NASA's LWS grant NNX08AQ34G. NCAR is sponsoredby the NSF.

  8. Numerical Simulations of High-Speed Chemically Reacting Flow

    Science.gov (United States)

    Ton, V. T.; Karagozian, A. R.; Marble, F. E.; Osher, S. J.; Engquist, B. E.

    1994-01-01

    The essentially nonoscillatory (ENO) shock-capturing scheme for the solution of hyperbolic equations is extended to solve a system of coupled conservation equations governing two-dimensional, time-dependent, compressible chemically reacting flow with full chemistry. The thermodynamic properties of the mixture are modeled accurately, and stiff kinetic terms are separated from the fluid motion by a fractional step algorithm. The methodology is used to study the concept of shock-induced mixing and combustion, a process by which the interaction of a shock wave with a jet of low-density hydrogen fuel enhances mixing through streamwise vorticity generation. Test cases with and without chemical reaction are explored here. Our results indicate that, in the temperature range examined, vorticity generation as well as the distribution of atomic species do not change significantly with the introduction of a chemical reaction and subsequent heat release. The actual diffusion of hydrogen is also relatively unaffected by the reaction process. This suggests that the fluid mechanics of this problem may be successfully decoupled from the combustion processes, and that computation of the mixing problem (without combustion chemistry) can elucidate much of the important physical features of the flow.

  9. Influence of blast furnace gas flow speed on dust deposition characteristics in butterfly valve region

    Directory of Open Access Journals (Sweden)

    Lixin WANG

    2016-02-01

    Full Text Available The blast furnace gas contains plenty of dust, which deposits easily on the bottom of seat sealing surface of the tri-eccentric butterfly valve in the pipeline, causing stuck and damage to the valve plate, thereby affects the production of the blast furnace and brings great economic loss. To derive the influence mechanism of effects of the blast furnace gas flow speed within the pipeline on the dust deposition laws in the butterfly valve region, a 3D model of the butterfly valve and its regional flow field is built with Pro/E software. Based on FLUENT module of ANSYS Workbench, along with standard k-ε turbulence model and DPM model, simulation analysis of moving trajectories of dust particles in butterfly valve region under 3 blast furnace gas flow speeds is conducted. Results show that the deposition mass of dust particles decreases firstly, then increases with the enlargement of valve plate opening angle under the blast furnace gas flow speed of 8 m/s, while decreases with the enlargement of valve plate opening under the blast furnace gas flow speeds of 12 m/s and 16 m/s. In the case of the valve plate opening angle of 15°, the deposition rate of dust particles increases with the growing of blast furnace gas flow speed, while decreases with the growing of blast furnace gas flow speed under the cases of valve plate opening angle of 45° and 75°. The research results provide a theoretical reference for the development of automatic dust removal system in the butterfly valve region of the blast furnace gas pipeline.

  10. Walking speed, rather than Expanded Disability Status Scale, relates to long-term patient-reported impact in progressive MS

    NARCIS (Netherlands)

    Bosma, L.V.A.E.; Kragt, J.J.; Polman, C.H.; Uitdehaag, B.M.J.

    2013-01-01

    Objective: To study the relationships between 1-2 year changes in well-known physician-rated measurements (Expanded Disability Status Scale (EDSS), Timed 25-Foot Walk (T25FW), 9-Hole Peg Test (9HPT)) and the long-term (= 5 years) outcome in patient-reported outcome (PRO) measures (Multiple Sclerosis

  11. Towards a better understanding of foot and ankle kinematics in rheumatoid arthritis: the effects of walking speed and structural impairments

    NARCIS (Netherlands)

    Dubbeldam, Rosemary; Dubbeldam, Rosemary

    2012-01-01

    From an early stage of the disease 40% to 60% of the Rheumatoid arthritis (RA) patients suffer from walking impairments such as pain, diminished mobility and problems with daily activities. With the recent development of optical recording technologies and detailed foot and ankle computer models,

  12. Towards a better understanding of foot and ankle kinematics in rheumtoid arthritis, the effects of walking speed and structural impairments

    NARCIS (Netherlands)

    Dubbeldam, R.

    2012-01-01

    From an early stage of the disease 40% to 60% of the Rheumatoid arthritis (RA) patients suffer from walking impairments such as pain, diminished mobility and problems with daily activities. With the recent development of optical recording technologies and detailed foot and ankle computer models,

  13. Distributed flow sensing for closed-loop speed control of a flexible fish robot.

    Science.gov (United States)

    Zhang, Feitian; Lagor, Francis D; Yeo, Derrick; Washington, Patrick; Paley, Derek A

    2015-10-23

    Flexibility plays an important role in fish behavior by enabling high maneuverability for predator avoidance and swimming in turbulent flow. This paper presents a novel flexible fish robot equipped with distributed pressure sensors for flow sensing. The body of the robot is molded from soft, hyperelastic material, which provides flexibility. Its Joukowski-foil shape is conducive to modeling the fluid analytically. A quasi-steady potential-flow model is adopted for real-time flow estimation, whereas a discrete-time vortex-shedding flow model is used for higher-fidelity simulation. The dynamics for the flexible fish robot yield a reduced model for one-dimensional swimming. A recursive Bayesian filter assimilates pressure measurements to estimate flow speed, angle of attack, and foil camber. The closed-loop speed-control strategy combines an inverse-mapping feedforward controller based on an average model derived for periodic actuation of angle-of-attack and a proportional-integral feedback controller utilizing the estimated flow information. Simulation and experimental results are presented to show the effectiveness of the estimation and control strategy. The paper provides a systematic approach to distributed flow sensing for closed-loop speed control of a flexible fish robot by regulating the flapping amplitude.

  14. Contribution of Step Length to Increase Walking and Turning Speed as a Marker of Parkinson's Disease Progression.

    Directory of Open Access Journals (Sweden)

    Nicolas Bayle

    Full Text Available When increasing ambulation speed in Parkinson's disease, step cadence increases more than stride length, indicating movement scaling difficulties that affect step generation in particular. We investigated whether step length variation when increasing ambulation speed was related to disease progression. Patients with Parkinson's disease (N = 39 and controls (N = 152 performed two timed ambulation tasks: at a 'free' (self-selected pace and then at 'maximal' speed. The total number of steps (including during turns and time to complete the task were clinically measured. The relative contribution of step length and cadence to increased ambulation speed was determined using two methods: the ratios of change in step length or in cadence to the change in ambulation speed, and the step length index. While the relative contribution of step length and cadence to increased ambulation speed was independent of age in both control and patient groups, in Parkinson's disease there was a negative correlation between time from diagnosis and the ratio of change in step length to change in ambulation speed (R = 0.54; p = 0.0004 and the step length index (R = 0.56, p = 0.0002. In parallel, there was a positive correlation between time since diagnosis and the ratio of change in cadence to change in ambulation speed (R = 0.57; p = 0.0002. The relative contribution of step length and cadence to increased ambulation speed is age invariant but a marker of Parkinson's disease advancement, and can be easily determined in the clinical setting.

  15. Skin friction measurements in high temperature high speed flows

    Science.gov (United States)

    Schetz, J. A.; Diller, Thomas E.; Wicks, A. L.

    1992-01-01

    An experimental investigation was conducted to measure skin friction along the chamber walls of supersonic combustors. A direct force measurement device was used to simultaneously measure an axial and transverse component of the small tangential shear force passing over a non-intrusive floating element. The floating head is mounted to a stiff cantilever beam arrangement with deflection due to the flow on the order of 0.00254 mm (0.0001 in.). This allowed the instrument to be a non-nulling type. A second gauge was designed with active cooling of the floating sensor head to eliminate non-uniform temperature effects between the sensor head and the surrounding wall. Samples of measurements made in combustor test facilities at NASA Langley Research Center and at the General Applied Science Laboratory (GASL) are presented. Skin friction coefficients between 0.001 - 0.005 were measured dependent on the facility and measurement location. Analysis of the measurement uncertainties indicate an accuracy to within +/- 10-15 percent of the streamwise component.

  16. Flow visualization of bubble behavior under two-phase natural circulation flow conditions using high speed digital camera

    Energy Technology Data Exchange (ETDEWEB)

    Lemos, Wanderley F.; Su, Jian, E-mail: wlemos@con.ufrj.br, E-mail: sujian@lasme.coppe.ufrj.br [Coordenacao dos Programas de Pos-Graduacao em Engenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil). Programa de Engenharia Nuclear; Faccini, Jose L.H., E-mail: faccini@ien.gov.br [Instituto de Engenharia Nuclear (IEN/CNEN-RJ), Rio de Janeiro, RJ (Brazil). Lab. de Termo-Hidraulica Experimental

    2013-07-01

    The The present work aims at identifying flow patterns and measuring interfacial parameters in two-phase natural circulation by using visualization technique with high-speed digital camera. The experiments were conducted in the Natural Circulation Circuit (CCN), installed at Nuclear Engineering Institute/CNEN. The thermo-hydraulic circuit comprises heater, heat exchanger, expansion tank, the pressure relief valve and pipes to interconnect the components. A glass tube is installed at the midpoint of the riser connected to the heater outlet. The natural circulation circuit is complemented by acquisition system of values of temperatures, flow and graphic interface. The instrumentation has thermocouples, volumetric flow meter, rotameter and high-speed digital camera. The experimental study is performed through analysis of information from measurements of temperatures at strategic points along the hydraulic circuit, besides natural circulation flow rates. The comparisons between analytical and experimental values are validated by viewing, recording and processing of the images for the flows patterns. Variables involved in the process of identification of flow regimes, dimensionless parameters, the phase velocity of the flow, initial boiling point, the phenomenon of 'flashing' pre-slug flow type were obtained experimentally. (author)

  17. Generating pulsatility by pump speed modulation with continuous-flow total artificial heart in awake calves.

    Science.gov (United States)

    Fukamachi, Kiyotaka; Karimov, Jamshid H; Sunagawa, Gengo; Horvath, David J; Byram, Nicole; Kuban, Barry D; Dessoffy, Raymond; Sale, Shiva; Golding, Leonard A R; Moazami, Nader

    2017-12-01

    The purpose of this study was to evaluate the effects of sinusoidal pump speed modulation of the Cleveland Clinic continuous-flow total artificial heart (CFTAH) on hemodynamics and pump flow in an awake chronic calf model. The sinusoidal pump speed modulations, performed on the day of elective sacrifice, were set at ±15 and ± 25% of mean pump speed at 80 bpm in four awake calves with a CFTAH. The systemic and pulmonary arterial pulse pressures increased to 12.0 and 12.3 mmHg (±15% modulation) and to 15.9 and 15.7 mmHg (±25% modulation), respectively. The pulsatility index and surplus hemodynamic energy significantly increased, respectively, to 1.05 and 1346 ergs/cm at ±15% speed modulation and to 1.51 and 3381 ergs/cm at ±25% speed modulation. This study showed that it is feasible to generate pressure pulsatility with pump speed modulation; the platform is suitable for evaluating the physiologic impact of pulsatility and allows determination of the best speed modulations in terms of magnitude, frequency, and profiles.

  18. Optimal spectral tracking - with application to speed dependent neural modulation of tibialis anterior during human treadmill walking

    DEFF Research Database (Denmark)

    Brittain, John-Stuart; Catton, Celia; Conway, Bernard A.

    2009-01-01

    include speed-modulated components at 7-12Hz (early swing) and 15-20Hz (pre-stance). Speed invariant components were identified at 8-15 and 15-20Hz during early and late swing, in agreement with previous studies. Modification to the method permits a sub-optimal alternative, encouraging the exploration...

  19. Positivity-preserving space-time CE/SE scheme for high speed flows

    KAUST Repository

    Shen, Hua

    2017-03-02

    We develop a space-time conservation element and solution element (CE/SE) scheme using a simple slope limiter to preserve the positivity of the density and pressure in computations of inviscid and viscous high-speed flows. In general, the limiter works with all existing CE/SE schemes. Here, we test the limiter on a central Courant number insensitive (CNI) CE/SE scheme implemented on hybrid unstructured meshes. Numerical examples show that the proposed limiter preserves the positivity of the density and pressure without disrupting the conservation law; it also improves robustness without losing accuracy in solving high-speed flows.

  20. Effects of Passive Porosity on Interacting Vortex Flows at Supersonic Speeds

    Science.gov (United States)

    Erickson, Gary E.

    2000-01-01

    A wind tunnel experiment was conducted in the NASA Langley Research Center (LaRC) Unitary Plan Wind Tunnel (UPW7) to determine the effects of passive surface porosity on vortex flow interactions about a general research fighter configuration at supersonic speeds. Optical flow measurement and flow visualization techniques were used and included pressure-sensitive paint (PSP), schlieren, and laser vapor screen (LVS). These techniques were combined with force and moment and conventional electronically-scanned pressure (ESP) measurements to quantify and to visualize the effects flow-through porosity applied to a wing leading-edge extension (LEX) mounted to a 65 deg cropped delta wing model.

  1. A Passenger Flow Risk Forecasting Algorithm for High-Speed Railway Transport Hub Based on Surveillance Sensor Networks

    Directory of Open Access Journals (Sweden)

    Zhengyu Xie

    2016-01-01

    Full Text Available Passenger flow risk forecasting is a vital task for safety management in high-speed railway transport hub. In this paper, we considered the passenger flow risk forecasting problem in high-speed railway transport hub. Based on the surveillance sensor networks, a passenger flow risk forecasting algorithm was developed based on spatial correlation. Computational results showed that the proposed forecasting approach was effective and significant for the high-speed railway transport hub.

  2. The influence of air flow speed on fire propagation in object

    Directory of Open Access Journals (Sweden)

    Jevtić Radoje

    2015-01-01

    Full Text Available Fire presents the process of the uncontrolled combustion that makes material damage and endangers human lives. It is important to know the factors that fire depends on for success projecting and realization of fire protection systems. One of such factors is different air flow that could be presented as wind, draft and the like. The simulation of different air flow speeds and its influences on fire propagation in object were analyzed in this paper.

  3. A Method of Urban Traffic Flow Speed Estimation Using Sparse Floating Car Data

    OpenAIRE

    WANG Xiaomeng; PENG Ling; CHI Tianhe

    2016-01-01

    The sample spatio-temporalsparsity is one of the major challenges for traffic estimation when using floating car data (FCD).Spatio-temporal characteristics of road traffic flow are analysed and applied to build a naive Bayes-based traffic estimation model which is proposed to estimate the missing traffic state of the roads which are not covered by samples. In the model, the adjacent period traffic flow speed of the target road segment is considered for the representation of the time character...

  4. Wind Speed Response of Sap Flow in Five Subtropical Trees Based on Wind Tunnel Experiments

    OpenAIRE

    Laplace, Sophie; Kume, Tomonori; Chu, Chia-Ren; Komatsu, Hikaru

    2013-01-01

    Aims: We evaluated the responses of tree sap flow to wind speeds in coniferous and broad-leaved plants under steady and unsteady wind conditions. Study Design: We performed sap flow and micro-meteorological measurements on two conifers, Chamaecyparis obtusa var. formosana and Araucaria cunninghamii, and three broadleaved species, Swietenia mahagoni, Michelia formosana and Plumeria acutifolia in a wind tunnel. Place and Duration of Study: Civil Engineering Department, National Central Universi...

  5. Stability Analysis of High-Speed Boundary-Layer Flow with Gas Injection (Briefing Charts)

    Science.gov (United States)

    2014-06-01

    boundary-layer flow with gas injection 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER Alexander V. Fedorov ...Release; Distribution Unlimited Stability analysis of high-speed boundary-layer flow with gas injection Alexander Fedorov and Vitaly Soudakov Moscow...Dispersion relation from WKB analysis*,**: *Guschin, V.R., & Fedorov , A.V., Fluid Dynamics, Vol. 24, No.1, 1989 **Guschin, V.R., & Fedorov , A.V., NASA

  6. Speeding for fun? Exploring the speeding behavior of riders of heavy motorcycles using the theory of planned behavior and psychological flow theory.

    Science.gov (United States)

    Chen, Ching-Fu; Chen, Cheng-Wen

    2011-05-01

    This paper focuses on a special segment of motorcyclists in Taiwan--riders of heavy motorcycles--and investigates their speeding behavior and its affecting factors. It extends the theory of planned behavior (TPB) to explore motorcyclist speeding behavior by including the variables of psychological flow theory. The levels of sensation-seeking and riding experience are also used as grouping variables to investigate group differences from the influences of their affecting factors on speeding behavior. The results reveal that the psychological flow variables have greater predictive power in explaining speeding behavior than the TPB variables, providing useful insights into the unique nature of this group of motorcyclists, who are more prone to engage in speeding. Group differences with regard to both sensation-seeking and rider experience in speeding behavior are highlighted, and the implications of the findings are discussed. Copyright © 2010 Elsevier Ltd. All rights reserved.

  7. The provision of a cane provides greater benefit to community-dwelling people after stroke with a baseline walking speed between 0.4 and 0.8 metres/second: an experimental study.

    Science.gov (United States)

    Nascimento, Lucas R; Ada, Louise; Teixeira-Salmela, Luci F

    2016-12-01

    To investigate the effect of the provision of a cane on walking ability in ambulatory people with chronic stroke. Experimental study. Clinics within the community. Twenty-four people on average 6 years after a stroke, who were not regular users of walking sticks. Participants were categorized as slow (0.8 metres/second) on the basis of their baseline walking ability. Walking with and without a cane. Walking ability was measured using the 10-m Walk Test and reported as speed (metres/second), step length (metres), and cadence (steps/minute). Overall, the provision of a cane produced no significant change in speed (0.05 metres/second, 95% CI -0.01 to 0.11) or cadence (-3 steps/minute; 95% CI -8 to 3), but a small increase in step length (0.04 metres, 95% CI 0.03 to 0.06). For the intermediate walkers, the cane increased speed by 0.18 metres/second (95% CI 0.11 to 0.24), step length by 0.07 metres (95% CI 0.05 to 0.09), but not cadence. The provision of a cane to the intermediate walkers also produced 0.27 metres/second (95% CI 0.18 to 0.36) more increase in speed compared with the fast walkers, and 0.12 metres/second (95% CI 0.03 to 0.21) more increase compared with the slow walkers. The provision of a cane produced most benefit to a subgroup of intermediate walkers in a group of community-dwelling people with chronic stroke whose walking had stabilized, without detriment to quality of walking. Copyright © 2016. Published by Elsevier Ltd.

  8. Material Derivative Measurements in High-Speed Flows by Four-Pulse Tomographic PIV

    NARCIS (Netherlands)

    Lynch, K.; Scarano, F.

    2013-01-01

    A tomographic PIV system is introduced for the instantaneous measurement of the material derivative of velocity (VMD). The system is able to operate with very short temporal separation and is therefore suitable for applications in high-speed flows. The method of operation consists of the imaging of

  9. the factors that affect the free flow speed on an arterial in ilorin, nigeria

    African Journals Online (AJOL)

    Generic factors (weather, environment, vehicles, fixed roadway characteristics, pedestrian and traffic streams) singly or jointly influence the free flow speed. This paper, therefore, presents the ... Adoption of design and analysis of traffic stream in Ilorin and other urban settlements in Nigeria is, therefore, recommended.

  10. the factors that affect the free flow speed on an arterial in ilorin, nigeria

    African Journals Online (AJOL)

    user

    attributes and (c) environment have been reported to influence the values in the American urban traffic streams and highways [3] and[4]. These authors showed from different studies that the percentage reduction due to the environment in the free flow speed are 8, 14, 15 and 17 – 18 respectively for wet pavement, high wind ...

  11. How to identify the speed limiting factor of a TCP flow

    NARCIS (Netherlands)

    Timmer, Mark

    2005-01-01

    This thesis develops a method for identifying the speed limiting factor of a TCP flow. Five factors are considered: the receive window, the send buffer, the network and two kinds of application layer factors. Criteria for recognizing each factor based on TCP header information are put forward. These

  12. Numerical Simulation of 3D Solid-Liquid Turbulent Flow in a Low Specific Speed Centrifugal Pump: Flow Field Analysis

    Directory of Open Access Journals (Sweden)

    Baocheng Shi

    2014-06-01

    Full Text Available For numerically simulating 3D solid-liquid turbulent flow in low specific speed centrifugal pumps, the iteration convergence problem caused by complex internal structure and high rotational speed of pump is always a problem for numeral simulation researchers. To solve this problem, the combination of three measures of dynamic underrelaxation factor adjustment, step method, and rotational velocity control means according to residual curves trends of operating parameters was used to improve the numerical convergence. Numeral simulation of 3D turbulent flow in a low specific speed solid-liquid centrifugal pump was performed, and the results showed that the improved solution strategy is greatly helpful to the numerical convergence. Moreover, the 3D turbulent flow fields in pumps have been simulated for the bottom ash-particles with the volume fraction of 10%, 20%, and 30% at the same particle diameter of 0.1 mm. The two-phase calculation results are compared with those of single-phase clean water flow. The calculated results gave the main region of the abrasion of the impeller and volute casing and improve the hydraulic design of the impeller in order to decrease the abrasion and increase the service life of the pump.

  13. An investigation of laser velocimetry measurements within high speed, complex flows

    Science.gov (United States)

    Maurice, Mark S.

    Laser velocimetry (LV) is a nonintrusive, optical method that measures particle velocities within a flow. Therefore, if LV measurements are to represent the structure of a flowfield, the particles must follow the dynamic motion of the fluid. However, in high speed, complex flows, the lag in particle response to fluid gradients can be substantial. In order to quantify velocity lag bias in high speed, mean velocity measurements, several flowfields are investigated experimentally and computationally. From measurements within the vortical flowfield of a supersonic delta wing at Mach 1.9, and for expansion flows at Mach 5.76, it is found that by coupling a particle equation of motion with the computational flowfield solutions, particle trajectories and velocity lag within complex flows can be predicted. For two primary flow structures, potential vortices and two-dimensional ideal shocks, it is found that relaxation distances can be quantified in terms of three dimensionless parameters. Results for these cases are presented graphically as an aid for test design and data analysis over a wide range of conditions. However, any analysis of velocity lag bias requires knowledge of the particle size distribution, which is often unknown in high speed flows. For a ten degree half-angle wedge at Mach Three, a methodology is presented which determines the mean particle diameter from measurements downstream of the shock, and then examines the remaining LV data throughout the flow. To extend this approach to flows with highly polydispersed particle sizes, an algorithm is developed which extracts the size distribution from the shape of LV velocity histograms. This method is applied to the investigation of a hypersonic inlet at Mach 5.76. Results show that despite the problem of velocity lag, measurements can still be used for computational code validation. In this final case, the developing boundary layer along the inlet ramp is accurately predicted, but the algebraic eddy viscosity

  14. Investigation on Flow-Induced Noise due to Backflow in Low Specific Speed Centrifugal Pumps

    Directory of Open Access Journals (Sweden)

    Qiaorui Si

    2013-01-01

    Full Text Available Flow-induced noise causes disturbances during the operation of centrifugal pumps and also affects their performance. The pumps often work at off-design conditions, mainly at part-load conditions, because of frequent changes in the pump device system. Consequently numerous unstable phenomena occur. In low specific speed centrifugal pumps the main disturbance is the inlet backflow, which is considered as one of the most important factors of flow-induced noise and vibration. In this study, a test rig of the flow-induced noise and vibration of the centrifugal pump was built to collect signals under various operating conditions. The three-dimensional unsteady flow of centrifugal pumps was calculated based on the Reynolds-averaged equations that resemble the shear stress transport (SST k-ω turbulence model. The results show that the blade passing frequency and shaft frequency are dominant in the spectrum of flow-induced noise, whereas the shaft component, amplitude value at shaft frequency, and peak frequencies around the shaft increase with decreasing flow. Through flow field analysis, the inlet backflow of the impeller occurs under 0.7 times the design flow. The pressure pulsation spectrum with backflow conditions validates the flow-induced noise findings. The velocity characteristics of the backflow zone at the inlet pipe were analyzed, and the dynamic characteristics of the backflow eddy during one impeller rotating period were simultaneously obtained by employing the backflow conditions. A flow visualization experiment was performed to confirm the numerical calculations.

  15. Applications of an adaptive unstructured solution algorithm to the analysis of high speed flows

    Science.gov (United States)

    Thareja, R. R.; Prabhu, R. K.; Morgan, K.; Peraire, J.; Peiro, J.

    1990-01-01

    An upwind cell-centered scheme for the solution of steady laminar viscous high-speed flows is implemented on unstructured two-dimensional meshes. The first-order implementation employs Roe's (1981) approximate Riemann solver, and a higher-order extension is produced by using linear reconstruction with limiting. The procedure is applied to the solution of inviscid subsonic flow over an airfoil, inviscid supersonic flow past a cylinder, and viscous hypersonic flow past a double ellipse. A detailed study is then made of a hypersonic laminar viscous flow on a 24-deg compression corner. It is shown that good agreement is achieved with previous predictions using finite-difference and finite-volume schemes. However, these predictions do not agree with experimental observations. With refinement of the structured grid at the leading edge, good agreement with experimental observations for the distributions of wall pressure, heating rate and skin friction is obtained.

  16. On-Chip Enucleation of Bovine Oocytes using Microrobot-Assisted Flow-Speed Control

    Directory of Open Access Journals (Sweden)

    Akihiko Ichikawa

    2013-06-01

    Full Text Available In this study, we developed a microfluidic chip with a magnetically driven microrobot for oocyte enucleation. A microfluidic system was specially designed for enucleation, and the microrobot actively controls the local flow-speed distribution in the microfluidic chip. The microrobot can adjust fluid resistances in a channel and can open or close the channel to control the flow distribution. Analytical modeling was conducted to control the fluid speed distribution using the microrobot, and the model was experimentally validated. The novelties of the developed microfluidic system are as follows: (1 the cutting speed improved significantly owing to the local fluid flow control; (2 the cutting volume of the oocyte can be adjusted so that the oocyte undergoes less damage; and (3 the nucleus can be removed properly using the combination of a microrobot and hydrodynamic forces. Using this device, we achieved a minimally invasive enucleation process. The average enucleation time was 2.5 s and the average removal volume ratio was 20%. The proposed new system has the advantages of better operation speed, greater cutting precision, and potential for repeatable enucleation.

  17. Influence of transcutaneous electrical nerve stimulation on spasticity, balance, and walking speed in stroke patients: A systematic review and meta-analysis.

    Science.gov (United States)

    Lin, Shuqin; Sun, Qi; Wang, Haifeng; Xie, Guomin

    2018-01-10

    To evaluate the influence of transcutaneous electrical nerve stimulation in patients with stroke through a systematic review and meta-analysis. PubMed, Embase, Web of Science, EBSCO, and Cochrane Library databases were searched systematically. Randomized controlled trials assessing the effect of transcutaneous electrical nerve stimulation vs placebo transcutaneous electrical nerve stimulation on stroke were included. Two investigators independently searched articles, extracted data, and assessed the quality of included studies. The primary outcome was modified Ashworth scale (MAS). Meta-analysis was performed using the random-effect model. Seven randomized controlled trials were included in the meta-analysis. Compared with placebo transcutaneous electrical nerve stimulation, transcutaneous electrical nerve stimulation supplementation significantly reduced MAS (standard mean difference (SMD) = -0.71; 95% confidence interval (95% CI) = -1.11 to -0.30; p = 0.0006), improved static balance with open eyes (SMD = -1.26; 95% CI = -1.83 to -0.69; p<0.0001) and closed eyes (SMD = -1.74; 95% CI = -2.36 to -1.12; p < 0.00001), and increased walking speed (SMD = 0.44; 95% CI = 0.05 to 0.84; p = 0.03), but did not improve results on the Timed Up and Go Test (SMD = -0.60; 95% CI=-1.22 to 0.03; p = 0.06). Transcutaneous electrical nerve stimulation is associated with significantly reduced spasticity, increased static balance and walking speed, but has no influence on dynamic balance.

  18. Using wind speed from a blade-mounted flow sensor for power and load assessment on modern wind turbines

    DEFF Research Database (Denmark)

    Pedersen, Mads M.; Larsen, Torben J.; Madsen, Helge Aa

    2017-01-01

    In this paper an alternative method to evaluate power performance and loads on wind turbines using a blade-mounted flow sensor is investigated. The hypothesis is that the wind speed measured at the blades has a high correlation with the power and loads such that a power or load assessment can...... be performed from a few hours or days of measurements. In the present study a blade-mounted five-hole pitot tube is used as the flow sensor as an alternative to the conventional approach, where the reference wind speed is either measured at a nearby met mast or on the nacelle using lidar technology or cup...... anemometers. From the flow sensor measurements, an accurate estimate of the wind speed at the rotor plane can be obtained. This wind speed is disturbed by the presence of the wind turbine, and it is therefore different from the free-flow wind speed. However, the recorded wind speed has a high correlation...

  19. A coupled implicit method for chemical non-equilibrium flows at all speeds

    Energy Technology Data Exchange (ETDEWEB)

    Shuen, J.S.; Choi, Y. (NASA Lewis Research Center, Cleveland, OH (United States)); Chen, K.H. (Univ. of Toledo, Cleveland, OH (United States))

    1993-06-01

    A time-accurate, coupled solution procedure is described for the chemical nonequilibrium Navier-Stokes equations over a wide range of Mach numbers. This method employs the strong conservation form of the governing equations, but uses primitive variables (p[sub g], u, v, h, Y[sub i]) as unknowns. Real gas properties and nonequilibrium chemistry are considered. Numerical tests include steady convergent-divergent nozzle flows with air dissociation/recombination chemistry, dump combustor flows with n-pentan air chemistry, and nonreacting unsteady driven cavity flows. Numerical results for both the steady and unsteady flows demonstrate the efficiency and robustness of the present algorithm for Mach numbers ranging from the incompressible limit to supersonic speeds. 26 refs., 10 figs.

  20. Effects of speed bottleneck on traffic flow with feedback control signal

    Science.gov (United States)

    Zhu, Kangli; Bi, Jiantao; Wu, Jianjun; Li, Shubin

    2016-09-01

    Various car-following models (CMs) have been developed to capture the complex characteristics of microscopic traffic flow, among which the coupled map CM can better reveal and reflect various phenomena of practical traffic flow. Capacity change at bottleneck contributes to high-density traffic flow upstream the bottleneck and contains very complex dynamic behavior. In this paper, we analyze the effect of speed bottleneck on the spatial-temporal evolution characteristics of traffic flow, and propose a method to reduce traffic congestion with the feedback control signal based on CM. Simulation results highlight the potential of using the feedback signal to control the stop-and-go wave and furthermore to alleviate the traffic congestion effectively.

  1. Noninvasive cardiac flow assessment using high speed magnetic resonance fluid motion tracking.

    Directory of Open Access Journals (Sweden)

    Kelvin Kian Loong Wong

    Full Text Available Cardiovascular diseases can be diagnosed by assessing abnormal flow behavior in the heart. We introduce, for the first time, a magnetic resonance imaging-based diagnostic that produces sectional flow maps of cardiac chambers, and presents cardiac analysis based on the flow information. Using steady-state free precession magnetic resonance images of blood, we demonstrate intensity contrast between asynchronous and synchronous proton spins. Turbulent blood flow in cardiac chambers contains asynchronous blood proton spins whose concentration affects the signal intensities that are registered onto the magnetic resonance images. Application of intensity flow tracking based on their non-uniform signal concentrations provides a flow field map of the blood motion. We verify this theory in a patient with an atrial septal defect whose chamber blood flow vortices vary in speed of rotation before and after septal occlusion. Based on the measurement of cardiac flow vorticity in our implementation, we establish a relationship between atrial vorticity and septal defect. The developed system has the potential to be used as a prognostic and investigative tool for assessment of cardiac abnormalities, and can be exploited in parallel to examining myocardial defects using steady-state free precession magnetic resonance images of the heart.

  2. Forecasting the Short-Term Passenger Flow on High-Speed Railway with Neural Networks

    Directory of Open Access Journals (Sweden)

    Mei-Quan Xie

    2014-01-01

    Full Text Available Short-term passenger flow forecasting is an important component of transportation systems. The forecasting result can be applied to support transportation system operation and management such as operation planning and revenue management. In this paper, a divide-and-conquer method based on neural network and origin-destination (OD matrix estimation is developed to forecast the short-term passenger flow in high-speed railway system. There are three steps in the forecasting method. Firstly, the numbers of passengers who arrive at each station or depart from each station are obtained from historical passenger flow data, which are OD matrices in this paper. Secondly, short-term passenger flow forecasting of the numbers of passengers who arrive at each station or depart from each station based on neural network is realized. At last, the OD matrices in short-term time are obtained with an OD matrix estimation method. The experimental results indicate that the proposed divide-and-conquer method performs well in forecasting the short-term passenger flow on high-speed railway.

  3. Flow field analysis of high-speed helium turboexpander for cryogenic refrigeration and liquefaction cycles

    Science.gov (United States)

    Sam, Ashish Alex; Ghosh, Parthasarathi

    2017-03-01

    Turboexpander constitutes one of the vital components of Claude cycle based helium refrigerators and liquefiers that are gaining increasing technological importance. These turboexpanders which are of radial inflow in configuration are generally high-speed micro turbines, due to the low molecular weight and density of helium. Any improvement in efficiency of these machines requires a detailed understanding of the flow field. Computational Fluid Dynamics analysis (CFD) has emerged as a necessary tool for the determination of the flow fields in cryogenic turboexpanders, which is often not possible through experiments. In the present work three-dimensional transient flow analysis of a cryogenic turboexpander for helium refrigeration and liquefaction cycles were performed using Ansys CFX®, to understand the flow field of a high-speed helium turboexpander, which in turn will help in taking appropriate decisions regarding modifications of established design methodology for improved efficiency of these machines. The turboexpander is designed based on Balje's nsds diagram and the inverse design blade profile generation formalism prescribed by Hasselgruber and Balje. The analyses include the study of several losses, their origins, the increase in entropy due to these losses, quantification of losses and the effects of various geometrical parameters on these losses. Through the flow field analysis it was observed that in the nozzle, flow separation at the nozzle blade suction side and trailing edge vortices resulted in loss generation, which calls for better nozzle blade profile. The turbine wheel flow field analysis revealed that the significant geometrical parameters of the turbine wheel blade like blade inlet angle, blade profile, tip clearance height and trailing edge thickness need to be optimised for improved performance of the turboexpander. The detailed flow field analysis in this paper can be used to improve the mean line design methodology for turboexpanders used

  4. Background Oriented Schlieren (BOS) measurement in supersonic flow with 4K high-speed camera

    Science.gov (United States)

    Ota, M.; Kurihara, K.; Arimoto, H.; Shida, K.; Inage, T.

    2017-02-01

    The Background Oriented Schlieren (BOS) technique is one of the novel measurement techniques and its application range is very wide. The principle of BOS is similar to that of the conventional schlieren technique, it exploits the bending of light ray caused by a refractive-index change corresponding to the density change in the medium. The BOS technique allows the quantitative measurement of density with very simple experimental setup and proper image analysis. Only a background and a digital camera are required for the experiment, so that even the real scale experiments can be realized. In recent years, the development of the high-speed camera is remarkable and so many high-speed phenomena can now be captured. To realize the precise measurement with BOS technique using high-speed camera, higher resolution (larger number of pixels) is desirable. In this paper, with a technical support from Nobby Tech Ltd., a 4K high-speed camera (4096 × 2160 pixels) is applied to the BOS measurement of the lateral jet/cross flow interaction filed in the supersonic wind tunnel test as a trial of the quantitative density measurement with higher resolution. The measurement system consists of a 4K high-speed camera and a pulsed laser for background illumination. A telecentric optical system is also employed to improve the spatial resolution of the measurement. The measurement results of BOS technique up to 1000 fps with higher resolution are discussed.

  5. Microscopic Theory of Traffic Flow Instability Governing Traffic Breakdown at Highway Bottlenecks: Growing Wave of Increase in Speed in Synchronized Flow

    CERN Document Server

    Kerner, Boris S

    2015-01-01

    We have revealed a growing local speed wave of increase in speed that can randomly occur in synchronized flow (S) at a highway bottleneck. The development of such a traffic flow instability leads to free flow (F) at the bottleneck; therefore, we call this instability as an S$\\rightarrow$F instability. Whereas the S$\\rightarrow$F instability leads to a local {\\it increase in speed} (growing acceleration wave), in contrast, the classical traffic flow instability introduced in 50s--60s and incorporated later in a huge number of traffic flow models leads to a growing wave of a local {\\it decrease in speed} (growing deceleration wave). We have found that the S$\\rightarrow$F instability can occur only, if there is a finite time delay in driver over-acceleration. The initial speed disturbance of increase in speed (called "speed peak") that initiates the S$\\rightarrow$F instability occurs usually at the downstream front of synchronized flow at the bottleneck. There can be many speed peaks with random amplitudes that ...

  6. In vivo imaging of ocular blood flow using high-speed ultrasound

    Science.gov (United States)

    Ketterling, Jeffrey A.; Urs, Raksha; Silverman, Ronald H.

    2017-01-01

    Clinical ophthalmic ultrasound is currently performed with mechanically scanned, single-element probes, but these are unable to provide useful information about blood flow with Doppler techniques. Linear arrays are well-suited for the detection of blood flow, but commercial systems generally exceed FDA ophthalmic safety limits. A high-speed plane-wave ultrasound approach with an 18-MHz linear array was utilized to characterize blood flow in the orbit and choroid. Acoustic intensity was measured and the plane-wave mode was within FDA limits. Data were acquired for up to 2 sec and up to 20,000 frames/s with sets of steered plane-wave transmissions that spanned 2*θ degrees where 0 degrees was normal to the array. Lateral resolution was characterized using compounding from 1 to 50 transmissions and -6-dB lateral beamwidths ranged from 320 to 180 μm, respectively. Compounded high-frame-rate data were post-processed using a singular value decomposition spatiotemporal filter and then flow was estimated at each pixel using standard Doppler processing methods. A 1-cm diameter rotating scattering phantom and a 2-mm diameter tube with a flow of blood-mimicking fluid were utilized to validate the flow-estimation algorithms. In vivo data were obtained from the posterior pole of the human eye which revealed regions of flow in the choroid and major orbital vessels supplying the eye. PMID:28275423

  7. MHD Modelling of Coronal Loops: Injection of High-Speed Chromospheric Flows

    Science.gov (United States)

    Petralia, A.; Reale, F.; Orlando, S.; Klimchuk, J. A.

    2014-01-01

    Context. Observations reveal a correspondence between chromospheric type II spicules and bright upward-moving fronts in the corona observed in the extreme-ultraviolet (EUV) band. However, theoretical considerations suggest that these flows are probably not the main source of heating in coronal magnetic loops. Aims. We investigate the propagation of high-speed chromospheric flows into coronal magnetic flux tubes and the possible production of emission in the EUV band. Methods. We simulated the propagation of a dense 104 K chromospheric jet upward along a coronal loop by means of a 2D cylindrical MHD model that includes gravity, radiative losses, thermal conduction, and magnetic induction. The jet propagates in a complete atmosphere including the chromosphere and a tenuous cool (approximately 0.8 MK) corona, linked through a steep transition region. In our reference model, the jet initial speed is 70 km per second, its initial density is 10(exp 11) per cubic centimeter, and the ambient uniform magnetic field is 10 G. We also explored other values of jet speed and density in 1D and different magnetic field values in 2D, as well as the jet propagation in a hotter (approximately 1.5 MK) background loop. Results. While the initial speed of the jet does not allow it to reach the loop apex, a hot shock-front develops ahead of it and travels to the other extreme of the loop. The shock front compresses the coronal plasma and heats it to about 10(exp 6) K. As a result, a bright moving front becomes visible in the 171 Angstrom channel of the SDO/AIA mission. This result generally applies to all the other explored cases, except for the propagation in the hotter loop. Conclusions. For a cool, low-density initial coronal loop, the post-shock plasma ahead of upward chromospheric flows might explain at least part of the observed correspondence between type II spicules and EUV emission excess.

  8. Walking speed is associated with self-perceived hearing handicap in high-functioning older adults: The Fujiwara-kyo study.

    Science.gov (United States)

    Tomioka, Kimiko; Harano, Akihiro; Hazaki, Kan; Morikawa, Masayuki; Iwamoto, Junko; Saeki, Keigo; Okamoto, Nozomi; Kurumatani, Norio

    2015-06-01

    The present study investigated whether physical performance and musculoskeletal pain (MSP) are associated with self-perceived hearing handicap (HH) among high-functioning older adults. We analyzed a total of 3982 community-dwelling high-functioning older adults (age 65 years and older). HH was assessed using the Hearing Handicap Inventory for Elderly-Screening. Self-reported hearing impairment (HI) was evaluated using a single question. We measured handgrip strength, walking speed (WS) and standing balance for assessments of physical performance. The severity of MSP assessed by interviews took into account its duration, limitation of daily activity and frequency. The prevalence of HH and HI in our sample was 22.2% and 28.1%, respectively. After adjusting for other two physical performance measures, MSP, sex, age, education, marital status, risk factors for hearing loss, instrumental activity of daily living, depression, cognitive function and self-reported HI, the odds ratios for HH in the second fastest, the second slowest, and the slowest WS quartile were 1.14 (95% CI = 0.81-1.58), 1.29 (95% CI = 0.92-1.79), and 1.58 (95% CI = 1.11-2.23), respectively, compared with the fastest WS quartile. A significant dose-response relationship was found between slower WS and HH (P for trend = 0.01). No significant association with HH was found in handgrip strength, standing balance and MSP. WS is associated with self-perceived HH in high-functioning older adults. The present study suggests that exercise programs to improve walking ability might be effective in preventing HH of self-sustainable older adults. © 2014 Japan Geriatrics Society.

  9. The effects of walking speed on minimum toe clearance and on the temporal relationship between minimum clearance and peak swing-foot velocity in unilateral trans-tibial amputees

    Science.gov (United States)

    De Asha, Alan R

    2014-01-01

    Background: Minimum toe clearance is a critical gait event because it coincides with peak forward velocity of the swing foot, and thus, there is an increased risk of tripping and falling. Trans-tibial amputees have increased risk of tripping compared to able-bodied individuals. Assessment of toe clearance during gait is thus clinically relevant. In able-bodied gait, minimum toe clearance increases with faster walking speeds, and it is widely reported that there is synchronicity between when peak swing-foot velocity and minimum toe clearance occur. There are no such studies involving lower-limb amputees. Objectives: To determine the effects of walking speed on minimum toe clearance and on the temporal relationship between clearance and peak swing-foot velocity in unilateral trans-tibial amputees. Study design: Cross-sectional. Methods: A total of 10 trans-tibial participants walked at slow, customary and fast speeds. Minimum toe clearance and the timings of minimum toe clearance and peak swing-foot velocity were determined and compared between intact and prosthetic sides. Results: Minimum toe clearance was reduced on the prosthetic side and, unlike on the intact side, did not increase with walking speed increase. Peak swing-foot velocity consistently occurred (~0.014 s) after point of minimum toe clearance on both limbs across all walking speeds, but there was no significant difference in the toe–ground clearance between the two events. Conclusion: The absence of speed related increases in minimum toe clearance on the prosthetic side suggests that speed related modulation of toe clearance for an intact limb typically occurs at the swing-limb ankle. The temporal consistency between peak foot velocity and minimum toe clearance on each limb suggests that swing-phase inter-segmental coordination is unaffected by trans-tibial amputation. Clinical relevance The lack of increase in minimum toe clearance on the prosthetic side at higher walking speeds may potentially

  10. The effects of walking speed on minimum toe clearance and on the temporal relationship between minimum clearance and peak swing-foot velocity in unilateral trans-tibial amputees.

    Science.gov (United States)

    De Asha, Alan R; Buckley, John G

    2015-04-01

    Minimum toe clearance is a critical gait event because it coincides with peak forward velocity of the swing foot, and thus, there is an increased risk of tripping and falling. Trans-tibial amputees have increased risk of tripping compared to able-bodied individuals. Assessment of toe clearance during gait is thus clinically relevant. In able-bodied gait, minimum toe clearance increases with faster walking speeds, and it is widely reported that there is synchronicity between when peak swing-foot velocity and minimum toe clearance occur. There are no such studies involving lower-limb amputees. To determine the effects of walking speed on minimum toe clearance and on the temporal relationship between clearance and peak swing-foot velocity in unilateral trans-tibial amputees. Cross-sectional. A total of 10 trans-tibial participants walked at slow, customary and fast speeds. Minimum toe clearance and the timings of minimum toe clearance and peak swing-foot velocity were determined and compared between intact and prosthetic sides. Minimum toe clearance was reduced on the prosthetic side and, unlike on the intact side, did not increase with walking speed increase. Peak swing-foot velocity consistently occurred (~0.014 s) after point of minimum toe clearance on both limbs across all walking speeds, but there was no significant difference in the toe-ground clearance between the two events. The absence of speed related increases in minimum toe clearance on the prosthetic side suggests that speed related modulation of toe clearance for an intact limb typically occurs at the swing-limb ankle. The temporal consistency between peak foot velocity and minimum toe clearance on each limb suggests that swing-phase inter-segmental coordination is unaffected by trans-tibial amputation. The lack of increase in minimum toe clearance on the prosthetic side at higher walking speeds may potentially increase risk of tripping. Findings indicate that determining the instant of peak swing

  11. Sensitivity of helioseismic measurements of normal-mode coupling to flows and sound-speed perturbations

    Science.gov (United States)

    Hanasoge, Shravan M.; Woodard, Martin; Antia, H. M.; Gizon, Laurent; Sreenivasan, Katepalli R.

    2017-09-01

    In this article, we derive and compute the sensitivity of measurements of coupling between normal modes of oscillation in the Sun to underlying flows. The theory is based on first-born perturbation theory, and the analysis is carried out using the formalism described by Lavely & Ritzwoller (1992). Albeit tedious, we detail the derivation and compute the sensitivity of specific pairs of coupled normal modes to anomalies in the interior. Indeed, these kernels are critical for the accurate inference of convective flow amplitudes and large-scale circulations in the solar interior. We resolve some inconsistencies in the derivation of Lavely & Ritzwoller (1992) and reformulate the fluid-continuity condition. We also derive and compute sound-speed kernels, paving the way for inverting for thermal anomalies alongside flows.

  12. A Method of Urban Traffic Flow Speed Estimation Using Sparse Floating Car Data

    Directory of Open Access Journals (Sweden)

    WANG Xiaomeng

    2016-07-01

    Full Text Available The sample spatio-temporalsparsity is one of the major challenges for traffic estimation when using floating car data (FCD.Spatio-temporal characteristics of road traffic flow are analysed and applied to build a naive Bayes-based traffic estimation model which is proposed to estimate the missing traffic state of the roads which are not covered by samples. In the model, the adjacent period traffic flow speed of the target road segment is considered for the representation of the time characteristic. And instead of Euclidean distance and topology relationship, urban traffic flow similarity relationships are mined to quantify the interior space features of urban traffic.The result demonstrates that the method is effective for missing traffic state estimation and more precision compared to traditional methods based on topology relationship.As a conclusion, the proposed model can solve the spatio-temporal sparsity problem effectively, which has a strong practical significance for traffic application based on FCD.

  13. Implementation of Speed Variation in the Structural Dynamic Assessment of Turbomachinery Flow-Path Components

    Science.gov (United States)

    Brown, Andrew M.; Davis, R. Benjamin; DeHaye, Michael

    2013-01-01

    During the design of turbomachinery flow path components, the assessment of possible structural resonant conditions is critical. Higher frequency modes of these structures are frequently found to be subject to resonance, and in these cases, design criteria require a forced response analysis of the structure with the assumption that the excitation speed exactly equals the resonant frequency. The design becomes problematic if the response analysis shows a violation of the HCF criteria. One possible solution is to perform "finite-life" analysis, where Miner's rule is used to calculate the actual life in seconds in comparison to the required life. In this situation, it is beneficial to incorporate the fact that, for a variety of turbomachinery control reasons, the speed of the rotor does not actually dwell at a single value but instead dithers about a nominal mean speed and during the time that the excitation frequency is not equal to the resonant frequency, the damage accumulated by the structure is diminished significantly. Building on previous investigations into this process, we show that a steady-state assumption of the response is extremely accurate for this typical case, resulting in the ability to quickly account for speed variation in the finite-life analysis of a component which has previously had its peak dynamic stress at resonance calculated. A technique using Monte Carlo simulation is also presented which can be used when specific speed time histories are not available. The implementation of these techniques can prove critical for successful turbopump design, as the improvement in life when speed variation is considered is shown to be greater than a factor of two

  14. Air movement around a worker in a low-speed flow field.

    Science.gov (United States)

    Johnson, A E; Fletcher, B; Saunders, C J

    1996-02-01

    A knowledge of the air movement around a worker in a low-speed airflow is important in a number of areas: containment testing of fume cupboards; testing of personal dust samplers; testing of LEV effectiveness; and measurement of worker exposure. Measurements of velocity vectors around the upper torsos of manikins and a human in low-speed airflows have been made using a laser Doppler anemometer. Both heated and unheated manikins, as well as a 'breathing' manikin were used. The results show that quite distinctive flow patterns develop with heated and unheated bodies. Comparison of the flows around two- and three-dimensional manikins with that around a human shows that only a three-dimensional heated manikin gives good results. The unheated breathing manikin gave results which were unrepresentative of the real situation. A suitable manikin for use in sampling or testing in low-speed airflows would have a heated, rounded, three-dimensional body of reasonably human dimensions and would be non-breathing and clothed.

  15. Numerical simulation of flow around a simplified high-speed train model using OpenFOAM

    Science.gov (United States)

    Ishak, I. A.; Ali, M. S. M.; Shaikh Salim, S. A. Z.

    2016-10-01

    Detailed understanding of flow physics on the flow over a high-speed train (HST) can be accomplished using the vast information obtained from numerical simulation. Accuracy of any simulation in solving and analyzing problems related to fluid flow is important since it measures the reliability of the results. This paper describes a numerical simulation setup for the flow around a simplified model of HST that utilized open source software, OpenFOAM. The simulation results including pressure coefficient, drag coefficient and flow visualization are presented and they agreed well with previously published data. This shows that OpenFOAM software is capable of simulating fluid flows around a simplified HST model. Additionally, the wall functions are implemented in order to minimize the overall number of grid especially near the wall region. This resulted in considerably smaller numbers of mesh resolution used in the current study compared to previous work, which leads to achievement of much reasonable time simulation and consequently reduces the total computational effort without affecting the final outcome.

  16. The 3D trajectory of the body centre of mass during adult human walking: evidence for a speed-curvature power law.

    Science.gov (United States)

    Tesio, Luigi; Rota, Viviana; Perucca, Laura

    2011-02-24

    During straight walking, the body centre of mass (CM) follows a 3D figure-of-eight ("bow-tie") trajectory about 0.2 m long and with sizes around 0.05 m on each orthogonal axis. This was shown in 18 healthy adults walking at 0.3 to 1.4 ms⁻¹ on a force-treadmill (Tesio and Rota, 2008). Double integration of force signals can provide both the changes of mechanical energy of the CM and its 3D displacements (Tesio et al., 2010). In the same subjects, the relationship between the tangential speed of the CM, Vt, the curvature, C, and its inverse--the radius of curvature, r(c), were analyzed. A "power law" (PL) model was applied, i.e. logVt was regressed over logr(c). A PL is known to apply to the most various goal-directed planar movements (e.g. drawing), where the coefficient of logr(c), β, usually takes values around 13. When the PL was fitted to the whole dataset, β was 0.346 and variance explanation, R², was 59.8%. However, when the data were split into low- and high-curvature subsets (LC, HC, arbitrary cut-off of C=0.05 mm⁻¹, r(c)=20mm), β was 0.185 in the LC (R² 0.214) and 0.486 in the HC (R² 0.536) tracts. R² on the whole dataset increased to 0.763 if the LC-HC classification of the forward speed and their interaction entered the model. The β coefficient, the curvature C, and the pendulum-like recovery of mechanical energy were lower during the double foot-ground contact phase, compared to the single contact. Along the CM trajectory, curvature and muscle power output peaked together around the inversions of lateral direction. Non-zero torsion values were randomly distributed along 60% of the trajectory, suggesting that this is not segmented into piecewise planar tracts. It is proposed that the trajectory can be segmented into one tract that is more actively controlled (tie) where a PL fits poorly and another tract which is more ballistic (bow) where a PL fits well. Results need confirmation through more appropriate 3D PL modelling. Copyright © 2010

  17. Curvature Effect in Shear Flow: Slowdown of Turbulent Flame Speeds with Markstein Number

    Science.gov (United States)

    Lyu, Jiancheng; Xin, Jack; Yu, Yifeng

    2017-12-01

    It is well-known in the combustion community that curvature effect in general slows down flame propagation speeds because it smooths out wrinkled flames. However, such a folklore has never been justified rigorously. In this paper, as the first theoretical result in this direction, we prove that the turbulent flame speed (an effective burning velocity) is decreasing with respect to the curvature diffusivity (Markstein number) for shear flows in the well-known G-equation model. Our proof involves several novel and rather sophisticated inequalities arising from the nonlinear structure of the equation. On a related fundamental issue, we solve the selection problem of weak solutions or find the "physical fluctuations" when the Markstein number goes to zero and solutions approach those of the inviscid G-equation model. The limiting solution is given by a closed form analytical formula.

  18. Numerical and Physical Modeling of the Response of Resonator Liners to Intense Sound and High Speed Grazing Flow Project

    Data.gov (United States)

    National Aeronautics and Space Administration — An innovative research program is proposed that numerically and physically models the response of resonator liners to intense sound and high speed grazing flow. The...

  19. A high-speed photographic system for flow visualization in a steam turbine

    Science.gov (United States)

    Barna, G. J.

    1973-01-01

    A photographic system was designed to visualize the moisture flow in a steam turbine. Good performance of the system was verified using dry turbine mockups in which an aerosol spray simulated, in a rough way, the moisture flow in the turbine. Borescopes and fiber-optic light tubes were selected as the general instrumentation approach. High speed motion-picture photographs of the liquid flow over the stator blade surfaces were taken using stroboscopic lighting. Good visualization of the liquid flow was obtained. Still photographs of drops in flight were made using short duration flash sources. Drops with diameters as small as 30 micrometers (0.0012 in.) could be resolved. In addition, motion pictures of a spray of water simulating the spray off the rotor blades and shrouds were taken at normal framing rates. Specially constructed light tubes containing small tungsten-halogen lamps were used. Sixteen millimeter photography was used in all cases. Two potential problems resulting from the two-phase turbine flow (attenuation and scattering of light by the fog present and liquid accumulation on the borescope mirrors) were taken into account in the photographic system design but not evaluated experimentally.

  20. Numerical Simulation of Non-Equilibrium Plasma Discharge for High Speed Flow Control

    Science.gov (United States)

    Balasubramanian, Ramakrishnan; Anandhanarayanan, Karupannasamy; Krishnamurthy, Rajah; Chakraborty, Debasis

    2017-06-01

    Numerical simulation of hypersonic flow control using plasma discharge technique is carried out using an in-house developed code CERANS-TCNEQ. The study is aimed at demonstrating a proof of concept futuristic aerodynamic flow control device. The Kashiwa Hypersonic and High Temperature wind tunnel study of plasma discharge over a flat plate had been considered for numerical investigation. The 7-species, 18-reaction thermo-chemical non-equilibrium, two-temperature air-chemistry model due Park is used to model the weakly ionized flow. Plasma discharge is modeled as Joule heating source terms in both the translation-rotational and vibrational energy equations. Comparison of results for plasma discharge at Mach 7 over a flat plate with the reference data reveals that the present study is able to mimic the exact physics of complex flow such as formation of oblique shock wave ahead of the plasma discharge region with a resultant rise in surface pressure and vibrational temperature up to 7000 K demonstrating the use of non-equilibrium plasma discharge for flow control at hypersonic speeds.

  1. Energy flow analysis of amputee walking shows a proximally-directed transfer of energy in intact limbs, compared to a distally-directed transfer in prosthetic limbs at push-off

    OpenAIRE

    Weinert-Aplin, RA; Howard, D; Twiste, M; Jarvis, HL; Bennett, A.N.; Baker, RJ

    2016-01-01

    Reduced capacity and increased metabolic cost of walking occurs in amputees, despite advances in prosthetic componentry. Joint powers can quantify deficiencies in prosthetic gait, but do not reveal how energy is exchanged between limb segments. This study aimed to quantify these energy exchanges during amputee walking. Optical motion and forceplate data collected during walking at a self-selected speed for cohorts of 10 controls, 10 unilateral trans-tibial, 10 unilateral trans-femoral and 10 ...

  2. Influence of blast furnace gas flow speed on dust deposition characteristics in butterfly valve region

    OpenAIRE

    Lixin WANG; Bin WANG; Fengshan HUANG

    2016-01-01

    The blast furnace gas contains plenty of dust, which deposits easily on the bottom of seat sealing surface of the tri-eccentric butterfly valve in the pipeline, causing stuck and damage to the valve plate, thereby affects the production of the blast furnace and brings great economic loss. To derive the influence mechanism of effects of the blast furnace gas flow speed within the pipeline on the dust deposition laws in the butterfly valve region, a 3D model of the butterfly valve and its regio...

  3. Methods for Prediction of High-Speed Reacting Flows in Aerospace Propulsion

    Science.gov (United States)

    Drummond, J. Philip

    2014-01-01

    Research to develop high-speed airbreathing aerospace propulsion systems was underway in the late 1950s. A major part of the effort involved the supersonic combustion ramjet, or scramjet, engine. Work had also begun to develop computational techniques for solving the equations governing the flow through a scramjet engine. However, scramjet technology and the computational methods to assist in its evolution would remain apart for another decade. The principal barrier was that the computational methods needed for engine evolution lacked the computer technology required for solving the discrete equations resulting from the numerical methods. Even today, computer resources remain a major pacing item in overcoming this barrier. Significant advances have been made over the past 35 years, however, in modeling the supersonic chemically reacting flow in a scramjet combustor. To see how scramjet development and the required computational tools finally merged, we briefly trace the evolution of the technology in both areas.

  4. Ultra-high-speed digital in-line holography system applied to particle-laden supersonic underexpanded jet flows

    DEFF Research Database (Denmark)

    Ingvorsen, Kristian Mark; Buchmann, Nicolas A.; Soria, Julio

    2012-01-01

    -fluid interactions in these high-speed flows special high performance techniques are required. The present work is an investigation into the applicability of magnified digital in-line holography with ultra-high-speed recording for the study of three-dimensional supersonic particle-laden flows. An optical setup...... for magnified digital in-line holography is created, using an ultra-high-speed camera capable of frame rates of up to 1.0MHz. To test the new technique an axisymmetric supersonic underexpanded particle-laden jet is investigated. The results show that the new technique allows for the acquisition of time resolved...

  5. Molecular-Based Optical Measurement Techniques for Transition and Turbulence in High-Speed Flow

    Science.gov (United States)

    Bathel, Brett F.; Danehy, Paul M.; Cutler, Andrew D.

    2013-01-01

    High-speed laminar-to-turbulent transition and turbulence affect the control of flight vehicles, the heat transfer rate to a flight vehicle's surface, the material selected to protect such vehicles from high heating loads, the ultimate weight of a flight vehicle due to the presence of thermal protection systems, the efficiency of fuel-air mixing processes in high-speed combustion applications, etc. Gaining a fundamental understanding of the physical mechanisms involved in the transition process will lead to the development of predictive capabilities that can identify transition location and its impact on parameters like surface heating. Currently, there is no general theory that can completely describe the transition-to-turbulence process. However, transition research has led to the identification of the predominant pathways by which this process occurs. For a truly physics-based model of transition to be developed, the individual stages in the paths leading to the onset of fully turbulent flow must be well understood. This requires that each pathway be computationally modeled and experimentally characterized and validated. This may also lead to the discovery of new physical pathways. This document is intended to describe molecular based measurement techniques that have been developed, addressing the needs of the high-speed transition-to-turbulence and high-speed turbulence research fields. In particular, we focus on techniques that have either been used to study high speed transition and turbulence or techniques that show promise for studying these flows. This review is not exhaustive. In addition to the probe-based techniques described in the previous paragraph, several other classes of measurement techniques that are, or could be, used to study high speed transition and turbulence are excluded from this manuscript. For example, surface measurement techniques such as pressure and temperature paint, phosphor thermography, skin friction measurements and

  6. Energy flow analysis of amputee walking shows a proximally-directed transfer of energy in intact limbs, compared to a distally-directed transfer in prosthetic limbs at push-off.

    Science.gov (United States)

    Weinert-Aplin, R A; Howard, D; Twiste, M; Jarvis, H L; Bennett, A N; Baker, R J

    2017-01-01

    Reduced capacity and increased metabolic cost of walking occurs in amputees, despite advances in prosthetic componentry. Joint powers can quantify deficiencies in prosthetic gait, but do not reveal how energy is exchanged between limb segments. This study aimed to quantify these energy exchanges during amputee walking. Optical motion and forceplate data collected during walking at a self-selected speed for cohorts of 10 controls, 10 unilateral trans-tibial, 10 unilateral trans-femoral and 10 bilateral trans-femoral amputees were used to determine the energy exchanges between lower limb segments. At push-off, consistent thigh and shank segment powers were observed between amputee groups (1.12W/kg vs. 1.05W/kg for intact limbs and 0.97W/kg vs. 0.99W/kg for prosthetic limbs), and reduced prosthetic ankle power, particularly in trans-femoral amputees (3.12W/kg vs. 0.87W/kg). Proximally-directed energy exchange was observed in the intact limbs of amputees and controls, while prosthetic limbs displayed distally-directed energy exchanges at the knee and hip. This study used energy flow analysis to show a reversal in the direction in which energy is exchanged between prosthetic limb segments at push-off. This reversal was required to provide sufficient energy to propel the limb segments and is likely a direct result of the lack of push-off power at the prosthetic ankle, particularly in trans-femoral amputees, and leads to their increased metabolic cost of walking. Copyright © 2016 IPEM. Published by Elsevier Ltd. All rights reserved.

  7. Quality evaluation of energy consumed in flow regulation method by speed variation in centrifugal pumps

    Science.gov (United States)

    Morales, S.; Culman, M.; Acevedo, C.; Rey, C.

    2014-06-01

    Nowadays, energy efficiency and the Electric Power Quality are two inseparable issues in the evaluation of three-phase induction motors, framed within the program of Rational and Efficient Use of Energy (RUE).The use of efficient energy saving devices has been increasing significantly in RUE programs, for example the use of variable frequency drives (VFD) in pumping systems.The overall objective of the project was to evaluate the impact on power quality and energy efficiency in a centrifugal pump driven by an induction three-phase motor, using the flow control method of speed variation by VFD. The fundamental purpose was to test the opinions continuously heard about the use of flow control methods in centrifugal pumps, analyzing the advantages and disadvantages that have been formulated deliberately in order to offer support to the industry in taking correct decisions. The VFD changes the speed of the motor-pump system increasing efficiency compared to the classical methods of regulation. However, the VFD originates conditions that degrade the quality of the electric power supplied to the system and therefore its efficiency, due to the nonlinearity and presence of harmonic currents. It was possible to analyze the power quality, ensuring that the information that comes to the industry is generally biased.

  8. Preconditioned conjugate-gradient methods for low-speed flow calculations

    Science.gov (United States)

    Ajmani, Kumud; Ng, Wing-Fai; Liou, Meng-Sing

    1993-01-01

    An investigation is conducted into the viability of using a generalized Conjugate Gradient-like method as an iterative solver to obtain steady-state solutions of very low-speed fluid flow problems. Low-speed flow at Mach 0.1 over a backward-facing step is chosen as a representative test problem. The unsteady form of the two dimensional, compressible Navier-Stokes equations is integrated in time using discrete time-steps. The Navier-Stokes equations are cast in an implicit, upwind finite-volume, flux split formulation. The new iterative solver is used to solve a linear system of equations at each step of the time-integration. Preconditioning techniques are used with the new solver to enhance the stability and convergence rate of the solver and are found to be critical to the overall success of the solver. A study of various preconditioners reveals that a preconditioner based on the Lower-Upper Successive Symmetric Over-Relaxation iterative scheme is more efficient than a preconditioner based on Incomplete L-U factorizations of the iteration matrix. The performance of the new preconditioned solver is compared with a conventional Line Gauss-Seidel Relaxation (LGSR) solver. Overall speed-up factors of 28 (in terms of global time-steps required to converge to a steady-state solution) and 20 (in terms of total CPU time on one processor of a CRAY-YMP) are found in favor of the new preconditioned solver, when compared with the LGSR solver.

  9. Concurrent Flame Growth, Spread and Extinction over Composite Fabric Samples in Low Speed Purely Forced Flow in Microgravity

    Science.gov (United States)

    Zhao, Xiaoyang; T'ien, James S.; Ferkul, Paul V.; Olson, Sandra L.

    2015-01-01

    As a part of the NASA BASS and BASS-II experimental projects aboard the International Space Station, flame growth, spread and extinction over a composite cotton-fiberglass fabric blend (referred to as the SIBAL fabric) were studied in low-speed concurrent forced flows. The tests were conducted in a small flow duct within the Microgravity Science Glovebox. The fuel samples measured 1.2 and 2.2 cm wide and 10 cm long. Ambient oxygen was varied from 21% down to 16% and flow speed from 40 cm/s down to 1 cm/s. A small flame resulted at low flow, enabling us to observe the entire history of flame development including ignition, flame growth, steady spread (in some cases) and decay at the end of the sample. In addition, by decreasing flow velocity during some of the tests, low-speed flame quenching extinction limits were found as a function of oxygen percentage. The quenching speeds were found to be between 1 and 5 cm/s with higher speed in lower oxygen atmosphere. The shape of the quenching boundary supports the prediction by earlier theoretical models. These long duration microgravity experiments provide a rare opportunity for solid fuel combustion since microgravity time in ground-based facilities is generally not sufficient. This is the first time that a low-speed quenching boundary in concurrent spread is determined in a clean and unambiguous manner.

  10. Transient and steady state performance analysis of power flow control in a DFIG variable speed wind turbine

    Science.gov (United States)

    Nwosu, Cajethan M.; Oti, Stephen E.; Ogbuka, Cosmas U.

    2017-01-01

    This paper presents transient and steady state performance analysis of power flow control in a 5.0 kW Doubly-Fed Induction Generator (DFIG) Variable Speed Wind Turbine (VSWT) under sub synchronous speed, super synchronous speed and synchronous speed modes of operation. Stator flux orientation is used for the control of the rotor-side converter (RSC) and DFIG whereas the grid (or stator) voltage orientation is the preferred choice for the control of the grid-side converter (GSC). In each of the three speeds modes, power is always supplied to the grid through the stator of the DFIG. The magnitude of net power (stator power plus rotor power) is less than stator power during the sub synchronous speed mode; it is greater than stator power during the super synchronous speed mode while it is equal to the stator power during the synchronous speed mode. In synchronous speed mode, the rotor power is zero indicating that power is neither supplied to the grid from the rotor nor supplied to the rotor from the grid; here the magnitude of net power is equal to stator power. The simulation results thus obtained in a MATLAB/SIMULINK environment laid credence to the controllability of power flow reversal in a DFIG-VSWT through back-to-back power electronic converter.

  11. Experiments performed with bubbly flow in vertical pipes at different flow conditions covering the transition region: simulation by coupling Eulerian, Lagrangian and 3D random walks models

    Science.gov (United States)

    Muñoz-Cobo, José; Chiva, Sergio; El Aziz Essa, Mohamed; Mendes, Santos

    2012-08-01

    Two phase flow experiments with different superficial velocities of gas and water were performed in a vertical upward isothermal cocurrent air-water flow column with conditions ranging from bubbly flow, with very low void fraction, to transition flow with some cap and slug bubbles and void fractions around 25%. The superficial velocities of the liquid and the gas phases were varied from 0.5 to 3 m/s and from 0 to 0.6 m/s, respectively. Also to check the effect of changing the surface tension on the previous experiments small amounts of 1-butanol were added to the water. These amounts range from 9 to 75 ppm and change the surface tension. This study is interesting because in real cases the surface tension of the water diminishes with temperature, and with this kind of experiments we can study indirectly the effect of changing the temperature on the void fraction distribution. The following axial and radial distributions were measured in all these experiments: void fraction, interfacial area concentration, interfacial velocity, Sauter mean diameter and turbulence intensity. The range of values of the gas superficial velocities in these experiments covered the range from bubbly flow to the transition to cap/slug flow. Also with transition flow conditions we distinguish two groups of bubbles in the experiments, the small spherical bubbles and the cap/slug bubbles. Special interest was devoted to the transition region from bubbly to cap/slug flow; the goal was to understand the physical phenomena that take place during this transition A set of numerical simulations of some of these experiments for bubbly flow conditions has been performed by coupling a Lagrangian code, that tracks the three dimensional motion of the individual bubbles in cylindrical coordinates inside the field of the carrier liquid, to an Eulerian model that computes the magnitudes of continuous phase and to a 3D random walk model that takes on account the fluctuation in the velocity field of the

  12. Impact of loaded sit-to-stand exercises at different speeds on the physiological cost of walking in children with spastic diplegia: A single-blind randomized clinical trial.

    Science.gov (United States)

    Kusumoto, Yasuaki; Nitta, Osamu; Takaki, Kenji

    2016-10-01

    In the present study, we aimed to determine whether similarly loaded sit-to-stand exercises at different speeds improve the physiological cost of walking in children with spastic diplegia. This design was a single-blind randomized clinical trial. Sixteen children with cerebral palsy (CP), aged 12-18 years, with a diagnosis of spastic diplegia, were randomly allocated to a slow loaded sit-to-stand exercise group (n=8) and a self-paced loaded sit-to-stand exercise group (n=8). Loaded sit-to-stand exercise was conducted at home for 15min, 4 sets per day, 3-4days per week, for 6 weeks. The patients were evaluated immediately before the intervention and after the training. Lower limb muscle strength using a hand-held dynamometer, selective voluntary motor control using SCALE, 6-min walk distance (6MWD), and Physiological Cost Index (PCI) were measured. The 6MWD showed a significant difference before and after intervention. PCI showed a significant difference between the two groups and the two time points. 6MWD and the PCI improved after intervention in the slow sit-to-stand exercise group. Compared to loaded sit-to-stand exercise at a regular speed, slow low-loaded sit-to-stand exercise improved the 6MWD and PCI in children with CP, suggesting that this decrease in speed during exercise improves the physiological cost of walking in these children. Copyright © 2016 Elsevier Ltd. All rights reserved.

  13. Flame speeds and curvature of premixed, spherically expanding flames advecting in a turbulent channel flow

    Science.gov (United States)

    Fries, Dan; Ochs, Bradley; Ranjan, Devesh; Menon, Suresh

    2016-11-01

    A new facility has been developed at the Georgia Institute of Technology to study sub- and supersonic combustion, which is based on classical flame bomb studies but incorporates a mean flow, allowing for a wider variety of turbulent conditions and the inclusion of effects like compressibility, while supporting shear-free spherical flames. Homogeneous, isotropic turbulence is generated via an active vane grid. Methane-air flame kernels advecting with the mean flow are generated using Laser Induced Breakdown ignition. The facility is accessing the thin reaction zone regime with uRMS' /SL0 = 6 . 9 - 22 , L11 /δF = 44 - 68 and Reλ = 190 - 550 . The flame kernels are probed with OH-Planar Laser Induced Fluorescence (PLIF). To validate the facility, results at Ū = 30 m/s are compared to existing data using a scaling derived from a spectral closure of the G-equation. This indicates the reacting flow remains Galilean invariant under the given conditions. The differences between global and local turbulent consumption speeds derived from OH-PLIF results are discussed with a focus on modeling efforts. The curvature of flame wrinkles is evaluated to examine the impact of different turbulent scales on flame development. This work was supported by the Air Force Office of Scientific Research under basic research Grant FA9550-15-1-0512 (Project monitor: Dr. Chiping Li).

  14. Requirements for Large Eddy Simulation Computations of Variable-Speed Power Turbine Flows

    Science.gov (United States)

    Ameri, Ali A.

    2016-01-01

    Variable-speed power turbines (VSPTs) operate at low Reynolds numbers and with a wide range of incidence angles. Transition, separation, and the relevant physics leading to them are important to VSPT flow. Higher fidelity tools such as large eddy simulation (LES) may be needed to resolve the flow features necessary for accurate predictive capability and design of such turbines. A survey conducted for this report explores the requirements for such computations. The survey is limited to the simulation of two-dimensional flow cases and endwalls are not included. It suggests that a grid resolution necessary for this type of simulation to accurately represent the physics may be of the order of Delta(x)+=45, Delta(x)+ =2 and Delta(z)+=17. Various subgrid-scale (SGS) models have been used and except for the Smagorinsky model, all seem to perform well and in some instances the simulations worked well without SGS modeling. A method of specifying the inlet conditions such as synthetic eddy modeling (SEM) is necessary to correctly represent the inlet conditions.

  15. IN VITRO FLOW ANALYSIS OF NOVEL DOUBLE-CUTTING, OPEN-PORT, ULTRAHIGH-SPEED VITRECTOMY SYSTEMS.

    Science.gov (United States)

    Zehetner, Claus; Moelgg, Marion; Bechrakis, Emmanouil; Linhart, Caroline; Bechrakis, Nikolaos E

    2017-10-09

    To analyze the performance and flow characteristics of novel double-cutting, open-port, 23-, 25-, and 27-gauge ultrahigh-speed vitrectomy systems. In vitro fluidic measurements were performed to assess the volumetric aspiration profiles of several vitrectomy systems in basic salt solution and egg white. Double-cutting open-port vitrectomy probes delivered stable aspiration flow rates that were less prone to flow variation affected by the cutting speed. Increase in cutting frequency to the maximum level resulted in flow reduction of less than 10% (0.0%-9.5%). Commercially available 23-, 25-, and 27-G double-cutting probes exhibited higher egg-white and basic salt solution flow rates at all evaluated cut rates, with aspirational efficiencies being 1.1 to 2.9 times the flow rates of standard single-blade vitrectomy probes of the same caliber at the maximum preset vacuum. The highest relative differences were observed at faster cut rates. The newly introduced double-cutting open-port vitrectomy probes delivered stable aspiration flow rates that were less prone to flow variation affected by the cutting speed. The fluidic principle of constant flow even at the highest cut rates and low vacuum levels might impact surgical strategies, especially when performing manipulations close to the retina.

  16. Critical speed for capillary-gravity surface flows in the dispersive shallow water limit

    Science.gov (United States)

    Pham, Chi-Tuong; Nore, Caroline; Brachet, Marc-Étienne

    2005-06-01

    The stability of perfect-fluid capillary-gravity surface flows past a cylindrical obstacle is studied in the shallow water limit, using the two-dimensional compressible Euler equations, with leading-order dispersive corrections. Stationary solutions with different contact angles are obtained by Newton branch following, based on Fourier pseudospectral methods, using mapped Chebychev polynomials. Stable and unstable branches are found to meet, through a saddle-node bifurcation, at a critical speed beyond which no stationary solution exists. For large obstacles, the stable branch is compared with the stationary solutions of the compressible Euler equation without dispersion. Boundary layers are investigated. In this regime, the unstable dynamics are shown to lead to a finite-time dewetting singularity.

  17. Determination of volume fractions in two-phase flows from sound speed measurement

    Energy Technology Data Exchange (ETDEWEB)

    Chaudhuri, Anirban [Los Alamos National Laboratory; Sinha, Dipen N. [Los Alamos National Laboratory; Osterhoudt, Curtis F. [University of Alaska

    2012-08-15

    Accurate measurement of the composition of oil-water emulsions within the process environment is a challenging problem in the oil industry. Ultrasonic techniques are promising because they are non-invasive and can penetrate optically opaque mixtures. This paper presents a method of determining the volume fractions of two immiscible fluids in a homogenized two-phase flow by measuring the speed of sound through the composite fluid along with the instantaneous temperature. Two separate algorithms are developed by representing the composite density as (i) a linear combination of the two densities, and (ii) a non-linear fractional formulation. Both methods lead to a quadratic equation with temperature dependent coefficients, the root of which yields the volume fraction. The densities and sound speeds are calibrated at various temperatures for each fluid component, and the fitted polynomial is used in the final algorithm. We present results when the new algorithm is applied to mixtures of crude oil and process water from two different oil fields, and a comparison of our results with a Coriolis meter; the difference between mean values is less than 1%. Analytical and numerical studies of sensitivity of the calculated volume fraction to temperature changes and calibration errors are also presented.

  18. High-Speed Turbulent Reacting Flows: Intrinsic Flame Instability and its Effects on the Turbulent Cascade

    Science.gov (United States)

    Poludnenko, Alexei

    2016-11-01

    Turbulent reacting flows are pervasive both in our daily lives on Earth and in the Universe. They power modern society being at the heart of many energy generation and propulsion systems, such as gas turbines, internal combustion and jet engines. On astronomical scales, thermonuclear turbulent flames are the driver of some of the most powerful explosions in the Universe, knows as Type Ia supernovae. Despite this ubiquity in Nature, turbulent reacting flows still pose a number of fundamental questions often exhibiting surprising and unexpected behavior. In this talk, we will discuss several such phenomena observed in direct numerical simulations of high-speed, premixed, turbulent flames. We show that turbulent flames in certain regimes are intrinsically unstable even in the absence of the surrounding combustor walls or obstacles, which can support the thermoacoustic feedback. Such instability can fundamentally change the structure and dynamics of the turbulent cascade, resulting in a significant (and anisotropic) redistribution of kinetic energy from small to large scales. In particular, three effects are observed. 1) The turbulent burning velocity can develop pulsations with significant peak-to-peak amplitudes. 2) Unstable burning can result in pressure build-up and the formation of pressure waves or shocks when the flame speed approaches or exceeds the speed of a Chapman-Jouguet deflagration. 3) Coupling of pressure and density gradients across the flame can lead to the anisotropic generation of turbulence inside the flame volume and flame acceleration. We extend our earlier analysis, which relied on a simplified single-step reaction model, by demonstrating existence of these effects in realistic chemical flames (hydrogen and methane) and in thermonuclear flames in degenerate, relativistic plasmas found in stellar interiors. Finally, we discuss the implications of these results for subgrid-scale LES combustion models. This work was supported by the Air Force

  19. Effects of Bell Speed and Flow Rate on Evaporation of Water Spray from a Rotary Bell Atomizer

    Directory of Open Access Journals (Sweden)

    Rajan Ray

    2015-05-01

    Full Text Available A phase doppler anemometer (PDA was used to determine the effects of evaporation on water spray for three rotary bell atomizer operational variable parameters: shaping air, bell speed and liquid flow. Shaping air was set at either 200 standard liters per minute (L/min or 300 L/min, bell speed was set to 30, 40 or 50 thousand rotations per minute (krpm and water flow rate was varied between 100, 200 or 300 cubic centimeters per minute (cm3/min. The total evaporation between 22.5 and 37.5 cm from the atomizer (cm3/s was calculated for all the combinations of those variables. Evaporation rate increased with higher flow rate and bell speed but no statistically significant effects were obtained for variable shaping air on interactions between parameters.

  20. An Improved Discrete-Time Model for Heterogeneous High-Speed Train Traffic Flow

    Science.gov (United States)

    Xu, Yan; Jia, Bin; Li, Ming-Hua; Li, Xin-Gang

    2016-03-01

    This paper aims to present a simulation model for heterogeneous high-speed train traffic flow based on an improved discrete-time model (IDTM). In the proposed simulation model, four train control strategies, including departing strategy, traveling strategy, braking strategy, overtaking strategy, are well defined to optimize train movements. Based on the proposed simulation model, some characteristics of train traffic flow are investigated. Numerical results indicate that the departure time intervals, the station dwell time, the section length, and the ratio of fast trains have different influence on traffic capacity and train average velocity. The results can provide some theoretical support for the strategy making of railway departments. Supported by the National Basic Research Program of China under Grant No. 2012CB725400, the National Natural Science Foundation of China under Grant No. 71222101, the Research Foundation of State Key Laboratory of Rail Traffic Control and Safety under Grant No. RCS2014ZT16, and the Fundamental Research Funds for the Central Universities No. 2015YJS088, Beijing Jiaotong University

  1. Two-dimensional computational modeling of high-speed transient flow in gun tunnel

    Science.gov (United States)

    Mohsen, A. M.; Yusoff, M. Z.; Hasini, H.; Al-Falahi, A.

    2017-09-01

    In this work, an axisymmetric numerical model was developed to investigate the transient flow inside a 7-meter-long free piston gun tunnel. The numerical solution of the gun tunnel was carried out using the commercial solver Fluent. The governing equations of mass, momentum, and energy were discretized using the finite volume method. The dynamic zone of the piston was modeled as a rigid body, and its motion was coupled with the hydrodynamic forces from the flow solution based on the six-degree-of-freedom solver. A comparison of the numerical data with the theoretical calculations and experimental measurements of a ground-based gun tunnel facility showed good agreement. The effects of parameters such as working gases and initial pressure ratio on the test conditions in the facility were examined. The pressure ratio ranged from 10 to 50, and gas combinations of air-air, helium-air, air-nitrogen, and air-CO2 were used. The results showed that steady nozzle reservoir conditions can be maintained for a longer duration when the initial conditions across the diaphragm are adjusted. It was also found that the gas combination of helium-air yielded the highest shock wave strength and speed, but a longer test time was achieved in the test section when using the CO2 test gas.

  2. Experiment of Flow Control Using Laser Energy Deposition Around High Speed Propulsion System

    Science.gov (United States)

    Lee, HyoungJin; Jeung, InSeuck; Lee, SangHun; Kim, Seihwan

    2011-11-01

    An experimental investigation was conducted to examine the effect of a pulsed Nd:YAG laser energy deposition on the shock structures in supersonic/hypersonic flow and quiescent air. The effect of the laser energy and pressure in the blast wave generation were also investigated. As a result, the strength of plasma and blast wave becomes stronger as pressure or laser energy increase. And the breakdown threshold of air by laser energy deposition is 0.015 bar at 508 mJ laser energy, the blast wave threshold generation in air by laser energy deposition is 0.100 bar at same laser energy. As qualitative analysis, schlieren images are also obtained. After the series of experiments, the effect of laser energy deposition (LED) on high speed flow around the shock—shock interaction created by a wedge and blunt body. By LED, the structure of shock—shock interaction was collapsed momentary and the pressure of the stagnation point was fluctuated while interference of wave.

  3. Quasi-three dimensional hydraulic design and performance calculation of high specific speed mixed-flow pump

    Science.gov (United States)

    Su, M.; Zhang, Y. X.; Zhang, J. Y.; Hou, H. C.

    2016-05-01

    According to the basic parameters of 211-80 high specific speed mixed-flow pump, based on the quasi-three dimensional flow theory, the hydraulic design of impeller and its matching spaced guide vanes for high specific speed mixed flow pump was completed, in which the iterative calculation of S 1, S 2 stream surfaces was employed to obtain meridional flow fields and the point-by-point integration method was employed to draw blade camber lines. Blades are thickened as well as blade leading edges are smoothed in the conformal mapping surface. Subsequently the internal fields of the whole flow passage of the designed pump were simulated by using RANS equations with RNG k-ε two-equation turbulent model. The results show that, compared with the 211-80 model, the hydraulic efficiency of the designed pump at the optimal flow rate increases 9.1%. The hydraulic efficiency of designed pump in low flow rate condition (78% designed flow rate) increases 6.46%. The hydraulic efficiency in high flow rate areas increases obviously and there is no bad phenomenon of suddenly decrease of hydraulic efficiency in model pump. From the distributions of velocity and pressure fields, it can be seen that the flow in impeller is uniform and the increase of pressure is gentle. There are no obvious impact phenomenon on impeller inlet and obvious wake shedding vortex phenomenon from impeller outlet to guide vanes inlet.

  4. Why not walk faster?

    Science.gov (United States)

    Usherwood, James Richard

    2005-09-22

    Bipedal walking following inverted pendulum mechanics is constrained by two requirements: sufficient kinetic energy for the vault over midstance and sufficient gravity to provide the centripetal acceleration required for the arc of the body about the stance foot. While the acceleration condition identifies a maximum walking speed at a Froude number of 1, empirical observation indicates favoured walk-run transition speeds at a Froude number around 0.5 for birds, humans and humans under manipulated gravity conditions. In this study, I demonstrate that the risk of 'take-off' is greatest at the extremes of stance. This is because before and after kinetic energy is converted to potential, velocities (and so required centripetal accelerations) are highest, while concurrently the component of gravity acting in line with the leg is least. Limitations to the range of walking velocity and stride angle are explored. At walking speeds approaching a Froude number of 1, take-off is only avoidable with very small steps. With realistic limitations on swing-leg frequency, a novel explanation for the walk-run transition at a Froude number of 0.5 is shown.

  5. Step-wise changes in glacier flow speed coincide with calving and glacial earthquakes at Helheim Glacier, Greenland

    DEFF Research Database (Denmark)

    Nettles, M.; Larsen, T. B.; Elósegui, P.

    2008-01-01

    Geodetic observations show several large, sudden increases in flow speed at Helheim Glacier, one of Greenland's largest outlet glaciers, during summer, 2007. These step-like accelerations, detected along the length of the glacier, coincide with teleseismically detected glacial earthquakes and major...... at Greenland's largest outlet glaciers, on timescales as short as minutes to hours, and clarify the mechanism by which glacial earthquakes occur. Citation: Nettles, M., et al. (2008), Step-wise changes in glacier flow speed coincide with calving and glacial earthquakes at Helheim Glacier, Greenland....

  6. CUFID-query: accurate network querying through random walk based network flow estimation.

    Science.gov (United States)

    Jeong, Hyundoo; Qian, Xiaoning; Yoon, Byung-Jun

    2017-12-28

    Functional modules in biological networks consist of numerous biomolecules and their complicated interactions. Recent studies have shown that biomolecules in a functional module tend to have similar interaction patterns and that such modules are often conserved across biological networks of different species. As a result, such conserved functional modules can be identified through comparative analysis of biological networks. In this work, we propose a novel network querying algorithm based on the CUFID (Comparative network analysis Using the steady-state network Flow to IDentify orthologous proteins) framework combined with an efficient seed-and-extension approach. The proposed algorithm, CUFID-query, can accurately detect conserved functional modules as small subnetworks in the target network that are expected to perform similar functions to the given query functional module. The CUFID framework was recently developed for probabilistic pairwise global comparison of biological networks, and it has been applied to pairwise global network alignment, where the framework was shown to yield accurate network alignment results. In the proposed CUFID-query algorithm, we adopt the CUFID framework and extend it for local network alignment, specifically to solve network querying problems. First, in the seed selection phase, the proposed method utilizes the CUFID framework to compare the query and the target networks and to predict the probabilistic node-to-node correspondence between the networks. Next, the algorithm selects and greedily extends the seed in the target network by iteratively adding nodes that have frequent interactions with other nodes in the seed network, in a way that the conductance of the extended network is maximally reduced. Finally, CUFID-query removes irrelevant nodes from the querying results based on the personalized PageRank vector for the induced network that includes the fully extended network and its neighboring nodes. Through extensive

  7. High-speed PIV measurements of the near-wall flow field over hairy surfaces

    Science.gov (United States)

    Winzen, Andrea; Klaas, Michael; Schröder, Wolfgang

    2013-03-01

    The geometry of the barn owl wing, that is, the planform, the camber line, and the thickness distribution, differs significantly from the wing geometry of other bird species of comparable weight and size. Moreover, the owl wing possesses special features like a velvet-like surface, fringes on the trailing edge, and a serrated leading edge. The influence on the flow field of one of the specific adaptations of the owl wing, namely the velvet-like surface structure on the suction side, was analyzed via high-speed particle-image velocimetry. Measurements were performed in a Reynolds number range of 40,000 ≤ Re c ≤ 120,000 based on the chord length and angles of attack of 0° ≤ α ≤ 6°. As a reference, a clean wing model which possesses the geometry of a natural owl wing with its distinct nose region and large thickness in conjunction with a small chordwise position of the maximum thickness was measured. A separation bubble on the suction side of the wing was found to be the dominant flow feature. The results were compared with measurements performed with the same model geometry covered with two artificial surface structures that resemble the surface of the natural wing to investigate the influence of these surfaces on the flow field. The first artificial textile, referred to as velvet 1, was selected to imitate the filament length, density, and thus the softness of the natural surface. Velvet 2, the second artificial texture, possesses longer, softer filaments and a preferred filament direction. A strong influence of the surface structures on the flow field was found for both velvet structures. The velvet seems to force the transition process in the wall-bounded shear layer at higher Reynolds numbers by redistributing the turbulent kinetic energy and thus enables the flow to reattach earlier. This leads to a stabilization and in some cases even to a reduction of the size of the separation bubble on the suction side of the wing.

  8. Numerical Study of Evaporation and Motion Characteristics of Liquid Nitrogen Droplet in High-Speed Gas Flow

    Science.gov (United States)

    Ruan, Y.; Chen, L.; Liu, X.; Chen, S.; Hou, Y.

    2017-12-01

    In the cryogenic wind tunnel, cooling the circulating gas to cryogenic temperature by spraying liquid nitrogen (LN2) is an efficient way to increase the Reynolds number. The evaporation and motion of LN2 droplets in the high-speed gas flow is the critical process that determines the cooling rate, cooling capacity and the safe operation of the down-stream compressor. In this study, a numerical model of droplet motion and evaporation in high-speed gas flow is developed and verified against experimental data. The droplet evaporation rate, diameter and velocity are obtained during the evaporation process under different gas temperatures and flow velocities. The results show that the gas temperature has dominant influence on the droplet evaporation rate. High flow speed can increase droplet evaporation effectively at the beginning process. Evaporation of droplets with different diameters follows a similar trend. The absolute evaporation rate increases with the increase of droplet diameter while the relative evaporation amount is highest for the smallest droplet due to its high area-volume ratio. This numerical study provides insight for understanding the evaporation of LN2 droplets in high-speed gas flow and useful guidelines for the design of LN2 spray cooling.

  9. Method of high speed flow field influence and restrain on laser communication

    Science.gov (United States)

    Meng, Li-xin; Wang, Chun-hui; Qian, Cun-zhu; Wang, Shuo; Zhang, Li-zhong

    2013-08-01

    For laser communication performance which carried by airplane or airship, due to high-speed platform movement, the air has two influences in platform and laser communication terminal window. The first influence is that aerodynamic effect causes the deformation of the optical window; the second one is that a shock wave and boundary layer would be generated. For subsonic within the aircraft, the boundary layer is the main influence. The presence of a boundary layer could change the air density and the temperature of the optical window, which causes the light deflection and received beam spot flicker. Ultimately, the energy hunting of the beam spot which reaches receiving side increases, so that the error rate increases. In this paper, aerodynamic theory is used in analyzing the influence of the optical window deformation due to high speed air. Aero-optics theory is used to analyze the influence of the boundary layer in laser communication link. Based on this, we focused on working on exploring in aerodynamic and aero-optical effect suppression method in the perspective of the optical window design. Based on planning experimental aircraft types and equipment installation location, we optimized the design parameters of the shape and thickness of the optical window, the shape and size of air-management kit. Finally, deformation of the optical window and air flow distribution were simulated by fluid simulation software in the different mach and different altitude fly condition. The simulation results showed that the optical window can inhibit the aerodynamic influence after optimization. In addition, the boundary layer is smoothed; the turbulence influence is reduced, which meets the requirements of the airborne laser communication.

  10. Study on Bubbly Two-Phase Flow Across Twisted Tube Bundles Based on Quasi 3D High Speed Video

    OpenAIRE

    Jicheng Zhou; Dongsheng Zhu

    2013-01-01

    In flooded evaporators, refrigerants are boiling outside the tubes. This paper focuses on the bubbly two-phase flow characteristics in twisted tube bundles. The quasi 3-D high speed video method and computational fluid dynamics are carried out to understand the effects which angles between the major axis of the cylinder and vertical direction ( ) and bubble diameters have on the motion behaviours of bubbly flow.  is adjusted to 0°, ...

  11. Large eddy simulation and direct numerical simulation of high speed turbulent reacting flows

    Science.gov (United States)

    Adumitroaie, V.; Frankel, S. H.; Madnia, C. K.; Givi, P.

    The objective of this research is to make use of Large Eddy Simulation (LES) and Direct Numerical Simulation (DNS) for the computational analyses of high speed reacting flows. Our efforts in the first phase of this research conducted within the past three years have been directed in several issues pertaining to intricate physics of turbulent reacting flows. In our previous 5 semi-annual reports submitted to NASA LaRC, as well as several technical papers in archival journals, the results of our investigations have been fully described. In this progress report which is different in format as compared to our previous documents, we focus only on the issue of LES. The reason for doing so is that LES is the primary issue of interest to our Technical Monitor and that our other findings were needed to support the activities conducted under this prime issue. The outcomes of our related investigations, nevertheless, are included in the appendices accompanying this report. The relevance of the materials in these appendices are, therefore, discussed only briefly within the body of the report. Here, results are presented of a priori and a posterior analyses for validity assessments of assumed Probability Density Function (PDF) methods as potential subgrid scale (SGS) closures for LES of turbulent reacting flows. Simple non-premixed reacting systems involving an isothermal reaction of the type A + B yields Products under both chemical equilibrium and non-equilibrium conditions are considered. A priori analyses are conducted of a homogeneous box flow, and a spatially developing planar mixing layer to investigate the performance of the Pearson Family of PDF's as SGS models. A posteriori analyses are conducted of the mixing layer using a hybrid one-equation Smagorinsky/PDF SGS closure. The Smagorinsky closure augmented by the solution of the subgrid turbulent kinetic energy (TKE) equation is employed to account for hydrodynamic fluctuations, and the PDF is employed for modeling the

  12. Using wind speed from a blade-mounted flow sensor for power and load assessment on modern wind turbines

    Directory of Open Access Journals (Sweden)

    M. M. Pedersen

    2017-11-01

    Full Text Available In this paper an alternative method to evaluate power performance and loads on wind turbines using a blade-mounted flow sensor is investigated. The hypothesis is that the wind speed measured at the blades has a high correlation with the power and loads such that a power or load assessment can be performed from a few hours or days of measurements.In the present study a blade-mounted five-hole pitot tube is used as the flow sensor as an alternative to the conventional approach, where the reference wind speed is either measured at a nearby met mast or on the nacelle using lidar technology or cup anemometers. From the flow sensor measurements, an accurate estimate of the wind speed at the rotor plane can be obtained. This wind speed is disturbed by the presence of the wind turbine, and it is therefore different from the free-flow wind speed. However, the recorded wind speed has a high correlation with the actual power production as well as the flap-wise loads as it is measured close to the blade where the aerodynamic forces are acting.Conventional power curves are based on at least 180 h of 10 min mean values, but using the blade-mounted flow sensor both the observation average time and the overall assessment time can potentially be shortened. The basis for this hypothesis is that the sensor is able to provide more observations with higher accuracy, as the sensor follows the rotation of the rotor and because of the high correlation between the flow at the blades and the power production. This is the research question addressed in this paper.The method is first tested using aeroelastic simulations where the dependence of the radial position and effect of multiple blade-mounted flow sensors are also investigated. Next the method is evaluated on the basis of full-scale measurements on a pitch-regulated, variable-speed 3.6 MW wind turbine.It is concluded that the wind speed derived from the blade-mounted flow sensor is highly correlated with the

  13. An O(n log n) Algorithm for the Two-Machine Flow Shop Problem with Controllable Machine Speeds

    NARCIS (Netherlands)

    C.P.M. van Hoesel; A.P.M. Wagelmans (Albert); M. van Vliet (Mario)

    1996-01-01

    textabstractPresents an algorithm which determines the optimal permutations for all machine speeds in O(n log n) time where the algorithm n is the number of jobs. Description of the two-machine flow shop problem; Use of the algorithm as an elementary dominance relation; Description of the algorithm;

  14. Irrigant flow in the root canal: experimental validation of an unsteady Computational Fluid Dynamics model using high-speed imaging

    NARCIS (Netherlands)

    Boutsioukis, C.; Boutsioukis, C.; Verhaagen, B.; Versluis, Michel; Kastrinakis, E.; van der Sluis, L.W.M.

    2010-01-01

    Aim  To compare the results of a Computational Fluid Dynamics (CFD) simulation of the irrigant flow within a prepared root canal, during final irrigation with a syringe and a needle, with experimental high-speed visualizations and theoretical calculations of an identical geometry and to evaluate the

  15. Irrigant flow in the root canal: experimental validation of an unsteady computational fluid dynamics model using high-speed imaging

    NARCIS (Netherlands)

    Boutsioukis, C.; Verhaagen, B.; Versluis, M.; Kastrinakis, E.; van der Sluis, L.W.M.

    2010-01-01

    Aim  To compare the results of a Computational Fluid Dynamics (CFD) simulation of the irrigant flow within a prepared root canal, during final irrigation with a syringe and a needle, with experimental high-speed visualizations and theoretical calculations of an identical geometry and to evaluate the

  16. Automated high-speed video analysis of the bubble dynamics in subcooled flow boiling

    Energy Technology Data Exchange (ETDEWEB)

    Maurus, Reinhold; Ilchenko, Volodymyr; Sattelmayer, Thomas [Technische Univ. Muenchen, Lehrstuhl fuer Thermodynamik, Garching (Germany)

    2004-04-01

    Subcooled flow boiling is a commonly applied technique for achieving efficient heat transfer. In the study, an experimental investigation in the nucleate boiling regime was performed for water circulating in a closed loop at atmospheric pressure. The test-section consists of a rectangular channel with a one side heated copper strip and a very good optical access. For the optical observation of the bubble behaviour the high-speed cinematography is used. Automated image processing and analysis algorithms developed by the authors were applied for a wide range of mass flow rates and heat fluxes in order to extract characteristic length and time scales of the bubbly layer during the boiling process. Using this methodology, a huge number of bubble cycles could be analysed. The structure of the developed algorithms for the detection of the bubble diameter, the bubble lifetime, the lifetime after the detachment process and the waiting time between two bubble cycles is described. Subsequently, the results from using these automated procedures are presented. A remarkable novelty is the presentation of all results as distribution functions. This is of physical importance because the commonly applied spatial and temporal averaging leads to a loss of information and, moreover, to an unjustified deterministic view of the boiling process, which exhibits in reality a very wide spread of bubble sizes and characteristic times. The results show that the mass flux dominates the temporal bubble behaviour. An increase of the liquid mass flux reveals a strong decrease of the bubble life - and waiting time. In contrast, the variation of the heat flux has a much smaller impact. It is shown in addition that the investigation of the bubble history using automated algorithms delivers novel information with respect to the bubble lift-off probability. (Author)

  17. The influence of current speed and vegetation density on flow structure in two macrotidal eelgrass canopies

    Science.gov (United States)

    Lacy, Jessica R.; Wyllie-Echeverria, Sandy

    2011-01-01

    The influence of eelgrass (Zostera marina) on near-bed currents, turbulence, and drag was investigated at three sites in two eelgrass canopies of differing density and at one unvegetated site in the San Juan archipelago of Puget Sound, Washington, USA. Eelgrass blade length exceeded 1 m. Velocity profiles up to 1.5 m above the sea floor were collected over a spring-neap tidal cycle with a downward-looking pulse-coherent acoustic Doppler profiler above the canopies and two acoustic Doppler velocimeters within the canopies. The eelgrass attenuated currents by a minimum of 40%, and by more than 70% at the most densely vegetated site. Attenuation decreased with increasing current speed. The data were compared to the shear-layer model of vegetated flows and the displaced logarithmic model. Velocity profiles outside the meadows were logarithmic. Within the canopies, most profiles were consistent with the shear-layer model, with a logarithmic layer above the canopy. However, at the less-dense sites, when currents were strong, shear at the sea floor and above the canopy was significant relative to shear at the top of the canopy, and the velocity profiles more closely resembled those in a rough-wall boundary layer. Turbulence was strong at the canopy top and decreased with height. Friction velocity at the canopy top was 1.5–2 times greater than at the unvegetated, sandy site. The coefficient of drag CD on the overlying flow derived from the logarithmic velocity profile above the canopy, was 3–8 times greater than at the unvegetated site (0.01–0.023 vs. 2.9 × 10−3).

  18. Characteristic analysis on the pressure fluctuation in the impeller of a low specific speed mixed flow pump

    Science.gov (United States)

    Zhang, W. W.; Yu, Z. Y.; Zhu, B. S.

    2016-05-01

    To explore the pressure fluctuation characteristics of a low speed specific speed mixed flow pump caused by rotor-stator interaction, the unsteady flow was simulated with CFX for the whole flow passage of a mixed flow pump with a specific speed of 148.8. The structured mesh of the computation domain was generated with ICEM CFD and TurboGrid, and mesh-independent analysis was done in the design condition. Through the comparison with the experiment data, the reliability of the simulation was verified. In different locations of the impeller passage, monitoring points were set. With Fast Fourier Transform (FFT), the characteristic analysis on the pressure fluctuation in the impeller passage was done for three flow rate conditions (0.75Qd, Qd, 1.25Qd). The results show that the pressure fluctuation amplitude increases from the inlet to the outlet. And the maximum values in different flow rates exist near the hub of the outlet; The pressure fluctuation is small in the design condition, but the largest in the small flow rate condition, accompanied by the secondary dominant frequencies with large amplitudes; In the small flow rate condition and design condition, the dominant frequency varies from the inlet to the outlet because the combine action of the impeller and guide vane; while in the large flow rate condition, the pressure fluctuation in the whole impeller passage is affected significantly by the guide vane, and the domain frequency is 8 times the rotational frequency of impeller. In addition, the change of pressure fluctuation from the pressure surface to the suction surface in the off-design conditions is investigated, and the results demonstrates that the intensity of the pressure fluctuation in the impeller passage is closely related with the impeller as well as the distribution of the vorticity and the pressure.

  19. Verification of drag-reduction capabilities of stiff compliant coatings in air flow at moderate speeds

    Directory of Open Access Journals (Sweden)

    Andrey V. Boiko

    2011-12-01

    Full Text Available Skin frictional drag reduction efficiency of “stiff” compliant coating was investigated in a wind tunnel experiment. Flat plate compliant coating inserts were installed in a wind tunnel and the measurements of skin frictional drag and velocity field were carried out. The compliant coatings with varying viscoelastic properties had been prepared using different composition. In order to optimize the coating thickness, the most important design parameter, the dynamic viscoelastic properties had been determined experimentally. The aging of the materials (variation of their properties during half a year was documented as well. A design procedure proposed by Kulik et al. (2008 was applied to get an optimal value for the coating thickness. Along with the drag measurement using the strain balance, velocity and pressure were measured for different coatings. The compliant coatings with the thickness h = 7mm achieved 4∼5% drag reduction within a velocity range 30∼40 m/s. The drag reduction mechanism of the attenuation of turbulence velocity fluctuations due to the compliant coating was demonstrated. It is envisioned that larger drag reduction effect is obtainable at higher flow velocities for high speed trains and subsonic aircrafts.

  20. Flow Structure Downstream of a Mechanical Heart Valve during Systole: Investigation Using High-Speed Particle Image Velocimetry

    Science.gov (United States)

    Oshkai, Peter; Haji-Esmaeili, Farida

    2007-11-01

    High speed digital particle image velocimetry is employed to study turbulent flow through a bileaflet mechanical heart valve during systolic and diastolic phases of a cardiac cycle. Unsteady vortex shedding from the valve's leaflets displays distinct characteristic frequencies, depending on the opening angle of each leaflet. Small- and large-scale transverse oscillations of the separated shear layers are studied using global quantitative flow imaging approach. Implementation of high-speed digital particle image velocimetry technique yields quantitative information about vortex shedding frequencies and trajectories of the shed vortices downstream of the valve. Turbulent flow structures including jet-like regions and shed vortices are characterized in terms of patterns of instantaneous and time-averaged velocity, vorticity, and streamline topology.

  1. Walking economy during cued versus non-cued self-selected treadmill walking in persons with Parkinson's disease.

    Science.gov (United States)

    Gallo, Paul M; McIsaac, Tara L; Garber, Carol Ewing

    2014-01-01

    Gait impairments related to Parkinson's disease (PD) include variable step length and decreased walking velocity, which may result in poorer walking economy. Auditory cueing is a common method used to improve gait mechanics in PD that has been shown to worsen walking economy at set treadmill walking speeds. It is unknown if auditory cueing has the same effects on walking economy at self-selected treadmill walking speeds. To determine if auditory cueing will affect walking economy at self-selected treadmill walking speeds and at speeds slightly faster and slower than self-selected. Twenty-two participants with moderate PD performed three, 6-minute bouts of treadmill walking at three speeds (self-selected and ± 0.22 m·sec-1). One session used cueing and the other without cueing. Energy expenditure was measured and walking economy was calculated (energy expenditure/power). Poorer walking economy and higher energy expenditure occurred during cued walking at a self-selected and a slightly faster walking speed, but there was no apparent difference at the slightly slower speed. These results suggest that potential gait benefits of auditory cueing may come at an energy cost and poorer walking economy for persons with PD at least at some treadmill walking speeds.

  2. 3D scanning PIV applied to an air flow in a motored engine using digital high-speed video

    Science.gov (United States)

    Brücker, Ch

    1997-12-01

    3D scanning particle image velocimetry (SPIV) provides particle images in a large set of parallel light-sheet planes using a rapid scanning light-sheet which samples the flow in depth from which the three-dimensional flow field can be reconstructed in the scanned volume. Together with a digital high-speed video technique and a high-speed rotating drum scanner for 3D beam scanning, first 3D SPIV measurements were carried out in a motored model engine with a transparent cylinder and piston crown. Attention was focused on the generation of small-scale structures during compression strokes. Using a spatial cross-correlation of particle images in the overlapping sheets, the 3D flow field could be recovered from the sheet-wise tomographic recorded flow volume. This demonstrates the potential of 3D SPIV in engine flows since 3D information can be obtained from a single view and therefore the method can be applied in actual research engines already in use without any additional modification. The first results of the feasibility study have shown complex flow at the very end of compression which is characterized here by meandering monopolar and dipolar vortices within the main swirling flow which interact with the centre. It is suggested that the observed vortex splitting and shearing is an important contribution to the creation of turbulence.

  3. Active control of massively separated high-speed/base flows with electric arc plasma actuators

    Science.gov (United States)

    DeBlauw, Bradley G.

    The current project was undertaken to evaluate the effects of electric arc plasma actuators on high-speed separated flows. Two underlying goals motivated these experiments. The first goal was to provide a flow control technique that will result in enhanced flight performance for supersonic vehicles by altering the near-wake characteristics. The second goal was to gain a broader and more sophisticated understanding of these complex, supersonic, massively-separated, compressible, and turbulent flow fields. The attainment of the proposed objectives was facilitated through energy deposition from multiple electric-arc plasma discharges near the base corner separation point. The control authority of electric arc plasma actuators on a supersonic axisymmetric base flow was evaluated for several actuator geometries, frequencies, forcing modes, duty cycles/on-times, and currents. Initially, an electric arc plasma actuator power supply and control system were constructed to generate the arcs. Experiments were performed to evaluate the operational characteristics, electromagnetic emission, and fluidic effect of the actuators in quiescent ambient air. The maximum velocity induced by the arc when formed in a 5 mm x 1.6 mm x 2 mm deep cavity was about 40 m/s. During breakdown, the electromagnetic emission exhibited a rise and fall in intensity over a period of about 340 ns. After breakdown, the emission stabilized to a near-constant distribution. It was also observed that the plasma formed into two different modes: "high-voltage" and "low-voltage". It is believed that the plasma may be switching between an arc discharge and a glow discharge for these different modes. The two types of plasma do not appear to cause substantial differences on the induced fluidic effects of the actuator. In general, the characterization study provided a greater fundamental understanding of the operation of the actuators, as well as data for computational model comparison. Preliminary investigations

  4. Investigation of High-Speed Erythrocyte Flow and Erythrocyte-Wall Impact in a Lab-on-a-Chip.

    Science.gov (United States)

    Li, Ping; Zheng, Lu; Zhang, Di; Xie, Yonghui; Feng, Yi; Xie, Gongnan

    2016-11-01

    To better understand erythrocyte high-speed motion, collision characteristics, and collision-induced hemolysis probability in rotary blood pumps, a visual experimental investigation of high-speed erythrocyte flow and erythrocyte-wall collision in a lab-on-a-chip was performed. The erythrocyte suspension was driven by a microsyringe pump connected to the microchip, and the erythrocyte flow and erythrocyte-wall impact process were observed and imaged by an optical microscope and a high-speed camera. Two types of microchips with different impact surfaces (flat and curved) were employed. The motion and deformation features before and after collision were studied in detail. The results show that erythrocytes not only move along the flow direction in the flow plane but also rotate and roll in three-dimensional space. Erythrocytes keep discoid shape during the movement in the straight channel, but their deformations during collision are mainly classified into two types: erythrocyte structure is still stable and the erythrocyte performance can be ensured to a certain extent in the TypeA deformation, while the TypeB deformation makes the membrane more likely to fracture on the stretched side, increasing the probability of hemolysis. Furthermore, the movements and deformations of the erythrocytes after collision are analyzed and classified into two types: bouncing and slipping. Moreover, a simulation method for the flow in microchip was performed and validated through a comparison of the streamlines and experimental erythrocytes tracks, which can be further employed to predict the high-speed blood flow, associated with collision process in mechanical blood pump. Copyright © 2016 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

  5. Comparison between Mother, ActiGraph wGT3X-BT, and a hand tally for measuring steps at various walking speeds under controlled conditions

    DEFF Research Database (Denmark)

    Riel, Henrik; Rathleff, Camilla Rams; Kalstrup, Pernille Møller

    2016-01-01

    Walking is endorsed as health enhancing and is the most common type of physical activity among older adults. Accelerometers are superior to self-reports when measuring steps, however, if they are to be used by clinicians the validity is of great importance. The aim of this study was to investigat...

  6. The combined effects of guidance force, bodyweight support and gait speed on muscle activity during able-bodied walking in the Lokomat

    NARCIS (Netherlands)

    van Kammen, Klaske; Boonstra, Anne M.; van der Woude, Lucas H. V.; Reinders - Messelink, Heelen; den Otter, Rob

    Background: The ability to provide automated movement guidance is unique for robot assisted gait trainers such as the Lokomat. For the design of training protocols for the Lokomat it is crucial to understand how movement guidance affects the patterning of muscle activity that underlies walking, and

  7. Investigation of the Shear Flow Effect and Tip Clearance on a Low Speed Axial Flow Compressor Cascade

    Directory of Open Access Journals (Sweden)

    Mahesh Varpe

    2013-01-01

    Full Text Available This paper explores the effect of inlet shear flow on the tip leakage flow in an axial flow compressor cascade. A flow with a high shear rate is generated in the test section of an open circuit cascade wind tunnel by using a combination of screens with a prescribed solidity. It is observed that a stable shear flow of shear rate 1.33 is possible and has a gradual decay rate until 15 times the height of the shear flow generator downstream. The computational results obtained agree well with the available experimental data on the baseline configuration. The detailed numerical analysis shows that the tip clearance improves the blade loading near the tip through the promotion of favorable incidence by the tip leakage flow. The tip clearance shifts the centre of pressure on the blade surface towards the tip. It, however, has no effect on the distribution of end wall loss and deviation angle along the span up to 60% from the hub. In the presence of a shear inflow, the end wall effects are considerable. On the other hand, with a shear inflow, the effects of tip leakage flow are observed to be partly suppressed. The shear flow reduces the tip leakage losses substantially in terms of kinetic energy associated with it.

  8. Increase of economy of torque flow pump with high specific speed

    Science.gov (United States)

    Gusak, A. G.; Krishtop, I. V.; German, V. F.; Baga, V. N.

    2017-08-01

    Torque flow pumps are widely spread types of energy machines, which are used in majority of modern branches of industry for pumping of dirty media. The main task of researchers of torque flow pumps is increase of such pumps effectiveness for higher feed. Hydraulic losses for torque flow pumps are caused by working process of such pumps and are inevitable. Decrease of losses can be obtained by means of optimization of hydraulic flow part geometry. Modern approach to design of pump outlet introduces new constructive solutions which can increase economy of torque flow pumps. The aim of this research is increase of economy of torque flow pumps by means of application of spatial outlet and investigation of its geometry on pump characteristics. Analytical and numerical methods of liquid flow research for hydraulic flow part of torque flow pump were used in this paper. Moreover, influence of hydraulic flow part geometry of different designs of “Turo” type torque flow pumps outlets on pump characteristics was investigated. Numerical research enabled to study process of energy transfer of torque flow pump and evaluate influence of geometrical dimensions of spatial spiral outlet on its characteristics. Besides numerical research confirmed introduced regularity of peripheral velocity distribution in outlet. Velocity moment distribution in outlet was obtained during implementation of numerical research. Implemented bench tests of torque flow pump prototypes enabled to obtain real characteristics of pump and confirm effectiveness of spatial geometry of outlet application for such pump.

  9. High-Speed Visual Analysis of Fluid Flow and Heat Transfer in Oscillating Heat Pipes with Different Diameters

    Directory of Open Access Journals (Sweden)

    Xiangdong Liu

    2016-10-01

    Full Text Available The oscillating heat pipe (OHP is a new member in the family of heat pipes, and it has great potential applications in energy conservation. However, the fluid flow and heat transfer in the OHP as well as the fundamental effects of inner diameter on them have not been fully understood, which are essential to the design and optimization of the OHP in real applications. Therefore, by combining the high-speed visualization method and infrared thermal imaging technique, the fluid flow and thermal performance in the OHPs with inner diameters of 1, 2 and 3 mm are presented and analyzed. The results indicate that three fluid flow motions, including small oscillation, bulk oscillation and circulation, coexist or, respectively, exist alone with the increasing heating load under different inner diameters, with three flow patterns occurring in the OHPs, viz. bubbly flow, slug flow and annular flow. These fluid flow motions are closely correlated with the heat and mass transfer performance in the OHPs, which can be reflected by the characteristics of infrared thermal images of condensers. The decrease in the inner diameter increases the frictional flow resistance and capillary instability while restricting the nucleate boiling in OHPs, which leads to a smaller proportion of bubbly flow, a larger proportion of short slug flow, a poorer thermal performance, and easier dry-out of working fluid. In addition, when compared with the 2 mm OHP, the increasing role of gravity induces the thermosyphon effect and weakens the ‘bubble pumping’ action, which results in a little smaller and bigger thermal resistances of 3 mm OHP under small and bulk oscillation of working fluid, respectively.

  10. Quantitative visualization of high-speed 3D turbulent flow structures using holographic interferometric tomography

    Science.gov (United States)

    Timmerman, B. H.; Watt, D. W.; Bryanston-Cross, P. J.

    1999-02-01

    Using holographic interferometry the three-dimensional structure of unsteady and large-scale motions within subsonic and transonic turbulent jet flows has been studied. The instantaneous 3D flow structure is obtained by tomographic reconstruction techniques from quantitative phase maps recorded using a rapid-switching, double reference beam, double pulse laser system. The reconstruction of the jets studied here reveal a three-dimensional nature of the flow. In particular an increasing complexity can be seen in the turbulence as the flow progresses from the jet nozzle. Furthermore, a coherent three-dimensional, possibly rotating, structure can be seen to exist within these jets. The type of flow features illustrated here are not just of fundamental importance for understanding the behavior of free jet flows, but are also common to a number of industrial applications, ranging from the combustion flow within an IC engine to the transonic flow through the stages of a gas turbine.

  11. A computer code for multiphase all-speed transient flows in complex geometries. MAST version 1.0

    Science.gov (United States)

    Chen, C. P.; Jiang, Y.; Kim, Y. M.; Shang, H. M.

    1991-01-01

    The operation of the MAST code, which computes transient solutions to the multiphase flow equations applicable to all-speed flows, is described. Two-phase flows are formulated based on the Eulerian-Lagrange scheme in which the continuous phase is described by the Navier-Stokes equation (or Reynolds equations for turbulent flows). Dispersed phase is formulated by a Lagrangian tracking scheme. The numerical solution algorithms utilized for fluid flows is a newly developed pressure-implicit algorithm based on the operator-splitting technique in generalized nonorthogonal coordinates. This operator split allows separate operation on each of the variable fields to handle pressure-velocity coupling. The obtained pressure correction equation has the hyperbolic nature and is effective for Mach numbers ranging from the incompressible limit to supersonic flow regimes. The present code adopts a nonstaggered grid arrangement; thus, the velocity components and other dependent variables are collocated at the same grid. A sequence of benchmark-quality problems, including incompressible, subsonic, transonic, supersonic, gas-droplet two-phase flows, as well as spray-combustion problems, were performed to demonstrate the robustness and accuracy of the present code.

  12. Stride lengths, speed and energy costs in walking of Australopithecus afarensis: using evolutionary robotics to predict locomotion of early human ancestors

    OpenAIRE

    Sellers, William I; Cain, Gemma M; Wang, Weijie; Crompton, Robin H

    2005-01-01

    This paper uses techniques from evolutionary robotics to predict the most energy-efficient upright walking gait for the early human relative Australopithecus afarensis, based on the proportions of the 3.2 million year old AL 288-1 ‘Lucy’ skeleton, and matches predictions against the nearly contemporaneous (3.5–3.6 million year old) Laetoli fossil footprint trails. The technique creates gaits de novo and uses genetic algorithm optimization to search for the most efficient patterns of simulated...

  13. Effect of Nordic Walking and Water Aerobics Training on Body Composition and the Blood Flow in Lower Extremities in Elderly Women

    Directory of Open Access Journals (Sweden)

    Jasiński Ryszard

    2015-03-01

    Full Text Available Nordic walking and water aerobics are very popular forms of physical activity in the elderly population. The aim of the study was to evaluate the influence of regular health training on the venous blood flow in lower extremities and body composition in women over 50 years old. Twenty-four women of mean age 57.9 (± 3.43 years, randomly divided into three groups (Nordic walking, water aerobics, and non-training, participated in the study. The training lasted 8 weeks, with one-hour sessions twice a week. Dietary habits were not changed. Before and after training vein refilling time and the function of the venous pump of the lower extremities were measured by photoplethysmography. Body composition was determined by bioelectrical impedance. Eight weeks of Nordic walking training improved the venous blood flow in lower extremities and normalized body composition in the direction of reducing chronic venous disorder risk factors. The average values of the refilling time variable (p = 0.04, p = 0.02, respectively decreased in both the right and the left leg. After training a statistically significant increase in the venous pump function index was found only in the right leg (p = 0.04. A significant increase in fat-free mass, body cell mass and total body water was observed (p = 0.01, whereas body mass, the body mass index, and body fat decreased (p < 0.03. With regard to water aerobic training, no similar changes in the functions of the venous system or body composition were observed.

  14. Interstellar clouds in high-speed, supersonic flows: Two-dimensional simulations

    Science.gov (United States)

    Schiano, A. V. R.; Christiansen, Wayne A.; Knerr, Jeffrey M.

    1995-01-01

    We present a series of gasdynamical simulations of the interaction of a dense, cool interstellar cloud with a high-speed, supersonic wind that confines and accelerates the embedded cloud. Our goal is to attempt to determine if such clouds can survive various potentially disruptive instabilities, that occur at their peripheries, long enough to be accelerated to speeds which are comparable to the wind velocity. These simulations are performed using two-dimensional, Eulerian gas dynamics on both an axisymmetric (about the cloud axis) and 'slab' geometric grid. The spatial and temporal resolutions of the simulations are varied over a wide range to investigate the effects of small-scale instabilities on the overall acceleration of clouds and the development of large-scale, disruptive instabilities. Also, we study the effects of wind/cloud Mach number variations by changing the wind speed constant at about 12 km/s (which corresponds to a cloud temperature of 10,000 K). The current simulations track the evolution of clouds as they are accelerated to speeds approximately 4-5 times greater than their internal sound speeds. Furthermore, the models with the highest resolution were extended far beyond quasi-linear Rayleigh-Taylor growth times reaching 6-7 Rayleigh-Taylor growth times for the largest scale instabilities before being terminated because of the accumulation of errors at the rear grid boundary.

  15. Cadence® High-Speed PCB Layout Flow Workshop

    CERN Document Server

    2003-01-01

    Last release of Cadence High-Speed PCB Design methodology (PE142) based on Concept-HDL schematic editor, Constraint Manager, SPECCTRAQuest signal integrity analysis tool and ALLEGRO layout associated with SPECCTRA auto router tools, is now enough developed and stable to be taken into account for high-speed board designs at CERN. The implementation of this methodology, build around the new Constraint Manager program, is essential when you have to develop a board having a lot of high-speed design rules such as terminated lines, large bus structures, maximum length, timing, crosstalk etc.. that could not be under control by traditional method. On more conventional designs, formal aspect of the methodology could avoid misunderstanding between hardware and ALLEGRO layout designers, minimizing prototype iteration, development time and price. The capability to keep trace of the original digital designer intents in schematic or board layout, loading formal constraints in EDMS, could also be considered for LHC electro...

  16. Cadence® High High-Speed PCB Design Flow Workshop

    CERN Document Server

    2006-01-01

    Last release of Cadence High-Speed PCB Design methodology (PE142) based on Concept-HDL schematic editor, Constraint Manager, SPECCTRAQuest signal integrity analysis tool and ALLEGRO layout associated with SPECCTRA auto router tools, is now enough developed and stable to be taken into account for high-speed board designs at CERN. The implementation of this methodology, build around the new Constraint Manager program, is essential when you have to develop a board having a lot of high-speed design rules such as terminated lines, large bus structures, maximum length, timing, crosstalk etc.. that could not be under control by traditional method. On more conventional designs, formal aspect of the methodology could avoid misunderstanding between hardware and ALLEGRO layout designers, minimizing prototype iteration, development time and price. The capability to keep trace of the original digital designer intents in schematic or board layout, loading formal constraints in EDMS, could also be considered for LHC electro...

  17. Modified Motor Vehicles Travel Speed Models on the Basis of Curb Parking Setting under Mixed Traffic Flow

    Directory of Open Access Journals (Sweden)

    Zhenyu Mei

    2012-01-01

    Full Text Available The ongoing controversy about in what condition should we set the curb parking has few definitive answers because comprehensive research in this area has been lacking. Our goal is to present a set of heuristic urban street speed functions under mixed traffic flow by taking into account impacts of curb parking. Two impacts have been defined to classify and quantify the phenomena of motor vehicles' speed dynamics in terms of curb parking. The first impact is called Space impact, which is caused by the curb parking types. The other one is the Time impact, which results from the driver maneuvering in or out of parking space. In this paper, based on the empirical data collected from six typical urban streets in Nanjing, China, two models have been proposed to describe these phenomena for one-way traffic and two-way traffic, respectively. An intensive experiment has been conducted in order to calibrate and validate these proposed models, by taking into account the complexity of the model parameters. We also provide guidelines in terms of how to cluster and calculate those models' parameters. Results from these models demonstrated promising performance of modeling motor vehicles' speed for mixed traffic flow under the influence of curb parking.

  18. Nordic Walking Practice Might Improve Plantar Pressure Distribution

    Science.gov (United States)

    Perez-Soriano, Pedro; Llana-Belloch, Salvador; Martinez-Nova, Alfonso; Morey-Klapsing, G.; Encarnacion-Martinez, Alberto

    2011-01-01

    Nordic walking (NW), characterized by the use of two walking poles, is becoming increasingly popular (Morgulec-Adamowicz, Marszalek, & Jagustyn, 2011). We studied walking pressure patterns of 20 experienced and 30 beginner Nordic walkers. Plantar pressures from nine foot zones were measured during trials performed at two walking speeds (preferred…

  19. Biomechanical conditions of walking

    CERN Document Server

    Fan, Y F; Luo, L P; Li, Z Y; Han, S Y; Lv, C S; Zhang, B

    2015-01-01

    The development of rehabilitation training program for lower limb injury does not usually include gait pattern design. This paper introduced a gait pattern design by using equations (conditions of walking). Following the requirements of reducing force to the injured side to avoid further injury, we developed a lower limb gait pattern to shorten the stride length so as to reduce walking speed, to delay the stance phase of the uninjured side and to reduce step length of the uninjured side. This gait pattern was then verified by the practice of a rehabilitation training of an Achilles tendon rupture patient, whose two-year rehabilitation training (with 24 tests) has proven that this pattern worked as intended. This indicates that rehabilitation training program for lower limb injury can rest on biomechanical conditions of walking based on experimental evidence.

  20. Infrared thermography investigation of transitional flow over isolated roughness at high speed

    NARCIS (Netherlands)

    Ye, Q.; Schrijer, F.F.J.; Scarano, F.

    The transitional flow features over and downstream of isolated roughness elements in hypersonic flow are investigated by means of infrared thermography. The local heat flux distribution in the wake of the roughness element reveals the footprint of multiple streamwise counter-rotating vortex pairs.

  1. Dynamic walking features and improved walking performance in multiple sclerosis patients treated with fampridine (4-aminopyridine).

    Science.gov (United States)

    Keune, Philipp M; Cocks, Adam J; Young, William R; Burschka, Janina M; Hansen, Sascha; Hofstadt-van Oy, Ulrich; Oschmann, Patrick; Muenssinger, Jana

    2015-09-24

    Impaired walking capacity is a frequent confinement in Multiple Sclerosis (MS). Patients are affected by limitations in coordination, walking speed and the distance they may cover. Also abnormal dynamic walking patterns have been reported, involving continuous deceleration over time. Fampridine (4-aminopyridine), a potassium channel blocker, may improve walking in MS. The objective of the current study was to comprehensively examine dynamic walking characteristics and improved walking capacity in MS patients treated with fampridine. A sample of N = 35 MS patients (EDSS median: 4) underwent an electronic walking examination prior to (Time 1), and during treatment with fampridine (Time 2). Patients walked back and forth a distance of 25 ft for a maximum period of 6 min (6-minute 25-foot-walk). Besides the total distance covered, average speed on the 25-foot distance and on turns was determined separately for each test minute, at Time 1 and Time 2. Prior to fampridine administration, 27/35 patients (77 %) were able to complete the entire 6 min of walking, while following the administration, 34/35 patients (97 %) managed to walk for 6 min. In this context, walking distance considerably increased and treatment was associated with faster walking and turning across all six test minutes (range of effect sizes: partial eta squared = .34-.72). Importantly, previously reported deceleration across test minutes was consistently observable at Time 1 and Time 2. Fampridine administration is associated with improved walking speed and endurance. Regardless of a treatment effect of fampridine, the previously identified, abnormal dynamic walking feature, i.e. the linear decline in walking speed, may represent a robust feature. The dynamic walking feature might hence be considered as a candidate for a new outcome measure in clinical studies involving interventions other than symptomatic treatment, such as immune-modulating medication. DRKS00009228 (German Clinical Trials Register

  2. Characterization of a Laser-Generated Perturbation in High-Speed Flow for Receptivity Studies

    Science.gov (United States)

    2014-01-01

    with disturbances that are difficult to characterize, such as those created by jets11 and speakers .12 The few high-speed studies of the receptivity to...laser to a small region in the freestream of a wind tunnel. This creates a laser-induced breakdown plasma in the freestream. This plasma quickly...continuous light source. In this case, the light source used was a xenon arc lamp. Variations in the light intensity and in the room temperature are accounted

  3. Investigation on internal flow of draft tube at overload condition in low specific speed Francis turbine

    Science.gov (United States)

    Tamura, Yuta; Tani, Kiyohito

    2016-11-01

    The cavitating vortices causes the unsteady phenomena like the pressure fluctuation, the noise and the vibration in the draft tube at the overload condition which is the far operating point from the design point. Because the full load was normally near the design point, there were few troubles due to cavitating vortices at the full load. Today, however, the design point is sometimes set to lower load to achieve the high efficiency from the partial load to the full load in low specific speed Francis turbines, which have good performance to a change in a discharge. Then, the full load is relatively further from the design point. As the result, the potential for the cavitating vortices at the full load is increased. To control of the unsteady phenomena at the full load, the study focused on the cavitating vortices at the overload condition is important. This paper presents the unsteady behavior of the cavitating vortices at the overload condition with the scaled model of specific speed NQE=0.083. On the experimental approach, the pressure pulsation in the upper draft tube was measured and the unsteady behavior of cavitating vortices was taken movies with a high speed camera. On the numerical approach, Computational Fluid Dynamics (CFD) adopting a two-phase unsteady analysis was carried out. The pressure fluctuation and the velocity distribution of two runners, an original and a newly designed, were compared.

  4. Numerical investigation of the flow phenomena around a low specific speed Francis turbine's guide vane cascade

    Science.gov (United States)

    Chitrakar, Sailesh; Singh Thapa, Biraj; Dahlhaug, Ole Gunnar; Prasad Neopane, Hari

    2016-11-01

    Guide vanes of Francis turbines convey a significant influence on the flow field at the inlet of the runner. This influence is in the form of pressure pulsation, caused due to rotor-stator-interaction. A guide vane cascade containing a single blade passage was developed to predict the flow field experimentally. Firstly, this paper investigates flow phenomena around the guide vane cascade through computational techniques. A numerical model is prepared with three different turbulence models. The velocity distribution obtained from these models are compared with experimental results at two circumferential midspan locations. Secondly, the influence of increasing the clearance gap on the flow is studied. Such gaps are expected to increase when the flow containing eroding particles passes through the turbine. This paper also shows that the pressure difference between the pressure and the suction side of guide vane influences the leakage flow through the gap. Hence, reduction of the pressure gradient will reduce leakages through clearance gaps, hereby condensing the subsequent effect of pressure pulsations and erosion. This study also shows that the effect of the gap is prominent in the near wall regions which are close to the gap, whereas it dissipates gradually towards the midspan.

  5. Treadmill Interface for Virtual Reality vs. Overground Walking: A Comparison of Gait in Individuals with and without Pain.

    Science.gov (United States)

    Powell, Wendy; Stevens, Brett; Simmonds, Maureen

    2009-01-01

    A treadmill (TR) interfaced with a virtual reality (VR) system can provide an engaging environment that could improve activity adherence and walking function for individuals with pain. Furthermore, inclusion of discrete visual and auditory cues into the VR environment (e.g. manipulation of optic flow speed or audio beat frequency) could improve walking. This study compared gait characteristics (speed and cadence) of a baseline over ground walk (OVR) with a TR walk as part of a project to develop gait referenced visual and auditory frequency cues. Thirty-six participants aged between 22 and 80 years, with pain (n=19) and without pain (n=17) took part. A 2 x 2 MANOVA conducted on the speed and cadence for all participants showed a significant difference between pain and control groups for speed (F1,34=9.56, p1,34=5.75, p1,34=81.39, p1,34=25.46, p<0.01). Differences between OVR and TR walking indicate that visual or auditory cues for VR walk training should be referenced according to TR baseline measures.

  6. Speeding up the flash calculations in two-phase compositional flow simulations - The application of sparse grids

    KAUST Repository

    Wu, Yuanqing

    2015-03-01

    Flash calculations have become a performance bottleneck in the simulation of compositional flow in subsurface reservoirs. We apply a sparse grid surrogate model to substitute the flash calculation and thus try to remove the bottleneck from the reservoir simulation. So instead of doing a flash calculation in each time step of the simulation, we just generate a sparse grid approximation of all possible results of the flash calculation before the reservoir simulation. Then we evaluate the constructed surrogate model to approximate the values of the flash calculation results from this surrogate during the simulations. The execution of the true flash calculation has been shifted from the online phase during the simulation to the offline phase before the simulation. Sparse grids are known to require only few unknowns in order to obtain good approximation qualities. In conjunction with local adaptivity, sparse grids ensure that the accuracy of the surrogate is acceptable while keeping the memory usage small by only storing a minimal amount of values for the surrogate. The accuracy of the sparse grid surrogate during the reservoir simulation is compared to the accuracy of using a surrogate based on regular Cartesian grids and the original flash calculation. The surrogate model improves the speed of the flash calculations and the simulation of the whole reservoir. In an experiment, it is shown that the speed of the online flash calculations is increased by about 2000 times and as a result the speed of the reservoir simulations has been enhanced by 21 times in the best conditions.

  7. Walking Problems

    Science.gov (United States)

    ... your legs or feet Movement disorders such as Parkinson's disease Diseases such as arthritis or multiple sclerosis Vision or balance problems Treatment of walking problems depends on the cause. Physical therapy, surgery, or mobility aids may help.

  8. Application of X-ray micro-computed tomography on high-speed cavitating diesel fuel flows

    Energy Technology Data Exchange (ETDEWEB)

    Mitroglou, N.; Lorenzi, M.; Gavaises, M. [City University London, School of Mathematics Computer Science and Engineering, London (United Kingdom); Santini, M. [University of Bergamo, Department of Engineering, Bergamo (Italy)

    2016-11-15

    The flow inside a purpose built enlarged single-orifice nozzle replica is quantified using time-averaged X-ray micro-computed tomography (micro-CT) and high-speed shadowgraphy. Results have been obtained at Reynolds and cavitation numbers similar to those of real-size injectors. Good agreement for the cavitation extent inside the orifice is found between the micro-CT and the corresponding temporal mean 2D cavitation image, as captured by the high-speed camera. However, the internal 3D structure of the developing cavitation cloud reveals a hollow vapour cloud ring formed at the hole entrance and extending only at the lower part of the hole due to the asymmetric flow entry. Moreover, the cavitation volume fraction exhibits a significant gradient along the orifice volume. The cavitation number and the needle valve lift seem to be the most influential operating parameters, while the Reynolds number seems to have only small effect for the range of values tested. Overall, the study demonstrates that use of micro-CT can be a reliable tool for cavitation in nozzle orifices operating under nominal steady-state conditions. (orig.)

  9. The role of particle-turbulence interactions on the pressure field near high-speed shear flows

    Science.gov (United States)

    Capecelatro, Jesse; Shallcross, Gregory; Buchta, David

    2017-11-01

    Heavy particles in turbulent flows, such as water droplets in air, are well-known to modify the carrier-phase velocity fluctuations. In high-speed flows, the turbulence provides a mechanism to radiate pressure fluctuations, which are usually considered in the safety and reliability of engineering applications, such as those environments near high-speed jets on aircraft carriers. In this presentation, we analyze the potential for reducing near-field pressure fluctuations via turbulence modulation by a disperse phase. Direct numerical simulations of particle-laden mixing layers are conducted for a range of Mach numbers, volume fractions, and Stokes numbers. Different turbulence regimes are identified based on the strength of interphase coupling characterized by the mass loading. The pressure intensity is observed to decrease with a comparable decrease in the turbulent kinetic energy. This reduction is found to be transient as the average volume fraction decreases with shear layer growth. In addition, we derive an evolution equation for the pressure variance in the presence of a disperse phase to quantify the particle-turbulence coupling mechanisms responsible for the observed reduction.

  10. Unstructured Grid Viscous Flow Simulation Over High-Speed Research Technology Concept Airplane at High-Lift Conditions

    Science.gov (United States)

    Ghaffari, Farhad

    1999-01-01

    Numerical viscous solutions based on an unstructured grid methodology are presented for a candidate high-speed civil transport configuration, designated as the Technology Concept Airplane (TCA), within the High-Speed Research (HSR) program. The numerical results are obtained on a representative TCA high-lift configuration that consisted of the fuselage and the wing, with deflected full-span leading-edge and trailing-edge flaps. Typical on-and off-surface flow structures, computed at high-lift conditions appropriate for the takeoff and landing, indicated features that are generally plausible. Reasonable surface pressure correlations between the numerical results and the experimental data are obtained at free-stream Mach number M(sub infinity) = 0.25 and Reynolds number based on bar-c R(sub c) = 8 x 10(exp 6) for moderate angles of attack of 9.7 deg. and 13.5 deg. However, above and below this angle-of-attack range, the correlation between computed and measured pressure distributions starts to deteriorate over the examined angle-of-attack range. The predicted longitudinal aerodynamic characteristics are shown to correlate very well with existing experimental data across the examined angle-of-attack range. An excellent agreement is also obtained between the predicted lift-to-drag ratio and the experimental data over the examined range of flow conditions.

  11. Approximating actual flows in physical infrastructure networks: the case of the Yangtze River Delta high-speed railway network

    Directory of Open Access Journals (Sweden)

    Zhang Weiyang

    2016-03-01

    Full Text Available Previous empirical research on urban networks has used data on infrastructure networks to guesstimate actual inter-city flows. However, with the exception of recent research on airline networks in the context of the world city literature, relatively limited attention has been paid to the degree to which the outline of these infrastructure networks reflects the actual flows they undergird. This study presents a method to improve our estimation of urban interaction in and through infrastructure networks by focusing on the example of passenger railways, which is arguably a key potential data source in research on urban networks in metropolitan regions. We first review common biases when using infrastructure networks to approximate actual inter-city flows, after which we present an alternative approach that draws on research on operational train scheduling. This research has shown that ‘dwell time’ at train stations reflects the length of the alighting and boarding process, and we use this insight to estimate actual interaction through the application of a bimodal network projection function. We apply our method to the high-speed railway (HSR network within the Yangtze River Delta (YRD region, discuss the difference between our modelled network and the original network, and evaluate its validity through a systemic comparison with a benchmark dataset of actual passenger flows.

  12. Numerical analysis of high-speed Lithium jet flow under vacuum conditions

    Energy Technology Data Exchange (ETDEWEB)

    Gordeev, Sergej, E-mail: sergej.gordeev@kit.edu; Groeschel, Friedrich; Stieglitz, Robert

    2016-11-01

    The EVEDA Li test loop (ELTL) [1] is aimed at validating the hydraulic stability of the Lithium (Li) target at a velocity up to 20 m/s at vacuum (≈10{sup −3} Pa). The ELTL has been designed to demonstrate the feasibility of the major components providing a neutron production liquid Li target for IFMIF. The rectangular shaped Li jet (cross-section 25 mm × 100 mm) necessitates for heat removal flow velocities of 15–20 m/s along a concave shaped back wall (curvature radius 250 mm) towards the outlet pipe, where the Li jet is subjected to vacuum before it finally enters the collecting quench tank. During the validation experiments within the ELTL acoustic waves within the target outlet pipe have been recorded, indicating potential cavitation processes in the jet impinging region, which may cause premature failures. In order to identify potential cavitation phenomena in correlation with the free jet flow in the outlet pipe a numerical study has been performed. The comparison measured and simulated acoustic emissions exhibits that experimentally deduced cavitation area coincides with the location of the jet wall impingement. The simulations further reveal that a part of the fluid after striking the wall even flows opposite to the gravity vector. This reversed flow is inherently unstable and characterized by waves at first growing and then bursting into droplets. The intense generation of small droplets increases significantly the Li free surface area and lead to a production of Li vapour, which is captured by the jet flow and reintroduced in the main flow. As the static pressure is recovered downstream due to jet impact, the vapour bubbles collapse and hence cavitation likely occurs.

  13. End-wall and profile losses in a low-speed axial flow compressor rotor

    Science.gov (United States)

    Lakshminarayana, B.; Sitaram, N.; Zhang, J.

    1985-01-01

    The blade-to-blade variation of relative stagnation pressure losses in the tip region inside the rotor of a single-stage, axial-flow compressor, is presented and interpreted in this paper. The losses are measured at two flow coefficients (one at the design point and the other at the near peak pressure rise point) to discern the effect of blade loading on the end-wall losses. The tip clearance losses are found to increase with an increase in the pressure rise coefficient. The losses away from the tip region and near the hub regions are measured downstream. The losses are integrated and interpreted in this paper.

  14. Assessment of Power Potential of Tidal Currents and Impacts of Power Extraction on Flow Speeds in Indonesia

    Science.gov (United States)

    Orhan, K.; Mayerle, R.

    2016-12-01

    A methodology comprising of the estimates of power yield, evaluation of the effects of power extraction on flow conditions, and near-field investigations to deliver wake characteritics, recovery and interactions is described and applied to several straits in Indonesia. Site selection is done with high-resolution, three-dimensional flow models providing sufficient spatiotemporal coverage. Much attention has been given to the meteorological forcing, and conditions at the open sea boundaries to adequately capture the density gradients and flow fields. Model verification using tidal records shows excellent agreement. Sites with adequate depth for the energy conversion using horizontal axis tidal turbines, average kinetic power density greater than 0.5 kW/m2, and surface area larger than 0.5km2 are defined as energy hotspots. Spatial variation of the average extractable electric power is determined, and annual tidal energy resource is estimated for the straits in question. The results showed that the potential for tidal power generation in Indonesia is likely to exceed previous predictions reaching around 4,800MW. To assess the impact of the devices, flexible mesh models with higher resolutions have been developed. Effects on flow conditions, and near-field turbine wakes are resolved in greater detail with triangular horizontal grids. The energy is assumed to be removed uniformly by sub-grid scale arrays of turbines, and calculations are made based on velocities at the hub heights of the devices. An additional drag force resulting in dissipation of the pre-existing kinetic power from %10 to %60 within a flow cross-section is introduced to capture the impacts. It was found that the effect of power extraction on water levels and flow speeds in adjacent areas is not significant. Results show the effectivess of the method to capture wake characteritics and recovery reasonably well with low computational cost.

  15. Photogrammetric Measurement of Recession Rates of Low Temperature Ablators Subjected to High Speed Flow

    Science.gov (United States)

    2011-06-01

    approximately 20 to 30 seconds ( Bjorge , Reeder, Subramanian, Crafton, & Fonov, 2005). 49 Figure 8 illustrates the tunnel with the Mach 2.94...Astronautics, Inc. Bjorge , S., Reeder, M., Subramanian, C., Crafton, J., & Fonov, S. (2005). Flow Around an Object Projected from a Cavity into a Supersonic

  16. An investigational study of minimum rotational pump speed to avoid retrograde flow in three centrifugal blood pumps in a pediatric extracorporeal life support model.

    Science.gov (United States)

    Clark, Joseph B; Guan, Yulong; McCoach, Robert; Kunselman, Allen R; Myers, John L; Undar, Akif

    2011-05-01

    During extracorporeal life support with centrifugal blood pumps, retrograde pump flow may occur when the pump revolutions decrease below a critical value determined by the circuit resistance and the characteristics of the pump. We created a laboratory model to evaluate the occurrence of retrograde flow in each of three centrifugal blood pumps: the Rotaflow, the CentriMag, and the Bio-Medicus BP-50. At simulated patient pressures of 60, 80, and 100 mmHg, each pump was evaluated at speeds from 1000 to 2200 rpm and flow rates were measured. Retrograde flow occurred at low revolution speeds in all three centrifugal pumps. The Bio-Medicus pump was the least likely to demonstrate retrograde flow at low speeds, followed by the Rotaflow pump. The CentriMag pump showed the earliest transition to retrograde flow, as well as the highest degree of retrograde flow. At every pump speed evaluated, the Bio-Medicus pump delivered the highest antegrade flow and the CentriMag pump delivered the least.

  17. Aerothermal and aeroelastic response prediction of aerospace structures in high-speed flows using direct numerical simulation

    Science.gov (United States)

    Ostoich, Christopher Mark

    Future high-speed air vehicles will be lightweight, flexible, and reusable. Ve- hicles fitting this description are subject to severe thermal and fluid dynamic loading from multiple sources such as aerothermal heating, propulsion sys- tem exhaust, and high dynamic pressures. The combination of low-margin design requirements and extreme environmental conditions emphasizes the occurrence of fluid-thermal-structural coupling. Numerous attempts to field such vehicles have been unsuccessful over the past half-century due par- tially to the inability of traditional design and analysis practices to predict the structural response in this flight regime. In this thesis, a high-fidelity computational approach is used to examine the fluid-structural response of aerospace structures in high-speed flows. The method is applied to two cases: one involving a fluid-thermal interaction problem in a hypersonic flow and the other a fluid-structure interaction study involving a turbulent boundary layer and a compliant panel. The coupled fluid-thermal investigation features a nominally rigid alu- minum spherical dome fixed to a ceramic panel holder placed in a Mach 6.59 laminar boundary layer. The problem was originally studied by Glass and Hunt in a 1988 wind tunnel experiment in the NASA Langley 8-Foot High Temperature Tunnel and is motivated by thermally bowed body panels designed for the National Aerospace Plane. In this work, the compressible Navier-Stokes equations for a thermally perfect gas and the transient heat equation in the structure are solved simultaneously using two high-fidelity solvers coupled at the solid-fluid interface. Predicted surface heat fluxes are within 10% of the measured values in the dome interior with greater differ- ences found near the dome edges where uncertainties concerning the exper- imental model's construction likely influence the thermal dynamics. On the flat panel holder, the local surface heat fluxes approach those on the wind- ward dome face

  18. Quantum random walks and their convergence to Evans–Hudson ...

    Indian Academy of Sciences (India)

    Quantum dynamical semigroup; Evans–Hudson flow; quantum random walk. 1. Introduction. The aim of this article is to investigate convergence of random walks on von Neumann algebra to Evans–Hudson flows. Here the random walks and Evans–Hudson flows are gene- ralizations of classical Markov chains and Markov ...

  19. Composite continuous time random walks

    Science.gov (United States)

    Hilfer, Rudolf

    2017-12-01

    Random walks in composite continuous time are introduced. Composite time flow is the product of translational time flow and fractional time flow [see Chem. Phys. 84, 399 (2002)]. The continuum limit of composite continuous time random walks gives a diffusion equation where the infinitesimal generator of time flow is the sum of a first order and a fractional time derivative. The latter is specified as a generalized Riemann-Liouville derivative. Generalized and binomial Mittag-Leffler functions are found as the exact results for waiting time density and mean square displacement.

  20. Obstacle optimization for panic flow--reducing the tangential momentum increases the escape speed.

    Science.gov (United States)

    Jiang, Li; Li, Jingyu; Shen, Chao; Yang, Sicong; Han, Zhangang

    2014-01-01

    A disastrous form of pedestrian behavior is a stampede occurring in an event involving a large crowd in a panic situation. To deal with such stampedes, the possibility to increase the outflow by suitably placing a pillar or some other shaped obstacles in front of the exit has been demonstrated. We present a social force based genetic algorithm to optimize the best design of architectural entities to deal with large crowds. Unlike existing literature, our simulation results indicate that appropriately placing two pillars on both sides but not in front of the door can maximize the escape efficiency. Human experiments using 80 participants correspond well with the simulations. We observed a peculiar property named tangential momentum, the escape speed and the tangential momentum are found to be negatively correlated. The idea to reduce the tangential momentum has practical implications in crowd architectural design.

  1. Setup of an experimental device for high-speed debris flows generating 2D impulse waves

    OpenAIRE

    Bateman Pinzón, Allen; Bregoli, Francesco; Medina Iglesias, Vicente César de; Rast, Manuel; Bentz, Clara

    2011-01-01

    Landslides and debris flows falling into reservoirs, natural lakes, fjords or seas can generate impulse waves, which can be assimilated to tsunami-water waves. Such wave’s behavior can be highly destructive regarding dams and other structures and infrastructures as well as people living along shorelines. Destructive observed past events, such Vajont Dam in Italy (1963) or Lituya Bay in Alaska (1958), are not enough to describe and finally properly prevent the phenomenon. Experimental studies ...

  2. A natural flow wing design employing 3-D nonlinear analysis applied at supersonic speeds

    Science.gov (United States)

    Bauer, Steven X. S.; Wood, Richard M.; Brown, S. Melissa

    1989-01-01

    A wing-design study has been conducted on a 65-deg-swept leading-edge delta wing in which a near-conical geometry was employed to take advantage of the naturally occurring conical flow which arises over such a wing in a supersonic flow field. Three-dimensional nonlinear analysis methods were used in the study. In preliminary design, wing planform, design conditions, and near-conical concept were derived and a baseline standard wing (conventional airfoil distribution) and a baseline near-conical wing were chosen. During the initial analysis, a full-potential solver was employed to determine the aerodynamic characteristics of the baseline standard delta wing and the near-conical delta wing. Modifications due to airfoil thickness, leading-edge radius, and camber were then applied to the baseline near-conical wing. The final design employed a Euler solver to analyze the best wing configurations found in the initial design, and to extend this study to develop a more refined wing. Benefits due to each modification are discussed, and a final natural flow wing geometry is chosen and its aerodynamic characteristics are compared with the baseline wings.

  3. High-Speed Synchrotron X-ray Imaging Studies of the Ultrasound Shockwave and Enhanced Flow during Metal Solidification Processes

    Energy Technology Data Exchange (ETDEWEB)

    Tan, Dongyue; Lee, Tung Lik; Khong, Jia Chuan; Connolley, Thomas; Fezzaa, Kamel; Mi, Jiawei

    2015-03-31

    The highly dynamic behavior of ultrasonic bubble implosion in liquid metal, the multiphase liquid metal flow containing bubbles and particles, and the interaction between ultrasonic waves and semisolid phases during solidification of metal were studied in situ using the complementary ultrafast and high-speed synchrotron X-ray imaging facilities housed, respectively, at the Advanced Photon Source, Argonne National Laboratory, US, and Diamond Light Source, UK. Real-time ultrafast X-ray imaging of 135,780 frames per second revealed that ultrasonic bubble implosion in a liquid Bi-8 wt pctZn alloy can occur in a single wave period (30 kHz), and the effective region affected by the shockwave at implosion was 3.5 times the original bubble diameter. Furthermore, ultrasound bubbles in liquid metal move faster than the primary particles, and the velocity of bubbles is 70 similar to 100 pct higher than that of the primary particles present in the same locations close to the sonotrode. Ultrasound waves can very effectively create a strong swirling flow in a semisolid melt in less than one second. The energetic flow can detach solid particles from the liquid-solid interface and redistribute them back into the bulk liquid very effectively.

  4. High-Speed Synchrotron X-ray Imaging Studies of the Ultrasound Shockwave and Enhanced Flow during Metal Solidification Processes

    Science.gov (United States)

    Tan, Dongyue; Lee, Tung Lik; Khong, Jia Chuan; Connolley, Thomas; Fezzaa, Kamel; Mi, Jiawei

    2015-07-01

    The highly dynamic behavior of ultrasonic bubble implosion in liquid metal, the multiphase liquid metal flow containing bubbles and particles, and the interaction between ultrasonic waves and semisolid phases during solidification of metal were studied in situ using the complementary ultrafast and high-speed synchrotron X-ray imaging facilities housed, respectively, at the Advanced Photon Source, Argonne National Laboratory, US, and Diamond Light Source, UK. Real-time ultrafast X-ray imaging of 135,780 frames per second revealed that ultrasonic bubble implosion in a liquid Bi-8 wt pctZn alloy can occur in a single wave period (30 kHz), and the effective region affected by the shockwave at implosion was 3.5 times the original bubble diameter. Furthermore, ultrasound bubbles in liquid metal move faster than the primary particles, and the velocity of bubbles is 70 ~ 100 pct higher than that of the primary particles present in the same locations close to the sonotrode. Ultrasound waves can very effectively create a strong swirling flow in a semisolid melt in less than one second. The energetic flow can detach solid particles from the liquid-solid interface and redistribute them back into the bulk liquid very effectively.

  5. Effects of Boundary-Layer Thickness on Unsteady Flow Characteristics Inside Open Cavities at Subsonic and Transonic Speeds

    Science.gov (United States)

    Yang, Dang-Guo; Li, Jian-Qiang; Fan, Zhao-Lin; Luo, Xin-Fu

    An experimental study was conducted in a 0.6m by 0.6m wind-tunnel to analyze effects of boundary-layer thickness on unsteady flow characteristics inside a rectangular open cavity at subsonic and transonic speeds. The sound pressure level (SPL) distributions at the centerline of the cavity floor and Sound pressure frequency spectrum (SPFS) characteristics on some measurement positions presented herein was obtained with cavity length-to-depth ratio (L/D) of 8 over Mach numbers (Ma) of 0.6 and 1.2 at a Reynolds numbers (Re) of 1.23 × 107 and 2.02 × 107 per meter under different boundary-layer thickness to cavity-depth ratios (δ/D). The experimental angle of attack, yawing and rolling angles were 0°. The results indicate that decrease in δ/D leads to severe flow separation and unsteady pressure fluctuation, which induces increase in SPL at same measurement points inside the cavity at Ma of 0.6. At Ma of 1.2, decrease in δ/D results in enhancing compressible waves. Generally, decrease in δ/D induces more flow self-sustained oscillation frequencies. It also makes severer aerodynamic noise inside the open cavity.

  6. Walking with springs

    Science.gov (United States)

    Sugar, Thomas G.; Hollander, Kevin W.; Hitt, Joseph K.

    2011-04-01

    Developing bionic ankles poses great challenges due to the large moment, power, and energy that are required at the ankle. Researchers have added springs in series with a motor to reduce the peak power and energy requirements of a robotic ankle. We developed a "robotic tendon" that reduces the peak power by altering the required motor speed. By changing the required speed, the spring acts as a "load variable transmission." If a simple motor/gearbox solution is used, one walking step would require 38.8J and a peak motor power of 257 W. Using an optimized robotic tendon, the energy required is 21.2 J and the peak motor power is reduced to 96.6 W. We show that adding a passive spring in parallel with the robotic tendon reduces peak loads but the power and energy increase. Adding a passive spring in series with the robotic tendon reduces the energy requirements. We have built a prosthetic ankle SPARKy, Spring Ankle with Regenerative Kinetics, that allows a user to walk forwards, backwards, ascend and descend stairs, walk up and down slopes as well as jog.

  7. A new particle-like method for high-speed flows with chemical non-equilibrium

    Directory of Open Access Journals (Sweden)

    Fábio Rodrigues Guzzo

    2010-04-01

    Full Text Available The present work is concerned with the numerical simulation of hypersonic blunt body flows with chemical non-equilibrium. New theoretical and numerical formulations for coupling the chemical reaction to the fluid dynamics are presented and validated. The fluid dynamics is defined for a stationary unstructured mesh and the chemical reaction process is defined for “finite quantities” moving through the stationary mesh. The fluid dynamics is modeled by the Euler equations and the chemical reaction rates by the Arrhenius law. Ideal gases are considered. The thermodynamical data are based on JANNAF tables and Burcat’s database. The algorithm proposed by Liou, known as AUSM+, is implemented in a cell-centered based finite volume method and in an unstructured mesh context. Multidimensional limited MUSCL interpolation method is used to perform property reconstructions and to achieve second-order accuracy in space. The minmod limiter is used. The second order accuracy, five stage, Runge-Kutta time-stepping scheme is employed to perform the time march for the fluid dynamics. The numerical code VODE, which is part of the CHEMKIN-II package, is adopted to perform the time integration for the chemical reaction equations. The freestream reacting fluid is composed of H2 and air at the stoichiometric ratio. The emphasis of the present paper is on the description of the new methodology for handling the coupling of chemical and fluid mechanic processes, and its validation by comparison with the standard time-splitting procedure. The configurations considered are the hypersonic flow over a wedge, in which the oblique detonation wave is induced by an oblique shock wave, and the hypersonic flow over a blunt body. Differences between the solutions obtained with each formulation are presented and discussed, including the effects of grid refinement in each case. The primary objective of such comparisons is the validation of the proposed methodology. Moreover, for

  8. Multi-Scale Visualization Analysis of Bus Flow Average Travel Speed in Qingdao

    Science.gov (United States)

    Yong, HAN; Man, GAO; Xiao-Lei, ZHANG; Jie, LI; Ge, CHEN

    2016-11-01

    Public transportation is a kind of complex spatiotemporal behaviour. The traffic congestion and environmental pollution caused by the increase in private cars is becoming more and more serious in our city. Spatiotemporal data visualization is an effective tool for studying traffic, transforming non-visual data into recognizable images, which can reveal where/when congestion is formed, developed and disappeared in space and time simultaneously. This paper develops a multi-scale visualization of average travel speed derived from floating bus data, to enable congestion on urban bus networks to be shown and analyzed. The techniques of R language, Echarts, WebGL are used to draw statistical pictures and 3D wall map, which show the congestion in Qingdao from the view of space and time. The results are as follows:(1) There is a more severely delay in Shibei and Shinan areas than Licun and Laoshan areas; (2) The high congestion usually occurs on Hong Kong Middle Road, Shandong Road, Nanjing Road, Liaoyang West Road and Taiping Road;(3) There is a similar law from Monday to Sunday that the congestion is severer in the morning and evening rush hours than other hours; (4) On Monday morning the severity of congestion is higher than on Friday morning, and on Friday evening the severity is higher than on Monday evening. The research results will help to improve the public transportation of Qingdao.

  9. Localised, high-speed flows within the hydrogen-deficient planetary nebula Abell 78

    Science.gov (United States)

    Meaburn, J.; Lopez, J. A.; Bryce, M.; Redman, M. P.

    1998-06-01

    The remarkable velocity structure of the different components of the hydrogen-deficient planetary nebula Abell 78 have been revealed by obtaining spatially resolved profiles of the [O i] 6300 Angstromsii\\ line with the Manchester echelle spectrometer combined with the 2.1 m San Pedro Martir telescope. The outer, diffuse, hydrogen-rich, 124'' diameter shell is expanding radially at 40 km s^{-1}$. The irregular, knotty, hydrogen-deficient 89arcsec \\times 52arcsec \\ inner shell has a similar overall expansion velocity but more complex kinematical structure. Similar to A 30, velocity `spikes' are found in the position-velocity arrays of [O {sc i}] 6300 Angstromsii\\ profiles from the inner shell. These extend to a further -140 km s^{-1} than the radial velocity of the approaching side of this inner shell. The [O {sc i}] 6300 Angstromsii\\ bright, hydrogen-deficient core knots are distributed throughout an elongated disk expanding at \\approx 25 km s^{-1}. There is kinematical evidence that `polar bullets' are being ejected perpendicularly to this central feature at 380 km s^{-1}. Altogether `velocity spikes' and other high-speed knots in the pv arrays of [O {sc i}] 6300 Angstromsii\\ profiles are found over a 455 km s^{-1}$ range of radial velocities. Many of the kinematical phenomena are considered to be a consequence of the mass-loaded, shocked, wind from the central star.

  10. Bed Evolution under Rapidly Varying Flows by a New Method for Wave Speed Estimation

    Directory of Open Access Journals (Sweden)

    Khawar Rehman

    2016-05-01

    Full Text Available This paper proposes a sediment-transport model based on coupled Saint-Venant and Exner equations. A finite volume method of Godunov type with predictor-corrector steps is used to solve a set of coupled equations. An efficient combination of approximate Riemann solvers is proposed to compute fluxes associated with sediment-laden flow. In addition, a new method is proposed for computing the water depth and velocity values along the shear wave. This method ensures smooth solutions, even for flows with high discontinuities, and on domains with highly distorted grids. The numerical model is tested for channel aggradation on a sloping bottom, dam-break cases at flume-scale and reach-scale with flat bottom configurations and varying downstream water depths. The proposed model is tested for predicting the position of hydraulic jump, wave front propagation, and for predicting magnitude of bed erosion. The comparison between results based on the proposed scheme and analytical, experimental, and published numerical results shows good agreement. Sensitivity analysis shows that the model is computationally efficient and virtually independent of mesh refinement.

  11. The use of relative coupling intervals in horses during walk

    DEFF Research Database (Denmark)

    Olsen, Emil; Pfau, Thilo

    Walking speed varies between over-ground trials and a speed-independent gait-parameter does not exist for use in horses. We introduce relative (R) lateral (L) and diagonal (D) coupling intervals (CI) and hypothesize that both are independent of walking speed. Four horses were walked over 8 Kistler...... for either RLCI or RDCI. RLCI and RDCI can thus be applied as speed-independent stride-to-stride variability parameters in horses during walk over-ground. This might prove useful for detection of gait deficits caused by spinal cord injury....

  12. Treadmill walking with body weight support in subacute non-ambulatory stroke improves walking capacity more than overground walking: a randomised trial.

    Science.gov (United States)

    Dean, Catherine M; Ada, Louise; Bampton, Julie; Morris, Meg E; Katrak, Pesi H; Potts, Stephanie

    2010-01-01

    Is treadmill walking with body weight support during inpatient rehabilitation detrimental to walking quality compared with assisted overground walking? Does it result in better walking capacity, perception of walking or community participation? Analysis of secondary outcomes of a randomised trial with concealed allocation, assessor blinding and intention-to-treat analysis. 126 patients unable to walk within 4 weeks of a stroke who were undergoing inpatient rehabilitation. The experimental group undertook up to 30 minutes of treadmill walking with body weight support via an overhead harness per day while the control group undertook up to 30 minutes of overground walking. The secondary outcomes were walking quality and capacity, walking perception, community participation and falls. Six months after entering the study, there was no difference between the groups of independent walkers in terms of speed (MD 0.10 m/s, 95% CI -0.06 to 0.26) or stride (MD 6 cm, 95% CI -7 to 19). The independent walkers in the experimental group walked 57 m further (95% CI 1 to 113) in the 6 min walk than those in the control group. The experimental group (walkers and non-walkers) rated their walking 1 point out of 10 (95% CI 0.1 to 1.9) higher than the control group. There was no difference between the groups in community participation or number of falls. Treadmill training with body weight support results in better walking capacity and perception of walking compared to overground walking without deleterious effects on walking quality.

  13. Respostas cardiorrespiratórias e perceptivas para as mesmas velocidades de caminhada e corrida Respuestas cardiorrespiratorias y perceptivas para las mismas velocidades de caminata y carrera Cardiorespiratory and perceptual responses to walking and running at the same speed

    Directory of Open Access Journals (Sweden)

    Walace David Monteiro

    2009-10-01

    seleccionaron 12 hombres adultos jóvenes y homogeneizados criteriosamente en cuanto a sexo, edad, características antropométricas, condición aeróbica y experiencia en ejercicios en cinta sin fin. En sesiones preliminares, se determinó individualmente la VTCC. Posteriormente, en tres días diferentes, los individuos caminaron y corrieron, en orden balanceado, a cada una de las siguientes velocidades: VTCC, VTCC - 0,5 km/h y VTCC + 0,5 km/h, con obtención de medidas de gases expirados, de la frecuencia cardíaca (FC y de la percepción de esfuerzo. RESULTADOS: El protocolo para detección de la VTCC se mostró altamente reproducible (r=0,92; p0,05. CONCLUSIÓN: La caminata a velocidades superiores a la VTCC tiende a ser más estresante desde el punto de vista fisiológico y perceptivo. Parece conveniente determinar individualmente la VTCC y normalizar la forma de locomoción para una prescripción más fisiológica y fidedigna de la intensidad de los ejercicios aeróbicos.BACKGROUND: It is possible that different forms of locomotion, when carried out at the same speed, may have a distinct influence on the physiological and perceptual responses to exercise. OBJECTIVE: To compare the cardiorespiratory responses and the subjective perception of the effort to walk and run at the same speed, as determined from the walk-run transition speed (WRTS. METHODS: From an initial sample of 453 subjects enrolled in the compulsory military service, 12 young adult men were selected and carefully homogenized as to age, sex, anthropometric characteristics, aerobic condition and experience in a treadmill. In preliminary sessions, the individual WRTS was determined. Thereafter, on three different days, the subjects walked and ran in balanced order, in each of the following speeds: WRTS; WRTS - 0.5 km/h; WRTS + 0.5 km/h, so as to obtain exhaled gases, heart rate (HR and perception of effort measurements. RESULTS: The protocol for WRTS detection was highly reproducible (r = 0.92, p 0

  14. Effects of Injection Timing on Fluid Flow Characteristics of Partially Premixed Combustion Based on High-Speed Particle Image Velocimetry

    KAUST Repository

    Izadi Najafabadi, Mohammad

    2017-03-28

    Partially Premixed Combustion (PPC) is a promising combustion concept ,based on judicious tuning of the charge stratification, to meet the increasing demands of emission legislation and to improve fuel efficiency. Longer ignition delays of PPC in comparison with conventional diesel combustion provide better fuel/air mixture which decreases soot and NO emissions. Moreover, a proper injection timing and strategy for PPC can improve the combustion stability as a result of a higher level of fuel stratification in comparison with the Homogeneous Charge Compression Ignition (HCCI) concept. Injection timing is the major parameter with which to affect the level of fuel and combustion stratification and to control the combustion phasing and the heat release behavior. The scope of the present study is to investigate the fluid flow characteristics of PPC at different injection timings. To this end, high-speed Particle Image Velocimetry (PIV) is implemented in a light-duty optical engine to measure fluid flow characteristics, including the flow fields, mean velocity and cycle-resolved turbulence, inside the piston bowl as well as the squish region with a temporal resolution of 1 crank angle degree at 800 rpm. Two injectors, having 5 and 7 holes, were compared to see their effects on fluid flow and heat release behavior for different injection timings. Reactive and non-reactive measurements were performed to distinguish injection-driven and combustion-driven turbulence. Formation of vortices and higher turbulence levels enhance the air/fuel interaction, changing the level of fuel stratification and combustion duration. Results demonstrate clearly how turbulence level correlates with heat release behavior, and provide a quantitative dataset for validation of numerical simulations.

  15. The Effects of Uncertainty in Speed-Flow Curve Parameters on a Large-Scale Model

    DEFF Research Database (Denmark)

    Manzo, Stefano; Nielsen, Otto Anker; Prato, Carlo Giacomo

    2014-01-01

    -delay functions express travel time as a function of traffic flows and the theoretical capacity of the modeled facility. The U.S. Bureau of Public Roads (BPR) formula is one of the most extensively applied volume delay functions in practice. This study investigated uncertainty in the BPR parameters. Initially......, BPR parameters were estimated by analyzing observed traffic data related to the Danish highway network. Then, BPR parameter distributions were generated by using the resampling bootstrap technique. Finally, the generated parameter vectors were used to implement sensitivity tests on the four......-stage Danish national transport model. The results clearly highlight the importance to modeling purposes of taking into account BPR formula parameter uncertainty, expressed as a distribution of values rather than assumed point values. Indeed, the model output demonstrates a noticeable sensitivity to parameter...

  16. Effect of Body Composition on Walking Economy

    Directory of Open Access Journals (Sweden)

    Maciejczyk Marcin

    2016-12-01

    Full Text Available Purpose. The aim of the study was to evaluate walking economy and physiological responses at two walking speeds in males with similar absolute body mass but different body composition. Methods. The study involved 22 young men with similar absolute body mass, BMI, aerobic performance, calf and thigh circumference. The participants differed in body composition: body fat (HBF group and lean body mass (HLBM group. In the graded test, maximal oxygen uptake (VO2max and maximal heart rate were measured. Walking economy was evaluated during two walks performed at two different speeds (4.8 and 6.0 km ‧ h-1. Results. The VO2max was similar in both groups, as were the physiological responses during slow walking. The absolute oxygen uptake or oxygen uptake relative to body mass did not significantly differentiate the studied groups. The only indicator significantly differentiating the two groups was oxygen uptake relative to LBM. Conclusions. Body composition does not significantly affect walking economy at low speed, while during brisk walking, the economy is better in the HLBM vs. HBF group, provided that walking economy is presented as oxygen uptake relative to LBM. For this reason, we recommend this manner of oxygen uptake normalization in the evaluation of walking economy.

  17. Comparison of two 6-minute walk tests to assess walking capacity in polio survivors.

    Science.gov (United States)

    Brehm, Merel-Anne; Verduijn, Suzan; Bon, Jurgen; Bredt, Nicoline; Nollet, Frans

    2017-11-21

    To compare walking dynamics and test-retest reliability for 2 frequently applied walk tests in polio survivors: the 6-minute walk test (6MWT) to walk as far as possible; and the 6-minute walking energy cost test (WECT) at comfortable speed. Observational study. Thirty-three polio survivors, able to walk ≥ 150 m. On the same day participants performed a 6MWT and a WECT, which were repeated 1-3 weeks later. For each test, distance walked, heart rate and reduction in speed were assessed. The mean distance walked and mean heart rate were significantly higher in the 6MWT (441 m (standard deviation) (SD 79.7); 118 bpm (SD 19.2)) compared with the WECT (366 m (SD 67.3); 103 bpm (SD 14.3)); pwalked distance was 42 m (9.7% change from the mean) and 50 m (13.7%) on the 6MWT and WECT, respectively. Both the 6MWT and the WECT are reliable to assess walking capacity in polio survivors, with slightly superior sensitivity to detect change for the 6MWT. Differences in walking dynamics confirm that the tests cannot be used interchangeably. The 6MWT is recommended for measuring maximal walking capacity and the WECT for measuring submaximal walking capacity.

  18. RIVERSIDE WALK

    Directory of Open Access Journals (Sweden)

    Pablo Fernández Marmisole

    2015-06-01

    Full Text Available Since 2009, and as part of the Neighborhood Law (Ley de Barrios of Catalonia there is a strategic plan to integrate neighborhoods Baró de Viver and Bon Pastor in the city of Barcelona. The guidelines of the plan are to improve public space and to better connect neighborhoods to each other and the adjoining districts and municipalities. Within the strategy includes opening the Besos River to the urban territory through green corridors and installation of equipment. In this sense, the argument is to provide qualified public space to encourage the urban cohesiveness of the neighborhoods through the creation of a new Riverside Walk. The project consists in converting an urban highway into a pacified walk. The stroll also attempts to pacify the area by removing the visual and acoustic pollution caused by the Ronda Litoral (Highway next to the Besos River. In response to this problem the project consists in covering the Ronda Litoral, creating 1.5km of qualified public space, where a set of vegetation and the generation of sun areas will create different spaces that invigorate the territory and connect the neighborhoods. The platform covering the Ronda Litoral includes peaceful meetings with each and every one of the streets that are right with it. The Riverside Walk will be found within less than 400m from 4 metro stations and will have three pedestrian walkways as an access to Barcelona from the neighboring municipality of Santa Coloma. The installation of common equipment, to be shared by the two neighborhoods in the central part of the Riverside Walk is a guiding principle of the integrated strategy. Within the guidelines of the plan for the area of Ley de Barrios lies the importance of public participation; in that sense it is contemplated a participatory process from the initial design phase of the stroll, where subject for debate, reflection and proposal neighbors will design the walk and their equipment. The process will contemplate since the

  19. Pressure enhancement associated with meridional flow in high-speed solar wind: possible evidence for an interplanetary magnetic flux rope

    Directory of Open Access Journals (Sweden)

    C.-Y. Tu

    1997-02-01

    Full Text Available A sizable total-pressure (magnetic pressure plus kinetic pressure enhancement was found within the high-speed wind stream observed by Helios 2 in 1976 near 0.3 AU. The proton density and temperature and the magnetic magnitude simultaneously increased for about 6 h. This pressure rise was associated with a comparatively large southward flow velocity component (with Vz ≈ –100 km · s–1 and magnetic-field rotation. The pressure enhancement was associated with unusual features in the electron distribution function. It shows a wide angular distribution of electron counting rates in the low-energy (57.8 eV channel, while previous to the enhancement it exhibits a wide angular distribution of electron count rate in the high-energy (112, 221 and 309 eV channels, perhaps indicating the mirroring of electrons in the converging field lines of the background magnetic field. These fluid and kinetic phenomena may be explained as resulting from an interplanetary magnetic flux rope which is not fully convected by the flow but moves against the background wind towards the Sun.

  20. Development of a TDLAS sensor for temperature and concentration of H2 O in high speed and high temperature flows

    Science.gov (United States)

    Sheehe, Suzanne; O'Byrne, Sean

    2017-06-01

    The development of a sensor for simultaneous temperature concentration of H2 O and temperature in high speed flows is presented. H2 O is a desirable target sensing species because it is a primary product in combustion systems; both temperature and concentration profiles can be used to assess both the extent of the combustion and the flow field characteristics. Accurate measurements are therefore highly desirable. The sensor uses a vertical-cavity surface emitting laser (VCSEL) scanned at 50 kHz from 7172 to 7186 cm-1. Temperatures and concentrations are extracted from the spectra by fitting theoretical spectra to the experimental data. The theoretical spectra are generated using GENSPECT in conjunction with line parameters from the HITRAN 2012 database. To validate the theoretical spectra, experimental spectra of H2 O were obtained at known temperatures (290-550 K) and pressures (30 torr) in a heated static gas cell. The results show that some theoretical lines deviate from the experimental lines. New line-strengths are calculated assuming that the line assignments and broadening parameters in HITRAN are correct. This data is essential for accurate H2 O concentration and temperature measurements at low pressure and high temperature conditions. US Air Force Asian Office of Aerospace Research and Development Grant FA2386-16-1-4092.

  1. Walking on high heels changes muscle activity and the dynamics of human walking significantly

    DEFF Research Database (Denmark)

    Simonsen, Erik B; Svendsen, Morten Bo Søndergaard; Nørreslet, Andreas

    2012-01-01

    The aim of the study was to investigate the distribution of net joint moments in the lower extremities during walking on high-heeled shoes compared with barefooted walking at identical speed. Fourteen female subjects walked at 4 km/h across three force platforms while they were filmed by five...... joint abductor moment. Several EMG parameters increased significantly when walking on high-heels. The results indicate a large increase in bone-on-bone forces in the knee joint directly caused by the increased knee joint extensor moment during high-heeled walking, which may explain the observed higher...

  2. Rotary pump speed modulation for generating pulsatile flow and phasic left ventricular volume unloading in a bovine model of chronic ischemic heart failure.

    Science.gov (United States)

    Soucy, Kevin G; Giridharan, Guruprasad A; Choi, Young; Sobieski, Michael A; Monreal, Gretel; Cheng, Allen; Schumer, Erin; Slaughter, Mark S; Koenig, Steven C

    2015-01-01

    Rotary blood pumps operate at a constant speed (rpm) that diminishes vascular pulsatility and variation in ventricular end-systolic and end-diastolic volumes, which may contribute to adverse events, including aortic insufficiency and gastrointestinal bleeding. In this study, pump speed modulation algorithms for generating pulsatility and variation in ventricular end-systolic and end-diastolic volumes were investigated in an ischemic heart failure (IHF) bovine model (n = 10) using a clinically implanted centrifugal-flow left ventricular assist device (LVAD). Hemodynamic and hematologic measurements were recorded during IHF baseline, constant pumps speeds, and asynchronous (19-60 cycles/min) and synchronous (copulse and counterpulse) pump speed modulation profiles using low relative pulse speed (±25%) of 3,200 ± 800 rpm and high relative pulse speed (±38%) of 2,900 ± 1,100 rpm. End-organ perfusion, hemodynamics, and pump parameters were measured to characterize pulsatility, myocardial workload, and LVAD performance for each speed modulation profile. Speed modulation profiles augmented aortic pulse pressure, surplus hemodynamic energy, and end-organ perfusion (p Pump speed modulation increases pulsatility and improves cardiac function and end-organ perfusion, but the asynchronous mode provides the technologic advantage of sensorless control. Investigation of asynchronous pump speed modulation during long-term support is warranted to test the hypothesis that operating an LVAD with speed modulation will minimize adverse events in patients supported by an LVAD that may be associated with long-term operation at a constant pump speed. Copyright © 2015 International Society for Heart and Lung Transplantation. Published by Elsevier Inc. All rights reserved.

  3. Comparison of walking overground and in a Computer Assisted Rehabilitation Environment (CAREN in individuals with and without transtibial amputation

    Directory of Open Access Journals (Sweden)

    Gates Deanna H

    2012-11-01

    Full Text Available Abstract Background Due to increased interest in treadmill gait training, recent research has focused on the similarities and differences between treadmill and overground walking. Most of these studies have tested healthy, young subjects rather than impaired populations that might benefit from such training. These studies also do not include optic flow, which may change how the individuals integrate sensory information when walking on a treadmill. This study compared overground walking to treadmill walking in a computer assisted virtual reality environment (CAREN in individuals with and without transtibial amputations (TTA. Methods Seven individuals with traumatic TTA and 27 unimpaired controls participated. Subjects walked overground and on a treadmill in a CAREN at a normalized speed. The CAREN applied optic flow at the same speed that the subject walked. Temporal-spatial parameters, full body kinematics, and kinematic variability were collected during all trials. Results Both subject groups decreased step time and control subjects decreased step length when walking in the CAREN. Differences in lower extremity kinematics were small (○ and did not exceed the minimal detectable change values for these measures. Control subjects exhibited decreased transverse and frontal plane range of motion of the pelvis and trunk when walking in the CAREN, while patients with TTA did not. Both groups exhibited increased step width variability during treadmill walking in the CAREN, but only minor changes in kinematic variability. Conclusions The results of this study suggest that treadmill training in a virtual environment should be similar enough to overground that changes should carry over. Caution should be made when comparing step width variability and step time results from studies utilizing a treadmill to those overground.

  4. Comparison of walking overground and in a Computer Assisted Rehabilitation Environment (CAREN) in individuals with and without transtibial amputation.

    Science.gov (United States)

    Gates, Deanna H; Darter, Benjamin J; Dingwell, Jonathan B; Wilken, Jason M

    2012-11-14

    Due to increased interest in treadmill gait training, recent research has focused on the similarities and differences between treadmill and overground walking. Most of these studies have tested healthy, young subjects rather than impaired populations that might benefit from such training. These studies also do not include optic flow, which may change how the individuals integrate sensory information when walking on a treadmill. This study compared overground walking to treadmill walking in a computer assisted virtual reality environment (CAREN) in individuals with and without transtibial amputations (TTA). Seven individuals with traumatic TTA and 27 unimpaired controls participated. Subjects walked overground and on a treadmill in a CAREN at a normalized speed. The CAREN applied optic flow at the same speed that the subject walked. Temporal-spatial parameters, full body kinematics, and kinematic variability were collected during all trials. Both subject groups decreased step time and control subjects decreased step length when walking in the CAREN. Differences in lower extremity kinematics were small (< 2.5(○)) and did not exceed the minimal detectable change values for these measures. Control subjects exhibited decreased transverse and frontal plane range of motion of the pelvis and trunk when walking in the CAREN, while patients with TTA did not. Both groups exhibited increased step width variability during treadmill walking in the CAREN, but only minor changes in kinematic variability. The results of this study suggest that treadmill training in a virtual environment should be similar enough to overground that changes should carry over. Caution should be made when comparing step width variability and step time results from studies utilizing a treadmill to those overground.

  5. S5-3: Dynamic Invariants in Walking through an Aperture While Holding a Tray with Two Hands

    Directory of Open Access Journals (Sweden)

    Endre Kadar

    2012-10-01

    Full Text Available Gibson's (1979 The Ecological Approach to Visual Perception ecological approach to visual perception is based on several key notions (i.e., affordance, optic flow, and invariants. Early research focused on identifying invariants (π-numbers to describe affordances using geometric body-scaled measures. Kadar and Koszeghy (2010 International Journal of Sport Psychology 41(3 80–81 generalized π-numbers to invariant functions (π-functions to allow dynamically scaled description of driving through gates of variable width. The present study further investigated the dynamic invariants of human locomotion in walking towards and passing through gates. Six participants were instructed to walk through gates of four different sizes with either comfortable or fast walking speed while holding a tray by two hands. Consistent with the results of Kadar and Koszeghy (2010 dynamically-scaled π-functions were identified. The speed control of the approach phase was further assessed in relation to the use of the optical τ parameter derived from optic flow specifying estimated time to contact with the virtual plane defined by the frontal surfaces of the aperture. Aperture size and walking speed have influenced the control of speed at the approach phase: the derivative of τ in the neighborhood of the aperture increased with increasing width of the aperture. Analysis of the approach phase suggests a need for searching an even higher-level invariant structure of the dynamics of this passing through task.

  6. Accurate prediction of complex free surface flow around a high speed craft using a single-phase level set method

    Science.gov (United States)

    Broglia, Riccardo; Durante, Danilo

    2017-11-01

    This paper focuses on the analysis of a challenging free surface flow problem involving a surface vessel moving at high speeds, or planing. The investigation is performed using a general purpose high Reynolds free surface solver developed at CNR-INSEAN. The methodology is based on a second order finite volume discretization of the unsteady Reynolds-averaged Navier-Stokes equations (Di Mascio et al. in A second order Godunov—type scheme for naval hydrodynamics, Kluwer Academic/Plenum Publishers, Dordrecht, pp 253-261, 2001; Proceedings of 16th international offshore and polar engineering conference, San Francisco, CA, USA, 2006; J Mar Sci Technol 14:19-29, 2009); air/water interface dynamics is accurately modeled by a non standard level set approach (Di Mascio et al. in Comput Fluids 36(5):868-886, 2007a), known as the single-phase level set method. In this algorithm the governing equations are solved only in the water phase, whereas the numerical domain in the air phase is used for a suitable extension of the fluid dynamic variables. The level set function is used to track the free surface evolution; dynamic boundary conditions are enforced directly on the interface. This approach allows to accurately predict the evolution of the free surface even in the presence of violent breaking waves phenomena, maintaining the interface sharp, without any need to smear out the fluid properties across the two phases. This paper is aimed at the prediction of the complex free-surface flow field generated by a deep-V planing boat at medium and high Froude numbers (from 0.6 up to 1.2). In the present work, the planing hull is treated as a two-degree-of-freedom rigid object. Flow field is characterized by the presence of thin water sheets, several energetic breaking waves and plungings. The computational results include convergence of the trim angle, sinkage and resistance under grid refinement; high-quality experimental data are used for the purposes of validation, allowing to

  7. Phase-resolved optical coherence tomography and optical Doppler tomography for imaging blood flow in human skin with fast scanning speed and high velocity sensitivity

    NARCIS (Netherlands)

    Zhao, YH; Chen, ZP; Saxer, CE; Xiang, SH; de Boer, JF; Nelson, JS

    2000-01-01

    We have developed a novel phase-resolved optical coherence tomography (OCT) and optical Doppler tomography (ODT) system that uses phase information derived from a Hilbert transformation to image blood flow in human skin with fast scanning speed and high velocity sensitivity. Using the phase change

  8. Corrigendum to ;Numerical dissipation control in high order shock-capturing schemes for LES of low speed flows; [J. Comput. Phys. 307 (2016) 189-202

    Science.gov (United States)

    Kotov, D. V.; Yee, H. C.; Wray, A. A.; Sjögreen, Björn; Kritsuk, A. G.

    2018-01-01

    The authors regret for the typographic errors that were made in equation (4) and missing phrase after equation (4) in the article ;Numerical dissipation control in high order shock-capturing schemes for LES of low speed flows; [J. Comput. Phys. 307 (2016) 189-202].

  9. Comparison of high speed PIV experiments, unsteady pressure measurements and DES computations of a transonic Ariane 5 base-flow using POD : An experimental study

    NARCIS (Netherlands)

    Schrijer, F.F.J.; Horchler, T.; Deck, S; van Gent, P.L.

    2017-01-01

    The present work is conducted in the framework of the ESA TRP “Launcher Base Flows and Shock Interactions Regions Improved Load Characterization”, where high speed PIV measurements and unsteady pressure measurements performed in the DNW-HST on a 1:60 scale Ariane 5 are compared to simulations using

  10. Hydraulic performance numerical simulation of high specific speed mixed-flow pump based on quasi three-dimensional hydraulic design method

    Science.gov (United States)

    Zhang, Y. X.; Su, M.; Hou, H. C.; Song, P. F.

    2013-12-01

    This research adopts the quasi three-dimensional hydraulic design method for the impeller of high specific speed mixed-flow pump to achieve the purpose of verifying the hydraulic design method and improving hydraulic performance. Based on the two families of stream surface theory, the direct problem is completed when the meridional flow field of impeller is obtained by employing iterative calculation to settle the continuity and momentum equation of fluid. The inverse problem is completed by using the meridional flow field calculated in the direct problem. After several iterations of the direct and inverse problem, the shape of impeller and flow field information can be obtained finally when the result of iteration satisfies the convergent criteria. Subsequently the internal flow field of the designed pump are simulated by using RANS equations with RNG k-ε two-equation turbulence model. The static pressure and streamline distributions at the symmetrical cross-section, the vector velocity distribution around blades and the reflux phenomenon are analyzed. The numerical results show that the quasi three-dimensional hydraulic design method for high specific speed mixed-flow pump improves the hydraulic performance and reveal main characteristics of the internal flow of mixed-flow pump as well as provide basis for judging the rationality of the hydraulic design, improvement and optimization of hydraulic model.

  11. A high-density EEG study of differences between three high speeds of simulated forward motion from optic flow in adult participants

    Directory of Open Access Journals (Sweden)

    Kenneth eVilhelmsen

    2015-10-01

    Full Text Available A high-density EEG study was conducted to investigate evoked and oscillatory brain activity in response to high speeds of simulated forward motion. Participants were shown an optic flow pattern consisting of a virtual road with moving poles at either side of it, simulating structured forward motion at different driving speeds (25, 50, and 75 km/h with a static control condition between each motion condition. Significant differences in N2 latencies and peak amplitudes between the three speeds of visual motion were found in parietal channels of interest P3 and P4. As motion speed increased, peak latency increased while peak amplitude decreased which might indicate that higher driving speeds are perceived as more demanding resulting in longer latencies, and as fewer neurons in the motion sensitive areas of the adult brain appear to be attuned to such high visual speeds this could explain the observed inverse relationship between speed and amplitude. In addition, significant differences between alpha de-synchronizations for forward motion and alpha synchronizations in the static condition were found in the parietal midline (PM source. It was suggested that the alpha de-synchronizations reflect an activated state related to the visual processing of simulated forward motion, whereas the alpha synchronizations in response to the static condition reflect a deactivated resting period.

  12. Applicability of linearized-theory attached-flow methods to design and analysis of flap systems at low speeds for thin swept wings with sharp leading edges

    Science.gov (United States)

    Carlson, Harry W.; Darden, Christine M.

    1987-01-01

    Low-speed experimental force and data on a series of thin swept wings with sharp leading edges and leading and trailing-edge flaps are compared with predictions made using a linearized-theory method which includes estimates of vortex forces. These comparisons were made to assess the effectiveness of linearized-theory methods for use in the design and analysis of flap systems in subsonic flow. Results demonstrate that linearized-theory, attached-flow methods (with approximate representation of vortex forces) can form the basis of a rational system for flap design and analysis. Even attached-flow methods that do not take vortex forces into account can be used for the selection of optimized flap-system geometry, but design-point performance levels tend to be underestimated unless vortex forces are included. Illustrative examples of the use of these methods in the design of efficient low-speed flap systems are included.

  13. Effects of a Flexibility and Relaxation Programme, Walking, and Nordic Walking on Parkinson's Disease

    Directory of Open Access Journals (Sweden)

    I. Reuter

    2011-01-01

    Full Text Available Symptoms of Parkinson's disease (PD progress despite optimized medical treatment. The present study investigated the effects of a flexibility and relaxation programme, walking, and Nordic walking (NW on walking speed, stride length, stride length variability, Parkinson-specific disability (UPDRS, and health-related quality of life (PDQ 39. 90 PD patients were randomly allocated to the 3 treatment groups. Patients participated in a 6-month study with 3 exercise sessions per week, each lasting 70 min. Assessment after completion of the training showed that pain was reduced in all groups, and balance and health-related quality of life were improved. Furthermore, walking, and Nordic walking improved stride length, gait variability, maximal walking speed, exercise capacity at submaximal level, and PD disease-specific disability on the UPDRS in addition. Nordic walking was superior to the flexibility and relaxation programme and walking in improving postural stability, stride length, gait pattern and gait variability. No significant injuries occurred during the training. All patients of the Nordic walking group continued Nordic walking after completing the study.

  14. Community walking can be assessed using a 10-metre timed walk test.

    Science.gov (United States)

    Kempen, J C E; de Groot, V; Knol, D L; Polman, C H; Lankhorst, G J; Beckerman, H

    2011-08-01

    A decline in mobility is a common feature of multiple sclerosis (MS). Community walking scales are used to categorize patients in their ability to move independently. The first purpose of this study was to determine which specific gait speed corresponded with the categories of the Modified Functional Walking Categories (MFWC). The second purpose was to determine the Minimally Important Change (MIC) in absolute gait speed using the MFWC and Expanded Disability Status Scale (EDSS) as external criteria. MS patients were measured six times in 6 years. Gait velocity was measured with the 10-metre timed walk test (10-m TWT), the severity of MS was determined with the EDSS, and community walking was assessed with the MFWC. For each category of the MFWC, Receiver Operating Characteristic (ROC) curves were used to find the best possible cut-off point on the 10-m TWT. The MIC in absolute gait speed was determined using a change of one category on the MFWC or one point on the EDSS. A strong relationship was found between gait speed and the MFWC; all areas under the ROC curves (AUCs) were between 0.74 and 0.86. The MIC in absolute gait speed could not be determined, because the AUCs were below the threshold of 0.70 and changes in gait speed were small. Gait speed is related to community walking, but an MIC in absolute gait speed could not be determined using a minimally important change on the MFWC or the EDSS as external criteria.

  15. Investigation of Performance and Rotor Tip Flow Field in a Low Speed Research Compressor with Circumferential Groove Casing Treatment at Varying Tip Clearance

    Directory of Open Access Journals (Sweden)

    Matthias Rolfes

    2017-01-01

    Full Text Available Experimental investigations in a single-stage low speed axial research compressor are presented. The influence of four different rotor tip clearances on the overall compressor performance and on the rotor tip flow field is investigated in configurations with and without circumferential groove casing treatments. Piezo-resistive pressure transducers are used to capture the unsteady flow field in the rotor tip region. The investigated casing groove is effectively working at the three largest investigated tip clearance sizes. The largest achieved operating range increase by the groove is 6.9%. The groove can delay the upstream movement of the flow interface between leakage flow and main flow and thus increase the stable operating range. Rotating instabilities are shown to exist at large tip clearance sizes in throttled operating conditions. Their amplitudes can be damped by the casing groove. No modal activities could be detected in the current single-stage compressor build.

  16. A new approach to live reaction monitoring using active flow technology in ultra-high-speed HPLC with mass spectral detection.

    Science.gov (United States)

    Kocic, Danijela; Andrew Shalliker, R

    2015-12-01

    A new type of chromatography column referred to as a parallel segmented flow (PSF) column enables ultra-high-speed high-performance liquid chromatography-MS to be undertaken. This occurs because the separation efficiency obtained on PSF columns has been shown in prior studies to be superior to conventional columns, and the flow stream is split radially inside the outlet end fitting of the column, rather than in an axial post-column flow stream split. As a result, the flow through the column can be five times higher than the flow through the MS. In this work, the degradation of amino acids in dilute nitric acid was used to illustrate the process. Separations were obtained in less than 12 s, although the reinjection process was initiated 6 s after the previous injection. The degradation rate constant of tryptophan, in the presence of tyrosine and phenylalanine, was determined. Copyright © 2015 John Wiley & Sons, Ltd.

  17. GUD WIP: Gait-Understanding-Driven Walking-In-Place.

    Science.gov (United States)

    Wendt, Jeremy D; Whitton, Mary C; Brooks, Frederick P

    2010-03-01

    Many Virtual Environments require walking interfaces to explore virtual worlds much larger than available real-world tracked space. We present a model for generating virtual locomotion speeds from Walking-In-Place (WIP) inputs based on walking biomechanics. By employing gait principles, our model - called Gait-Understanding-Driven Walking-In-Place (GUD WIP) - creates output speeds which better match those evident in Real Walking, and which better respond to variations in step frequency, including realistic starting and stopping. The speeds output by our implementation demonstrate considerably less within-step fluctuation than a good current WIP system - Low-Latency, Continuous-Motion (LLCM) WIP - while still remaining responsive to changes in user input. We compared resulting speeds from Real Walking, GUD WIP, and LLCM-WIP via user study: The average output speeds for Real Walking and GUD WIP respond consistently with changing step frequency - LLCM-WIP is far less consistent. GUD WIP produces output speeds that are more locally consistent (smooth) and step-frequency-to-walk-speed consistent than LLCM-WIP.

  18. Functional electrical stimulation-assisted walking for persons with incomplete spinal injuries

    DEFF Research Database (Denmark)

    Ladouceur, M.; Barbeau, H.

    2000-01-01

    This study investigated the changes in maximal overground walking speed (MOWS) that occurred during; walking training with a functional electrical stimulation (FES) orthosis by chronic spinal cord injured persons with incomplete motor function loss. The average walking: speed over a distance of 10...

  19. APPLICABILITY OF THE OPEN SOURCE PACKAGE OPENFOAM FOR NUMERICAL MODELING SEPARATED FLOW AROUND AN AIRCRAFT AT SUBSONIC AND SUPERSONIC SPEEDS

    Directory of Open Access Journals (Sweden)

    V. T. Kalugin

    2014-01-01

    Full Text Available Applicability of the open source package OpenFOAM for numerical modeling different separated flows have been considered in the cases studies of the influence of vortices and their interaction with lifting surfaces, features of the flow field of rapidly rotating aerial vehicles at presence of separation flow and study of supersonic separated flow field in flight controls.

  20. Pedestrian speeds on stairs: an initial step for a simulation model

    OpenAIRE

    Fujiyama, T.; Tyler, N.

    2004-01-01

    In order to predict a pedestrian’s walking speed on stairs from his/her characteristics of and those of the stairs, the relationship between the walking speed of a pedestrian on stairs and his/her characteristics, and the relationship between the pedestrians’ walking speeds on stairs and the stair-gradients were investigated. It is suggested that Leg Extensor Power shows a strong correlation to walking speeds of elderly people on stairs, the stair-gradient has a linear relationshi...

  1. Influence of air flow, temperature and agitation speed in the batch acetification process to obtain orange vinegar (Citrus sinensis var.W. Navel

    Directory of Open Access Journals (Sweden)

    María Ferreyra

    2012-03-01

    Full Text Available This paper describes the influence of process variables to produce orange vinegar. Orange juice was fermented with Saccharomyces cerevisiae until reach 14% v/v. The biooxidation was carried out with Acetobacter sp., in submerge culture using a laboratory scale fermentor. In order to avoid the inhibitory effect of ethanol on acetic acid bacteria, the orange wine was diluted to 6% v/v with a mineral solution. It was performed a factorial design 2k to study the influence of variables. It was studied air flow rate/agitation at levels of 0.3-0.6 vvm and 200-400 rpm and the effect of air flow rate/temperature at 0.4-0.6 vvm and 25- 30°C, respectively. Duplicate treatments were carried out and the results were evaluated in terms of productivity and fermentation yield. Statistical design (p-value<0.05 was analyzed using Statgraphics Centurion XV Corporate software. Treatments performed at 200 rpm and different air flow levels, did not show significant differences on acetification rate. At higher agitation speed and air flow rates, the productivity was high. The best yields were obtained at lower air flows levels and higher agitation speed. Temperature did not present statistically differences on studied variables. The best yield was obtained at 400 rpm and 0.3 vvm at 25°C. It can be concluded that agitation speed plays an important role for a better acetification rate however higher air flow rates causes less yields.

  2. Outflow of traffic from the national capital Kuala Lumpur to the north, south and east coast highways using flow, speed and density relationships

    Directory of Open Access Journals (Sweden)

    Nik Hashim Nik Mustapha

    2016-12-01

    Full Text Available The functional relationships between flow (veh/km, density (veh/h and speed (km/h in traffic congestion have a long history of research. However, their findings and techniques persist to be relevant to this day. The analysis is pertinent, particularly in finding the best fit for the three major highways in Malaysia, namely the KL-Karak Highway, KL-Seremban Highway and KL-Ipoh Highway. The trans-logarithm function of density–speed model was compared to the classical models of Greenshields, Greenberg, Underwood and Drake et al. using data provided by the Transport Statistics Malaysia 2014. The results of regression analysis revealed that the Greenshields and Greenberg models were statistically significant. The trans-logarithm function was also tested and the results were nonetheless without exception. Its usefulness in addition to statistical significance related to the derived economic concepts of maximum speed and the related number of vehicles, flow and density and the limits of free speed were relevant in comparing the individual levels of traffic congestion between highways. For instance, KL-Karak Highway was least congested compared to KL-Seremban Highway and KL-Ipoh Highway. Their maximum speeds, based on three lanes carriage capacity of one direction, were 33.4 km/h for KL-Karak, 15.9 km/h for KL-Seremban, and 21.1 km/h for KL-Ipoh. Their corresponding flows were approximated at 1080.9 veh/h, 1555.4 veh/h, and 1436.6 veh/h.

  3. Effects of walking trainings on walking function among stroke survivors: a systematic review.

    Science.gov (United States)

    Ilunga Tshiswaka, Daudet; Bennett, Crystal; Franklin, Cheyanne

    2018-03-01

    Physical function is often compromised as a result of stroke event. Although interventions propose different strategies that seek to improve stroke survivors' physical function, a need remains to evaluate walking training studies aimed at improving such physical function. The aim of this review was to assess the available literature that highlights the impact of walking training on enhancing walking for stroke survivors. We performed a systematic literature review of online databases - Google Scholar, PubMed, CINHAL, Cochrane Library, Scopus, and EBSCO - with the following inclusion criteria: manuscript published from 2005 to 2016, written in English, with treatment and control groups, for walking training studies aimed at improving physical function among stroke survivors. Findings indicated that walking speed, walking distance, and gait speed were the most used outcome variables for measuring improved physical function among stroke survivors. Importantly, proposed interventions involved either overground or treadmill walking trainings, if not both. Preserved locomotor improvements were not noted in all interventions at follow-up. Some interventions that used walking treadmill training augmented by auditory stimulations reported significant improvements in physical function compared with overground walking training augmented by auditory stimulations. The imperative to improve physical function among stroke survivors with physical impairment is paramount, as it allows survivors to be socially, emotionally, and physically more independent. In general, we note an insufficiency of research on the interaction between physical function and socialization among stroke survivors.

  4. Electron Temperatures and Flow Speeds of the Low Solar Corona: MACS Results from the Total Solar Eclipse of 29 March 2006 in Libya

    Science.gov (United States)

    Reginald, Nelson L.; Davila, Joseph M.; SaintCyr, O.; Rabin, Douglas M.; Guhathakurta, Madhulika; Hassler, Donald M.; Gashut, Hadi

    2011-01-01

    An experiment was conducted in conjunction with the total solar eclipse on 29 March 2006 in Libya to measure both the electron temperature and its flow speed simultaneously at multiple locations in the low solar corona by measuring the visible K-coronal spectrum. Coronal model spectra incorporating the effects of electron temperature and its flow speed were matched with the measured K-coronal spectra to interpret the observations. Results show electron temperatures of (1.10 +/- 0.05) MK, (0.70 +/- 0.08) MK, and (0.98 +/- 0.12) MK, at 1.1 Solar Radius from Sun center in the solar north, east and west, respectively, and (0.93 +/- 0.12) MK, at 1.2 Solar Radius from Sun center in the solar west. The corresponding outflow speeds obtained from the spectral fit are (103 +/- 92) km/s, (0 + 10) km/s, (0+10) km/s, and (0+10) km/s. Since the observations were taken only at 1.1 Solar Radius and 1.2 Solar Radius from Sun center, these speeds, consistent with zero outflow, are in agreement with expectations and provide additional confirmation that the spectral fitting method is working. The electron temperature at 1.1 Solar Radius from Sun center is larger at the north (polar region) than the east and west (equatorial region).

  5. Celestial Walk: A Terminating Oblivious Walk for Convex Subdivisions

    OpenAIRE

    Kuijper, Wouter; Ermolaev, Victor; Devillers, Olivier

    2017-01-01

    We present a new oblivious walking strategy for convex subdivisions. Our walk is faster than the straight walk and more generally applicable than the visibility walk. To prove termination of our walk we use a novel monotonically decreasing distance measure.

  6. Walking for art's sake

    CERN Multimedia

    2005-01-01

      The man who compared himself to a proton ! On 20 May, Gianni Motti went down into the LHC tunnel and walked around the 27 kilometres of the underground ring at an average, unaccelerated pace of 5 kph. This was an artistic rather than an athletic performance, aimed at drawing a parallel between the fantastic speed of the beams produced by the future accelerator and the leisurely stroll of a human. The artist, who hails from Lombardy, was accompanied by cameraman Ivo Zanetti, who filmed the event from start to finish, and physicist Jean-Pierre Merlo. The first part of the film can be seen at the Villa Bernasconi, 8 route du Grand-Lancy, Grand Lancy, until 26 June.

  7. Walking for art's sake

    CERN Multimedia

    2005-01-01

    The man who compared himself to a proton ! On 20 May, Gianni Motti went down into the LHC tunnel and walked around the 27 kilometres of the underground ring at an average, unaccelerated pace of 5 kph. This was an artistic rather than an athletic performance, aimed at drawing a parallel between the fantastic speed of the beams produced by the future accelerator and the leisurely stroll of a human. The artist, who hails from Lombardy, was accompanied by cameraman Ivo Zanetti, who filmed the event from start to finish, and physicist Jean-Pierre Merlo. The first part of the film can be seen at the Villa Bernasconi, 8 route du Grand-Lancy, Grand Lancy, until 26 June.

  8. Does long-distance walking improve or deteriorate walking stability of transtibial amputees?

    Science.gov (United States)

    Wong, Duo Wai-Chi; Lam, Wing Kai; Yeung, L F; Lee, Winson C C

    2015-10-01

    Falls are common in transtibial amputees which are linked to their poor stability. While amputees are encouraged to walk more, they are more vulnerable to fatigue which leads to even poorer walking stability. The objective of this study was to evaluate the dynamic stability of amputees after long-distance walking. Six male unilateral transtibial amputees (age: 53 (SD: 8.8); height: 170cm (SD: 3.4); weight: 75kg (SD: 4.7)) performed two sessions (30minutes each) of treadmill walking, separated by a short period of gait tests. Gait tests were performed before the walking (baseline) and after each session of treadmill walking. Gait parameters and their variability across repeated steps at each of the three conditions were computed. There were no significant differences in walking speed, step length, stance time, time of occurrence, and magnitude of peak angular velocities of the knee and hip joint (P>0.05). However, variability of knee and hip angular velocity after 30-minute walking was significantly higher than the baseline (Pamputees to restore their walking stability after further continuous walking. Copyright © 2015 Elsevier Ltd. All rights reserved.

  9. Fire-Walking

    Science.gov (United States)

    Willey, David

    2010-01-01

    This article gives a brief history of fire-walking and then deals with the physics behind fire-walking. The author has performed approximately 50 fire-walks, took the data for the world's hottest fire-walk and was, at one time, a world record holder for the longest fire-walk (www.dwilley.com/HDATLTW/Record_Making_Firewalks.html). He currently…

  10. Desflurane usage during anesthesia with and without N2O using FLOW-i Automatic Gas Control with three different wash-in speeds.

    Science.gov (United States)

    De Medts, Robrecht; Carette, Rik; De Wolf, Andre M; Hendrickx, Jan F A

    2017-06-09

    AGC(®) (Automatic Gas Control) is the FLOW-i's automated low flow tool (Maquet, Solna, Sweden) that target controls the inspired O2 (FIO2) and end-expired desflurane concentration (FAdes) while (by design) exponentially decreasing fresh gas flow (FGF) during wash-in to a maintenance default FGF of 300 mL min(-1). It also offers a choice of wash-in speeds for the inhaled agents. We examined AGC performance and hypothesized that the use of lower wash-in speeds and N2O both reduce desflurane usage (Vdes). After obtaining IRB approval and patient consent, 78 ASA I-II patients undergoing abdominal surgery were randomly assigned to 1 of 6 groups (n = 13 each), depending on carrier gas (O2/air or O2/N2O) and wash-in speed (AGC speed 2, 4, or 6) of desflurane, resulting in groups air/2, air/4, air/6, N2O/2, N2O/4, and N2O/6. The target for FIO2 was set at 35%, while the FAdes target was selected so that the AGC displayed 1.3 MAC (corrected for the additive affect of N2O if used). AGC was activated upon starting mechanical ventilation. Varvel's criteria were used to describe performance of achieving the targets. Patient demographics, end-expired N2O concentration, MAC, FGF, and Vdes were compared using ANOVA. Data are presented as mean ± standard deviation, except for Varvel's criteria (median ± quartiles). Patient demographics did not differ among the groups. Median performance error was -2-0% for FIO2 and -3-1% for FAdes; median absolute performance error was 1-2% for FIO2 and 0-3% for FAdes. MAC increased faster in N2O groups, but total MAC decreased 0.1-0.25 MAC below that in the O2/air groups after 60 min. The effect of wash-in speed on Vdes faded over time. N2O decreased Vdes by 62%. AGC performance for O2 and desflurane targeting is excellent. After 1 h, the wash-in speeds tested are unlikely to affect desflurane usage. N2O usage decreases Vdes proportionally with its reduction in FAtdes.

  11. Investigation of Unsteady Flow Field in a Low-Speed One and a Half Stage Axial Compressor. Part 2; Effects of Tip Gap Size On the Tip Clearance Flow Structure at Near Stall Operation

    Science.gov (United States)

    Hah, Chunill; Hathaway, Michael; Katz, Joseph

    2014-01-01

    The primary focus of this paper is to investigate the effect of rotor tip gap size on how the rotor unsteady tip clearance flow structure changes in a low speed one and half stage axial compressor at near stall operation (for example, where maximum pressure rise is obtained). A Large Eddy Simulation (LES) is applied to calculate the unsteady flow field at this flow condition with both a small and a large tip gaps. The numerically obtained flow fields at the small clearance matches fairly well with the available initial measurements obtained at the Johns Hopkins University with 3-D unsteady PIV in an index-matched test facility which renders the compressor blades and casing optically transparent. With this setup, the unsteady velocity field in the entire flow domain, including the flow inside the tip gap, can be measured. The numerical results are also compared with previously published measurements in a low speed single stage compressor (Maerz et al. [2002]). The current study shows that, with the smaller rotor tip gap, the tip clearance vortex moves to the leading edge plane at near stall operating condition, creating a nearly circumferentially aligned vortex that persists around the entire rotor. On the other hand, with a large tip gap, the clearance vortex stays inside the blade passage at near stall operation. With the large tip gap, flow instability and related large pressure fluctuation at the leading edge are observed in this one and a half stage compressor. Detailed examination of the unsteady flow structure in this compressor stage reveals that the flow instability is due to shed vortices near the leading edge, and not due to a three-dimensional separation vortex originating from the suction side of the blade, which is commonly referred to during a spike-type stall inception. The entire tip clearance flow is highly unsteady. Many vortex structures in the tip clearance flow, including the sheet vortex system near the casing, interact with each other. The

  12. Investigation of Unsteady Tip Clearance Flow in a Low-Speed One and Half Stage Axial Compressor with LES And PIV

    Science.gov (United States)

    Hah, Chunill; Hathaway, Michael; Katz, Joseph; Tan, David

    2015-01-01

    The primary focus of this paper is to investigate how a rotor's unsteady tip clearance flow structure changes in a low speed one and half stage axial compressor when the rotor tip gap size is increased from 0.5 mm (0.49% of rotor tip blade chord, 2% of blade span) to 2.4 mm (2.34% chord, 4% span) at the design condition are investigated. The changes in unsteady tip clearance flow with the 0.62 % tip gap as the flow rate is reduced to near stall condition are also investigated. A Large Eddy Simulation (LES) is applied to calculate the unsteady flow field at these three flow conditions. Detailed Stereoscopic PIV (SPIV) measurements of the current flow fields were also performed at the Johns Hopkins University in a refractive index-matched test facility which renders the compressor blades and casing optically transparent. With this setup, the unsteady velocity field in the entire flow domain, including the flow inside the tip gap, can be measured. Unsteady tip clearance flow fields from LES are compared with the PIV measurements and both LES and PIV results are used to study changes in tip clearance flow structures. The current study shows that the tip clearance vortex is not a single structure as traditionally perceived. The tip clearance vortex is formed by multiple interlaced vorticities. Therefore, the tip clearance vortex is inherently unsteady. The multiple interlaced vortices never roll up to form a single structure. When phased-averaged, the tip clearance vortex appears as a single structure. When flow rate is reduced with the same tip gap, the tip clearance vortex rolls further upstream and the tip clearance vortex moves further radially inward and away from the suction side of the blade. When the tip gap size is increased at the design flow condition, the overall tip clearance vortex becomes stronger and it stays closer to the blade suction side and the vortex core extends all the way to the exit of the blade passage. Measured and calculated unsteady flow

  13. Testing of a hot- and cold-wire probe to measure simultaneously the speed and temperature in supercritical CO{sub 2} flow

    Energy Technology Data Exchange (ETDEWEB)

    Vukoslavcevic, Petar V.; Radulovic, Ivana M. [University of Montenegro, Podgorica (Czechoslovakia); Wallace, James M. [University of Maryland, MD (United States)

    2005-10-01

    The use of hot-wire anemometry in carbon dioxide flow under supercritical conditions has been analyzed and implemented for the first time. A two-sensor probe to simultaneously measure streamwise velocity and temperature in this flow has been designed and constructed. A calibration and test flow loop that can provide supercritical state conditions above the critical point has been also designed, fabricated and tested. The temperature and velocity flow fields of the flow loop can be varied at constant pressure. It has been found that, above the pseudo-critical temperature, the velocity sensor response fits King's cooling law with a high correlation coefficient. The dependence of the King's law parameters on temperature can be accurately presented with second or higher order polynomial or exponential fits, depending on the extent of the temperature range. Below the pseudocritical temperature the data is scattered, and the variation with temperature of the King's law parameters, determined from calibration, is irregular. The influence on this data scatter of the strong variation of the fluid properties near the critical point is analyzed, and a possibility to reduce it is proposed. The temperature sensor response both above and below the pseudocritical temperature is similar to the response under normal conditions. It is linear with a very high correlation coefficient between the calibration data and the fitted curve. It is also shown that the temperature response is not affected by variation of the flow's speed. (orig.)

  14. Control of low-speed turbulent separated flow over a backward-facing ramp. Ph.D. Thesis - Old Dominion Univ.

    Science.gov (United States)

    Lin, John C.

    1992-01-01

    The relative performance and flow phenomena associated with several devices for controlling turbulent separated flow were investigated at low speeds. Relative performance of the devices was examined for flow over a curved, backward-facing ramp in a wind tunnel, and the flow phenomena were examined in a water tunnel using dye-flow visualization. Surface static pressure measurements and oil-flow visualization results from the wind tunnel tests indicated that transverse grooves, longitudinal grooves, submerged vortex generators, vortex generator jets (VGJ's), Viets' fluidic flappers, elongated arches at positive angle of attack, and large-eddy breakup devices (LEBU's) at positive angle of attack placed near the baseline separation location reduce flow separation and increase pressure recovery. Spanwise cylinders reduce flow separation but decrease pressure recovery downstream. Riblets, passive porous surfaces, swept grooves, Helmholtz resonators, and arches and LEBU's with angle of attack less than or = 0 degrees had no significant effect in reducing the extent of the separation region. Wall-cooling computations indicated that separation delay on a partially-cooled ramp is nearly the same as on a fully-cooled ramp, while minimizing the frictional drag increase associated with the wall cooling process. Dry-flow visualization tests in the water tunnel indicated that wishbone vortex generators in the forward orientation shed horseshoe vortices; wishbone vortex generators oriented in the reverse direction and doublet vortex generators shed streamwise counterrotating vortices; a spanewise cylinder located near the wall and LEBU's at angle of attack = -10 degrees produced eddies or transverse vortices which rotated with the same sign as the mean vorticity in a turbulent boundary layer; and the most effective VGJ's produced streamwise co-rotating vortices. Comparative wind-tunnel test results indicated that transferring momentum from the outer region of a turbulent boundary

  15. Development of smoothed particle hydrodynamics method for analysis of high-speed two-phase flows in hydropower spillways

    Science.gov (United States)

    Nakayama, Akihiko; Leong, Lap Yan; Kong, Wei Song

    2017-04-01

    The basic formulation of the smoothed particle hydrodynamics (SPH) has been re-examined for analysis of gas-liquid two-phase flows with large density differences. The improved method has been verified in the calculation of dam-break flow and has been applied to an open-channel flow over steep sloped stepped spillway. In the calculation of the flow over the steps, not only is the trapped air but entrained air bubbles and water droplets are reproduced well. The detailed variation of the time-averaged mean quantities will have to be further examined but overall prediction with relatively small number of particles is done well.

  16. A study of high speed flows in an aircraft transition duct. Ph.D. Thesis - Iowa State Univ.

    Science.gov (United States)

    Reichert, Bruce A.

    1991-01-01

    The study of circular-to-rectangular transition duct flows with and without inlet swirl is presented. A method was devised to create a swirling, solid body rotational flow with minimal associated disturbances. Details of the swirl generator design and construction are discussed. Coefficients based on velocities and total and static pressures measured in cross stream planes at four axial locations within the transition duct along with surface static pressures and surface oil film visualization are presented for both nonswirling and swirling incoming flows. A method was developed to acquire trace gas measurements within the transition duct at high flow velocities. Statistical methods are used to help interpret the trace gas results.

  17. Lee-surface heating and flow phenomena on space shuttle orbiters at large angles of attack and hypersonic speeds

    Science.gov (United States)

    Hefner, J. N.

    1972-01-01

    The lee-surface flow phenomena on a delta-wing orbiter and a straight-wing orbiter have been investigated at angles of attack between 0 deg and 50 deg at a Mach number of 6. Limited studies of the delta-wing orbiter were conducted at a Mach number of 19. Heat-transfer data, pressure distributions, and oil-flow studies were employed to experimentally examine the nature of the surface flow and the severity of the lee-surface heating. The effects of Reynolds number on the flow field and heating were investigated. Problem areas are defined and areas for further study are recommended.

  18. Effectiveness of Motorcycle speed controlled by speed hump

    Directory of Open Access Journals (Sweden)

    Pornsiri Urapa

    2014-09-01

    Full Text Available Speed humps are one of the traffic calming measures widely accepted to control vehicle speed in the local road. Humps standards from the western countries are designed mainly for the passenger car. This study, therefore, aims to reveal the effectiveness of speed hump to control the motorcycle speed. This study observes the free-flow speed of the riders at the total of 20 speed bumps and humps. They are 0.3-14.8 meter in width and 5-18 centimeter in height. The results reveal that the 85th percentile speeds reduce 15-65 percent when crossing the speed bumps and speed humps. Besides, this study develops the speed model to predict the motorcycle mean speed and 85th percentile speed. It is found that speed humps follow the ITE standard can control motorcycle crossing speeds to be 25-30 Kph which are suitable to travel on the local road.

  19. Ablation of silicate particles in high-speed continuum and transition flow with application to the collection of interplanetary dust particles

    Science.gov (United States)

    Rulison, Aaron J.; Flagan, Richard C.; Ahrens, Thomas J.; Miller, Wayne F.

    1991-04-01

    The ablative deceleration of spheres in the continuum and slip regimes is studied using spherical 7.1-micron-diam soda-lime glass particles launched from vacuum at about 4500 m/sec speed through a 13-micron-thick plastic film into a capture chamber containing Xe at 0.1 or 0.2 atm pressure and 295 K temperature. The results of SEM examinations of the collected ablated particles showed that the ratio of the ablated-particle radius (Rf) to the initial radius (R0) increased with gas pressure (from Rf/R0 about 0.67 at 0.1 atm, to about 0.88 at 0.2 atm). A model was developed to describe the ablation and deceleration of spheres in high-speed continuum and slip flow. The pressure dependence predicted by the model agreed with experimental results.

  20. Novel experimental technique for 3D investigation of high-speed cavitating diesel fuel flows by X-ray micro computed tomography

    Science.gov (United States)

    Lorenzi, M.; Mitroglou, N.; Santini, M.; Gavaises, M.

    2017-03-01

    An experimental technique for the estimation of the temporal-averaged vapour volume fraction within high-speed cavitating flow orifices is presented. The scientific instrument is designed to employ X-ray micro computed tomography (microCT) as a quantitative 3D measuring technique applied to custom designed, large-scale, orifice-type flow channels made from Polyether-ether-ketone (PEEK). The attenuation of the ionising electromagnetic radiation by the fluid under examination depends on its local density; the transmitted radiation through the cavitation volume is compared to the incident radiation, and combination of radiographies from sufficient number of angles leads to the reconstruction of attenuation coefficients versus the spatial position. This results to a 3D volume fraction distribution measurement of the developing multiphase flow. The experimental results obtained are compared against the high speed shadowgraph visualisation images obtained in an optically transparent nozzle with identical injection geometry; comparison between the temporal mean image and the microCT reconstruction shows excellent agreement. At the same time, the real 3D internal channel geometry (possibly eroded) has been measured and compared to the nominal manufacturing CAD drawing of the test nozzle.

  1. Improvement of oxygen transfer coefficient during Penicillium canescens culture. Influence of turbine design, agitation speed, and air flow rate on xylanase production.

    Science.gov (United States)

    Gaspar, A; Strodiot, L; Thonart, P

    1998-01-01

    To improve xylanase productivity from Penicillium canescens 10-10c culture, an optimization of oxygen supply is required. Because the strain is sensitive to shear forces, leading to lower xylanase productivity as to morphological alteration, vigorous mixing is not desired. The influence of turbine design, agitation speed, and air flow rate on K1a (global mass transfer coefficient, h(-1)) and enzyme production is discussed. K1a values increased with agitation speed and air flow rate, whatever the impeller, in our assay conditions. Agitation had more influence on K1a values than air flow, when a disk-mounted blade's impeller (DT) is used; an opposite result was obtained with a hub-mounted pitched blade's impeller (PBT). Xylanase production appeared as a function of specific power (W/m3), and an optimum was found in 20 and 100 L STRs fitted with DT impellers. On the other hand, the use of a hub-mounted pitched blade impeller (PBT8), instead of a disk-mounted blade impeller (DT4), reduced the lag time of hemicellulase production and increased xylanase productivity 1.3-fold.

  2. Central and peripheral blood flow during exercise with a continuous-flow left ventricular assist device: constant versus increasing pump speed: a pilot study

    DEFF Research Database (Denmark)

    Brassard, Patrice; Jensen, Annette S; Nordsborg, Nikolai

    2011-01-01

    with work rate would increase organ blood flow. Methods and Results- Invasively determined CO and leg blood flow and Doppler-determined cerebral perfusion were measured during 2 incremental cycle exercise tests on the same day in 8 patients provided with a HeartMate II LVAD. In random order, patients...

  3. Energetics and biomechanics of inclined treadmill walking in obese adults.

    Science.gov (United States)

    Ehlen, Kellie A; Reiser, Raoul F; Browning, Raymond C

    2011-07-01

    Brisk walking is a recommended form of exercise for obese individuals. However, lower-extremity joint loads and the associated risk of musculoskeletal injury or pathological disease increase with walking speed. Walking uphill at a slower speed is an alternative form of moderate intensity exercise that may reduce joint loading. The purpose of this study was to quantify the energetics and biomechanics of level and uphill walking in obese adults. We hypothesized that compared to brisk level walking, walking slower up a moderate incline would reduce lower-extremity net muscle moments while providing appropriate cardiovascular stimulus. Twelve obese adult volunteers, with mass of 100.5±15.7 kg and body mass index of 33.4±2.6 kg·m (mean±SD), participated in this study. We measured oxygen consumption, ground reaction forces, and three-dimensional lower-extremity kinematics while subjects walked on a dual-belt force-measuring treadmill at several speed (0.50-1.75 m·s) and grade (0°-9°) combinations. We calculated metabolic rate, loading rates, and net muscle moments at the hip, knee, and ankle for each condition. Metabolic rates were similar across trials and were of moderate intensity (48.5%-59.8% of VO2max). Walking slower uphill significantly reduced loading rates and lower-extremity net muscle moments compared with faster level walking. Peak knee extension and adduction moments were reduced by ∼19% and 26%, respectively, when subjects walked up a 6° incline at 0.75 m·s versus level walking at 1.50 m·s. These results suggest that walking at a relatively slow speed up a moderate incline is a potential exercise strategy that may reduce the risk of musculoskeletal injury/pathological disease while providing proper cardiovascular stimulus in obese adults.

  4. Two- and 6-minute walk tests assess walking capability equally in neuromuscular diseases.

    Science.gov (United States)

    Andersen, Linda Kahr; Knak, Kirsten Lykke; Witting, Nanna; Vissing, John

    2016-02-02

    This methodologic study investigates if the 2-minute walk test (2MWT) can be a valid alternative to the 6-minute walk test (6MWT) to describe walking capability in patients with neuromuscular diseases. Patients (n = 115) with different neuromuscular diseases were invited to participate on 2 test days, each consisting of 1 2MWT and 1 6MWT separated by a minimum 30-minute period of rest. The order of the walk tests was randomly assigned via sealed envelopes. A group of 38 healthy controls completed 1 6MWT. The mean walking distance for the 2MWT was 142.8 meters and for the 6MWT 405.3 meters. The distance walked in the 2MWT was highly correlated to the distance walked in the 6MWT (r = 0.99, p walking speed from the first to last minute in the 6MWT, both among patients and healthy controls, which was not evident in the 2MWT. Results were consistent across diagnoses and levels of disease severity. The 2MWT is a potential alternative to the 6MWT to describe walking capability among patients with neuromuscular diseases during clinical trials. © 2016 American Academy of Neurology.

  5. Development and Implementation of 3-D, High Speed Capacitance Tomography for Imaging Large-Scale, Cold-Flow Circulating Fluidized Bed

    Energy Technology Data Exchange (ETDEWEB)

    Marashdeh, Qussai [Tech4imaging LLC, Columbus, OH (United States)

    2013-02-01

    A detailed understanding of multiphase flow behavior inside a Circulating Fluidized Bed (CFB) requires a 3-D technique capable of visualizing the flow field in real-time. Electrical Capacitance Volume Tomography (ECVT) is a newly developed technique that can provide such measurements. The attractiveness of the technique is in its low profile sensors, fast imaging speed and scalability to different section sizes, low operating cost, and safety. Moreover, the flexibility of ECVT sensors enable them to be designed around virtually any geometry, rendering them suitable to be used for measurement of solid flows in exit regions of the CFB. Tech4Imaging LLC has worked under contract with the U.S. Department of Energy's National Energy Technology Laboratory (DOE NETL) to develop an ECVT system for cold flow visualization and install it on a 12 inch ID circulating fluidized bed. The objective of this project was to help advance multi-phase flow science through implementation of an ECVT system on a cold flow model at DOE NETL. This project has responded to multi-phase community and industry needs of developing a tool that can be used to develop flow models, validate computational fluid dynamics simulations, provide detailed real-time feedback of process variables, and provide a comprehensive understating of multi-phase flow behavior. In this project, a complete ECVT system was successfully developed after considering different potential electronics and sensor designs. The system was tested at various flow conditions and with different materials, yielding real-time images of flow interaction in a gas-solid flow system. The system was installed on a 12 inch ID CFB of the US Department of Energy, Morgantown Labs. Technical and economic assessment of Scale-up and Commercialization of ECVT was also conducted. Experiments conducted with larger sensors in conditions similar to industrial settings are very promising. ECVT has also the potential to be developed for imaging multi

  6. Development and Application of Advanced Optical Diagnostics for the Study of High Speed Flows in Micro Systems

    National Research Council Canada - National Science Library

    Lempert, Walter

    2000-01-01

    .... In particular, Molecular Tagging Velocimetry (MTV) measurements have been performed, using acetone vapor as a molecular tracer, in the flow produced by a 1 mm diameter, pressure matched, sonic nozzle...

  7. Elastic coupling of limb joints enables faster bipedal walking.

    Science.gov (United States)

    Dean, J C; Kuo, A D

    2009-06-06

    The passive dynamics of bipedal limbs alone are sufficient to produce a walking motion, without need for control. Humans augment these dynamics with muscles, actively coordinated to produce stable and economical walking. Present robots using passive dynamics walk much slower, perhaps because they lack elastic muscles that couple the joints. Elastic properties are well known to enhance running gaits, but their effect on walking has yet to be explored. Here we use a computational model of dynamic walking to show that elastic joint coupling can help to coordinate faster walking. In walking powered by trailing leg push-off, the model's speed is normally limited by a swing leg that moves too slowly to avoid stumbling. A uni-articular spring about the knee allows faster but uneconomical walking. A combination of uni-articular hip and knee springs can speed the legs for improved speed and economy, but not without the swing foot scuffing the ground. Bi-articular springs coupling the hips and knees can yield high economy and good ground clearance similar to humans. An important parameter is the knee-to-hip moment arm that greatly affects the existence and stability of gaits, and when selected appropriately can allow for a wide range of speeds. Elastic joint coupling may contribute to the economy and stability of human gait.

  8. PowerPoint: Time-Flow Photography: Experimental Imagery with Continuous Motion and Long Shutter Speeds by Rick Doble

    OpenAIRE

    Doble, Rick

    2014-01-01

    For the first time in the history of photography, digital photographers can now experiment with photographic effects and immediately review the results. This capability, which is crucial for experimentation, opens up a new world of imagery with slow shutter speeds that 'paint' light in a variety of ways. Yet some people believe that the effects of movement in slow-exposure photography are about the same and accidental. Nothing could be further from the truth. There is a quite sophisticated vo...

  9. Common muscle synergies for balance and walking

    Directory of Open Access Journals (Sweden)

    Stacie A Chvatal

    2013-05-01

    Full Text Available Little is known about the integration of neural mechanisms for balance and locomotion. Muscle synergies have been studied independently in standing balance and walking, but not compared. Here, we hypothesized that reactive balance and walking are mediated by common set of lower-limb muscle synergies. In humans, we examined muscle activity during multidirectional support-surface perturbations during standing and walking, as well as unperturbed walking at two speeds. We show that most muscle synergies used in perturbations responses during standing were also used in perturbation responses during walking, suggesting common neural mechanisms for reactive balance across different contexts. We also show that most muscle synergies using in reactive balance were also used during unperturbed walking, suggesting that neural circuits mediating locomotion and reactive balance recruit a common set of muscle synergies to achieve task-level goals. Differences in muscle synergies across conditions reflected differences in the biomechanical demands of the tasks. For example, muscle synergies specific to walking perturbations may reflect biomechanical challenges associated with single limb stance, and muscle synergies used during sagittal balance recovery in standing but not walking were consistent with maintaining the different desired center of mass motions in standing versus walking. Thus, muscle synergies specifying spatial organization of muscle activation patterns may define a repertoire of biomechanical subtasks available to different neural circuits governing walking and reactive balance and may be recruited based on task-level goals. Muscle synergy analysis may aid in dissociating deficits in spatial versus temporal organization of muscle activity in motor deficits. Muscle synergy analysis may also provide a more generalizable assessment of motor function by identifying whether common modular mechanisms are impaired across the performance of multiple

  10. What Is Walking Pneumonia?

    Science.gov (United States)

    ... pneumonia: What does it mean? What is walking pneumonia? How is it different from regular pneumonia? Answers from Eric J. Olson, M.D. Walking pneumonia is an informal term for pneumonia that isn' ...

  11. Walking with coffee: Why does it spill?

    Science.gov (United States)

    Mayer, H. C.; Krechetnikov, R.

    2012-04-01

    In our busy lives, almost all of us have to walk with a cup of coffee. While often we spill the drink, this familiar phenomenon has never been explored systematically. Here we report on the results of an experimental study of the conditions under which coffee spills for various walking speeds and initial liquid levels in the cup. These observations are analyzed from the dynamical systems and fluid mechanics viewpoints as well as with the help of a model developed here. Particularities of the common cup sizes, the coffee properties, and the biomechanics of walking proved to be responsible for the spilling phenomenon. The studied problem represents an example of the interplay between the complex motion of a cup, due to the biomechanics of a walking individual, and the low-viscosity-liquid dynamics in it.

  12. Walking-Beam Solar-Cell Conveyor

    Science.gov (United States)

    Feder, H.; Frasch, W.

    1982-01-01

    Microprocessor-controlled walking-beam conveyor moves cells between work stations in automated assembly line. Conveyor has arm at each work station. In unison arms pick up all solar cells and advance them one station; then beam retracks to be in position for next step. Microprocessor sets beam stroke, speed, and position.

  13. Locomotor sequence learning in visually guided walking.

    Science.gov (United States)

    Choi, Julia T; Jensen, Peter; Nielsen, Jens Bo

    2016-04-01

    Voluntary limb modifications must be integrated with basic walking patterns during visually guided walking. In this study we tested whether voluntary gait modifications can become more automatic with practice. We challenged walking control by presenting visual stepping targets that instructed subjects to modify step length from one trial to the next. Our sequence learning paradigm is derived from the serial reaction-time (SRT) task that has been used in upper limb studies. Both random and ordered sequences of step lengths were used to measure sequence-specific and sequence-nonspecific learning during walking. In addition, we determined how age (i.e., healthy young adults vs. children) and biomechanical factors (i.e., walking speed) affected the rate and magnitude of locomotor sequence learning. The results showed that healthy young adults (age 24 ± 5 yr,n= 20) could learn a specific sequence of step lengths over 300 training steps. Younger children (age 6-10 yr,n= 8) had lower baseline performance, but their magnitude and rate of sequence learning were the same compared with those of older children (11-16 yr,n= 10) and healthy adults. In addition, learning capacity may be more limited at faster walking speeds. To our knowledge, this is the first study to demonstrate that spatial sequence learning can be integrated with a highly automatic task such as walking. These findings suggest that adults and children use implicit knowledge about the sequence to plan and execute leg movement during visually guided walking. Copyright © 2016 the American Physiological Society.

  14. Speed from light: growth rate and bulk flow at z ˜ 0.1 from improved SDSS DR13 photometry

    Science.gov (United States)

    Feix, M.; Branchini, E.; Nusser, A.

    2017-06-01

    Observed galaxy luminosities (derived from redshifts) hold information on the large-scale peculiar velocity field in the form of spatially correlated scatter, which allows for bounds on bulk flows and the growth rate of matter density perturbations using large galaxy redshift surveys. We apply this luminosity approach to galaxies from the recent SDSS Data Release 13. Our goal is twofold. First, we take advantage of the recalibrated photometry to identify possible systematic errors relevant to our previous analysis of earlier data. Second, we seek improved constraints on the bulk flow and the normalized growth rate fσ8 at z ˜ 0.1. Our results confirm the robustness of our method. Bulk flow amplitudes, estimated in two redshift bins with 0.02 z1 z2 generation photometric catalogues.

  15. High-speed (20  kHz) digital in-line holography for transient particle tracking and sizing in multiphase flows.

    Science.gov (United States)

    Guildenbecher, Daniel R; Cooper, Marcia A; Sojka, Paul E

    2016-04-10

    High-speed (20 kHz) digital in-line holography (DIH) is applied for 3D quantification of the size and velocity of fragments formed from the impact of a single water drop onto a thin film of water and burning aluminum particles from the combustion of a solid rocket propellant. To address the depth-of-focus problem in DIH, a regression-based multiframe tracking algorithm is employed, and out-of-plane experimental displacement accuracy is shown to be improved by an order-of-magnitude. Comparison of the results with previous DIH measurements using low-speed recording shows improved positional accuracy with the added advantage of detailed resolution of transient dynamics from single experimental realizations. The method is shown to be particularly advantageous for quantification of particle mass flow rates. For the investigated particle fields, the mass flows rates, which have been automatically measured from single experimental realizations, are found to be within 8% of the expected values.

  16. COMPUTER MODELING IN DEFORM-3D FOR ANALYSIS OF PLASTIC FLOW IN HIGH-SPEED HOT EXTRUSION OF BIMETALLIC FORMATIVE PARTS OF DIE TOOLING

    Directory of Open Access Journals (Sweden)

    I. V. Kachanov

    2015-01-01

    Full Text Available The modern development of industrial production is closely connected with the use of science-based and high technologies to ensure competitiveness of the manufactured products on the world market. There is also much tension around an energy- and resource saving problem which can be solved while introducing new technological processes and  creation of new materials that provide productivity increase through automation and improvement of tool life. Development and implementation of such technologies are rather often considered as time-consuming processes  which are connected with complex calculations and experimental investigations. Implementation of a simulation modelling for materials processing using modern software products serves an alternative to experimental and theoretical methods of research.The aim of this paper is to compare experimental results while obtaining bimetallic samples of a forming tool through the method of speed hot extrusion and the results obtained with the help of computer simulation using DEFORM-3D package and a finite element method. Comparative analysis of plastic flow of real and model samples has shown that the obtained models provide high-quality and reliable picture of plastic flow during high-speed hot extrusion. Modeling in DEFORM-3D make it possible to eliminate complex calculations and significantly reduce a number of experimental studies while developing new technological processes.

  17. COUPLED LAGRANGE-EULER MODEL FOR SIMULATION OF BUBBLY FLOW IN VERTICAL PIPES CONSIDERING TURBULENT 3D RANDOM WALKS MODELS AND BUBBLES INTERACTION EFFECTS

    OpenAIRE

    Ali Abd El Aziz Essa ., Mohamed

    2012-01-01

    Una nueva aproximación euleriana-lagarangiana, en su forma de acople en dos vías, para la simulación de flujo de burbujas, agua-aire es presentada en la tesis, en la que se incluyen los efectos de las colisiones entre burbujas, así como las posibles roturas o coalescencia de burbujas. Esta aproximación utiliza el modelo Continuous Random Walk, CRW, para tener en cuenta las fluctuaciones de la velocidad. Esta aproximación se enmarca dentro de un modelo de turbulencia k-epsilon para la fase ...

  18. Numerical analysis of the flow pattern and vortex breakdown over a pitching delta wing at supersonic speeds

    Science.gov (United States)

    Hadidoolabi, M.; Ansarian, H.

    2017-05-01

    A supersonic compressible flow over a 60° swept delta wing with a sharp leading edge undergoing pitching oscillations is computationally studied. Numerical simulations are performed by the finite volume method with the use of the k- ω turbulence model for various Mach numbers and angles of attack. Variations of flow patterns in a crossflow plane, hysteresis loops associated with the vortex core location, and vortex breakdown positions during a pitching cycle are investigated. Trends for various Mach numbers, mean angles of attack, pitching amplitudes, and pitching frequencies are illustrated.

  19. Wind Tunnel Investigation of the Effects of Surface Porosity and Vertical Tail Placement on Slender Wing Vortex Flow Aerodynamics at Supersonic Speeds

    Science.gov (United States)

    Erickson, Gary E.

    2007-01-01

    A wind tunnel experiment was conducted in the NASA Langley Research Center (LaRC) Unitary Plan Wind Tunnel (UPWT) to determine the effects of passive surface porosity and vertical tail placement on vortex flow development and interactions about a general research fighter configuration at supersonic speeds. Optical flow measurement and flow visualization techniques were used that featured pressure sensitive paint (PSP), laser vapor screen (LVS), and schlieren, These techniques were combined with conventional electronically-scanned pressure (ESP) and six-component force and moment measurements to quantify and to visualize the effects of flow-through porosity applied to a wing leading edge extension (LEX) and the placement of centerline and twin vertical tails on the vortex-dominated flow field of a 65 cropped delta wing model. Test results were obtained at free-stream Mach numbers of 1.6, 1.8, and 2.1 and a Reynolds number per foot of 2.0 million. LEX porosity promoted a wing vortex-dominated flow field as a result of a diffusion and weakening of the LEX vortex. The redistribution of the vortex-induced suction pressures contributed to large nose-down pitching moment increments but did not significantly affect the vortex-induced lift. The trends associated with LEX porosity were unaffected by vertical tail placement. The centerline tail configuration generally provided more stable rolling moments and yawing moments compared to the twin wing-mounted vertical tails. The strength of a complex system of shock waves between the twin tails was reduced by LEX porosity.

  20. Different instructions during the ten-meter walking test determined significant increases in maximum gait speed in individuals with chronic hemiparesis Diferentes instruções durante teste de velocidade de marcha determinam aumento significativo na velocidade máxima de indivíduos com hemiparesia crônica

    Directory of Open Access Journals (Sweden)

    Lucas R. Nascimento

    2012-04-01

    Full Text Available OBJECTIVE: To evaluate the effects of different instructions for the assessment of maximum walking speed during the ten-meter walking test with chronic stroke subjects. METHODS: Participants were instructed to walk under four experimental conditions: (1 comfortable speed, (2 maximum speed (simple verbal command, (3 maximum speed (modified verbal command-"catch a bus" and (4 maximum speed (verbal command + demonstration. Participants walked three times in each condition and the mean time to cover the intermediate 10 meters of a 14-meter corridor was registered to calculate the gait speed (m/s. Repeated-measures ANOVAs, followed by planned contrasts, were employed to investigate differences between the conditions (α=5%. Means, standard deviations and 95% confidence intervals (CI were calculated. RESULTS: The mean values for the four conditions were: (1 0.74m/s; (2 0.85 m/s; (3 0.93 m/s; (4 0.92 m/s, respectively, with significant differences between the conditions (F=40.9; pOBJETIVO: Avaliar os efeitos de diferentes instruções para avaliação da velocidade de marcha máxima de indivíduos hemiparéticos durante o teste de caminhada de 10 metros. MÉTODOS: Os indivíduos deambularam em quatro condições experimentais: (1 velocidade habitual, (2 velocidade máxima (comando verbal simples, (3 velocidade máxima (comando verbal modificado: pegar ônibus, (4 velocidade máxima (comando verbal + demonstração. Solicitou-se a cada participante que deambulasse três vezes em cada condição, e a média do tempo necessário para percorrer os 10 metros intermediários de um corredor de 14 metros foi utilizada para cálculo da velocidade (m/s. A ANOVA de medidas repetidas, com contrastes pré-planejados, foi utilizada para comparação dos dados (α=5%, sendo apresentados valores de média, desvio-padrão e intervalos de confiança (IC de 95%. RESULTADOS: As médias de velocidade para as quatro condições foram: (1 0,74m/s; (2 0,85m/s; (3 0,93m/s; (4

  1. High-speed counting and sizing of cells in an impedance flow microcytometer with compact electronic instrumentation

    DEFF Research Database (Denmark)

    Castillo-Fernandez, Oscar; Rodriguez-Trujíllo, Romén; Gomila, Gabriel

    2014-01-01

    Here we describe a high-throughput impedance flow cytometer on a chip. This device was built using compact and inexpensive electronic instrumentation. The system was used to count and size a mixed cell sample containing red blood cells and white blood cells. It demonstrated a counting capacity of...

  2. Consistent lattice Boltzmann modeling of low-speed isothermal flows at finite Knudsen numbers in slip-flow regime: Application to plane boundaries

    Science.gov (United States)

    Silva, Goncalo; Semiao, Viriato

    2017-07-01

    The first nonequilibrium effect experienced by gaseous flows in contact with solid surfaces is the slip-flow regime. While the classical hydrodynamic description holds valid in bulk, at boundaries the fluid-wall interactions must consider slip. In comparison to the standard no-slip Dirichlet condition, the case of slip formulates as a Robin-type condition for the fluid tangential velocity. This makes its numerical modeling a challenging task, particularly in complex geometries. In this work, this issue is handled with the lattice Boltzmann method (LBM), motivated by the similarities between the closure relations of the reflection-type boundary schemes equipping the LBM equation and the slip velocity condition established by slip-flow theory. Based on this analogy, we derive, as central result, the structure of the LBM boundary closure relation that is consistent with the second-order slip velocity condition, applicable to planar walls. Subsequently, three tasks are performed. First, we clarify the limitations of existing slip velocity LBM schemes, based on discrete analogs of kinetic theory fluid-wall interaction models. Second, we present improved slip velocity LBM boundary schemes, constructed directly at discrete level, by extending the multireflection framework to the slip-flow regime. Here, two classes of slip velocity LBM boundary schemes are considered: (i) linear slip schemes, which are local but retain some calibration requirements and/or operation limitations, (ii) parabolic slip schemes, which use a two-point implementation but guarantee the consistent prescription of the intended slip velocity condition, at arbitrary plane wall discretizations, further dispensing any numerical calibration procedure. Third and final, we verify the improvements of our proposed slip velocity LBM boundary schemes against existing ones. The numerical tests evaluate the ability of the slip schemes to exactly accommodate the steady Poiseuille channel flow solution, over

  3. Two- and 6-minute walk tests assess walking capability equally in neuromuscular diseases

    DEFF Research Database (Denmark)

    Andersen, Linda Kahr; Knak, Kirsten Lykke; Witting, Nanna

    2016-01-01

    OBJECTIVE: This methodologic study investigates if the 2-minute walk test (2MWT) can be a valid alternative to the 6-minute walk test (6MWT) to describe walking capability in patients with neuromuscular diseases. METHODS: Patients (n = 115) with different neuromuscular diseases were invited...... to participate on 2 test days, each consisting of 1 2MWT and 1 6MWT separated by a minimum 30-minute period of rest. The order of the walk tests was randomly assigned via sealed envelopes. A group of 38 healthy controls completed 1 6MWT. RESULTS: The mean walking distance for the 2MWT was 142.8 meters...... and for the 6MWT 405.3 meters. The distance walked in the 2MWT was highly correlated to the distance walked in the 6MWT (r = 0.99, p walking speed from the first to last minute in the 6MWT, both among patients and healthy controls, which was not evident in the 2MWT...

  4. How does wearable robotic exoskeleton affect overground walking performance measured with the 10-m and six-minute walk tests after a basic locomotor training in healthy individuals?

    Science.gov (United States)

    Gagnon, Dany H; Cunha, Jérémie Da; Boyer-Delestre, Mael; Bosquet, Laurent; Duclos, Cyril

    2017-10-01

    It is still unknown to what extent overground walking with a WRE is equivalent to natural overground walking without a WRE. Hence, the interpretability of the 10-m (10MWT) and six-minute (6MWT) walk tests during overground walking with a WRE against reference values collected during natural overground walking without a WRE is challenging. This study aimed to 1) compare walking performance across three different overground walking conditions: natural walking without a WRE, walking with a WRE providing minimal assistance (active walking), and walking with a WRE proving complete assistance (passive walking) and 2) assess the association and the agreement between the 10MWT and the 6MWT during passive and active walking with a WRE. Seventeen healthy individuals who underwent basic locomotor training with a WRE performed the 10MWT (preferred and maximal speeds) and the 6MWT under the three conditions. For the 10MWT, the speed progressively and significantly decreased from natural walking without a WRE (preferred: 1.40±0.18m/s; maximal: 2.16±0.19m/s), to active walking with a WRE (preferred: 0.48±0.10m/s; maximal: 0.61±0.14m/s), and to passive walking with a WRE (preferred: 0.38±0.09m/s; maximal: 0.42±0.10m/s). For the 6MWT, total distances decreased from walking without a WRE (609±53.9m), to active walking with a WRE (196.6±42.6m), and to passive walking with a WRE (144.3±33.3m). The 10MWT and 6MWT provide distinct information and can't be used interchangeably to document speed only during active walking with the WRE. Speed and distance drastically decrease during active and, even more so, passive walking with the WRE in comparison to walking without a WRE. Selection of walking tests should depend on the level of assistance provided by the WRE. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Relation Between Aerobic Capacity and Walking Ability in Older Adults With a Lower-Limb Amputation

    NARCIS (Netherlands)

    Wezenberg, Daphne; van der Woude, Lucas H.; Faber, Willemijn X.; de Haan, Arnold; Houdijk, Han

    Objectives: To determine the relative aerobic load, walking speed, and walking economy of older adults with a lower-limb prosthesis, and to predict the effect of an increased aerobic capacity on their walking ability. Design: Cross-sectional. Setting: Human motion laboratory at a rehabilitation

  6. Detection of Abnormal Muscle Activations during Walking Following Spinal Cord Injury (SCI)

    Science.gov (United States)

    Wang, Ping; Low, K. H.; McGregor, Alison H.; Tow, Adela

    2013-01-01

    In order to identify optimal rehabilitation strategies for spinal cord injury (SCI) participants, assessment of impaired walking is required to detect, monitor and quantify movement disorders. In the proposed assessment, ten healthy and seven SCI participants were recruited to perform an over-ground walking test at slow walking speeds. SCI…

  7. Aerobic treadmill plus Bobath walking training improves walking in subacute stroke: a randomized controlled trial.

    Science.gov (United States)

    Eich, H-J; Mach, H; Werner, C; Hesse, S

    2004-09-01

    To evaluate the immediate and long-term effects of aerobic treadmill plus Bobath walking training in subacute stroke survivors compared with Bobath walking training alone. Randomized controlled trial. Rehabilitation unit. Fifty patients, first-time supratentorial stroke, stroke interval less than six weeks, Barthel Index (0-100) from 50 to 80, able to walk a minimum distance of 12 m with either intermittent help or stand-by while walking, cardiovascular stable, minimum 50 W in the bicycle ergometry, randomly allocated to two groups, A and B. Group A 30 min of treadmill training, harness secured and minimally supported according to patients' needs, and 30 min of physiotherapy, every workday for six weeks, speed and inclination of the treadmill were adjusted to achieve a heart rate of HR: (Hrmax-HRrest)*0.6+HRrest; in group B 60 min of daily physiotherapy for six weeks. Primary outcome variables were the absolute improvement of walking velocity (m/s) and capacity (m), secondary were gross motor function including walking ability (score out of 13) and walking quality (score out of 41), blindly assessed before and after the intervention, and at follow-up three months later. Patients tolerated the aerobic training well with no side-effects, significantly greater improvement of walking velocity and capacity both at study end (p =0.001 versus p =0.002) and at follow-up (p Bobath walking training in moderately affected stroke patients was better than Bobath walking training alone with respect to the improvement of walking velocity and capacity. The treatment approach is recommended in patients meeting the inclusion criteria. A multicentre trial should follow to strengthen the evidence.

  8. Effects of Initial Stance of Quadruped Trotting on Walking Stability

    Directory of Open Access Journals (Sweden)

    Peisun Ma

    2008-11-01

    Full Text Available It is very important for quadruped walking machine to keep its stability in high speed walking. It has been indicated that moment around the supporting diagonal line of quadruped in trotting gait largely influences walking stability. In this paper, moment around the supporting diagonal line of quadruped in trotting gait is modeled and its effects on body attitude are analyzed. The degree of influence varies with different initial stances of quadruped and we get the optimal initial stance of quadruped in trotting gait with maximal walking stability. Simulation results are presented.

  9. Japanese elderly persons walk faster than non-Asian elderly persons: a meta-regression analysis.

    Science.gov (United States)

    Ando, Masataka; Kamide, Naoto

    2015-11-01

    [Purpose] The purpose of this study was to clarify ethnic differences in walking speed by comparing walking speed in both Japanese and non-Asian elderly individuals and to investigate the necessity of consideration of ethnic differences in walking speed. [Subjects and Methods] Articles that reported comfortable walking speeds for community-dwelling elderly individuals were identified from electronic databases. Articles that involved community-dwelling individuals who were 60 years old or older and well functioning were included in the study. Articles that involved Asians were excluded. Weighted means for 5-m walking times were calculated as walking speeds from the Japanese and non-Asian sample data. The effects of age, gender, and ethnicity on 5-m walking times were then investigated using meta-regression analysis. [Results] Twenty studies (34 groups) were included for Japanese, and 16 studies (28 groups) were included for non-Asians. The weighted mean 5-m walking time was estimated to be 4.15 sec (95% confidence interval [CI]: 3.87-4.44) for Japanese and 4.24 sec (95% CI: 4.09-4.40) for non-Asians. Furthermore, using meta-regression analysis adjusted for age and gender, the 5-m walking time was 0.40 sec faster (95% CI: 0.03-0.77) for Japanese than for non-Asian elderly individuals. [Conclusion] Walking speed appeared faster for Japanese community-dwelling elderly individuals than for non-Asian elderly individuals.

  10. Speed and exercise intensity of recreational walkers.

    Science.gov (United States)

    Murtagh, Elaine M; Boreham, Colin A G; Murphy, Marie H

    2002-10-01

    Brisk walking has been identified as an activity suited to meet American College of Sport Medicine/Centers for Disease Control and Prevention recommendations for moderate intensity exercise (55-69% HR(max), 40-59% VO(2)R). However, little is known about whether recreational walkers self-select a pace which elicits this intensity and how they interpret the term "brisk walking." The walking speed of 82 adults was covertly observed in a public park. Fifty-nine of these participants demonstrated their interpretation of "brisk walking" and the speed was noted. Eleven of these subjects subsequently walked on a treadmill at their observed and "brisk walk" speeds. Heart rate (HR), respiratory gases, and ratings of perceived exertion (RPE) were measured. Mean observed and "brisk" walking speeds were 1.56 +/- 0.17 m. s(-1) and 1.79 +/- 0.19 m x s(-1) respectively (P exercise intensities during the treadmill test (n = 11) were 59.0 +/- 13.4% VO(2max) and 67.3 +/- 11.6% HR(max) for the observed speed (1.60 + 0.24 m x s(-1)). The brisk speed (1.86 +/- 0.12 m x s(-1)) equated to 68.6 +/- 14.9% VO(2max) and 78.5 +/- 15.5% HR(max). The speed and intensity selected by this group of walkers meets current recommendations for moderate intensity exercise. Instructing individuals to "walk briskly" prompts more vigorous activity. Copyright 2002 American Health Foundation and Elsevier Science (USA)

  11. Turbulent Vortex-Flow Simulation Over a 65 deg Sharp and Blunt Leading-Edge Delta Wing at Subsonic Speeds

    Science.gov (United States)

    Ghaffari, Farhad

    2005-01-01

    Turbulent thin-layer, Reynolds-Averaged Navier-Stokes solutions, based on a multi-block structured grid, are presented for a 65 deg delta wing having either a sharp leading edge (SLE) or blunt leading edge (BLE) geometry. The primary objective of the study is to assess the prediction capability of the method for simulating the leading-edge flow separation and the ensuing vortex flow characteristics. Computational results are obtained for two angles of attack of approximately 13 and 20 deg, at free-stream Mach number of 0.40 and Reynolds number of 6 million based on the wing mean aerodynamic chord. The effects of two turbulence models of Baldwin-Lomax with Degani-Schiff (BL/DS) and the Spalart-Allmaras (SA) on the numerical results are also discussed. The computations also explore the effects of two numerical flux-splitting schemes, i.e., flux difference splitting (fds) and flux vector splitting (fvs), on the solution development and convergence characteristics. The resulting trends in solution sensitivity to grid resolution for the selected leading-edge geometries, angles of attack, turbulence models and flux splitting schemes are also presented. The validity of the numerical results is evaluated against a unique set of experimental wind-tunnel data that was obtained in the National Transonic Facility at the NASA Langley Research Center.

  12. Development of a Molecular Tagging Velocimetry Technique for Non-Intrusive Velocity Measurements in Low-Speed Gas Flows

    Science.gov (United States)

    Andre, M. A.; Bardet, P. M.; Cadell, S. R.; Woods, B.; Burns, R. A.; Danehy, P. M.

    2017-01-01

    N2O molecular tagging velocimetry (N2O-MTV) is developed for use in very-high-temperature reactor environments. Tests were carried out to determine the optimum excitation wavelength, tracer concentration, and timing parameters for the laser system. Using NO tracers obtained from photo-dissociation of N2O, velocity profiles are successfully obtained in air, nitrogen, and helium for a large range of parameters: temperature from 295 to 781 K, pressure from 1 to 3 bars, with a velocity precision of 0.01 m/s. Furthermore, by using two read pulses at adjustable time delays, the velocity dynamic range can be increased. An unprecedented dynamic range of 5,000 has been obtained to successfully resolve the flow during a helium blowdown from 1000 m/s down to 0.2 m/s. This technique is also applied to the high-temperature test facility (HTTF) at Oregon State University (OSU) during a depressurized condition cooldown (DCC) event. Details of these measurements are presented in a companion paper. This technique shows a strong potential for fundamental understanding of gas flows in nuclear reactors and to provide benchmark experimental data to validate numerical simulations.

  13. Walking football as sustainable exercise for older adults - A pilot investigation

    DEFF Research Database (Denmark)

    Reddy, Peter; Dias, Irundika; Holland, Carol

    2017-01-01

    walking football every week, is it sustainable and rewarding, (2) the intensity and locomotor pattern of walking football, (3) the scale and nature of walking football health benefits and (4) possible cognitive benefits of playing walking football through measures of processing speed, selective...... and divided attention and updating and inhibition components of executive function.
 'Walking football' and 'waiting list' groups were compared before and after 12 weeks of one-hour per week football. Walking football was found to be engaging, sustainable for older adults and moderately intensive; however......, selective health and cognitive benefits were not found from this brief intervention....

  14. Walking with coffee: when and why coffee spills

    Science.gov (United States)

    Mayer, Hans C.; Krechetnikov, Rouslan

    2011-11-01

    In our busy lives, almost all of us have to walk with a cup of coffee. Needless to say, under certain conditions we spill that precious liquid. This is a common example of the interplay between the mechanics of the complex motion of a walking individual and the fluid dynamics of a low viscosity liquid contained in a cup. We report on the results of an experimental investigation undertaken to explore the particular conditions under which coffee spills. Frame-by-frame analysis of recorded movies helps to elucidate the trajectory of the cup for various walking speeds and initial liquid levels. These kinematics, including both regular and irregular motions, are connected to instances during walking that result in spilled liquid. The coupling between mechanical aspects of walking and the fluid motion are analyzed based on which we determine a basic operational space with which one can confidently walk with cup in hand.

  15. Simulation of bubbly flow in vertical pipes by coupling Lagrangian and Eulerian models with 3D random walks models: Validation with experimental data using multi-sensor conductivity probes and Laser Doppler Anemometry

    Energy Technology Data Exchange (ETDEWEB)

    Munoz-Cobo, Jose L., E-mail: jlcobos@iqn.upv.es [Instituto de Ingenieria Energetica, Universidad Politecnica de Valencia, Valencia (Spain); Chiva, Sergio [Department of Mechanical Engineering and Construction, Universitat Jaume I, Castellon (Spain); Essa, Mohamed Ali Abd El Aziz [Instituto de Ingenieria Energetica, Universidad Politecnica de Valencia, Valencia (Spain); Mendes, Santos [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon (Mexico)

    2012-01-15

    Highlights: Black-Right-Pointing-Pointer We have simulated bubbly flow in vertical pipes by coupling a Lagrangian model to an Eulerian one, and to a 3D random walk model. Black-Right-Pointing-Pointer A set of experiments in a vertical column with isothermal co-current two phase flow have been performed and used to validate the previous model. Black-Right-Pointing-Pointer We have investigated the influence of the turbulence induced by the bubbles on the results. Black-Right-Pointing-Pointer Comparison of experimental and computed results has been performed for different boundary conditions. - Abstract: A set of two phase flow experiments for different conditions ranging from bubbly flow to cap/slug flow have been performed under isothermal concurrent upward air-water flow conditions in a vertical column of 3 m height. Special attention in these experiments was devoted to the transition from bubbly to cap/slug flow. The interfacial velocity of the bubbles and the void fraction distribution was obtained using 2 and 4 sensors conductivity probes. Numerical simulations of these experiments for bubbly flow conditions were performed by coupling a Lagrangian code with an Eulerian one. The first one tracks the 3D motion of the individual bubbles in cylindrical coordinates (r, {phi}, z) inside the fluid field under the action of the following forces: buoyancy, drag, lift, wall lubrication. Also we have incorporated a 3D stochastic differential equation model to account for the random motion of the individual bubbles in the turbulent velocity field of the carrier liquid. Also we have considered the deformations undergone by the bubbles when they touch the walls of the pipe and are compressed until they rebound. The velocity and turbulence fields of the liquid phase were computed by solving the time dependent conservation equations in its Reynolds Averaged Transport Equation form (RANS). The turbulent kinetic energy k, and the dissipation rate {epsilon} transport equations

  16. Walking model with no energy cost.

    Science.gov (United States)

    Gomes, Mario; Ruina, Andy

    2011-03-01

    We have numerically found periodic collisionless motions of a walking model consisting of linked rigid objects. Unlike previous designs, this model can walk on level ground at noninfinitesimal speed with zero energy input. The model avoids collisional losses by using an internal mode of oscillation: swaying of the upper body coupled to the legs by springs. Appropriate synchronized internal oscillations set the foot-strike collision to zero velocity. The concept might be of use for energy-efficient robots and may also help to explain aspects of human and animal locomotion efficiency.

  17. Calibration of a γ-Reθ transition model and its validation in low-speed flows with high-order numerical method

    Directory of Open Access Journals (Sweden)

    Wang Yuntao

    2015-06-01

    Full Text Available Based on the Reynolds-averaged Navier–Stokes (RANS equations and structured grid technology, the calibration and validation of γ-Reθ transition model is preformed with fifth-order weighted compact nonlinear scheme (WCNS, and the purpose of the present work is to improve the numerical accuracy for aerodynamic characteristics simulation of low-speed flow with transition model on the basis of high-order numerical method study. Firstly, the empirical correlation functions involved in the γ-Reθ transition model are modified and calibrated with experimental data of turbulent flat plates. Then, the grid convergence is studied on NLR-7301 two-element airfoil with the modified empirical correlation. At last, the modified empirical correlation is validated with NLR-7301 two-element airfoil and high-lift trapezoidal wing from transition location, velocity profile in boundary layer, surface pressure coefficient and aerodynamic characteristics. The numerical results illustrate that the numerical accuracy of transition length and skin friction behind transition location are improved with modified empirical correlation function, and obviously increases the numerical accuracy of aerodynamic characteristics prediction for typical transport configurations in low-speed range.

  18. Walk Leader certificate

    OpenAIRE

    Public Health Agency

    2015-01-01

    The Walking for Health programme was established in 2001 and continues to be an integral part of Government policy to address the health and wellbeing of the population in Northern Ireland. The programme is delivered through HSC Trusts across Northern Ireland and is supported by the Public Health Agency. Walking for Health aims to encourage inactive people to increase their level of physical activity by participating in local led health walks.

  19. Which walking capacity tests to use in multiple sclerosis? A multicentre study providing the basis for a core set.

    Science.gov (United States)

    Gijbels, Domien; Dalgas, Ulrik; Romberg, Anders; de Groot, Vincent; Bethoux, Francois; Vaney, Claude; Gebara, Benoit; Medina, Carme Santoyo; Maamâgi, Heigo; Rasova, Kamila; de Noordhout, Benoit Maertens; Knuts, Kathy; Feys, Peter

    2012-03-01

    Many different walking capacity test formats are being used. It is unclear whether walking speed, obtained from short tests, and walking distance, obtained from long tests, provide different clinical information. To determine the differential effect of various short and long walk test formats on gait velocity, and the actual relationship between walking speed and walking distance in multiple sclerosis (MS) patients with diverse ambulation status. A cross-sectional multicentre study design was applied. Ambulatory MS patients (Expanded Disability Status Scale (EDSS) 0-6.5; n = 189) were tested at 11 sites. Short tests consisted of the Timed 25-Foot Walk (static start, fastest speed) and 10-Metre Walk Test (dynamic start, usual and fastest speed). Long tests consisted of the 2- and 6-Minute Walk Tests (fastest speed). Subjects were divided into mild (EDSS 0-4; n = 99) or moderate (EDSS 4.5-6.5; n = 79) disability subgroups. In both subgroups, the start protocol, instructed pace and length of test led to significantly different gait velocities. Fastest walking speed and 6-Minute walking distance showed the strongest correlation (R (2) = 0.78 in mild and R (2) = 0.81 in moderate MS; p tests' relative estimation errors for 6-Minute walking distance were 8-12% in mildly and 15-16% in moderately affected subjects. Based on the 2-Minute Walk Test, estimation errors significantly reduced to approximately 5% in both subgroups. A single short test format at fastest speed accurately describes an MS patient's general walking capacity. For intervention studies, a long test is to be considered. We propose the Timed 25-Foot Walk and 2-Minute Walk Test as standards. Further research on responsiveness is needed.

  20. Biomechanical implications of walking with indigenous footwear.

    Science.gov (United States)

    Willems, Catherine; Stassijns, Gaetane; Cornelis, Wim; D'Août, Kristiaan

    2017-04-01

    This study investigates biomechanical implications of walking with indigenous "Kolhapuri" footwear compared to barefoot walking among a population of South Indians. Ten healthy adults from South India walked barefoot and indigenously shod at voluntary speed on an artificial substrate. The experiment was repeated outside, on a natural substrate. Data were collected from (1) a heel-mounted 3D-accelerometer recording peak impact at heel contact, (2) an ankle-mounted 3D-goniometer (plantar/dorsiflexion and inversion/eversion), and (3) sEMG electrodes at the m. tibialis anterior and the m. gastrocnemius medialis. Data show that the effect of indigenous footwear on the measured variables, compared to barefoot walking, is relatively small and consistent between substrates (even though subjects walked faster on the natural substrate). Walking barefoot, compared to shod walking yields higher impact accelerations, but the differences are small and only significant for the artificial substrate. The main rotations of the ankle joint are mostly similar between conditions. Only the shod condition shows a faster ankle rotation over the rapid eversion motion on the natural substrate. Maximal dorsiflexion in late stance differs between the footwear conditions on an artificial substrate, with the shod condition involving a less dorsiflexed ankle, and the plantar flexion at toe-off is more extreme when shod. Overall the activity pattern of the external foot muscles is similar. The indigenous footwear studied (Kolhapuri) seems to alter foot biomechanics only in a subtle way. While offering some degree of protection, walking in this type of footwear resembles barefoot gait and this type of indigenous footwear might be considered "minimal". © 2017 The Authors American Journal of Physical Anthropology Published by Wiley Periodicals, Inc.

  1. Validity of the shuttle walk test as a functional assessment of walking ability in individuals with polyneuropathy.

    Science.gov (United States)

    Erdmann, Peter G; Teunissen, Laurien L; van den Berg, Leonard H; Notermans, Nicolette C; Schröder, Carin D; Bongers, Bart C; van Meeteren, Nico L U

    2017-10-01

    This study assessed the validity of the shuttle walk test (SWT) to evaluate walking ability in patients with polyneuropathy. Forty-one patients with chronic idiopathic axonal polyneuropathy (CIAP) and 49 patients with multifocal motor neuropathy (MMN) performed both the 10-meter walk test (10MWT) and the SWT. Face validity was assessed by evaluating whether patients considered both tests to reflect their walking ability (Likert scale: 1 = not at all, 10 = very well). Concurrent validity was determined by Spearman rank-correlation analyses performed on the outcomes of both tests. Mean (SD) scores for how well the 10MWT and SWT reflected daily walking ability were 6.8 (1.3) and 7.4 (1.6) (p = 0.117) in patients with CIAP and 6.9 (1.2) and 7.9 (1.0) (p = 0.001) in patients with MMN, respectively. Correlation scores between both tests ranged from -0.70 to -0.82, except for 18 patients with MMN with a "normal" walking speed at the 10MWT (-0.21). The SWT seems a valid instrument for assessing walking ability in individuals with CIAP and MMN. Moreover, the SWT seems to be useful for investigating the symptoms elicited by walking long distances and may be more sensitive to changes when compared to the 10MWT. Implications for Rehabilitation Patients with polyneuropathy mainly experience problems when walking long distances. The 10-meter walk test does not possess sufficient psychometrics to diagnose walking abilities in these circumstances. The shuttle walk test is a valid instrument for assessing walking ability in individuals with polyneuropathy and might be the preferred instrument of choice when compared to the 10-meter walk test.

  2. Telegrapher's equation with variable propagation speeds

    OpenAIRE

    Masoliver, Jaume, 1951-; Weiss, George H. (George Herbert), 1930-

    1994-01-01

    All derivations of the one-dimensional telegraphers equation, based on the persistent random walk model, assume a constant speed of signal propagation. We generalize here the model to allow for a variable propagation speed and study several limiting cases in detail. We also show the connections of this model with anomalous diffusion behavior and with inertial dichotomous processes.

  3. High-speed mixture fraction and temperature imaging of pulsed, turbulent fuel jets auto-igniting in high-temperature, vitiated co-flows

    Science.gov (United States)

    Papageorge, Michael J.; Arndt, Christoph; Fuest, Frederik; Meier, Wolfgang; Sutton, Jeffrey A.

    2014-07-01

    In this manuscript, we describe an experimental approach to simultaneously measure high-speed image sequences of the mixture fraction and temperature fields during pulsed, turbulent fuel injection into a high-temperature, co-flowing, and vitiated oxidizer stream. The quantitative mixture fraction and temperature measurements are determined from 10-kHz-rate planar Rayleigh scattering and a robust data processing methodology which is accurate from fuel injection to the onset of auto-ignition. In addition, the data processing is shown to yield accurate temperature measurements following ignition to observe the initial evolution of the "burning" temperature field. High-speed OH* chemiluminescence (CL) was used to determine the spatial location of the initial auto-ignition kernel. In order to ensure that the ignition kernel formed inside of the Rayleigh scattering laser light sheet, OH* CL was observed in two viewing planes, one near-parallel to the laser sheet and one perpendicular to the laser sheet. The high-speed laser measurements are enabled through the use of the unique high-energy pulse burst laser system which generates long-duration bursts of ultra-high pulse energies at 532 nm (>1 J) suitable for planar Rayleigh scattering imaging. A particular focus of this study was to characterize the fidelity of the measurements both in the context of the precision and accuracy, which includes facility operating and boundary conditions and measurement of signal-to-noise ratio (SNR). The mixture fraction and temperature fields deduced from the high-speed planar Rayleigh scattering measurements exhibited SNR values greater than 100 at temperatures exceeding 1,300 K. The accuracy of the measurements was determined by comparing the current mixture fraction results to that of "cold", isothermal, non-reacting jets. All profiles, when properly normalized, exhibited self-similarity and collapsed upon one another. Finally, example mixture fraction, temperature, and OH* emission

  4. Community walking can be assessed using a 10-metre timed walk test

    NARCIS (Netherlands)

    Kempen, J.C.E.; de Groot, V.; Knol, D.; Polman, C.H.; Lankhorst, G.J.; Beckerman, H.

    2011-01-01

    Background: A decline in mobility is a common feature of multiple sclerosis (MS). Community walking scales are used to categorize patients in their ability to move independently. The first purpose of this study was to determine which specific gait speed corresponded with the categories of the

  5. Purification of quinoline yellow components using high-speed counter-current chromatography by stepwise increasing the flow-rate of the mobile phase.

    Science.gov (United States)

    Oka, Hisao; Harada, Ken-Ichi; Suzuki, Masanao; Fujii, Kiyonaga; Iwaya, Masato; Ito, Yuko; Goto, Tomomi; Matsumoto, Hiroshi; Ito, Yoichiro

    2003-03-14

    Quinoline yellow (Color Index No. 47005) consists of multiple components that show a large difference in their partition coefficients (K), ranging from 0.03 to 3.3 in the solvent system tert.-butyl methyl ether (MTBE)-1-butanol-acetonitrile-aqueous 0.1 M trifluoroacetic acid (TFA). Consequently, it requires an excessively long elution time for the simultaneous separation of all components by the standard high-speed counter-current chromatography technique, which uses a constant flow-rate of the mobile phase. In order to overcome this problem, we increased the flow-rate of the mobile phase stepwise from 0.1 to 2.0 mL/min. Using this new procedure, six components (0.2-6.1 mg) were successfully isolated from 25 mg of a commercial quinoline yellow preparation in a single run using a two-phase solvent system composed of MTBE-1-butanol-acetonitrile-aqueous 0.1 M TFA (1:3:1:5, v/v). The purified components were analyzed by high-performance liquid chromatography, electrospray ionization mass spectrometry, and nuclear magnetic resonance spectroscopy.

  6. The role of plantigrady and heel-strike in the mechanics and energetics of human walking with implications for the evolution of the human foot.

    Science.gov (United States)

    Webber, James T; Raichlen, David A

    2016-12-01

    Human bipedal locomotion is characterized by a habitual heel-strike (HS) plantigrade gait, yet the significance of walking foot-posture is not well understood. To date, researchers have not fully investigated the costs of non-heel-strike (NHS) walking. Therefore, we examined walking speed, walk-to-run transition speed, estimated locomotor costs (lower limb muscle volume activated during walking), impact transient (rapid increase in ground force at touchdown) and effective limb length (ELL) in subjects (n=14) who walked at self-selected speeds using HS and NHS gaits. HS walking increases ELL compared with NHS walking since the center of pressure translates anteriorly from heel touchdown to toe-off. NHS gaits led to decreased absolute walking speeds (P=0.012) and walk-to-run transition speeds (P=0.0025), and increased estimated locomotor energy costs (Pmaximum walking speeds in HS gaits are linked to the increased ELL compared with NHS gaits. However, HS walking significantly increases impact transient values at all speeds (P<0.0001). These trade-offs may be key to understanding the functional benefits of HS walking. Given the current debate over the locomotor mechanics of early hominins and the range of foot landing postures used by nonhuman apes, we suggest the consistent use of HS gaits provides key locomotor advantages to striding bipeds and may have appeared early in hominin evolution. © 2016. Published by The Company of Biologists Ltd.

  7. A Model of Cognitive Speed.

    Science.gov (United States)

    Fulford, Catherine P.

    2001-01-01

    Introduces a model of cognitive speed and considers its relevance to research and practice. Topics include information processing; semantic cognitive flow; compressed speech; speed-reading; cognitive speed and interaction; and implications for distance education, video multimedia, computer-assisted instruction, hypermedia, interactive multimedia,…

  8. Quantum random walks and their convergence to Evans–Hudson ...

    Indian Academy of Sciences (India)

    Using coordinate-free basic operators on toy Fock spaces, quantum random walks are defined following the ideas of Attal and Pautrat. Extending the result for one dimensional noise, strong convergence of quantum random walks associated with bounded structure maps to Evans–Hudson flow is proved under suitable ...

  9. Development of N_2O-MTV for low-speed flow and in-situ deployment to an integral effect test facility

    Science.gov (United States)

    André, Matthieu A.; Burns, Ross A.; Danehy, Paul M.; Cadell, Seth R.; Woods, Brian G.; Bardet, Philippe M.

    2018-01-01

    A molecular tagging velocity (MTV) technique is developed to non-intrusively measure velocity in an integral effect test (IET) facility simulating a high-temperature helium-cooled nuclear reactor in accident scenarios. In these scenarios, the velocities are expected to be low, on the order of 1 m/s or less, which forces special requirements on the MTV tracer selection. Nitrous oxide (N_2O) is identified as a suitable seed gas to generate NO tracers capable of probing the flow over a large range of pressure, temperature, and flow velocity. The performance of N_2O-MTV is assessed in the laboratory at temperature and pressure ranging from 295 to 781 K and 1 to 3 atm. MTV signal improves with a temperature increase, but decreases with a pressure increase. Velocity precision down to 0.004 m/s is achieved with a probe time of 40 ms at ambient pressure and temperature. Measurement precision is limited by tracer diffusion, and absorption of the tag laser beam by the seed gas. Processing by cross-correlation of single-shot images with high signal-to-noise ratio reference images improves the precision by about 10% compared to traditional single-shot image correlations. The instrument is then deployed to the IET facility. Challenges associated with heat, vibrations, safety, beam delivery, and imaging are addressed in order to successfully operate this sensitive instrument in-situ. Data are presented for an isothermal depressurized conduction cooldown. Velocity profiles from MTV reveal a complex flow transient driven by buoyancy, diffusion, and instability taking place over short (30 min) time scales at sub-meter per second speed. The precision of the in-situ results is estimated at 0.027, 0.0095, and 0.006 m/s for a probe time of 5, 15, and 35 ms, respectively.

  10. More Adults Are Walking

    Centers for Disease Control (CDC) Podcasts

    2012-07-31

    This podcast is based on the August 2012 CDC Vital Signs report. While more adults are walking, only half get the recommended amount of physical activity. Listen to learn how communities, employers, and individuals may help increase walking.  Created: 7/31/2012 by Centers for Disease Control and Prevention (CDC).   Date Released: 8/7/2012.

  11. Learning-Walk Continuum

    Science.gov (United States)

    Finch, Peter Dallas

    2010-01-01

    The continuum of learning walks can be viewed in stages with various dimensions including frequency, participants, purpose and the presence of an instructional framework within which the instructional practice is viewed. Steps in the continuum progress as the learning walks are conducted more frequently. One way to ensure this is accomplished is…

  12. walk in CAIRO

    DEFF Research Database (Denmark)

    2011-01-01

    Research-baseret audio walk om revolutionen i Cairo med start på Teater Grob (første version, 2011) og Helsingør Teater (anden version, 2012).......Research-baseret audio walk om revolutionen i Cairo med start på Teater Grob (første version, 2011) og Helsingør Teater (anden version, 2012)....

  13. Minimal Walking Technicolor

    DEFF Research Database (Denmark)

    Foadi, Roshan; Frandsen, Mads Toudal; A. Ryttov, T.

    2007-01-01

    , pseudoscalars, vector mesons and other fields predicted by the minimal walking theory. We construct their self-interactions and interactions with standard model fields. Using the Weinberg sum rules, opportunely modified to take into account the walking behavior of the underlying gauge theory, we find...

  14. Lévy walks

    Science.gov (United States)

    Zaburdaev, V.; Denisov, S.; Klafter, J.

    2015-04-01

    Random walk is a fundamental concept with applications ranging from quantum physics to econometrics. Remarkably, one specific model of random walks appears to be ubiquitous across many fields as a tool to analyze transport phenomena in which the dispersal process is faster than dictated by Brownian diffusion. The Lévy-walk model combines two key features, the ability to generate anomalously fast diffusion and a finite velocity of a random walker. Recent results in optics, Hamiltonian chaos, cold atom dynamics, biophysics, and behavioral science demonstrate that this particular type of random walk provides significant insight into complex transport phenomena. This review gives a self-consistent introduction to Lévy walks, surveys their existing applications, including latest advances, and outlines further perspectives.

  15. Walking Skill Can Be Assessed in Older Adults: Validity of the Figure-of-8 Walk Test

    Science.gov (United States)

    Brach, Jennifer S.; Piva, Sara R.; VanSwearingen, Jessie M.

    2010-01-01

    Background The Figure-of-8 Walk Test (F8W) involves straight and curved paths and was designed to represent walking skill in everyday life. Objective The purposes of this study were to validate the measure in older adults with walking difficulties and to explore correlates of the curved-path walking measure not represented by a straight-path walking measure. Design Fifty-one community-dwelling older adults with mobility disability participated in 2 baseline visits as part of an intervention study. Methods The F8W time, steps, and smoothness and measures of gait (gait speed, modified Gait Abnormality Rating Scale [GARS-M]), physical function (Late Life Function and Disabilities Index [LLFDI], Survey of Activities and Fear of Falling in the Elderly [SAFFE], Gait Efficacy Scale [GES], Physical Performance Test [PPT], and fall history), and movement control and planning (gait variability, Trail Making Test B [Trails B]) were recorded in each test session. Bivariate correlations for the F8W with each variable were conducted to examine concurrent and construct validity. Adjusted linear regression analyses were performed to explore the variance in mobility explained by F8W independent of gait speed. Results Figure-of-8 Walk Test time correlated with gait (gait speed, r=−.570; GARS-M, r=.281), physical function (LLFDI function, r=−.469; SAFFE restriction subscale, r=.370; PPT, r=−.353), confidence in walking (GES, r=−.468), and movement control (step length coefficient of variation, r=.279; step width coefficient of variation, r=−.277; Trails B, r=.351). Figure-of-8 Walk Test steps correlated with step width variability (r=−.339) and was related to fear of falling (t=−2.50). All correlations were significant (Pmeasure of walking skill among older adults with mobility disability and may provide information complementary to gait speed. PMID:19959654

  16. Running for exercise mitigates age-related deterioration of walking economy.

    Science.gov (United States)

    Ortega, Justus D; Beck, Owen N; Roby, Jaclyn M; Turney, Aria L; Kram, Rodger

    2014-01-01

    Impaired walking performance is a key predictor of morbidity among older adults. A distinctive characteristic of impaired walking performance among older adults is a greater metabolic cost (worse economy) compared to young adults. However, older adults who consistently run have been shown to retain a similar running economy as young runners. Unfortunately, those running studies did not measure the metabolic cost of walking. Thus, it is unclear if running exercise can prevent the deterioration of walking economy. To determine if and how regular walking vs. running exercise affects the economy of locomotion in older adults. 15 older adults (69 ± 3 years) who walk ≥ 30 min, 3x/week for exercise, "walkers" and 15 older adults (69 ± 5 years) who run ≥ 30 min, 3x/week, "runners" walked on a force-instrumented treadmill at three speeds (0.75, 1.25, and 1.75 m/s). We determined walking economy using expired gas analysis and walking mechanics via ground reaction forces during the last 2 minutes of each 5 minute trial. We compared walking economy between the two groups and to non-aerobically trained young and older adults from a prior study. Older runners had a 7-10% better walking economy than older walkers over the range of speeds tested (p = .016) and had walking economy similar to young sedentary adults over a similar range of speeds (p =  .237). We found no substantial biomechanical differences between older walkers and runners. In contrast to older runners, older walkers had similar walking economy as older sedentary adults (p =  .461) and ∼ 26% worse walking economy than young adults (peconomy whereas walking for exercise appears to have minimal effect on the age-related deterioration in walking economy.

  17. Biomechanical analysis of rollator walking

    DEFF Research Database (Denmark)

    Alkjaer, T; Larsen, Peter K; Pedersen, Gitte

    2006-01-01

    The rollator is a very popular walking aid. However, knowledge about how a rollator affects the walking patterns is limited. Thus, the purpose of the study was to investigate the biomechanical effects of walking with and without a rollator on the walking pattern in healthy subjects.......The rollator is a very popular walking aid. However, knowledge about how a rollator affects the walking patterns is limited. Thus, the purpose of the study was to investigate the biomechanical effects of walking with and without a rollator on the walking pattern in healthy subjects....

  18. Calf exercise-induced vasodilation is blunted in healthy older adults with increased walking performance fatigue.

    Science.gov (United States)

    Gonzales, Joaquin U; Defferari, Elizabeth; Fisher, Amy; Shephard, Jordan; Proctor, David N

    2014-09-01

    Vascular aging as measured by central arterial stiffness contributes to slow walking speed in older adults, but the impact of age-related changes in peripheral vascular function on walking performance is unclear. The aim of this study was to test the hypothesis that calf muscle-specific vasodilator responses are associated with walking performance fatigue in healthy older adults. Forty-five older (60-78yrs) adults performed a fast-paced 400m walk test. Twelve of these adults exhibited fatigue as defined by slowing of walking speed (≥0.02m/s) measured during the first and last 100m segments of the 400m test. Peak calf vascular conductance was measured following 10min of arterial occlusion using strain-gauge plethysmography. Superficial femoral artery (SFA) vascular conductance response to graded plantar-flexion exercise was measured using Doppler ultrasound. No difference was found for peak calf vascular conductance between adults that slowed walking speed and those that maintained walking speed (p>0.05); however, older adults that slowed walking speed had a lower SFA vascular conductance response to calf exercise (at highest workload: slowed group, 2.4±0.9 vs. maintained group, 3.6±0.9ml/kg/min/mmHg; pcalf exercise hemodynamics are associated with walking performance fatigability in older adults. Copyright © 2014 Elsevier Inc. All rights reserved.

  19. Dynamic optimization of a biped model: Energetic walking gaits with different mechanical and gait parameters

    Directory of Open Access Journals (Sweden)

    Kang An

    2015-05-01

    Full Text Available Energy consumption is one of the problems for bipedal robots walking. For the purpose of studying the parameter effects on the design of energetic walking bipeds with strong adaptability, we use a dynamic optimization method on our new walking model to first investigate the effects of the mechanical parameters, including mass and length distribution, on the walking efficiency. Then, we study the energetic walking gait features with the combinations of walking speed and step length. Our walking model is designed upon Srinivasan’s model. Dynamic optimization is used for a free search with minimal constraints. The results show that the cost of transport of a certain gait increases with the increase in the mass and length distribution parameters, except for that the cost of transport decreases with big length distribution parameter and long step length. We can also find a corresponding range of walking speed and step length, in which the variation in one of the two parameters has no obvious effect on the cost of transport. With fixed mechanical parameters, the cost of transport increases with the increase in the walking speed. There is a speed–step length relationship for walking with minimal cost of transport. The hip torque output strategy is adjusted in two situations to meet the walking requirements.

  20. Lower Extremity Strength Is Correlated with Walking Function After Incomplete SCI.

    Science.gov (United States)

    DiPiro, Nicole D; Holthaus, Katy D; Morgan, Patrick J; Embry, Aaron E; Perry, Lindsay A; Bowden, Mark G; Gregory, Chris M

    2015-01-01

    Lower extremity strength has been reported to relate to walking ability, however, the relationship between voluntary lower extremity muscle function as measured by isokinetic dynamometry and walking have not been thoroughly examined in individuals with incomplete spinal cord injury (iSCI). To determine the extent to which measures of maximal voluntary isometric contraction (MVIC) and rate of torque development (RTD) in the knee extensor (KE) and plantar flexor (PF) muscle groups correlate with self-selected overground walking speed and spatiotemporal characteristics of walking. Twenty-two subjects with chronic (>6 months) iSCI participated in a cross-sectional study. Values for MVIC and RTD in the KE and PF muscle groups were determined by isokinetic dynamometry. Walking speed and spatiotemporal characteristics of walking were measured during overground walking. MVIC in the KE and PF muscle groups correlated significantly with walking speed. RTD was significantly correlated with walking speed in both muscle groups, the more-involved PF muscle group showing the strongest correlation with walking speed (r = 0.728). RTD in the KE and PF muscle groups of the more-involved limb was significantly correlated with single support time of the more-involved limb. These data demonstrate that lower extremity strength is associated with walking ability after iSCI. Correlations for the muscle groups of the move-involved side were stronger compared to the less-involved limb. In addition, PF function is highlighted as a potential limiting factor to walking speed along with the importance of RTD.

  1. Alzheimer random walk

    Science.gov (United States)

    Odagaki, Takashi; Kasuya, Keisuke

    2017-09-01

    Using the Monte Carlo simulation, we investigate a memory-impaired self-avoiding walk on a square lattice in which a random walker marks each of sites visited with a given probability p and makes a random walk avoiding the marked sites. Namely, p = 0 and p = 1 correspond to the simple random walk and the self-avoiding walk, respectively. When p> 0, there is a finite probability that the walker is trapped. We show that the trap time distribution can well be fitted by Stacy's Weibull distribution b(a/b){a+1}/{b}[Γ({a+1}/{b})]-1x^a\\exp(-a/bx^b)} where a and b are fitting parameters depending on p. We also find that the mean trap time diverges at p = 0 as p- α with α = 1.89. In order to produce sufficient number of long walks, we exploit the pivot algorithm and obtain the mean square displacement and its Flory exponent ν(p) as functions of p. We find that the exponent determined for 1000 step walks interpolates both limits ν(0) for the simple random walk and ν(1) for the self-avoiding walk as [ ν(p) - ν(0) ] / [ ν(1) - ν(0) ] = pβ with β = 0.388 when p ≪ 0.1 and β = 0.0822 when p ≫ 0.1. Contribution to the Topical Issue "Continuous Time Random Walk Still Trendy: Fifty-year History, Current State and Outlook", edited by Ryszard Kutner and Jaume Masoliver.

  2. Ways of Walking

    DEFF Research Database (Denmark)

    Eslambolchilar, Parisa; Bødker, Mads; Chamberlain, Alan

    2016-01-01

    and their envisaged development, we argue that interaction designers must increasingly consider a multitude of perspectives that relate to walking in order to frame design problems appropriately. In this paper, we consider a number of perspectives on walking, and we discuss how these may inspire the design of mobile...... technologies. Drawing on insights from non-representational theory, we develop a partial vocabulary with which to engage with qualities of pedestrian mobility, and we outline how taking more mindful approaches to walking may enrich and inform the design space of handheld technologies....

  3. A High-Speed Continuous Recording High Flow Gas Sampler for Measuring Methane Emissions from Pneumatic Devices at Oil and Natural Gas Production Facilities

    Science.gov (United States)

    Ferrara, T.; Howard, T. M.

    2016-12-01

    Studies attempting to reconcile facility level emission estimates of sources at oil and gas facilities with basin wide methane flux measurements have had limited success. Pneumatic devices are commonly used at oil and gas production facilities for process control or liquid pumping. These devices are powered by pressurized natural gas from the well, so they are known methane sources at these sites. Pneumatic devices are estimated to contribute 14% to 25% of the total greenhouse gas emissions (GHG) from production facilities. Measurements of pneumatic devices have shown that malfunctioning or poorly maintained control systems may be emitting significantly more methane than currently estimated. Emission inventories for these facilities use emission factors from EPA that are based on pneumatic device measurements made in the early 1990's. Recent studies of methane emissions from production facilities have attempted to measure emissions from pneumatic devices by several different methods. These methods have had limitations including alteration of the system being measured, the inability to distinguish between leaks and venting during normal operation, or insufficient response time to account of the time based emission events. We have developed a high speed recording high flow sampler that is capable of measuring the transient emissions from pneumatic devices. This sampler is based on the well-established high flow measurement technique used in oil and gas for quantifying component leak rates. In this paper we present the results of extensive laboratory controlled release testing. Additionally, test data from several field studies where this sampler has been used to measure pneumatic device emissions will be presented.

  4. Control of Triple-Shock Configurations and Vortex Structures Forming in High Speed Flows of Gaseous Media past an AD Body under the Action of External Energy Sources

    Directory of Open Access Journals (Sweden)

    Olga A. Azarova

    2017-02-01

    Full Text Available The problem of supersonic streamlining of an aerodynamic (AD body, “a plate blunted by a cylinder”, by a flow with the freestream Mach number M = 4 containing an external energy source has been studied, taking into account physicochemical transformations. The results of the effect of the ratio of specific heats γ changing in the range from 1.1 to 1.4 on the dynamics of triple-shock configurations and vortex-contact structures are presented for the interaction of an energy source with the bow shock wave. The energy source is modeled via the heated rarefied layer (filament. The angles in the triple-shock configurations, the stagnation pressure, together with the frontal drag force, have been studied dependent on the specific heats ratio γ, the characteristics of the energy source, and also on the angle of the incident shock. Vortex-contact structures have been researched for the Mach numbers 7, 8, 9, as well as the generation of the Richtmyer-Meshkov instability accompanying the formation of a triple-shock configuration. The results show a strong influence of the specific heats ratio of the gas medium and the parameters of the energy source on the triple-shock configuration and aerodynamic characteristics of the body. This conclusion can be useful for aerospace applications in the area of the design of nozzles, intakes, and high speed flying vehicles. Additionally, the results show the possibility of flow control in the atmospheres of other planets using external energy deposition.

  5. The walk ratio: Investigation of invariance across walking conditions and gender in community-dwelling older people.

    Science.gov (United States)

    Bogen, Bård; Moe-Nilssen, Rolf; Ranhoff, Anette Hylen; Aaslund, Mona Kristin

    2018-02-21

    The step length-cadence ratio, also called the walk ratio (WR; cm/steps/min) is a measure of cautious gait, poor balance control or impaired gait, but has not been investigated for both genders in a general population of older adults across different speeds and conditions. The participants were community-dwelling volunteers between 70 and 81 years. They walked 6.5 m under four different conditions: At preferred speed, fast speed, during a dual task condition and on an uneven surface. Step length (cm) and cadence (steps/minute) was captured using a body-worn sensor. Both cadence and step lengths were adjusted for body height. 70 older adults participated (mean age 75.5 (SD 3.4), 60 percent women). The WR was 0.60 cm/steps/min (SD 0.07) during preferred speed walking, 0.58 cm/steps/min (SD 0.07) during fast walking, 0.68 cm/steps/min (SD 0.18) during dual task-walking and 0.59 cm/steps/min (0.07) during uneven surface-walking. In planned pairwise comparisons, the WR during dual task was significantly different from preferred speed walking (mean difference -0.087 cm/steps/min, 95% CI -0.140, -0.033), from fast speed walking (mean difference -0.098 cm/steps/min, 95% CI -0.154, -0.041) and uneven surface walking (mean difference 0.092 cm/steps/min, 95% CI 0.040, 0.145). There were no gender differences except during the fast walking condition, where women had a significantly lower WR than the men (0.56 cm/steps/min vs 0.61 cm/steps/min, p = 0.002). We found that the WR is invariant during different speeds, and during an uneven surface condition, but is affected during a dual task-condition, when attention must be divided between a cognitive and a motor task. Copyright © 2018. Published by Elsevier B.V.

  6. Walking to health.

    Science.gov (United States)

    Morris, J N; Hardman, A E

    1997-05-01

    Walking is a rhythmic, dynamic, aerobic activity of large skeletal muscles that confers the multifarious benefits of this with minimal adverse effects. Walking, faster than customary, and regularly in sufficient quantity into the 'training zone' of over 70% of maximal heart rate, develops and sustains physical fitness: the cardiovascular capacity and endurance (stamina) for bodily work and movement in everyday life that also provides reserves for meeting exceptional demands. Muscles of the legs, limb girdle and lower trunk are strengthened and the flexibility of their cardinal joints preserved; posture and carriage may improve. Any amount of walking, and at any pace, expends energy. Hence the potential, long term, of walking for weight control. Dynamic aerobic exercise, as in walking, enhances a multitude of bodily processes that are inherent in skeletal muscle activity, including the metabolism of high density lipoproteins and insulin/glucose dynamics. Walking is also the most common weight-bearing activity, and there are indications at all ages of an increase in related bone strength. The pleasurable and therapeutic, psychological and social dimensions of walking, whilst evident, have been surprisingly little studied. Nor has an economic assessment of the benefits and costs of walking been attempted. Walking is beneficial through engendering improved fitness and/or greater physiological activity and energy turnover. Two main modes of such action are distinguished as: (i) acute, short term effects of the exercise; and (ii) chronic, cumulative adaptations depending on habitual activity over weeks and months. Walking is often included in studies of exercise in relation to disease but it has seldom been specifically tested. There is, nevertheless, growing evidence of gains in the prevention of heart attack and reduction of total death rates, in the treatment of hypertension, intermittent claudication and musculoskeletal disorders, and in rehabilitation after heart

  7. Tracking of Bubble Trajectories in Vertical Pipes in Bubbly Flow Regime by Coupling Lagrangian, Eulerian and 3D Random Walks Models: Validation with Experimental Data

    Directory of Open Access Journals (Sweden)

    José L. Muñoz-Cobo

    2012-09-01

    Full Text Available A set of air-water experiments has been performed under isothermal upward concurrent flow conditions, in a vertical column. The interfacial velocity, the bubble interfacial area and the void fraction distributions have been measured. Numerical simulation of these experiments were performed by coupling a Lagrangian code which tracks the 3D motion of the individual bubbles, with an Eulerian one. In the Eulerian solver the velocity and turbulence fields of the liquid phase were computed by solving the time dependent conservation equations in its Reynolds Averaged Transport Equation form (RANS. The turbulent kinetic energy k, and the dissipation rate transport equations were simultaneously solved by using the k, epsilon model in a (r,z grid by the finite volume method and the SIMPLER algorithm. Both Lagrangian and Eulerian calculations were performed in parallel and an iterative self-consistent method was developed. The turbulence induced by the bubbles is an important issue considered in this paper, in order to obtain good predictions of the void fraction distribution and the interfacial velocity at different gas and liquid flow conditions. The Eulerian Code was upgraded from an axisymmetric 2D code to a 3D code in order to improve the turbulence solution. The results of the 3D CFD code have been tested and show a good agreement with the experimental results. In this paper special attention is given to the coupling between the different models.

  8. The walk is never random: subtle landscape effects shape gene flow in a continuous white-tailed deer population in the Midwestern United States

    Science.gov (United States)

    Robinson, Stacie J.; Samuel, Michael D.; Lopez, Davin L.; Shelton, Paul

    2012-01-01

    One of the pervasive challenges in landscape genetics is detecting gene flow patterns within continuous populations of highly mobile wildlife. Understanding population genetic structure within a continuous population can give insights into social structure, movement across the landscape and contact between populations, which influence ecological interactions, reproductive dynamics or pathogen transmission. We investigated the genetic structure of a large population of deer spanning the area of Wisconsin and Illinois, USA, affected by chronic wasting disease. We combined multiscale investigation, landscape genetic techniques and spatial statistical modelling to address the complex questions of landscape factors influencing population structure. We sampled over 2000 deer and used spatial autocorrelation and a spatial principal components analysis to describe the population genetic structure. We evaluated landscape effects on this pattern using a spatial autoregressive model within a model selection framework to test alternative hypotheses about gene flow. We found high levels of genetic connectivity, with gradients of variation across the large continuous population of white-tailed deer. At the fine scale, spatial clustering of related animals was correlated with the amount and arrangement of forested habitat. At the broader scale, impediments to dispersal were important to shaping genetic connectivity within the population. We found significant barrier effects of individual state and interstate highways and rivers. Our results offer an important understanding of deer biology and movement that will help inform the management of this species in an area where overabundance and disease spread are primary concerns.

  9. Implementation of a Wireless Haptic Controller for Humanoid Robot Walking

    OpenAIRE

    Kim, Eun-Su; Kim, Man-Seok; Kim, Johwan; Kim, Sang Woo; Kim, Jong-Wook

    2010-01-01

    This paper provides an innovative work concerning the principle and controller implementation on humanoid walking. A new humanoid model is described in three orthogonal planes, and kinematics equations are established based on the phenomena of projection and rotation. The feasibility of the proposed model is validated through the simulation result of variable-speed walking optimized by uDEAS with mere change in the stride cycle. Moreover, we newly succeeded in simulation of direction turning ...

  10. Which walking capacity tests to use in multiple sclerosis? A multicentre study providing the basis for a core set

    NARCIS (Netherlands)

    Gijbels, D.; Dalgas, U.; Romberg, A.; de Groot, V.; Bethoux, F.; Vaney, C.; Gebara, B.; Santoyo, C.; Maamagi, H.; Rasova, K.; de Maertens, N.B.; Knuts, K.; Feys, P.

    2012-01-01

    Background: Many different walking capacity test formats are being used. It is unclear whether walking speed, obtained from short tests, and walking distance, obtained from long tests, provide different clinical information. Objectives: To determine the differential effect of various short and long

  11. Assessing Walking Ability in People with HTLV-1-Associated Myelopathy Using the 10 Meter Timed Walk and the 6 Minute Walk Test.

    Science.gov (United States)

    Adonis, Adine; Taylor, Graham P

    2016-01-01

    Five to ten million persons, are infected by HTLV-1 of which 3% will develop HTLV-1-associated myelopathy (HAM) a chronic, disabling inflammation of the spinal cord. Walking, a fundamental, complex, multi-functional task is demanding of multiple body systems. Restricted walking ability compromises activity and participation levels in people with HAM (pwHAM). Therapy aims to improve mobility but validated measures are required to assess change. Prospective observational study. To explore walking capacity in pwHAM, walking endurance using the 6 minute walk (6MW), and gait speed, using the timed 10m walk (10mTW). Out-patient setting in an inner London Teaching hospital. Prospective documentation of 10mTW and 6MW distance; walking aid usage and pain scores measured twice, a median of 18 months apart. Data analysis was completed for twenty-six pwHAM, (8♂; 18♀; median age: 57.8 years; median disease duration: 8 years). Median time at baseline to: complete 10m was 17.5 seconds, versus 21.4 seconds at follow up; 23% completed the 6MW compared to 42% at follow up and a median distance of 55m was covered compared to 71m at follow up. Using the 10mTW velocity to predict the 6MW distance, overestimated the distance walked in 6 minutes (pWalking capacity in pwHAM should be measured using the 10mTW for gait speed and the 6MW for endurance.

  12. Vaulting mechanics successfully predict decrease in walk–run transition speed with incline

    Science.gov (United States)

    Hubel, Tatjana Y.; Usherwood, James R.

    2013-01-01

    There is an ongoing debate about the reasons underlying gait transition in terrestrial locomotion. In bipedal locomotion, the ‘compass gait’, a reductionist model of inverted pendulum walking, predicts the boundaries of speed and step length within which walking is feasible. The stance of the compass gait is energetically optimal—at walking speeds—owing to the absence of leg compression/extension; completely stiff limbs perform no work during the vaulting phase. Here, we extend theoretical compass gait vaulting to include inclines, and find good agreement with previous observations of changes in walk–run transition speed (approx. 1% per 1% incline). We measured step length and frequency for humans walking either on the level or up a 9.8 per cent incline and report preferred walk–run, walk–compliant-walk and maximum walk–run transition speeds. While the measured ‘preferred’ walk–run transition speed lies consistently below the predicted maximum walking speeds, and ‘actual’ maximum walking speeds are clearly above the predicted values, the onset of compliant walking in level as well as incline walking occurs close to the predicted values. These findings support the view that normal human walking is constrained by the physics of vaulting, but preferred absolute walk–run transition speeds may be influenced by additional factors. PMID:23325739

  13. The walk is never random: subtle landscape effects shape gene flow in a continuous white-tailed deer population in the Midwestern United States.

    Science.gov (United States)

    Robinson, Stacie J; Samuel, Michael D; Lopez, Davin L; Shelton, Paul

    2012-09-01

    One of the pervasive challenges in landscape genetics is detecting gene flow patterns within continuous populations of highly mobile wildlife. Understanding population genetic structure within a continuous population can give insights into social structure, movement across the landscape and contact between populations, which influence ecological interactions, reproductive dynamics or pathogen transmission. We investigated the genetic structure of a large population of deer spanning the area of Wisconsin and Illinois, USA, affected by chronic wasting disease. We combined multiscale investigation, landscape genetic techniques and spatial statistical modelling to address the complex questions of landscape factors influencing population structure. We sampled over 2000 deer and used spatial autocorrelation and a spatial principal components analysis to describe the population genetic structure. We evaluated landscape effects on this pattern using a spatial autoregressive model within a model selection framework to test alternative hypotheses about gene flow. We found high levels of genetic connectivity, with gradients of variation across the large continuous population of white-tailed deer. At the fine scale, spatial clustering of related animals was correlated with the amount and arrangement of forested habitat. At the broader scale, impediments to dispersal were important to shaping genetic connectivity within the population. We found significant barrier effects of individual state and interstate highways and rivers. Our results offer an important understanding of deer biology and movement that will help inform the management of this species in an area where overabundance and disease spread are primary concerns. Published 2012. This article is a US Government work and is in the public domain in the USA.

  14. Walking skill can be assessed in older adults: validity of the Figure-of-8 Walk Test.

    Science.gov (United States)

    Hess, Rebecca J; Brach, Jennifer S; Piva, Sara R; VanSwearingen, Jessie M

    2010-01-01

    The Figure-of-8 Walk Test (F8W) involves straight and curved paths and was designed to represent walking skill in everyday life. The purposes of this study were to validate the measure in older adults with walking difficulties and to explore correlates of the curved-path walking measure not represented by a straight-path walking measure. Fifty-one community-dwelling older adults with mobility disability participated in 2 baseline visits as part of an intervention study. The F8W time, steps, and smoothness and measures of gait (gait speed, modified Gait Abnormality Rating Scale [GARS-M]), physical function (Late Life Function and Disabilities Index [LLFDI], Survey of Activities and Fear of Falling in the Elderly [SAFFE], Gait Efficacy Scale [GES], Physical Performance Test [PPT], and fall history), and movement control and planning (gait variability, Trail Making Test B [Trails B]) were recorded in each test session. Bivariate correlations for the F8W with each variable were conducted to examine concurrent and construct validity. Adjusted linear regression analyses were performed to explore the variance in mobility explained by F8W independent of gait speed. Figure-of-8 Walk Test time correlated with gait (gait speed, r=-.570; GARS-M, r=.281), physical function (LLFDI function, r=-.469; SAFFE restriction subscale, r=.370; PPT, r=-.353), confidence in walking (GES, r=-.468), and movement control (step length coefficient of variation, r=.279; step width coefficient of variation, r=-.277; Trails B, r=.351). Figure-of-8 Walk Test steps correlated with step width variability (r=-.339) and was related to fear of falling (t=-2.50). All correlations were significant (Pwalking skill among older adults with mobility disability and may provide information complementary to gait speed.

  15. Foot trajectory approximation using the pendulum model of walking.

    Science.gov (United States)

    Fang, Juan; Vuckovic, Aleksandra; Galen, Sujay; Conway, Bernard A; Hunt, Kenneth J

    2014-01-01

    Generating a natural foot trajectory is an important objective in robotic systems for rehabilitation of walking. Human walking has pendular properties, so the pendulum model of walking has been used in bipedal robots which produce rhythmic gait patterns. Whether natural foot trajectories can be produced by the pendulum model needs to be addressed as a first step towards applying the pendulum concept in gait orthosis design. This study investigated circle approximation of the foot trajectories, with focus on the geometry of the pendulum model of walking. Three able-bodied subjects walked overground at various speeds, and foot trajectories relative to the hip were analysed. Four circle approximation approaches were developed, and best-fit circle algorithms were derived to fit the trajectories of the ankle, heel and toe. The study confirmed that the ankle and heel trajectories during stance and the toe trajectory in both the stance and the swing phases during walking at various speeds could be well modelled by a rigid pendulum. All the pendulum models were centred around the hip with pendular lengths approximately equal to the segment distances from the hip. This observation provides a new approach for using the pendulum model of walking in gait orthosis design.

  16. Design of wheel-type walking-assist device

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Seung Ho; Kim, Seung Ho; Kim, Chang Hoi; Seo, Yong Chil; Jung, Kyung Min; Lee, Sung Uk

    2006-03-15

    In this research, a outdoor wheel-type walking-assist device is developed to help an elder having a poor muscular strength at legs for walking, sitting and standing up easily at outdoors, and also for going and downing stairs. In conceptually designing, the environments of an elder's activity, the size of an elder's body and a necessary function of helping an elder are considered. This device has 4 wheels for stability. When an elder walks in incline plane with the proposed device, a rear-wing is rotated to keep the supporting device horizontal, regardless of an angle of inclination. A height-controlling device, which can control the height of the supporting device for adjusting an elder's height, is varied vertically to help an elder to sit and stand-up easily. Moreover, a outdoor wheel-type walking-assist device is conceptually designed and is made. In order to design it, the preview research is investigated firstly. On the basis of the proposed walking-assist device, the outdoor walking-assist device is designed and made. The outdoor wheel-type walking-assist device can go and down stairs automatically. This device go up and down the stair of having maximum 20cm height and an angle of 25 degrees with maximum 4 sec/stairs speed, and move at flatland with 60cm/sec speed.

  17. Predicting metabolic rate during level and uphill outdoor walking using a low-cost GPS receiver.

    Science.gov (United States)

    de Müllenheim, Pierre-Yves; Dumond, Rémy; Gernigon, Marie; Mahé, Guillaume; Lavenu, Audrey; Bickert, Sandrine; Prioux, Jacques; Noury-Desvaux, Bénédicte; Le Faucheur, Alexis

    2016-08-01

    The objective of this study was to assess the accuracy of using speed and grade data obtained from a low-cost global positioning system (GPS) receiver to estimate metabolic rate (MR) during level and uphill outdoor walking. Thirty young, healthy adults performed randomized outdoor walking for 6-min periods at 2.0, 3.5, and 5.0 km/h and on three different grades: 1) level walking, 2) uphill walking on a 3.7% mean grade, and 3) uphill walking on a 10.8% mean grade. The reference MR [metabolic equivalents (METs) and oxygen uptake (V̇o2)] values were obtained using a portable metabolic system. The speed and grade were obtained using a low-cost GPS receiver (1-Hz recording). The GPS grade (Δ altitude/distance walked) was calculated using both uncorrected GPS altitude data and GPS altitude data corrected with map projection software. The accuracy of predictions using reference speed and grade (actual[SPEED/GRADE]) data was high [R(2) = 0.85, root-mean-square error (RMSE) = 0.68 MET]. The accuracy decreased when GPS speed and uncorrected grade (GPS[UNCORRECTED]) data were used, although it remained substantial (R(2) = 0.66, RMSE = 1.00 MET). The accuracy was greatly improved when the GPS speed and corrected grade (GPS[CORRECTED]) data were used (R(2) = 0.82, RMSE = 0.79 MET). Published predictive equations for walking MR were also cross-validated using actual or GPS speed and grade data when appropriate. The prediction accuracy was very close when either actual[SPEED/GRADE] values or GPS[CORRECTED] values (for level and uphill combined) or GPS speed values (for level walking only) were used. These results offer promising research and clinical applications related to the assessment of energy expenditure during free-living walking. Copyright © 2016 the American Physiological Society.

  18. Wind-Tunnel and Flight Test Results for the Measurements of Flow Variables at Supersonic Speeds Using Improved Wedge and Conical Probes

    Science.gov (United States)

    Bobbitt, Percy J.; Maglieri, Domenic J.; Banks, Daniel W.; Frederick, Michael A.; Fuchs, Aaron W.

    2012-01-01

    The results of supersonic wind-tunnel tests on three probes at nominal Mach numbers of 1.6,