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Sample records for linear stride characteristics

  1. Dynamics of Stride Interval Characteristics during Continuous Stairmill Climbing.

    PubMed

    Raffalt, Peter C; Vallabhajosula, Srikant; Renz, Jessica J; Mukherjee, Mukul; Stergiou, Nicholas

    2017-01-01

    It has been shown that statistical persistence in stride intervals characteristics exist during walking, running and cycling and were speed-dependent among healthy young adults. The purpose of this study was to determine if such statistical persistence in stride time interval, stride length and stride speed also exists during self-paced continuous stairmill climbing and if the strength is dependent on stepping rate. Stride time, stride length, and stride speed were collected from nine healthy participants during 3 min of stairmill climbing at 100, 110, and 120% of their preferred stepping rate (PSR) and 5 min of treadmill walking at preferred walking speed (PWS). The amount of variability (assessed by standard deviation and coefficient of variation) and dynamics (assessed by detrended fluctuation analysis and sample entropy) of the stride time, stride length, and stride speed time series were investigated. The amounts of variability were significantly higher during stairmill climbing for the stride time, stride length, and stride speed and did only change with increased stepping rate for stride speed. In addition to a more irregular pattern during stairmill climbing, the detrended fluctuation analysis (DFA) revealed that the stride length fluctuations were statistical anti-persistent for all subjects. On a group level both stride time and stride speed fluctuations were characterized by an uncorrelated pattern which was more irregular compared to that during treadmill walking. However, large inter-participant differences were observed for these two variables. In addition, the dynamics did not change with increase in stepping rate.

  2. Dynamics of Stride Interval Characteristics during Continuous Stairmill Climbing

    PubMed Central

    Raffalt, Peter C.; Vallabhajosula, Srikant; Renz, Jessica J.; Mukherjee, Mukul; Stergiou, Nicholas

    2017-01-01

    It has been shown that statistical persistence in stride intervals characteristics exist during walking, running and cycling and were speed-dependent among healthy young adults. The purpose of this study was to determine if such statistical persistence in stride time interval, stride length and stride speed also exists during self-paced continuous stairmill climbing and if the strength is dependent on stepping rate. Stride time, stride length, and stride speed were collected from nine healthy participants during 3 min of stairmill climbing at 100, 110, and 120% of their preferred stepping rate (PSR) and 5 min of treadmill walking at preferred walking speed (PWS). The amount of variability (assessed by standard deviation and coefficient of variation) and dynamics (assessed by detrended fluctuation analysis and sample entropy) of the stride time, stride length, and stride speed time series were investigated. The amounts of variability were significantly higher during stairmill climbing for the stride time, stride length, and stride speed and did only change with increased stepping rate for stride speed. In addition to a more irregular pattern during stairmill climbing, the detrended fluctuation analysis (DFA) revealed that the stride length fluctuations were statistical anti-persistent for all subjects. On a group level both stride time and stride speed fluctuations were characterized by an uncorrelated pattern which was more irregular compared to that during treadmill walking. However, large inter-participant differences were observed for these two variables. In addition, the dynamics did not change with increase in stepping rate. PMID:28878688

  3. Assessment of dairy cow locomotion in a commercial farm setting: the effects of walking speed on ground reaction forces and temporal and linear stride characteristics.

    PubMed

    Walker, A M; Pfau, T; Channon, A; Wilson, A

    2010-02-01

    Objectives of this study were to determine the effects of walking speed on ground reaction force (GRF) parameters and to explore inter- and intra-individual variability with unsupervised data collection in a commercial farm setting. We used eight high producing loose-housed Holstein Friesian cows consistently scored sound, with no veterinary treatment during the collection period. Cows walked freely (0.52-1.37 m/s) over a five force platform array, twice daily, following milking. GRF data were split into speed categories and temporal and kinetic gait parameters extracted. A general linear model was carried out to determine effects of speed. Variation in parameters between cows is inconsistent, while between speed categories (containing data from multiple cows) the parameters which vary are consistent. Stance and stride time were reduced with increasing speed but no change in peak vertical GRF or duty factor was found. This ability to track parameters within an individual over time aids detection of subtle changes associated with lameness. Copyright 2009 Elsevier Ltd. All rights reserved.

  4. Effect of stride length on overarm throwing delivery: A linear momentum response.

    PubMed

    Ramsey, Dan K; Crotin, Ryan L; White, Scott

    2014-12-01

    Changing stride length during overhand throwing delivery is thought to alter total body and throwing arm linear momentums, thereby altering the proportion of throwing arm momentum relative to the total body. Using a randomized cross-over design, nineteen pitchers (15 collegiate and 4 high school) were assigned to pitch two simulated 80-pitch games at ±25% of their desired stride length. An 8-camera motion capture system (240Hz) integrated with two force plates (960Hz) and radar gun tracked each throw. Segmental linear momentums in each plane of motion were summed yielding throwing arm and total body momentums, from which compensation ratio's (relative contribution between the two) were derived. Pairwise comparisons at hallmark events and phases identified significantly different linear momentum profiles, in particular, anteriorly directed total body, throwing arm, and momentum compensation ratios (P⩽.05) as a result of manipulating stride length. Pitchers with shorter strides generated lower forward (anterior) momentum before stride foot contact, whereas greater upward and lateral momentum (toward third base) were evident during the acceleration phase. The evidence suggests insufficient total body momentum in the intended throwing direction may potentially influence performance (velocity and accuracy) and perhaps precipitate throwing arm injuries. Copyright © 2014 Elsevier B.V. All rights reserved.

  5. Effects of glucose-fructose versus glucose ingestion on stride characteristics during prolonged treadmill running.

    PubMed

    Wilson, Patrick B; Ingraham, Stacy J

    2016-09-01

    Scarce research has examined the effects of carbohydrate composition on running stride characteristics. On two occasions, 14 males and 6 females completed a 120-min sub-maximal run followed by a 4-mile time trial. Participants consumed glucose (GLU) or glucose-fructose (GLU-FRU) beverages supplying 1.3 g/min carbohydrate. Substrate use, psychological affect [Feeling Scale (FS)], and stride characteristics (stride frequency, stride length, and contact time) were assessed. Effects were expressed as Cohen's d (90% confidence limits [90% CL]). CLs for stride frequency differences at 53 min (90% CL = 0.04-0.21) and 113 min (90% CL = 0.02-0.24) did not cover 0, indicating a positive effect of GLU-FRU. However, effect sizes were small (d = 0.13) and likely-to-very-likely trivial. Energy expenditure differences at sub-maximal end were very likely trivial (d = 0.08; 90% CL = 0.00-0.17), while FS ratings were possibly higher for GLU-FRU at 50 (d = 0.19; 90% CL = -0.10-0.48) and 110 min (d = 0.16; 90% CL = -0.13-0.45). During the time trial, stride length was possibly higher with GLU-FRU (d = 0.13; 90% CL = -0.08-0.33). Glucose-fructose co-ingestion has no significant effect on stride characteristics during constant-velocity running but may result in slightly higher stride length during self-paced running.

  6. Biomechanical characteristics of adults walking forward and backward in water at different stride frequencies.

    PubMed

    Cadenas-Sánchez, Cristina; Arellano, Raúl; Taladriz, Sonia; López-Contreras, Gracia

    2016-01-01

    The aim of this study was to examine spatiotemporal characteristics and joint angles during forward and backward walking in water at low and high stride frequency. Eight healthy adults (22.1 ± 1.1 years) walked forward and backward underwater at low (50 pulses) and high frequency (80 pulses) at the xiphoid process level with arms crossed at the chest. The main differences observed were that the participants presented a greater speed (0.58 vs. 0.85 m/s) and more asymmetry of the step length (1.24 vs. 1.48) at high frequency whilst the stride and step length (0.84 vs. 0.7 m and 0.43 vs. 0.35 m, respectively) were lower compared to low frequency (P < 0.05). Support phase duration was higher at forward walking than backward walking (61.2 vs. 59.0%). At initial contact, we showed that during forward walking, the ankle and hip presented more flexion than during backward walking (ankle: 84.0 vs. 91.8º and hip: 22.8 vs. 8.0º; P < 0.001). At final stance, the knee and hip were more flexed at low frequency than at high frequency (knee: 150.0 vs. 157.0º and hip: -12.2 vs. -14.5º; P < 0.001). The knee angle showed more flexion at forward walking (134.0º) than backward walking (173.1º) (P < 0.001). In conclusion, these results show how forward and backward walking in water at different frequencies differ and contribute to a better understanding of this activity in training and rehabilitation.

  7. Comparison of temporal and stride characteristics in myotonic dystrophies type 1 and 2 during dual-task walking.

    PubMed

    Radovanović, S; Perić, S; Savić-Pavićević, D; Dobričić, V; Pešović, J; Kostić, V; Rakočević-Stojanović, V

    2016-02-01

    We analyzed temporal and stride characteristics in patients with myotonic dystrophy type 1 (DM1) and type 2 (DM2) while performing dual mental and motor tasks, and investigated correlations between gait parameters and cognitive impairments. Dual-task walking was performed by 37 patients (20 DM1 and 17 DM2) and 48 healthy subjects divided into two groups, age- and gender-matched control group for DM1 (HC1) and age- and gender-matched control group for DM2 (HC2). The subjects performed a basic walking task, dual-motor task, dual-mental task, and combined motor and mental task. DM1 and DM2 patients differed significantly in temporal and stride characteristics compared to HC. Main differences in DM1 were slower gait and shorter stride length, while both DM1 and DM2 patients had a higher degree of variation of the swing time during dual-task gait, a parameter that reflects posture and balance. Impact of the cognitive dual task on gait pattern changes was also observed. Visuospatial ability correlated with gait changes in DM1, while executive functions had stronger influence in DM2 (p<0.01). Both patient groups had leg muscle weakness. Gait pattern was impaired in both patient groups concerning temporal and stride characteristics. Dual-task walking paradigm may discover mild initial gait changes and could provide early identification of fall risks and predict possible falls in DM patients. Copyright © 2015 Elsevier B.V. All rights reserved.

  8. Longitudinal assessment of neuropsychological and temporal/spatial gait characteristics of elderly fallers: taking it all in stride.

    PubMed

    MacAulay, Rebecca K; Allaire, Ted D; Brouillette, Robert M; Foil, Heather C; Bruce-Keller, Annadora J; Han, Hongmei; Johnson, William D; Keller, Jeffrey N

    2015-01-01

    Gait abnormalities are linked to cognitive decline and an increased fall risk within older adults. The present study addressed gaps from cross-sectional studies in the literature by longitudinally examining the interplay between temporal and spatial aspects of gait, cognitive function, age, and lower-extremity strength in elderly "fallers" and "non-fallers". Gait characteristics, neuropsychological and physical test performance were examined at two time points spaced a year apart in cognitively intact individuals aged 60 and older (N = 416). Mixed-model repeated-measure ANCOVAs examined temporal (step time) and spatial (stride length) gait characteristics during a simple and cognitive-load walking task in fallers as compared to non-fallers. Fallers consistently demonstrated significant alterations in spatial, but not temporal, aspects of gait as compared to non-fallers during both walking tasks. Step time became slower as stride length shortened amongst all participants during the dual task. Shorter strides and slower step times during the dual task were both predicted by worse executive attention/processing speed performance. In summary, divided attention significantly impacts spatial aspects of gait in "fallers", suggesting stride length changes may precede declines in other neuropsychological and gait characteristics, thereby selectively increasing fall risk. Our results indicate that multimodal intervention approaches that integrate physical and cognitive remediation strategies may increase the effectiveness of fall risk interventions.

  9. Selective Breeding and Short-Term Access to a Running Wheel Alter Stride Characteristics in House Mice.

    PubMed

    Claghorn, Gerald C; Thompson, Zoe; Kay, Jarren C; Ordonez, Genesis; Hampton, Thomas G; Garland, Theodore

    Postural and kinematic aspects of running may have evolved to support high runner (HR) mice to run approximately threefold farther than control mice. Mice from four replicate HR lines selectively bred for high levels of voluntary wheel running show many differences in locomotor behavior and morphology as compared with four nonselected control (C) lines. We hypothesized that HR mice would show stride alterations that have coadapted with locomotor behavior, morphology, and physiology. More specifically, we predicted that HR mice would have stride characteristics that differed from those of C mice in ways that parallel some of the adaptations seen in highly cursorial animals. For example, we predicted that limbs of HR mice would swing closer to the parasagittal plane, resulting in a two-dimensional measurement of narrowed stance width. We also expected that some differences between HR and C mice might be amplified by 6 d of wheel access, as is used to select breeders each generation. We used the DigiGait Imaging System (Mouse Specifics) to capture high-speed videos in ventral view as mice ran on a motorized treadmill across a range of speeds and then to automatically calculate several aspects of strides. Young adults of both sexes were tested both before and after 6 d of wheel access. Stride length, stride frequency, stance width, stance time, brake time, propel time, swing time, duty factor, and paw contact area were analyzed using a nested analysis of covariance, with body mass as a covariate. As expected, body mass and treadmill speed affected nearly every analyzed metric. Six days of wheel access also affected nearly every measure, indicating pervasive training effects, in both HR and C mice. As predicted, stance width was significantly narrower in HR than C mice. Paw contact area and duty factor were significantly greater in minimuscle individuals (subset of HR mice with 50%-reduced hind limb muscle mass) than in normal-muscled HR or C mice. We conclude that

  10. Partial body weight support treadmill training speed influences paretic and non-paretic leg muscle activation, stride characteristics, and ratings of perceived exertion during acute stroke rehabilitation.

    PubMed

    Burnfield, Judith M; Buster, Thad W; Goldman, Amy J; Corbridge, Laura M; Harper-Hanigan, Kellee

    2016-06-01

    Intensive task-specific training is promoted as one approach for facilitating neural plastic brain changes and associated motor behavior gains following neurologic injury. Partial body weight support treadmill training (PBWSTT), is one task-specific approach frequently used to improve walking during the acute period of stroke recovery (<1month post infarct). However, only limited data have been published regarding the relationship between training parameters and physiologic demands during this early recovery phase. To examine the impact of four walking speeds on stride characteristics, lower extremity muscle demands (both paretic and non-paretic), Borg ratings of perceived exertion (RPE), and blood pressure. A prospective, repeated measures design was used. Ten inpatients post unilateral stroke participated. Following three familiarization sessions, participants engaged in PBWSTT at four predetermined speeds (0.5, 1.0, 1.5 and 2.0mph) while bilateral electromyographic and stride characteristic data were recorded. RPE was evaluated immediately following each trial. Stride length, cadence, and paretic single limb support increased with faster walking speeds (p⩽0.001), while non-paretic single limb support remained nearly constant. Faster walking resulted in greater peak and mean muscle activation in the paretic medial hamstrings, vastus lateralis and medial gastrocnemius, and non-paretic medial gastrocnemius (p⩽0.001). RPE also was greatest at the fastest compared to two slowest speeds (p<0.05). During the acute phase of stroke recovery, PBWSTT at the fastest speed (2.0mph) promoted practice of a more optimal gait pattern with greater intensity of effort as evidenced by the longer stride length, increased between-limb symmetry, greater muscle activation, and higher RPE compared to training at the slowest speeds. Copyright © 2016 Elsevier B.V. All rights reserved.

  11. Physiological responses, rating of perceived exertion, and stride characteristics during walking on dry land and walking in water, both with and without a water current.

    PubMed

    Masumoto, Kenji; Hamada, Ayako; Tomonaga, Hiro-omi; Kodama, Kana; Hotta, Noboru

    2012-05-01

    Walking in water has been included in rehabilitation programs. However, there is a dearth of information regarding the influence of a water current on physiological responses, rating of perceived exertion (RPE), and stride characteristics of subjects while they walk in water. To compare physiological responses, RPE, and stride characteristics of subjects walking in water (with and without a current) with those of subjects walking on dry land. Repeated measures. University laboratory. 7 male adults (mean age = 21.6 y). Subjects walked on a treadmill on dry land and on an underwater treadmill immersed to the level of the xiphoid process. The walking speeds in water were set to be half of that on dry land. Oxygen consumption (VO2), respiratory-exchange ratio (RER), heart rate (HR), minute ventilation (VE), RPE (for breathing and legs, RPE-Br and RPE-Legs, respectively), systolic (SBP) and diastolic (DBP) blood pressures, and stride frequency (SF) were measured. In addition, stride length (SL) was calculated. There was no significant difference in the VO2, RER, HR, VE, RPE-Br, and RPE-Legs while walking in water with a current compared with walking on dry land (P > .05). Furthermore, VO2, RER, HR, VE, RPE-Br, RPE-Legs, SF, and SBP while walking in water were significantly higher with a water current than without (P < .05). These observations suggest that half the speed should be required to work at the similar metabolic costs and RPE while walking in water with a current, compared with walking on dry land. Furthermore, it was suggested that the physiological responses and RPE would be higher while walking in water with a current than without.

  12. Association of previous injury and speed with running style and stride-to-stride fluctuations.

    PubMed

    Mann, R; Malisoux, L; Nührenbörger, C; Urhausen, A; Meijer, K; Theisen, D

    2015-12-01

    Running-related injuries remain problematic among recreational runners. We evaluated the association between having sustained a recent running-related injury and speed, and the strike index (a measure of footstrike pattern, SI) and spatiotemporal parameters of running. Forty-four previously injured and 46 previously uninjured runners underwent treadmill running at 80%, 90%, 100%, 110%, and 120% of their preferred running speed. Participants wore a pressure insole device to measure SI, temporal parameters, and stride length (S(length)) and stride frequency (S(frequency)) over 2-min intervals. Coefficient of variation and detrended fluctuation analysis provided information on stride-to-stride variability and correlative patterns. Linear mixed models were used to compare differences between groups and changes with speed. Previously injured runners displayed significantly higher stride-to-stride correlations of SI than controls (P = 0.046). As speed increased, SI, contact time (T(contact)), stride time (T(stride)), and duty factor (DF) decreased (P < 0.001), whereas flight time (T(flight)), S(length), and S(frequency) increased (P < 0.001). Stride-to-stride variability decreased significantly for SI, T(contact), T(flight), and DF (P ≤ 0.005), as did correlative patterns for T(contact), T(stride), DF, S(length), and S(frequency) (P ≤ 0.044). Previous running-related injury was associated with less stride-to-stride randomness of footstrike pattern. Overall, runners became more pronounced rearfoot strikers as running speed increased.

  13. Relationship between shock attenuation and stride length during running at different velocities.

    PubMed

    Mercer, John A; Vance, Jason; Hreljac, Alan; Hamill, Joseph

    2002-08-01

    The purpose of the study was to investigate the characteristics of shock attenuation during high-speed running. Maximal running speed was identified for each subject [n = 8 males, 25 (SD 4.6) years; 80 (8.9) kg; 1.79 (0.06) m] as the highest speed that could be sustained for about 20 s on a treadmill. During testing, light-weight accelerometers were securely mounted to the surface of the distal antero-medial aspect of the leg and frontal aspect of the forehead. Subjects completed running conditions of 50, 60, 70, 80, 90, and 100% of their maximal speeds with each condition lasting about 20 s. Stride length, stride frequency, leg and head peak impact acceleration were recorded from the acceleration profiles. Shock attenuation was analyzed by extracting specific sections of the acceleration profiles and calculating the ratio of head to leg power spectral densities across the 10-20 Hz frequency range. Both stride length and stride frequency increased across speeds (P < 0.05) and were correlated with running speed (stride length r = 0.92, stride frequency r = 0.89). Shock attenuation increased about 20% per m x s(-1) across speeds (P< 0.05), which was similar to the 17% increase in stride length per m x s(-1). Additionally, shock attenuation was correlated with stride length (r = 0.71) but only moderately correlated with stride frequency (r = 0.40) across speeds. It was concluded that shock attenuation increased linearly with running speed and running kinematic changes were characterized primarily by stride length changes. Furthermore, the change in shock attenuation was due to increased leg not head peak impact acceleration across running speeds.

  14. Effects of a wearable exoskeleton stride management assist system (SMA®) on spatiotemporal gait characteristics in individuals after stroke: a randomized controlled trial.

    PubMed

    Buesing, Carolyn; Fisch, Gabriela; O'Donnell, Megan; Shahidi, Ida; Thomas, Lauren; Mummidisetty, Chaithanya K; Williams, Kenton J; Takahashi, Hideaki; Rymer, William Zev; Jayaraman, Arun

    2015-08-20

    Robots offer an alternative, potentially advantageous method of providing repetitive, high-dosage, and high-intensity training to address the gait impairments caused by stroke. In this study, we compared the effects of the Stride Management Assist (SMA®) System, a new wearable robotic device developed by Honda R&D Corporation, Japan, with functional task specific training (FTST) on spatiotemporal gait parameters in stroke survivors. A single blinded randomized control trial was performed to assess the effect of FTST and task-specific walking training with the SMA® device on spatiotemporal gait parameters. Participants (n=50) were randomly assigned to FTST or SMA. Subjects in both groups received training 3 times per week for 6-8 weeks for a maximum of 18 training sessions. The GAITRite® system was used to collect data on subjects' spatiotemporal gait characteristics before training (baseline), at mid-training, post-training, and at a 3-month follow-up. After training, significant improvements in gait parameters were observed in both training groups compared to baseline, including an increase in velocity and cadence, a decrease in swing time on the impaired side, a decrease in double support time, an increase in stride length on impaired and non-impaired sides, and an increase in step length on impaired and non-impaired sides. No significant differences were observed between training groups; except for SMA group, step length on the impaired side increased significantly during self-selected walking speed trials and spatial asymmetry decreased significantly during fast-velocity walking trials. SMA and FTST interventions provided similar, significant improvements in spatiotemporal gait parameters; however, the SMA group showed additional improvements across more parameters at various time points. These results indicate that the SMA® device could be a useful therapeutic tool to improve spatiotemporal parameters and contribute to improved functional mobility in

  15. Stride length: measuring its instantaneous value

    NASA Astrophysics Data System (ADS)

    Campiglio, G. C.; Mazzeo, J. R.

    2007-11-01

    Human gait has been studied from different viewpoints: kinematics, dynamics, sensibility and others. Many of its characteristics still remain open to research, both for normal gait and for pathological gait. Objective measures of some of its most significant spatial/temporal parameters are important in this context. Stride length, one of these parameters, is defined as the distance between two consecutive contacts of one foot with ground. On this work we present a device designed to provide automatic measures of stride length. Its features make it particularly appropriate for the evaluation of pathological gait.

  16. The desert ant odometer: a stride integrator that accounts for stride length and walking speed.

    PubMed

    Wittlinger, Matthias; Wehner, Rüdiger; Wolf, Harald

    2007-01-01

    Desert ants, Cataglyphis, use path integration as a major means of navigation. Path integration requires measurement of two parameters, namely, direction and distance of travel. Directional information is provided by a celestial compass, whereas distance measurement is accomplished by a stride integrator, or pedometer. Here we examine the recently demonstrated pedometer function in more detail. By manipulating leg lengths in foraging desert ants we could also change their stride lengths. Ants with elongated legs ('stilts') or shortened legs ('stumps') take larger or shorter strides, respectively, and misgauge travel distance. Travel distance is overestimated by experimental animals walking on stilts, and underestimated by animals walking on stumps - strongly indicative of stride integrator function in distance measurement. High-speed video analysis was used to examine the actual changes in stride length, stride frequency and walking speed caused by the manipulations of leg length. Unexpectedly, quantitative characteristics of walking behaviour remained almost unaffected by imposed changes in leg length, demonstrating remarkable robustness of leg coordination and walking performance. These data further allowed normalisation of homing distances displayed by manipulated animals with regard to scaling and speed effects. The predicted changes in homing distance are in quantitative agreement with the experimental data, further supporting the pedometer hypothesis.

  17. Linear and nonlinear stability characteristics of whistlers

    NASA Technical Reports Server (NTRS)

    Brinca, A. L.

    1972-01-01

    Linear and nonlinear propagating characteristics of right-hand polarized, slow electromagnetic, magnetoplasma waves (whistlers) are discussed in terms of stability and dispersion. An analysis of the stability of whistlers propagating at an angle to the static magnetic field is presented. A new mechanism is derived for the onset of stimulated emissions, and modulational instability for nonlinear whistlers are discussed.

  18. Stride variability in human gait: the effect of stride frequency and stride length.

    PubMed

    Danion, F; Varraine, E; Bonnard, M; Pailhous, J

    2003-08-01

    This study focused on spatial and temporal variability of the stride in human gait. We determined the role of stride frequency (F) and stride length (L) on those parameters. Eight healthy subjects walked on a treadmill using 25 different FL combinations (0.95stride parameters. In addition, stride variability was found (1) to be minimal at F=1 Hz; and (2) to increase with smaller L. During additional trials, subjects walked freely at various speeds. Although it is generally hypothesized that freely chosen behaviors are optimal in terms of variability, our data show that this is not always the case in human gait.

  19. Inertial sensor-based stride parameter calculation from gait sequences in geriatric patients.

    PubMed

    Rampp, Alexander; Barth, Jens; Schülein, Samuel; Gaßmann, Karl-Günter; Klucken, Jochen; Eskofier, Björn M

    2015-04-01

    A detailed and quantitative gait analysis can provide evidence of various gait impairments in elderly people. To provide an objective decision-making basis for gait analysis, simple applicable tests analyzing a high number of strides are required. A mobile gait analysis system, which is mounted on shoes, can fulfill these requirements. This paper presents a method for computing clinically relevant temporal and spatial gait parameters. Therefore, an accelerometer and a gyroscope were positioned laterally below each ankle joint. Temporal gait events were detected by searching for characteristic features in the signals. To calculate stride length, the gravity compensated accelerometer signal was double integrated, and sensor drift was modeled using a piece-wise defined linear function. The presented method was validated using GAITRite-based gait parameters from 101 patients (average age 82.1 years). Subjects performed a normal walking test with and without a wheeled walker. The parameters stride length and stride time showed a correlation of 0.93 and 0.95 between both systems. The absolute error of stride length was 6.26 cm on normal walking test. The developed system as well as the GAITRite showed an increased stride length, when using a four-wheeled walker as walking aid. However, the walking aid interfered with the automated analysis of the GAITRite system, but not with the inertial sensor-based approach. In summary, an algorithm for the calculation of clinically relevant gait parameters derived from inertial sensors is applicable in the diagnostic workup and also during long-term monitoring approaches in the elderly population.

  20. Mobile Stride Length Estimation with Deep Convolutional Neural Networks.

    PubMed

    Hannink, Julius; Kautz, Thomas; Pasluosta, Cristian; Barth, Jens; Schulein, Samuel; Gassmann, Karl-Gunter; Klucken, Jochen; Eskofier, Bjoern

    2017-03-09

    Accurate estimation of spatial gait characteristics is critical to assess motor impairments resulting from neurological or musculoskeletal disease. Currently, however, methodological constraints limit clinical applicability of state-ofthe- art double integration approaches to gait patterns with a clear zero-velocity phase. We describe a novel approach to stride length estimation that uses deep convolutional neural networks to map stride-specific inertial sensor data to the resulting stride length. The model is trained on a publicly available and clinically relevant benchmark dataset consisting of 1220 strides from 101 geriatric patients. Evaluation is done in a 10-fold cross validation and for three different stride definitions. Even though best results are achieved with strides defined from mid-stance to mid-stance with average accuracy and precision of 0.01 ± 5.37 cm, performance does not strongly depend on stride definition. The achieved precision outperforms state-of-the-art methods evaluated on the same benchmark dataset by 3.0 cm (36%). Due to the independence of stride definition, the proposed method is not subject to the methodological constrains that limit applicability of state-of-the-art double integration methods. Furthermore, it was possible to improve precision on the benchmark dataset. With more precise mobile stride length estimation, new insights to the progression of neurological disease or early indications might be gained. Due to the independence of stride definition, previously uncharted diseases in terms of mobile gait analysis can now be investigated by re-training and applying the proposed method.

  1. Stride Version 1.0

    SciTech Connect

    Seager, Mark K.

    1994-01-01

    STRIDE is a suite of benchmarks, 8 in total, which access a computers low level caches and memory in a variety of patterns. The resulting performance of the kernels provides significant insight into the performance that a real application may incur and dictate how certain algorithmic choices should be made.

  2. System interaction with linear and nonlinear characteristics

    SciTech Connect

    Lin, C.W. ); Tseng, W.S. )

    1991-01-01

    This book is covered under some of the following topics: seismic margins in piping systems, vibrational power flow in a cylindrical shell, inelastic pipework dynamics and aseismic design, an efficient method for dynamic analysis of a linearly elastic piping system with nonlinear supports.

  3. Central gait control mechanisms and the stride length - cadence relationship.

    PubMed

    Egerton, Thorlene; Danoudis, Mary; Huxham, Frances; Iansek, Robert

    2011-06-01

    The stride length - cadence relationship (SLCrel) was investigated to explore a theory of two alternate but inter-related pathways for gait control. Sixty-three healthy people in three age groups walked along a computerized walkway (GAITRite(®)) at five self-selected speeds from very slow to very fast, five cadences from 70 to 150 steps/min and five stride lengths from 0.8 to 1.6m. The data points from two walks in each level of each condition were examined for linear and quadratic relationships. In the self-selected speed condition 97% of participants had a positive linear or quadratic relationship of R(2)≥0.90. The quadratic relationships showed stride length decreased with very high cadences. When walks with cadences above 150 steps/min were removed, 95% of participants had a positive linear relationship of R(2)≥0.90. No age-related differences were found in slope or intercept of linear relationships or in maximum, minimum or range of stride length or cadence in the self-selected speed condition. In the cadence and stride length conditions, only 32% and 14% of positive linear or quadratic relationships were R(2)≥0.90. The near-invariant SLCrel, unaffected by ageing that exists for nearly all individuals when walking at self-selected speeds, indicates that the SLCrel may be used to simplify central control of automatic gait in healthy individuals. The current investigation also provides SLCrel data for healthy people which can be compared with patient populations. Crown Copyright © 2011. Published by Elsevier B.V. All rights reserved.

  4. Leg stiffness and stride frequency in human running.

    PubMed

    Farley, C T; González, O

    1996-02-01

    When humans and other mammals run, the body's complex system of muscle, tendon and ligament springs behaves like a single linear spring ('leg spring'). A simple spring-mass model, consisting of a single linear leg spring and a mass equivalent to the animal's mass, has been shown to describe the mechanics of running remarkably well. Force platform measurements from running animals, including humans, have shown that the stiffness of the leg spring remains nearly the same at all speeds and that the spring-mass system is adjusted for higher speeds by increasing the angle swept by the leg spring. The goal of the present study is to determine the relative importance of changes to the leg spring stiffness and the angle swept by the leg spring when humans alter their stride frequency at a given running speed. Human subjects ran on treadmill-mounted force platform at 2.5ms-1 while using a range of stride frequencies from 26% below to 36% above the preferred stride frequency. Force platform measurements revealed that the stiffness of the leg spring increased by 2.3-fold from 7.0 to 16.3 kNm-1 between the lowest and highest stride frequencies. The angle swept by the leg spring decreased at higher stride frequencies, partially offsetting the effect of the increased leg spring stiffness on the mechanical behavior of the spring-mass system. We conclude that the most important adjustment to the body's spring system to accommodate higher stride frequencies is that leg spring becomes stiffer.

  5. Concurrent Validity of the Polar s3 Stride Sensor for Measuring Walking Stride Velocity

    ERIC Educational Resources Information Center

    Grigg, Nicole; Smeathers, James; Wearing, Scott

    2011-01-01

    With this research, we sought to establish the accuracy of stride velocity data collected by the s3 Stride Sensor. Participants walked along a GAITRite mat at self-selected slow, preferred, and fast velocities, with two s3 Stride Sensors attached to their right foot. The start position was systematically varied such that the GAITRite system would…

  6. Concurrent Validity of the Polar s3 Stride Sensor for Measuring Walking Stride Velocity

    ERIC Educational Resources Information Center

    Grigg, Nicole; Smeathers, James; Wearing, Scott

    2011-01-01

    With this research, we sought to establish the accuracy of stride velocity data collected by the s3 Stride Sensor. Participants walked along a GAITRite mat at self-selected slow, preferred, and fast velocities, with two s3 Stride Sensors attached to their right foot. The start position was systematically varied such that the GAITRite system would…

  7. Cadence, Stride Rate and Stride Length during Triathlon Competition.

    PubMed

    Landers, Grant J; Blanksby, Brian A; Rackland, Timothy

    Triathlon research shows cycling alters the physiological response of subsequent running but, at present, biomechanical changes are unresolved. This study examined cycling cadence and running stride rate (SR) and length (SL) used by senior elite triathletes during competition. These variables were then compared to running and triathlon performance. Data from 51 elite male World Championships triathletes were analyzed via video recordings and Video Expert II Coach. Triathletes revealed consistent cadences throughout the majority of the cycle (96.8 +2.7 rpm) and run (90.9 +2.4 rpm) disciplines. However, a cadence increase (99.6 +5.7 rpm) was recorded at the completion of the cycle prior to running. Running SR and SL was significantly lower at the end of the run indicating a level of fatigue (p<0.01). Running SL was significantly and positively correlated with running and triathlon performance (p<0.01) suggesting those that could maintain a longer SL had a faster run and better final finishing position.

  8. Stride-to-stride variability while enumerating animal names among healthy young adults: result of stride velocity or effect of attention-demanding task?

    PubMed

    Dubost, Véronique; Annweiler, Cédric; Aminian, Kamiar; Najafi, Bijan; Herrmann, François R; Beauchet, Olivier

    2008-01-01

    The involvement of attention in the control of the walking-related rhythmic stepping mechanism remains unclear in contrast to control of balance phases in human walking. Concurrently to the dual-task related decrease in stride velocity, an increased stride-to-stride variability has been observed and interpreted as interference caused by competing demands for attention resources. It has been also shown that stride time variability depends on stride velocity, whereas the relationship between stride length variability and stride velocity remains controversial. It remains unknown whether dual-task related changes in stride time and stride length variability result from an effect of stride velocity and/or of the attention-demanding task. To determine the respective roles of stride velocity and attention-demanding task on dual-task related changes in stride time and stride length variability. Mean stride velocity, mean, standard deviation and coefficient of variation of stride time and stride length were collected using the ambulatory device Physilog in 40 healthy young adults while walking at self-selected speed and while walking with enumerating animal names. Enumerating animal names while walking provoked significant changes in gait but not in cognitive task performance. Balanced analyses of covariance with a repeated measures design showed that stride time variability increased significantly under dual-task condition independently of dual-task related decrease in stride velocity, while stride length variability did not change under dual-task. These results show that the dual-task related increase in stride time variability depends on the attention-demanding task rather than stride velocity, suggesting that healthy young adults devote a part of their attention to the control of the rhythmic stepping mechanism at normal self-selected walking speed.

  9. Non-linear characteristics of Rayleigh-Taylor instable perturbations

    NASA Astrophysics Data System (ADS)

    Fan, Zhengfeng; Luo, Jisheng

    2008-04-01

    The direct numerical simulation method is adopted to study the non-linear characteristics of Rayleigh-Taylor instable perturbations at the ablation front of a 200 μm planar CH ablation target. In the simulation, the classical electrical thermal conductivity is included, and NND difference scheme is used. The linear growth rates obtained from the simulation agree with the Takabe formula. The amplitude distribution of the density perturbation at the ablation front is obtained for the linear growth case. The non-linear characteristics of Rayleigh-Taylor instable perturbations are analyzed and the numerical results show that the amplitude distributions of the compulsive harmonics are very different from that of the fundamental perturbation. The characteristics of the amplitude distributions of the harmonics and their fast growth explain why spikes occur at the ablation front. The numerical results also show that non-linear effects have relations with the phase differences of double mode initial perturbations, and different phase differences lead to varied spikes.

  10. Non-Linear Vibration Characteristics of Clamped Laminated Shallow Shells

    NASA Astrophysics Data System (ADS)

    ABE, A.; KOBAYASHI, Y.; YAMADA, G.

    2000-07-01

    This paper examines non-linear free vibration characteristics of first and second vibration modes of laminated shallow shells with rigidly clamped edges. Non-linear equations of motion for the shells based on the first order shear deformation and classical shell theories are derived by means of Hamilton's principle. We apply Galerkin's procedure to the equations of motion in which eigenvectors for first and second modes of linear vibration obtained by the Ritz method are employed as trial functions. Then simultaneous non-linear ordinary differential equations are derived in terms of amplitudes of the first and second vibration modes. Backbone curves for the first and second vibration modes are solved numerically by the Gauss-Legendre integration method and the shooting method respectively. The effects of lamination sequences and transverse shear deformation on the behavior are discussed. It is also shown that the motion of the first vibration mode affects the response for the second vibration mode.

  11. Does femur length affect the stride length? Forensic implications.

    PubMed

    Krishan, Kewal

    2010-01-01

    All the long bones in the human body have a linear and positive relationship with stature. This principle has been used by forensic scientists and anthropologists to estimate stature in many kinds of medico-legal and forensic examinations. The present proposition states that the femur length may have a positive relationship with stride length. This relationship can help the forensic scientist to estimate stride length from the length of the femur and vice versa which can further be extended to formulate opinion in person's gait, biomechanics, movement, and posture analysis of the suspects in forensic case work. This can further be used to give opinion while handling certain evidences like closed-circuit television footage and video surveillance system in crime scene investigation.

  12. Effect of stride length on overarm throwing delivery: Part II: An angular momentum response.

    PubMed

    Ramsey, Dan K; Crotin, Ryan L

    2016-04-01

    This is the second component of a two-part series investigating 3D momentum profiles specific to overhand throwing, where altering stride reportedly influences throwing mechanics resulting in significantly different physiologic outcomes and linear momentum profiles. Using a randomized cross-over design, nineteen pitchers (15 collegiate and 4 high school) were assigned to pitch two simulated 80-pitch games at ±25% of their desired stride length. An 8-camera motion capture system (240Hz) integrated with two force plates (960Hz) and radar gun tracked each overhand throw. Segmental angular momentums were summed yielding throwing arm and total body momentums, from which compensation ratio's (relative contribution between the two) were derived. Pairwise comparisons at hallmark events and phases identified significantly different angular momentum profiles, in particular total body, throwing arm, and momentum compensation ratios (P⩽0.05) as a result of manipulating stride length. Sagittal, frontal, and transverse angular momentums were affected by stride length changes. Transverse magnitudes showed greatest effects for total body, throwing arm, and momentum compensation ratios. Since the trunk is the main contributor to linear and angular momentum, longer strides appear to better regulate transverse trunk momentum in double support, whereas shorter strides show increased momentum prior to throwing arm acceleration.

  13. Adaptability of stride-to-stride control of stepping movements in human walking.

    PubMed

    Bohnsack-McLagan, Nicole K; Cusumano, Joseph P; Dingwell, Jonathan B

    2016-01-25

    Humans continually adapt their movements as they walk on different surfaces, avoid obstacles, etc. External (environmental) and internal (physiological) noise-like disturbances, and the responses that correct for them, each contribute to locomotor variability. This variability may sometimes be detrimental (perhaps increasing fall risk), or sometimes beneficial (perhaps reflecting exploration of multiple task solutions). Here, we determined how humans regulated stride-to-stride fluctuations in walking when presented different task goals that allowed them to exploit inherent redundancies in different ways. Fourteen healthy adults walked on a treadmill under each of four conditions: constant speed only (SPD), constant speed and stride length (LEN), constant speed and stride time (TIM), or constant speed, stride length, and stride time (ALL). Multiple analyses tested competing hypotheses that participants might attempt to either equally satisfy all goals simultaneously, or instead adopt systematic intermediate strategies that only partly satisfied each individual goal. Participants exhibited similar average stepping behavior, but significant differences in variability and stride-to-stride serial correlations across conditions. Analyses of the structure of stride-to-stride fluctuation dynamics demonstrated humans resolved the competing goals presented not by minimizing errors equally with respect to all goals, but instead by trying to only partly satisfy each goal. Thus, humans exploit task redundancies even when they are explicitly removed from the task specifications. These findings may help identify when variability is predictive of, or protective against, fall risk. They may also help inform rehabilitation interventions to better exploit the positive contributions of variability, while minimizing the negative. Copyright © 2015 Elsevier Ltd. All rights reserved.

  14. Step activity and stride-to-stride fluctuations are negatively correlated in individuals with transtibial amputation

    PubMed Central

    Kent, Jenny A.; Stergiou, Nicholas; Wurdeman, Shane R.

    2016-01-01

    Background Variability occurs naturally from stride to stride in healthy gait. It has been shown that individuals with lower limb loss have significantly increased stride-to-stride fluctuations during walking. This is considered indicative of movement disorganization and is associated with less healthy movement. Given that lower limb prosthesis users perform on average less physical activity than able bodied individuals, the purpose of this study was to determine whether increased fluctuations also correspond to a reduced level of activity in daily life. Methods Twenty-two transtibial amputees wore an activity monitor (Actigraph, Pensacola, FL, USA) for 3 weeks. Lower limb kinematics during treadmill walking were measured using a 12-camera motion capture system. The largest Lyapunov exponent (λ) was calculated bilaterally at the ankle, knee and hip to quantify the stride-to-stride fluctuations of the lower limb joints. Pearson correlations were used to identify the relationships between the average daily step count over the 3 week collection period and λ. Findings Significant, moderate negative correlations between daily step count and λ were found at the intact ankle (r = 0.57, P = 0.005), and the knee on the affected side (r = 0.44, P = 0.038). No such correlation was found at any other lower limb joint. Interpretation The negative correlation evident at these two joints demonstrates that increased stride-to-stride fluctuations are related to decreased activity levels, however it remains unclear whether these changes in the stride-to-stride fluctuations promote decreased activity or whether less active individuals do not gain sufficient motor learning experience to achieve a skilled movement. PMID:26319219

  15. Heat transfer characteristics of a linear solar collector.

    PubMed

    Seraphin, B O

    1973-02-01

    The heat transfer characteristics of a linear solar energy collector are calculated as functions of dimensions, spectral quality of the selective absorber surface, optical flux concentration of the optical configuration, and thermal parameters and flow rate of the heat transfer medium. Carnot efficiency, exit temperature, and an upper limit to the amount of heat extracted are determined for systems in which liquid sodium serves as the heat transfer medium. The performance is evaluated for selective absorber surfaces representing the state of the art as well as for surfaces requiring a more mature thin-film technology.

  16. Linear contact interface parameter identification using dynamic characteristic equation

    NASA Astrophysics Data System (ADS)

    Jalali, Hassan

    2016-01-01

    The stiffness characteristics of the contact interfaces in joints or boundary conditions have a great effect on dynamic response of assembled structures. Predictive analytical/numerical modeling of mechanical structures is not possible without representing the contact interfaces accurately. Because of the complex mechanisms involved, contact interfaces introduce difficulties both in modeling the inherent dynamics and identification of the model parameters. In this paper an identification approach employing the dynamic characteristic equation is proposed for linear interface parameters. The proposed method is applicable to both analytical and numerical problems. The accuracy of the proposed method is investigated by simulation results of a beam with elastic boundary support and experimental results of a bolted lap-joint.

  17. Interaction effects of stride angle and strike pattern on running economy.

    PubMed

    Santos-Concejero, J; Tam, N; Granados, C; Irazusta, J; Bidaurrazaga-Letona, I; Zabala-Lili, J; Gil, S M

    2014-12-01

    This study aimed to investigate the relationship between stride angle and running economy (RE) in athletes with different foot strike patterns. 30 male runners completed 4 min running stages on a treadmill at different velocities. During the test, biomechanical variables such as stride angle, swing time, contact time, stride length and frequency were recorded using an optical measurement system. Their foot strike pattern was determined, and VO2 at velocities below the lactate threshold were measured to calculate RE. Midfoot/forefoot strikers had better RE than rearfoot strikers (201.5±5.6 ml · kg(-1) · km(-1) vs. 213.5±4.2 ml · kg(-1) · km(-1)respectively; p=0.019). Additionally, midfoot/fore-foot strikers presented higher stride angles than rearfoot strikers (p=0.043). Linear modelling analysis showed that stride angle is closely related to RE (r=0.62, p<0.001) and that the effect of stride angle on RE was different in the 2 groups. From an arbitrary value of 4°, a rearfoot strike pattern is likely to be more economical, whereas at any lower degree, the midfoot/forefoot strike pattern appears to be more desirable. A biomechanical running technique characterised by high stride angles and a midfoot/forefoot strike pattern is advantageous for a better RE. Athletes may find stride angle useful for improving RE. © Georg Thieme Verlag KG Stuttgart · New York.

  18. On Siegel's linearization theorem for fields of prime characteristic

    NASA Astrophysics Data System (ADS)

    Lindahl, Karl-Olof

    2004-05-01

    In 1981, Herman and Yoccoz (1983 Generalizations of some theorems of small divisors to non Archimedean fields Geometric Dynamics (Lecture Notes in Mathematics) ed J Palis Jr, pp 408-47 (Berlin: Springer) Proc. Rio de Janeiro, 1981) proved that Siegel's linearization theorem (Siegel C L 1942 Ann. Math. 43 607-12) is true also for non-Archimedean fields. However, the condition in Siegel's theorem is usually not satisfied over fields of prime characteristic. We consider the following open problem from non-Archimedean dynamics. Given an analytic function f defined over a complete, non-trivial valued field of characteristic p > 0, does there exist a convergent power series solution to the Schröder functional equation (2) that conjugates f to its linear part near an indifferent fixed point? We will give both positive and negative answers to this question, one of the problems being the presence of small divisors. When small divisors are present this brings about a problem of a combinatorial nature, where the convergence of the conjugacy is determined in terms of the characteristic of the state space and the powers of the monomials of f, rather than in terms of the diophantine properties of the multiplier, as in the complex case. In the case that small divisors are present, we show that quadratic polynomials are analytically linearizable if p = 2. We find an explicit formula for the coefficients of the conjugacy, and applying a result of Benedetto (2003 Am. J. Math. 125 581-622), we find the exact size of the corresponding Siegel disc and show that there is an indifferent periodic point on the boundary. In the case p > 2 we give a sufficient condition for divergence of the conjugacy for quadratic maps as well as for a certain class of power series containing a quadratic term (corollary 2.1).

  19. Identifying Stride-To-Stride Control Strategies in Human Treadmill Walking

    PubMed Central

    Dingwell, Jonathan B.; Cusumano, Joseph P.

    2015-01-01

    Variability is ubiquitous in human movement, arising from internal and external noise, inherent biological redundancy, and from the neurophysiological control actions that help regulate movement fluctuations. Increased walking variability can lead to increased energetic cost and/or increased fall risk. Conversely, biological noise may be beneficial, even necessary, to enhance motor performance. Indeed, encouraging more variability actually facilitates greater improvements in some forms of locomotor rehabilitation. Thus, it is critical to identify the fundamental principles humans use to regulate stride-to-stride fluctuations in walking. This study sought to determine how humans regulate stride-to-stride fluctuations in stepping movements during treadmill walking. We developed computational models based on pre-defined goal functions to compare if subjects, from each stride to the next, tried to maintain the same speed as the treadmill, or instead stay in the same position on the treadmill. Both strategies predicted average behaviors empirically indistinguishable from each other and from that of humans. These strategies, however, predicted very different stride-to-stride fluctuation dynamics. Comparisons to experimental data showed that human stepping movements were generally well-predicted by the speed-control model, but not by the position-control model. Human subjects also exhibited no indications they corrected deviations in absolute position only intermittently: i.e., closer to the boundaries of the treadmill. Thus, humans clearly do not adopt a control strategy whose primary goal is to maintain some constant absolute position on the treadmill. Instead, humans appear to regulate their stepping movements in a way most consistent with a strategy whose primary goal is to try to maintain the same speed as the treadmill at each consecutive stride. These findings have important implications both for understanding how biological systems regulate walking in general and

  20. Preferred and optimal stride frequency, stiffness and economy: changes with fatigue during a 1-h high-intensity run.

    PubMed

    Hunter, Iain; Smith, Gerald A

    2007-08-01

    Metabolic cost of submaximal running at constant speed is influenced by various factors including fatigue and kinematic characteristics. Metabolic costs typically drift upwards during extended running while stride characteristics often shift away from initial. When non-fatigued, experienced runners naturally optimize stride frequency in a manner that minimizes oxygen uptake. An initial objective was to determine whether runners demonstrate a similar self-optimizing capability when fatigued where stride characteristics have perhaps shifted away from the initial state. A secondary objective involved measurement of vertical and leg stiffness characteristics as a potential explanation for frequency changes with fatigue. We hypothesized that runners decrease stride frequency and stiffness with fatigue while optimizing these characteristics to minimize metabolic cost. Sixteen experienced runners completed a near maximal effort 1-h treadmill run at a constant speed. Preferred and optimal stride frequencies (PSF and OSF) were measured near the beginning and end of the hour run using frequencies +/-4 and +/-8% around PSF. From vertical force data recorded throughout the run, leg and vertical stiffness were determined. As expected, oxygen uptake significantly increased during the run from 45.9 to 47.4 ml kg(-1) min(-1) (P = 0.004). There was no difference between preferred and optimal stride frequencies at the beginning or the end of running (P = 0.978), however both PSF and OSF significantly decreased from 1.45 to 1.43 Hz (P = 0.026). All runners self-optimized stride frequency at the beginning and end of one-hour of running despite changes of optimal stride frequency. Stiffness and stride frequency changes were subject specific with some runners exhibiting little to no change. No clear relationship of frequency or stiffness changes to economy was found.

  1. The effect of uphill stride manipulation on race walking gait.

    PubMed

    Padulo, J

    2015-09-01

    Stride length analysis represents an easy method for assessing race walking kinematics. However, the stride parameters emerging from such an analysis have never been used to design a training protocol aimed at increasing stride length. With this aim, we investigated the effects of stride frequency manipulation during three weeks of uphill (2%) training on stride length at iso-efficiency speed. Twelve male race walkers were randomly allocated to one of two training groups: stride frequency manipulation (RWM, n=6) and free stride frequency (RWF, n=6). Kinematic parameters measured before and after the 3-week training in RWM showed increased stride length (4.54%; p<0.0001) and contact time (4.58%; p<0.001); inversely, a decreased stride frequency (4.44%; p<0.0001) and internal work (7.09%; p<0.05) were found. In RWF the effect of the training showed a decrease in stride length (1.18%; p<0.0001) and contact time (<1%; p<0.0001) with respect to baseline conditions and an increased stride frequency and internal work of 1.19% (p<0.0001). These results suggest that using slopes (2%) as RWM could help coaches to provide some training methods that would improve an athlete's performance, through increasing stride length without altering his or her race walking technique or metabolic demands.

  2. The effect of uphill stride manipulation on race walking gait

    PubMed Central

    2015-01-01

    Stride length analysis represents an easy method for assessing race walking kinematics. However, the stride parameters emerging from such an analysis have never been used to design a training protocol aimed at increasing stride length. With this aim, we investigated the effects of stride frequency manipulation during three weeks of uphill (2%) training on stride length at iso-efficiency speed. Twelve male race walkers were randomly allocated to one of two training groups: stride frequency manipulation (RWM, n=6) and free stride frequency (RWF, n=6). Results. Kinematic parameters measured before and after the 3-week training in RWM showed increased stride length (4.54%; p<0.0001) and contact time (4.58%; p<0.001); inversely, a decreased stride frequency (4.44%; p<0.0001) and internal work (7.09%; p<0.05) were found. In RWF the effect of the training showed a decrease in stride length (1.18%; p<0.0001) and contact time (<1%; p<0.0001) with respect to baseline conditions and an increased stride frequency and internal work of 1.19% (p<0.0001). These results suggest that using slopes (2%) as RWM could help coaches to provide some training methods that would improve an athlete's performance, through increasing stride length without altering his or her race walking technique or metabolic demands. PMID:26424932

  3. A new ultrasonic stride length measuring system.

    PubMed

    Maki, Hiromichi; Ogawa, Hidekuni; Yonezawa, Yoshiharu; Hahn, Allen W; Caldwell, W Morton

    2012-01-01

    We have developed a new ultrasonic stride length measuring system for analyzing the human gait. An ultrasonic transmitter, a radio transmitter, a pressure sensor and microcontroller are attached to the subject’s heel on the right shoe and in the direction of the left shoe. Two ultrasonic receivers, a radio receiver, a microcontroller and a 1GB SD memory card are installed on the left shoe. Ultrasonic receivers are attached to the toe and heel, in the direction of the right shoe. When the right foot contacts the ground, its heel-mounted ultrasonic and radio transmitters simultaneously transmit to the left shoe. However, radio propagation velocity is far faster than ultrasonic velocity. Therefore, the radio wave acts as a start signal to the radio receiver of the left shoe, indicating the start of ultrasound transmission from the right shoe. Upon receiving the start signal, the microcontroller timer starts to measure each ultrasound propagation time from the right shoe to the left shoe. Distance between right and left shoes is calculated with the time and ultrasound velocity and stored in the SD memory card. Stride length is calculated with a cosine function, by using the obtained distances and the distance between the toe and heel of the left shoe, by a conventional computer. The stride length can then be used for many characterizations of the subject’s gait.

  4. Walking Stride Rate Patterns in Children and Youth

    PubMed Central

    Bjornson, Kristie F.; Song, Kit; Zhou, Chuan; Coleman, Kim; Myaing, Mon; Robinson, Sarah L.

    2013-01-01

    Purpose To describe walking activity patterns in youth who are typically developing (TD) using a novel analysis of stride data and compare to youth with cerebral palsy (CP) and arthrogryposis (AR). Method Stride rate curves were developed from 5 days of StepWatch data for 428 youth ages 2 to 16 years who were TD. Results Patterns of stride rates changed with age in the TD group (P = .03 to < .001). Inactivity varied with age (P < .001); peak stride rate decreased with age (P < .001). Curves were stable over a 2-week time frame (P = .38 to .95). Youth with CP and AR have lower stride rate patterns (P = .04 to .001). Conclusion This is the first documentation of pediatric stride-rate patterns within the context of daily life. Including peak stride rates and levels of walking activity, this single visual format has potential clinical and research applications. PMID:22090075

  5. Gait in Huntington's disease and the stride length-cadence relationship.

    PubMed

    Danoudis, Mary; Iansek, Robert

    2014-10-01

    The progressive deterioration of gait in Huntington's disease (HD) leads to functional decline and loss of function. To understand the underlying mechanisms responsible for the gait changes in HD, we examined the automatic control of gait by measuring the relationship between stride length and cadence. The relationship is strongly linked in healthy adults during automatic gait but disrupted in pathological gait disorders, such as Parkinson's disease (PD). The stride length cadence relationship was compared between seventeen participants with HD, twenty with PD and twenty one healthy older adults (HOA). Participants had their gait recorded at self-selected preferred, very slow, slow, fast and very fast speeds. Linear regression analysis was used to determine the slope and intercept of the relationship which were compared between groups. The adjustment of stride length and cadence when changing gait speeds was measured and compared within and between groups. Linearity was strong in all but two participants with HD and one with PD. Slope did not differ between groups (p > 0.05) but intercept was lower in the HD and PD groups compared to HOA (p < 0.05). Stride length was shorter in the HD and PD groups compared to controls at preferred and most adjusted speed conditions (p < 0.05) but cadence did not differ between groups (p > 0.05) regardless of speed. The HD group adjusted stride length and cadence similar to HOA when changing speed. The range of cadence across speed conditions did not differ between groups. Scaling of stride length but not the regulation of cadence was found to be disrupted in participants with HD.

  6. Altered stride length in response to increasing exertion among baseball pitchers.

    PubMed

    Crotin, Ryan L; Kozlowski, Karl; Horvath, Peter; Ramsey, Dan K

    2014-03-01

    Overexertion caused by increased pitch counts can evoke protective biomechanical responses signified by decreased ball velocity, such as reduced throwing arm kinematics and kinetics. Among skilled pitchers, overexertion may not always present ball velocity decrements, because compensatory throwing biomechanics aid in maintaining peak ball velocity although lowering physiologic stress. Nineteen pitchers (collegiate and elite high school), randomly crossed over to pitch two simulated games at ± 25% of their desired stride length, were recorded by an eight-camera motion capture system (240 Hz) integrated with two piezoelectric force plates (960 Hz) and a professional model radar gun. HR, self-reported exertion scores, blood glucose and lactate, salivary biomarkers, peak linear hand and fastball velocities were examined. Repeated-measures ANOVA as well as independent and pairwise t-tests examined significant differences (P ≤ 0.05). Shortened strides reduced mean pitching HR by 11.1 bpm (P < 0.001), improved recovery capacity by 5.76% (P = 0.012), and lowered salivary cortisol from baseline (P = 0.001). Physiologic stress elevated with greater strides, because salivary alpha amylase was significantly elevated from baseline (P = 0.011) with no improvements evidenced in pitching HR or recovery capacity. Linear hand and ball velocities remained equivalent between stride conditions. Stride length can affect physical exertion without disrupting ball velocity, where shortening strides can plausibly respond to competitive exertion in baseball pitchers. Current pitch count standards and radar velocity accounts have not been proven efficacious in predicting exertion in professional and collegiate baseball, where biomechanical compensations arise to maintain ball velocity. In some instances, compensatory adaptations may be pathomechanic where future research identifying injurious movement patterns can advance injury prevention in professional baseball.

  7. Tactile stimuli affect long-range correlations of stride interval and stride length differently during walking.

    PubMed

    Chien, Jung Hung; Ambati, V N Pradeep; Huang, Chun-Kai; Mukherjee, Mukul

    2017-04-01

    Sensory feedback below the sole of the foot using sub-threshold mechanical noise significantly reduced postural sway in patients with diabetes and stroke. However, the effects of tactile parameters on walking are still elusive. Specifically, the effects of such parameters on human gait variability need to be studied because of possible rehabilitation outcomes in terms of bringing improvement in temporal and spatial gait parameters. The purpose of this study was to investigate whether different frequency and amplitude combinations of vibro-tactile stimulation of feet would affect stride-to-stride variability in healthy young adults. Ten healthy subjects walked on a treadmill at self-selected pace while wearing customized insoles fitted with tactors that vibrated at selected frequencies and amplitudes. The results show that the frequency manipulations of tactile stimulation altered the long-range correlations (LRCs) in stride length while amplitude manipulations affected the LRCs in stride interval without having any effect on the amount of gait variability. Our findings suggest that independent neural mechanisms may be responsible for coordinating LRCs of gait parameters in the spatial and temporal domains.

  8. Stride Search v. 1.0

    SciTech Connect

    Bosler, Peter

    2016-01-20

    Stride Search provides a flexible tool for detecting storms or other extreme climate events in high-resolution climate data sets saved on uniform latitude-longitude grids in standard NetCDF format. Users provide the software a quantitative description of a meteorological event they are interested in; the software searches a data set for locations in space and time that meet the user’s description. In its first stage, Stride Search performs a spatial search of the data set at each timestep by dividing a search domain into circular sectors of constant geodesic radius. Data from a netCDF file is read into memory for each circular search sector. If the data meet or exceed a set of storm identification criteria (defined by the user), a storm is recorded to a linked list. Finally, the linked list is examined and duplicate detections of the same storm are removed and the results are written to an output file. The first stage’s output file is read by a second program that builds storm. Additional identification criteria may be applied at this stage to further classify storms. Storm tracks are the software’s ultimate output and routines are provided for formatting that output for various external software libraries for plotting and tabulating data.

  9. Introducing Statistical Persistence Decay: A Quantification of Stride-to-Stride Time Interval Dependency in Human Gait.

    PubMed

    Raffalt, P C; Yentes, J M

    2017-09-25

    Stride-to-stride time intervals during human walking are characterised by predictability and statistical persistence quantified by sample entropy (SaEn) and detrended fluctuation analysis (DFA) which indicates a time dependency in the gait pattern. However, neither analyses quantify time dependency in a physical or physiological interpretable time scale. Recently, entropic half-life (ENT½) has been introduced as a measure of the time dependency on an interpretable time scale. A novel measure of time dependency, based on DFA, statistical persistence decay (SPD), was introduced. The present study applied SaEn, DFA, ENT½, and SPD in known theoretical signals (periodic, chaotic, and random) and stride-to-stride time intervals during overground and treadmill walking in healthy subjects. The analyses confirmed known properties of the theoretical signals. There was a significant lower predictability (p = 0.033) and lower statistical persistence (p = 0.012) during treadmill walking compared to overground walking. No significant difference was observed for ENT½ and SPD between walking condition, and they exhibited a low correlation. ENT½ showed that predictability in stride time intervals was halved after 11-14 strides and SPD indicated that the statistical persistency was deteriorated to uncorrelated noise after ~50 strides. This indicated a substantial time memory, where information from previous strides affected the future strides.

  10. Detrended Fluctuation Analysis and Adaptive Fractal Analysis of Stride Time Data in Parkinson's Disease: Stitching Together Short Gait Trials

    PubMed Central

    Liebherr, Magnus; Haas, Christian T.

    2014-01-01

    Variability indicates motor control disturbances and is suitable to identify gait pathologies. It can be quantified by linear parameters (amplitude estimators) and more sophisticated nonlinear methods (structural information). Detrended Fluctuation Analysis (DFA) is one method to measure structural information, e.g., from stride time series. Recently, an improved method, Adaptive Fractal Analysis (AFA), has been proposed. This method has not been applied to gait data before. Fractal scaling methods (FS) require long stride-to-stride data to obtain valid results. However, in clinical studies, it is not usual to measure a large number of strides (e.g., strides). Amongst others, clinical gait analysis is limited due to short walkways, thus, FS seem to be inapplicable. The purpose of the present study was to evaluate FS under clinical conditions. Stride time data of five self-paced walking trials ( strides each) of subjects with PD and a healthy control group (CG) was measured. To generate longer time series, stride time sequences were stitched together. The coefficient of variation (CV), fractal scaling exponents (DFA) and (AFA) were calculated. Two surrogate tests were performed: A) the whole time series was randomly shuffled; B) the single trials were randomly shuffled separately and afterwards stitched together. CV did not discriminate between PD and CG. However, significant differences between PD and CG were found concerning and . Surrogate version B yielded a higher mean squared error and empirical quantiles than version A. Hence, we conclude that the stitching procedure creates an artificial structure resulting in an overestimation of true . The method of stitching together sections of gait seems to be appropriate in order to distinguish between PD and CG with FS. It provides an approach to integrate FS as standard in clinical gait analysis and to overcome limitations such as short walkways. PMID:24465708

  11. Detrended fluctuation analysis and adaptive fractal analysis of stride time data in Parkinson's disease: stitching together short gait trials.

    PubMed

    Kirchner, Marietta; Schubert, Patric; Liebherr, Magnus; Haas, Christian T

    2014-01-01

    Variability indicates motor control disturbances and is suitable to identify gait pathologies. It can be quantified by linear parameters (amplitude estimators) and more sophisticated nonlinear methods (structural information). Detrended Fluctuation Analysis (DFA) is one method to measure structural information, e.g., from stride time series. Recently, an improved method, Adaptive Fractal Analysis (AFA), has been proposed. This method has not been applied to gait data before. Fractal scaling methods (FS) require long stride-to-stride data to obtain valid results. However, in clinical studies, it is not usual to measure a large number of strides (e.g., [Formula: see text][Formula: see text] strides). Amongst others, clinical gait analysis is limited due to short walkways, thus, FS seem to be inapplicable. The purpose of the present study was to evaluate FS under clinical conditions. Stride time data of five self-paced walking trials ([Formula: see text] strides each) of subjects with PD and a healthy control group (CG) was measured. To generate longer time series, stride time sequences were stitched together. The coefficient of variation (CV), fractal scaling exponents [Formula: see text] (DFA) and [Formula: see text] (AFA) were calculated. Two surrogate tests were performed: A) the whole time series was randomly shuffled; B) the single trials were randomly shuffled separately and afterwards stitched together. CV did not discriminate between PD and CG. However, significant differences between PD and CG were found concerning [Formula: see text] and [Formula: see text]. Surrogate version B yielded a higher mean squared error and empirical quantiles than version A. Hence, we conclude that the stitching procedure creates an artificial structure resulting in an overestimation of true [Formula: see text]. The method of stitching together sections of gait seems to be appropriate in order to distinguish between PD and CG with FS. It provides an approach to integrate FS as

  12. Altered fractal dynamics of gait: reduced stride-interval correlations with aging and Huntington's disease

    NASA Technical Reports Server (NTRS)

    Hausdorff, J. M.; Mitchell, S. L.; Firtion, R.; Peng, C. K.; Cudkowicz, M. E.; Wei, J. Y.; Goldberger, A. L.

    1997-01-01

    Fluctuations in the duration of the gait cycle (the stride interval) display fractal dynamics and long-range correlations in healthy young adults. We hypothesized that these stride-interval correlations would be altered by changes in neurological function associated with aging and certain disease states. To test this hypothesis, we compared the stride-interval time series of 1) healthy elderly subjects and young controls and of 2) subjects with Huntington's disease and healthy controls. Using detrended fluctuation analysis we computed alpha, a measure of the degree to which one stride interval is correlated with previous and subsequent intervals over different time scales. The scaling exponent alpha was significantly lower in elderly subjects compared with young subjects (elderly: 0.68 +/- 0.14; young: 0.87 +/- 0.15; P < 0.003). The scaling exponent alpha was also smaller in the subjects with Huntington's disease compared with disease-free controls (Huntington's disease: 0.60 +/- 0.24; controls: 0.88 +/-0.17; P < 0.005). Moreover, alpha was linearly related to degree of functional impairment in subjects with Huntington's disease (r = 0.78, P < 0.0005). These findings demonstrate that strike-interval fluctuations are more random (i.e., less correlated) in elderly subjects and in subjects with Huntington's disease. Abnormal alterations in the fractal properties of gait dynamics are apparently associated with changes in central nervous system control.

  13. Altered fractal dynamics of gait: reduced stride-interval correlations with aging and Huntington's disease

    NASA Technical Reports Server (NTRS)

    Hausdorff, J. M.; Mitchell, S. L.; Firtion, R.; Peng, C. K.; Cudkowicz, M. E.; Wei, J. Y.; Goldberger, A. L.

    1997-01-01

    Fluctuations in the duration of the gait cycle (the stride interval) display fractal dynamics and long-range correlations in healthy young adults. We hypothesized that these stride-interval correlations would be altered by changes in neurological function associated with aging and certain disease states. To test this hypothesis, we compared the stride-interval time series of 1) healthy elderly subjects and young controls and of 2) subjects with Huntington's disease and healthy controls. Using detrended fluctuation analysis we computed alpha, a measure of the degree to which one stride interval is correlated with previous and subsequent intervals over different time scales. The scaling exponent alpha was significantly lower in elderly subjects compared with young subjects (elderly: 0.68 +/- 0.14; young: 0.87 +/- 0.15; P < 0.003). The scaling exponent alpha was also smaller in the subjects with Huntington's disease compared with disease-free controls (Huntington's disease: 0.60 +/- 0.24; controls: 0.88 +/-0.17; P < 0.005). Moreover, alpha was linearly related to degree of functional impairment in subjects with Huntington's disease (r = 0.78, P < 0.0005). These findings demonstrate that strike-interval fluctuations are more random (i.e., less correlated) in elderly subjects and in subjects with Huntington's disease. Abnormal alterations in the fractal properties of gait dynamics are apparently associated with changes in central nervous system control.

  14. The effects of stride length and stride frequency on trunk coordination in human walking.

    PubMed

    Huang, Yunpeng; Meijer, Onno G; Lin, Jianhua; Bruijn, Sjoerd M; Wu, Wenhua; Lin, Xiaocong; Hu, Hai; Huang, Caihua; Shi, Lei; van Dieën, Jaap H

    2010-04-01

    In speeding-up normal walking, relative phase between horizontal thorax and pelvis rotations changes from more in-phase (synchronous) to more out-of-phase. In pathology (stroke, Parkinson's disease, low-back pain, pregnancy-related pelvic girdle pain), this often fails to happen. Even in healthy gait, however, these phenomena remain poorly understood. Thorax-pelvis relative phase may increase with either stride length, or stride frequency. Sixteen healthy male subjects walked on a treadmill at 0.5m/s, 1.0m/s, or 1.5m/s, with small, normal, or large steps. Increasing stride length (with lower frequency) led to larger spinal rotations, larger thorax-pelvis relative phase, and lower pelvis-leg relative phase, while the thorax continued to counterrotate with respect to the leg. With small steps, speeding-up hardly affected thorax-pelvis relative phase, and spinal amplitudes remained low. From a certain walking speed onwards, pelvis rotations start to contribute to stride length, and thus to speed (the "pelvic step"). This phenomenon appears to be driven, and the present study suggests, at least for higher speeds, that also thoracic counterrotations are driven, and not determined by the passive dynamics of the system. For patients, several strategies may exist to avoid large thorax-pelvis relative phase, and the concomitant large rotations of the spine: walking slowly, walking with small steps, adapting the timing of thorax rotations to that of the pelvis, or refraining from adapting the timing of pelvis rotations to the movements of the leg. Copyright 2010 Elsevier B.V. All rights reserved.

  15. Stride to stride variability in joint angle profiles during transitions from trot to canter in horses.

    PubMed

    Nauwelaerts, Sandra; Aerts, Peter; Clayton, Hilary

    2013-12-01

    Spontaneous transitions from anti-phase to in-phase manual coordination are explained in the Haken model that describes the two preferred states as stable regions that work as attractors in a stability landscape. Switching between states coincides with a temporary loss of stability. Coordination variability is believed to be indicative of such a loss of stability. In this study, the hypothesis was tested that an increase in variability in the angle profiles of the joints responsible for the transition will precede the transition. A full gait analysis of four miniature horses transitioning from trot to canter was performed. Joint angle profiles were determined for the joints of all four limbs and were time-normalised to stride duration. Per horse and per stride, the coefficient of variance was calculated as the mean standard deviation of the joint profile over all trials divided by the mean joint angle × 100. As hypothesised, the most proximal limb joints (hip, scapulothoracic, shoulder) followed the predictions to a large extent. The variability of the hip joint angle of the trailing hind limb showed a peak of variability at stride 0; this was quickly reduced after the transition was completed. The detection of this brief perturbation in the hip joint indicates the importance of this joint in the transition process. The hip joint is related to the movements of the limb, pelvis and back, which is one of the main differences between symmetrical and asymmetrical gaits.

  16. Linearized traveling wave amplifier with hard limiter characteristics

    NASA Technical Reports Server (NTRS)

    Kosmahl, H. G. (Inventor)

    1986-01-01

    A dynamic velocity taper is provided for a traveling wave tube with increased linearity to avoid intermodulation of signals being amplified. In a traveling wave tube, the slow wave structure is a helix including a sever. A dynamic velocity taper is provided by gradually reducing the spacing between the repeating elements of the slow wave structure which are the windings of the helix. The reduction which takes place coincides with the ouput point of helix. The spacing between the repeating elements of the slow wave structure is ideally at an exponential rate because the curve increases the point of maximum efficiency and power, at an exponential rate. A coupled cavity traveling wave tube having cavities is shown. The space between apertured discs is gradually reduced from 0.1% to 5% at an exponential rate. Output power (or efficiency) versus input power for a commercial tube is shown.

  17. A novel wearable laser device to regulate stride length in Parkinson's disease.

    PubMed

    Zhao, Yan; Ramesberger, Stefan; Fietzek, Urban M; D'Angelo, Lorenzo T; Luth, Tim C

    2013-01-01

    Decreased stride length is a highly relevant characteristic of the gait in patients with Parkinson's disease (PD). In this paper, a novel wearable laser device for stride length regulation is presented. The device is mounted to one foot and can project a red laser light strip to the floor as a visual cue for the other foot. In the experiment twelve healthy volunteers walked a 20 m straight walkway wearing the system on both feet. As an objective result, the stride length regulation reached an accuracy of 96.1 ± 2.5 (94.0 ± 3.5) % for a pre-defined stride length λdef= 55 (65) cm. The subjective evaluation by the participants using a questionnaire revealed that the visual cue projected from the laser device was considered a stable signal that did not shake during walking. 6 of 12 participants felt that this device was not interfering with their gait, 3 of 12 judged this aspect neutrally, and 3 of 12 considered it somehow bothersome.

  18. Stability characteristics of jets in linearly-stratified, rotating fluids

    NASA Astrophysics Data System (ADS)

    Chen, Rui-Rong; Boyer, Don L.; Tao, Lijun

    A series of laboratory experiments are conducted concerning an azimuthal jet of a linearly stratified rotating fluid in a cylindrical geometry. The jet is characterized by vertical and horizontal shear and the question of the stability of the flow is considered experimentally. The jet is driven by a source-sink method characterized by a volume flow rate of strength Q. BecauseQ has no direct geophysical significance a combined external set of dimensionless parameters is introduced. These include the Rossby, Richardson and Ekman numbers, the jet aspect ratio and two geometrical parameters. A RossbyRo against RichardsonRi number flow regime diagram is presented which shows that the wave mode of the instability generally decreases with increasingRo andRi, for fixedRi andRo, respectively. In accordance with Killworth's (1980) linear stability analysis, the wave mode for smallRi (Ri ⪉ 15) depends principally onRi with the instability being largely a baroclinic one. For largerRi(Ri ⪉ 100), again as predicted by Killworth's theory, the wave mode depends primarily onRo, the instability being a barotropic one. The regime diagram can be used to estimate the wave-length of jet instabilities in the atmosphere and oceans. These estimates suggest that the wave-lengths decrease with increasing jet velocity, decreasing jet width (equivalent to increasing horizontal shear) and increasing vertical shear, other parameters being fixed. An azimuthal topography aligned along the jet has the tendency to stabilize the jet in the sense that the amplitude of the instability is shown to be dramatically smaller in the presence of the topography, other parameters being fixed. The topography also tends to increase the wave-length of the instability. A scaling analysis is advanced, and supporting experimental data presented, relating the external and internal parameters utilized.

  19. Stride Leg Ground Reaction Forces Predict Throwing Velocity in Adult Recreational Baseball Pitchers.

    PubMed

    McNally, Michael P; Borstad, John D; Oñate, James A; Chaudhari, Ajit M W

    2015-10-01

    Ground reaction forces produced during baseball pitching have a significant impact in the development of ball velocity. However, the measurement of only one leg and small sample sizes in these studies curb the understanding of ground reaction forces as they relate to pitching. This study aimed to further clarify the role ground reaction forces play in developing pitching velocity. Eighteen former competitive baseball players with previous high school or collegiate pitching experience threw 15 fastballs from a pitcher's mound instrumented to measure ground reaction forces under both the drive and stride legs. Peak ground reaction forces were recorded during each phase of the pitching cycle, between peak knee height and ball release, in the medial/lateral, anterior/posterior, and vertical directions, and the peak resultant ground reaction force. Stride leg ground reaction forces during the arm-cocking and arm-acceleration phases were strongly correlated with ball velocity (r2 = 0.45-0.61), whereas drive leg ground reaction forces showed no significant correlations. Stepwise linear regression analysis found that peak stride leg ground reaction force during the arm-cocking phase was the best predictor of ball velocity (r2 = 0.61) among drive and stride leg ground reaction forces. This study demonstrates the importance of ground reaction force development in pitching, with stride leg forces being strongly predictive of ball velocity. Further research is needed to further clarify the role of ground reaction forces in pitching and to develop training programs designed to improve upper extremity mechanics and pitching performance through effective force development.

  20. Fractional characteristic times and dissipated energy in fractional linear viscoelasticity

    NASA Astrophysics Data System (ADS)

    Colinas-Armijo, Natalia; Di Paola, Mario; Pinnola, Francesco P.

    2016-08-01

    In fractional viscoelasticity the stress-strain relation is a differential equation with non-integer operators (derivative or integral). Such constitutive law is able to describe the mechanical behavior of several materials, but when fractional operators appear, the elastic and the viscous contribution are inseparable and the characteristic times (relaxation and retardation time) cannot be defined. This paper aims to provide an approach to separate the elastic and the viscous phase in the fractional stress-strain relation with the aid of an equivalent classical model (Kelvin-Voigt or Maxwell). For such equivalent model the parameters are selected by an optimization procedure. Once the parameters of the equivalent model are defined, characteristic times of fractional viscoelasticity are readily defined as ratio between viscosity and stiffness. In the numerical applications, three kinds of different excitations are considered, that is, harmonic, periodic, and pseudo-stochastic. It is shown that, for any periodic excitation, the equivalent models have some important features: (i) the dissipated energy per cycle at steady-state coincides with the Staverman-Schwarzl formulation of the fractional model, (ii) the elastic and the viscous coefficients of the equivalent model are strictly related to the storage and the loss modulus, respectively.

  1. Photon spectral characteristics of dissimilar 6 MV linear accelerators.

    PubMed

    Hinson, William H; Kearns, William T; deGuzman, Allan F; Bourland, J Daniel

    2008-05-01

    This work measures and compares the energy spectra of four dosimetrically matched 6 MV beams, generated from four physically different linear accelerators. The goal of this work is twofold. First, this study determines whether the spectra of dosimetrically matched beams are measurably different. This study also demonstrates that the spectra of clinical photon beams can be measured as a part of the beam data collection process for input to a three-dimensional (3D) treatment planning system. The spectra of 6 MV beams that are dosimetrically matched for clinical use were studied to determine if the beam spectra are similarly matched. Each of the four accelerators examined had a standing waveguide, but with different physical designs. The four accelerators were two Varian 2100C/Ds (one 6 MV/18 MV waveguide and one 6 MV/10 MV waveguide), one Varian 600 C with a vertically mounted waveguide and no bending magnet, and one Siemens MD 6740 with a 6 MV/10 MV waveguide. All four accelerators had percent depth dose curves for the 6 MV beam that were matched within 1.3%. Beam spectra were determined from narrow beam transmission measurements through successive thicknesses of pure aluminum along the central axis of the accelerator, made with a graphite Farmer ion chamber with a Lucite buildup cap. An iterative nonlinear fit using a Marquardt algorithm was used to find each spectrum. Reconstructed spectra show that all four beams have similar energy distributions with only subtle differences, despite the differences in accelerator design. The measured spectra of different 6 MV beams are similar regardless of accelerator design. The measured spectra show excellent agreement with those found by the auto-modeling algorithm in a commercial 3D treatment planning system that uses a convolution dose calculation algorithm. Thus, beam spectra can be acquired in a clinical setting at the time of commissioning as a part of the routine beam data collection.

  2. Characteristics of induced activity from medical linear accelerators

    SciTech Connect

    Wang Yizhen; Evans, Michael D.C.; Podgorsak, Ervin B.

    2005-09-15

    A study of the induced activity in a medical linear accelerator (linac) room was carried out on several linac installations. Higher beam energy, higher dose rate, and larger field size generally result in higher activation levels at a given point of interest, while the use of multileaf collimators (MLC) can also increase the activation level at the isocenter. Both theoretical and experimental studies reveal that the activation level in the morning before any clinical work increases from Monday to Saturday and then decreases during the weekend. This weekly activation picture keeps stable from one week to another during standard clinical operation of the linac. An effective half-life for a given point in the treatment room can be determined from the measured or calculated activity decay curves. The effective half-life for points inside the treatment field is longer than that for points outside of the field in the patient plane, while a larger field and longer irradiation time can also make the effective half-life longer. The activation level reaches its practical saturation value after a 30 min continuous irradiation, corresponding to 12 000 MU at a 'dose rate' of 400 MU/min. A 'dose' of 300 MU was given 20 times in 15 min intervals to determine the trends in the activation level in a typical clinical mode. As well, a long-term (85 h over a long weekend) decay curve was measured to evaluate the long-term decay of room activation after a typical day of clinical linac use. A mathematical model for the activation level at the isocenter has been established and shown to be useful in explaining and predicting the induced activity levels for typical clinical and experimental conditions. The activation level for a 22 MeV electron beam was also measured and the result shows it is essentially negligible.

  3. Stride length asymmetry in split-belt locomotion.

    PubMed

    Hoogkamer, Wouter; Bruijn, Sjoerd M; Duysens, Jacques

    2014-01-01

    The number of studies utilizing a split-belt treadmill is rapidly increasing in recent years. This has led to some confusion regarding the definitions of reported gait parameters. The purpose of this paper is to clearly present the definitions of the gait parameters that are commonly used in split-belt treadmill studies. We argue that the modified version of stride length for split-belt gait, which is different from the standard definition of stride length and actually is a measure of limb excursion, should be referred to as 'limb excursion' in future studies. Furthermore, the symmetry of stride length and stride time is specifically addressed. Copyright © 2013 Elsevier B.V. All rights reserved.

  4. Steps to take to enhance gait stability: the effect of stride frequency, stride length, and walking speed on local dynamic stability and margins of stability.

    PubMed

    Hak, Laura; Houdijk, Han; Beek, Peter J; van Dieën, Jaap H

    2013-01-01

    The purpose of the current study was to investigate whether adaptations of stride length, stride frequency, and walking speed, independently influence local dynamic stability and the size of the medio-lateral and backward margins of stability during walking. Nine healthy subjects walked 25 trials on a treadmill at different combinations of stride frequency, stride length, and consequently at different walking speeds. Visual feedback about the required and the actual combination of stride frequency and stride length was given during the trials. Generalized Estimating Equations were used to investigate the independent contribution of stride length, stride frequency, and walking speed on the measures of gait stability. Increasing stride frequency was found to enhance medio-lateral margins of stability. Backward margins of stability became larger as stride length decreased or walking speed increased. For local dynamic stability no significant effects of stride frequency, stride length or walking speed were found. We conclude that adaptations in stride frequency, stride length and/or walking speed can result in an increase of the medio-lateral and backward margins of stability, while these adaptations do not seem to affect local dynamic stability. Gait training focusing on the observed stepping strategies to enhance margins of stability might be a useful contribution to programs aimed at fall prevention.

  5. Steps to Take to Enhance Gait Stability: The Effect of Stride Frequency, Stride Length, and Walking Speed on Local Dynamic Stability and Margins of Stability

    PubMed Central

    Hak, Laura; Houdijk, Han; Beek, Peter J.; van Dieën, Jaap H.

    2013-01-01

    The purpose of the current study was to investigate whether adaptations of stride length, stride frequency, and walking speed, independently influence local dynamic stability and the size of the medio-lateral and backward margins of stability during walking. Nine healthy subjects walked 25 trials on a treadmill at different combinations of stride frequency, stride length, and consequently at different walking speeds. Visual feedback about the required and the actual combination of stride frequency and stride length was given during the trials. Generalized Estimating Equations were used to investigate the independent contribution of stride length, stride frequency, and walking speed on the measures of gait stability. Increasing stride frequency was found to enhance medio-lateral margins of stability. Backward margins of stability became larger as stride length decreased or walking speed increased. For local dynamic stability no significant effects of stride frequency, stride length or walking speed were found. We conclude that adaptations in stride frequency, stride length and/or walking speed can result in an increase of the medio-lateral and backward margins of stability, while these adaptations do not seem to affect local dynamic stability. Gait training focusing on the observed stepping strategies to enhance margins of stability might be a useful contribution to programs aimed at fall prevention. PMID:24349379

  6. Individual effects of stride length and frequency on shock attenuation during running.

    PubMed

    Mercer, John A; Devita, Paul; Derrick, Tim R; Bates, Barry T

    2003-02-01

    Shock attenuation during running is the process of absorbing impact energy due to the foot-ground collision, reducing shock wave amplitude between the foot and head. Shock attenuation is affected by changes in stride length and stride frequency, but it is not clear whether either parameter individually affects shock attenuation. To identify the independent affects of stride length (SL) and stride frequency (SF) on shock attenuation. Subjects ( N = 10) completed three experiments consisting of SL and SF manipulations relative to preferred stride length (PSL) and frequency (PSF). During experiment 1, stride length was manipulated (+15% PSL, PSL, -15% PSL) while stride frequency was always set to PSF. During experiment 2, stride frequency was manipulated (+15% PSF, PSF, -15% PSF) while stride length was always set to PSL. During experiment 3, stride length and stride frequency were manipulated concurrently (+10% PSL/-10% PSF, PSL/PSF, and -10% PSL/+10% PSF). Running velocity was always the product of stride length and stride frequency. Transfer functions were calculated using tibial and forehead surface mounted accelerometer data to represent shock attenuation. Shock attenuation changed only when stride length changed ( P < 0.05). Specifically, shock attenuation increased as stride length increased. It was concluded that changes in stride length not stride frequency affected shock attenuation.

  7. Gait variability among healthy adults: low and high stride-to-stride variability are both a reflection of gait stability.

    PubMed

    Beauchet, Olivier; Allali, Gilles; Annweiler, Cédric; Bridenbaugh, Stephanie; Assal, Frederic; Kressig, Reto W; Herrmann, François R

    2009-01-01

    It has been suggested that high stride-to-stride variability (STV) is a reflection of gait instability. However, both low and high STV has been shown in fallers and in nonfallers; therefore, the interpretation of STV of spatiotemporal gait parameters remains difficult. Thus, we sought to characterize and compare STV of spatial and temporal stride parameters among young and older healthy adults, and to determine the extent to which opposite results in STV could provide similar implications in terms of gait stability. Mean values of coefficients of variation of spatiotemporal gait parameters were collected from 30 young adults (14 men and 16 women; mean age 28.1 +/- 6.0 years) and 33 older adults (2 men and 31 women; mean age 74.4 +/- 7.1 years) walking at self-chosen normal walking speed over a GAITRite System. An age-related increase in STV was only observed with stride width (p = 0.012), whereas increased stride length and stance time variability in older adults were related to decreased walking speed (p = 0.006 and p = 0.018). In addition, both low and high STV was found in both groups of subjects and the highest value was observed for stride width (p < 0.001). The two main implications of the present results are that decreased walking speed should be taken into account when exploring age-related effects on gait variability, and that both low and high spatiotemporal STV may reflect gait stability in healthy adults.

  8. Gait dynamics, fractals and falls: finding meaning in the stride-to-stride fluctuations of human walking.

    PubMed

    Hausdorff, Jeffrey M

    2007-08-01

    Until recently, quantitative studies of walking have typically focused on properties of a typical or average stride, ignoring the stride-to-stride fluctuations and considering these fluctuations to be noise. Work over the past two decades has demonstrated, however, that the alleged noise actually conveys important information. The magnitude of the stride-to-stride fluctuations and their changes over time during a walk - gait dynamics - may be useful in understanding the physiology of gait, in quantifying age-related and pathologic alterations in the locomotor control system, and in augmenting objective measurement of mobility and functional status. Indeed, alterations in gait dynamics may help to determine disease severity, medication utility, and fall risk, and to objectively document improvements in response to therapeutic interventions, above and beyond what can be gleaned from measures based on the average, typical stride. This review discusses support for the idea that gait dynamics has meaning and may be useful in providing insight into the neural control of locomotion and for enhancing functional assessment of aging, chronic disease, and their impact on mobility.

  9. GAIT DYNAMICS, FRACTALS AND FALLS: FINDING MEANING IN THE STRIDE-TO-STRIDE FLUCTUATIONS OF HUMAN WALKING

    PubMed Central

    Hausdorff, Jeffrey M

    2007-01-01

    Until recently, quantitative studies of walking have typically focused on properties of a typical or average stride, ignoring the stride-to-stride fluctuations and considering these fluctuations to be noise. Work over the past two decades has demonstrated, however, that the alleged noise actually conveys important information. The magnitude of the stride-to-stride fluctuations and their changes over time during a walk – gait dynamics – may be useful in understanding the physiology of gait, in quantifying age-related and pathologic alterations in the locomotor control system, and in augmenting objective measurement of mobility and functional status Indeed, alterations in gait dynamics may help to determine disease severity, medication utility, and fall risk, and to objectively document improvements in response to therapeutic interventions, above and beyond what can be gleaned from measures based on the average, typical stride. This review discusses support for the idea that gait dynamics has meaning and may be useful in providing insight into the neural control of locomtion and for enhancing functional assessment of aging, chronic disease, and their impact on mobility. PMID:17618701

  10. Adaptation and Prosthesis Effects on Stride-to-Stride Fluctuations in Amputee Gait

    PubMed Central

    Wurdeman, Shane R.; Myers, Sara A.; Jacobsen, Adam L.; Stergiou, Nicholas

    2014-01-01

    Twenty-four individuals with transtibial amputation were recruited to a randomized, crossover design study to examine stride-to-stride fluctuations of lower limb joint flexion/extension time series using the largest Lyapunov exponent (λ). Each individual wore a “more appropriate” and a “less appropriate” prosthesis design based on the subject's previous functional classification for a three week adaptation period. Results showed decreased λ for the sound ankle compared to the prosthetic ankle (F1,23 = 13.897, p = 0.001) and a decreased λ for the “more appropriate” prosthesis (F1,23 = 4.849, p = 0.038). There was also a significant effect for the time point in the adaptation period (F2,46 = 3.164, p = 0.050). Through the adaptation period, a freezing and subsequent freeing of dynamic degrees of freedom was seen as the λ at the ankle decreased at the midpoint of the adaptation period compared to the initial prosthesis fitting (p = 0.032), but then increased at the end compared to the midpoint (p = 0.042). No differences were seen between the initial fitting and the end of the adaptation for λ (p = 0.577). It is concluded that the λ may be a feasible clinical tool for measuring prosthesis functionality and adaptation to a new prosthesis is a process through which the motor control develops mastery of redundant degrees of freedom present in the system. PMID:24956384

  11. A Comparative Analysis of Selected Mechanical Aspects of the Ice Skating Stride.

    ERIC Educational Resources Information Center

    Marino, G. Wayne

    This study quantitatively analyzes selected aspects of the skating strides of above-average and below-average ability skaters. Subproblems were to determine how stride length and stride rate are affected by changes in skating velocity, to ascertain whether the basic assumption that stride length accurately approximates horizontal movement of the…

  12. Direct evidence for distance measurement via flexible stride integration in the fiddler crab.

    PubMed

    Walls, Michael L; Layne, John E

    2009-01-13

    While on foraging excursions, fiddler crabs track their burrow location despite having no visual contact with it . They do this by path integration, a common navigational process in which motion vectors (the direction and distance of animals' movements) are summed to form a single "home vector" linking the current location with the point of origin. Here, we identify the mechanism by which the integrator measures distance, by decoupling motor output from both inertial and visual feedback. Fiddler crabs were passively translated to a position such that the home vector lay across an acetate sheet on the ground. After being frightened, crabs tried to escape but slipped as they did so. Detailed high-speed video analysis reveals that crabs measure distance by integrating strides, rather than linear acceleration or optic flow: the number of steps they took depended on both the length of the home vector and how large their steps were, whether they slipped and fell short or not. This is the most direct evidence to date of a stride integrator that is flexible enough to account for significant variation in stride length and frequency.

  13. Dynamic characteristics of a jacket type offshore structure considering non-linear behavior of pile foundations

    SciTech Connect

    Aaghaakouchak, A.A.; Asgarian, B.

    1996-12-31

    Dynamic characteristics of a typical six legged jacket type platform in Persian Gulf have been studied. An equivalent linearized pile stub has been used to model the pile-soil system. The properties of pile stub have been calculated for different levels of the pile-head deformations resulting from the action of different waves. Natural frequencies and mode shapes of resulting linear models have been determined and compared to each other.

  14. Effects of stride frequency and foot position at landing on braking force, hip torque, impact peak force and the metabolic cost of running in humans.

    PubMed

    Lieberman, Daniel E; Warrener, Anna G; Wang, Justin; Castillo, Eric R

    2015-11-01

    Endurance runners are often advised to use 90 strides min(-1), but how optimal is this stride frequency and why? Endurance runners are also often advised to maintain short strides and avoid landing with the feet too far in front of their hips or knees (colloquially termed 'overstriding'), but how do different kinematic strategies for varying stride length at the same stride frequency affect economy and impact peaks? Linear mixed models were used to analyze repeated measures of stride frequency, the anteroposterior position of the foot at landing, V̇O2 , lower extremity kinematics and vertical ground reaction forces in 14 runners who varied substantially in height and body mass and who were asked to run at 75, 80, 85, 90 and 95 strides min(-1) at 3.0 m s(-1). For every increase of 5 strides min(-1), maximum hip flexor moments in the sagittal plane increased by 5.8% (P<0.0001), and the position of the foot at landing relative to the hip decreased by 5.9% (P=0.003). Higher magnitudes of posteriorly directed braking forces were associated with increases in foot landing position relative to the hip (P=0.0005) but not the knee (P=0.54); increases in foot landing position relative to the knee were associated with higher magnitudes (P<0.0001) and rates of loading (P=0.07) of the vertical ground reaction force impact peak. Finally, the mean metabolically optimal stride frequency was 84.8±3.6 strides min(-1), with 50.4% of the variance explained by the trade-off between minimizing braking forces versus maximum hip flexor moments during swing. The results suggest that runners may benefit from a stride frequency of approximately 85 strides min(-1) and by landing at the end of swing phase with a relatively vertical tibia.

  15. An ultrasonic stride length measuring system employing two digital compasses.

    PubMed

    Maki, Hiromichi; Ogawa, Hidekuni; Yonezawa, Yoshiharu; Hahn, Allen W; Caldwell, W Morton

    2014-01-01

    We have developed an ultrasonic stride length measuring system for analyzing the human gait. All elements of the system are quite small and each fit into an appropriate package. An ultrasonic transmitter, a digital compass, a radio transmitter and a microcontroller are attached to the subject’s heel on the right shoe and in the direction of the left shoe. Two ultrasonic receivers, a digital compass, a radio receiver, a microcontroller and a 1GB SD memory card are installed on the left shoe. The ultrasonic receivers are attached to the toe and heel in the direction of the right shoe. The walking direction is thus detected by the compass attached on the right and left shoes, respectively. The stride length is detected by the difference between the radio wave and ultrasonic propagation velocities. The stride length is corrected by the detected walking direction, and then the corrected stride length is stored in the SD memory card. When downloaded, the memory card gives the accurate stride length which then is used to characterize the subject’s gait during daily activity.

  16. Increased intra-individual variability in stride length and reaction time in recurrent older fallers.

    PubMed

    Reelick, Miriam F; Kessels, Roy P C; Faes, Miriam C; Weerdesteyn, Vivian; Esselink, Rianne A J; Olde Rikkert, Marcel G M

    2011-01-01

    To study and compare both mean performance measures as well as intra-individual variability measures of stride length and reaction time in vulnerable recurrent and non-recurrent older fallers. Stride length during walking and walking while dual-tasking (GAITRite®) and choice reaction time (CANTAB®) were assessed in geriatric outpatients and their informal caregivers (n=60, ≥ 60 yrs). Logistic regression and Receiver Operating Characteristic (ROC) analysis were used to generate models with mean performance measures and intra-individual variability measures (coefficients of variation; CV=[sd/mean]x100)), as risk factors for recurrent falls. Reaction-time CV was higher in recurrent fallers than in non-recurrent fallers: 21.3% [9.3-47.7] vs 15.8% [8.3-34.9] (p=0.04). Also, stride-length CV was higher in recurrent fallers during performance of the verbal fluency dual-task: 4.5% [1.2-31.4] vs 3.5% [0.9-9.7] (p=0.017). The model with CVs provided an explained variance of 23.7%, and an area under the curve (AUC) of 0.73, which was higher than that of the model including mean performance measures (8.6% and 0.65 respectively). Older recurrent fallers are characterized by increased within-task variability in reaction time and stride length while dual-tasking. In addition, variability in performance is a more sensitive measure in discrimination of recurrent falls than mean performance itself, suggesting deterioration in neurocognitive regulation mechanisms as part of the causal pathway for recurrent falls.

  17. The effect of water height on stride frequency, stride length and heart rate during water treadmill exercise.

    PubMed

    Scott, R; Nankervis, K; Stringer, C; Westcott, K; Marlin, D

    2010-11-01

    Water treadmill exercise is often incorporated into rehabilitation programmes for horses yet little is known about the biomechanical and physiological responses to water walking. To establish whether stride frequency (SF) reached steady state as a result of 6 introductory water treadmill sessions and then to investigate the effect of increasing water height on SF, stride length (SL) and heart rate (HR). Nine horses with no previous experience of water treadmills completed 6 sessions of walking for between 15 and 30 min. Each horse was fitted with a leg mounted accelerometer to measure SF. The effect of session on SF was tested using univariate ANOVA. Eight horses completed 3 further sessions at each of the following water heights; proximal interphalangeal joint (PIP), carpus and ulna. SF, SL and HR at each water height were compared to a control (hoof height) using univariate ANOVA. When SF during introductory sessions 4-6 were compared, there was no significant effect of session on SF (P > 0.05). In the second part of the experiment, SF was 0.57 ± 0.03 strides/s at control, 0.54 ± 0.03 strides/s at the PIP joint, 0.51 ± 0.02 strides/s at the carpus and 0.52 ± 0.03 strides/s at the ulna. Stride frequency at carpal and ulna height was significantly lower than at control (P < 0.05). Stride length was 1.53 ± 0.09 m for control, 1.63 ± 0.10 m at the PIP joint, 1.71 ± 0.08 m at the carpus and 1.68 ± 0.10 m at the ulna. Stride length at carpal and ulna height was significantly greater than control (P < 0.05). There was no significant difference between HR during control and any other water height (P > 0.05). Horses reached steady state gait within the first 6 sessions of water treadmill exercise. Walking in water at the level of the carpus or ulna resulted in a lower SF compared to walking in water at hoof height. © 2010 EVJ Ltd.

  18. Characteristics of identifying linear dynamic models from impulse response data using Prony analysis

    SciTech Connect

    Trudnowski, D.J.

    1992-12-01

    The purpose of the study was to investigate the characteristics of fitting linear dynamic models to the impulse response of oscillatory dynamic systems using Prony analysis. Many dynamic systems exhibit oscillatory responses with multiple modes of oscillations. Although the underlying dynamics of such systems are often nonlinear, it is frequently possible and very useful to represent the system operating about some set point with a linear model. Derivation of such linear models can be done using two basic approaches: model the system using theoretical derivations and some linearization method such as a Taylor series expansion; or use a curve-fitting technique to optimally fit a linear model to specified system response data. Prony analysis belongs to the second class of system modeling because it is a method of fitting a linear model to the impulse response of a dynamic system. Its parallel formulation inherently makes it well suited for fitting models to oscillatory system data. Such oscillatory dynamic effects occur in large synchronous-generator-based power systems in the form of electromechanical oscillations. To study and characterize these oscillatory dynamics, BPA has developed computer codes to analyze system data using Prony analysis. The objective of this study was to develop a highly detailed understanding of the properties of using Prony analysis to fit models to systems with characteristics often encountered in power systems. This understanding was then extended to develop general rules-of-thumb'' for using Prony analysis. The general characteristics were investigated by performing fits to data from known linear models under controlled conditions. The conditions studied include various mathematical solution techniques; different parent system configurations; and a large variety of underlying noise characteristics.

  19. Characteristics of identifying linear dynamic models from impulse response data using Prony analysis

    SciTech Connect

    Trudnowski, D.J.

    1992-12-01

    The purpose of the study was to investigate the characteristics of fitting linear dynamic models to the impulse response of oscillatory dynamic systems using Prony analysis. Many dynamic systems exhibit oscillatory responses with multiple modes of oscillations. Although the underlying dynamics of such systems are often nonlinear, it is frequently possible and very useful to represent the system operating about some set point with a linear model. Derivation of such linear models can be done using two basic approaches: model the system using theoretical derivations and some linearization method such as a Taylor series expansion; or use a curve-fitting technique to optimally fit a linear model to specified system response data. Prony analysis belongs to the second class of system modeling because it is a method of fitting a linear model to the impulse response of a dynamic system. Its parallel formulation inherently makes it well suited for fitting models to oscillatory system data. Such oscillatory dynamic effects occur in large synchronous-generator-based power systems in the form of electromechanical oscillations. To study and characterize these oscillatory dynamics, BPA has developed computer codes to analyze system data using Prony analysis. The objective of this study was to develop a highly detailed understanding of the properties of using Prony analysis to fit models to systems with characteristics often encountered in power systems. This understanding was then extended to develop general ``rules-of-thumb`` for using Prony analysis. The general characteristics were investigated by performing fits to data from known linear models under controlled conditions. The conditions studied include various mathematical solution techniques; different parent system configurations; and a large variety of underlying noise characteristics.

  20. Characteristic evaluation of linear LED grating projector for high-speed shape measurement

    NASA Astrophysics Data System (ADS)

    Fujigaki, Motoharu; Yokoyama, Tsutomu; Oura, Yohei; Sakaguchi, Toshimasa; Asai, Daisuke; Murata, Yorinobu

    2013-06-01

    High-speed shape measurement is required to analysis the behavior of a breaking object, a vibrating object or a rotating object. A shape measurement by a phase shifting method can measure the shape with high spatial resolution because the coordinates can be obtained pixel by pixel. The key-device is a grating projector. The projector can shift the projected grating in high-speed. So, authors proposed a light source stepping method using a linear LED device. A grating projector is composed with the linear LED and a Ronchi ruling. Grating pattern can be projected when the linear LED is turned on. The phase of the projected grating on the object can be shifted with changing the position of lighted linear LED easily and quickly. Authors call this method a light source stepping method. In this paper, a linear LED grating projector is developed. The characteristic of the linear LED grating projector such as the wavelength, directional characteristics, response are evaluated. The results show that this projector is useful for high-speed shape measurement.

  1. A preliminary test of measurement of joint angles and stride length with wireless inertial sensors for wearable gait evaluation system.

    PubMed

    Watanabe, Takashi; Saito, Hiroki; Koike, Eri; Nitta, Kazuki

    2011-01-01

    The purpose of this study is to develop wearable sensor system for gait evaluation using gyroscopes and accelerometers for application to rehabilitation, healthcare and so on. In this paper, simultaneous measurement of joint angles of lower limbs and stride length was tested with a prototype of wearable sensor system. The system measured the joint angles using the Kalman filter. Signals from the sensor attached on the foot were used in the stride length estimation detecting foot movement automatically. Joint angles of the lower limbs were measured with stable and reasonable accuracy compared to those values measured with optical motion measurement system with healthy subjects. It was expected that the stride length measurement with the wearable sensor system would be practical by realizing more stable measurement accuracy. Sensor attachment position was suggested not to affect significantly measurement of slow and normal speed movements in a test with the rigid body model. Joint angle patterns measured in 10 m walking with a healthy subject were similar to common patterns. High correlation between joint angles at some characteristic points and stride velocity were also found adequately. These results suggested that the wireless wearable inertial sensor system could detect characteristics of gait.

  2. A Preliminary Test of Measurement of Joint Angles and Stride Length with Wireless Inertial Sensors for Wearable Gait Evaluation System

    PubMed Central

    Watanabe, Takashi; Saito, Hiroki; Koike, Eri; Nitta, Kazuki

    2011-01-01

    The purpose of this study is to develop wearable sensor system for gait evaluation using gyroscopes and accelerometers for application to rehabilitation, healthcare and so on. In this paper, simultaneous measurement of joint angles of lower limbs and stride length was tested with a prototype of wearable sensor system. The system measured the joint angles using the Kalman filter. Signals from the sensor attached on the foot were used in the stride length estimation detecting foot movement automatically. Joint angles of the lower limbs were measured with stable and reasonable accuracy compared to those values measured with optical motion measurement system with healthy subjects. It was expected that the stride length measurement with the wearable sensor system would be practical by realizing more stable measurement accuracy. Sensor attachment position was suggested not to affect significantly measurement of slow and normal speed movements in a test with the rigid body model. Joint angle patterns measured in 10 m walking with a healthy subject were similar to common patterns. High correlation between joint angles at some characteristic points and stride velocity were also found adequately. These results suggested that the wireless wearable inertial sensor system could detect characteristics of gait. PMID:21941531

  3. Stride length-cadence relationship is disrupted in below-knee prosthesis users.

    PubMed

    Howard, Charla; Wallace, Chris; Stokic, Dobrivoje S

    2013-09-01

    The aim of this study was to evaluate the linearity of the relationship between stride length and cadence (STRIDELC) over three self-selected speeds (normal, slow, fast) in below-knee prosthesis users (n=14, 11 men, mean age 43±12 years, mean time since amputation 9.2±6.9 years) in comparison to controls (n=20, 11 men, mean age 43±17 years). The step length-cadence relationship (STEPLC) was also calculated for the prosthetic and intact legs in prosthesis users and compared to the dominant leg of controls. The goodness of linear fit (R2) and slope over 3 speeds were used as outcome measures. Prosthesis users walked significantly slower than controls (slow-fast speed means 82-131 vs. 97-169 cm/s, respectively, ANOVA p<0.0001) due to both lower cadence (42-53 vs. 47-63 strides/min, p<0.0001) and shorter stride length (116-149 vs. 123-161 cm, p<0.0001). The R2 of STRIDELC relationship in below-knee prosthesis users (0.76±0.13) was significantly lower than in controls (0.91±0.03, p<0.001). The R2 values of STEPLC relationship between the prosthetic and intact legs in prosthesis users were correlated (r=0.85, p<0.001) and both (0.67±0.19, 0.58±0.21, respectively) were significantly smaller than in the dominant leg of controls (0.86±0.04, p<0.01). The slopes of STRIDELC and STEPLC were not different. The R2 of 0.84 for STRIDELC best discriminated prosthesis users from controls with high sensitivity (71%) and specificity (95%). The results indicate that coupling between stride/step length and cadence is disturbed in prosthesis users. Upon further investigation, the goodness of linear fit may prove to be useful in assessing prosthetic design, optimizing prosthetic fit, and predicting clinical outcomes. Copyright © 2013 Elsevier B.V. All rights reserved.

  4. Stride rate recommendations for moderate-intensity walking.

    PubMed

    Rowe, David A; Welk, Gregory J; Heil, Dan P; Mahar, Matthew T; Kemble, Charles D; Calabró, M Andrés; Camenisch, Karin

    2011-02-01

    Current physical activity guidelines recommend physical activity of at least moderate intensity to gain health benefits. Previous studies have recommended a moderate-intensity walking cadence of 100 steps per minute for adults, but the influence of height or stride length has not been investigated. the purpose of the current study was to determine the role of height and stride length in moderate-intensity walking cadence in adults. seventy-five adults completed three treadmill walking trials and three overground walking trials at slow, medium, and fast walking speeds while V˙O2 was measured using indirect calorimetry. Five stride length-related variables were also measured. mixed model regression analysis demonstrated that height explained as much variability in walking intensity at a given cadence as did two different measures of leg length and two different stride length tests. the previous general recommendations of 100 steps per minute were supported for use where a simple public health message is needed. Depending on height, moderate-intensity walking cadence can vary by more than 20 steps per minute, from 90 to 113 steps per minute for adults 198 to 152 cm tall, respectively. Height should therefore be taken into consideration for more precise evaluation or prescription of walking cadence in adults to provide health benefits.

  5. Persistent fluctuations in stride intervals under fractal auditory stimulation.

    PubMed

    Marmelat, Vivien; Torre, Kjerstin; Beek, Peter J; Daffertshofer, Andreas

    2014-01-01

    Stride sequences of healthy gait are characterized by persistent long-range correlations, which become anti-persistent in the presence of an isochronous metronome. The latter phenomenon is of particular interest because auditory cueing is generally considered to reduce stride variability and may hence be beneficial for stabilizing gait. Complex systems tend to match their correlation structure when synchronizing. In gait training, can one capitalize on this tendency by using a fractal metronome rather than an isochronous one? We examined whether auditory cues with fractal variations in inter-beat intervals yield similar fractal inter-stride interval variability as isochronous auditory cueing in two complementary experiments. In Experiment 1, participants walked on a treadmill while being paced by either an isochronous or a fractal metronome with different variation strengths between beats in order to test whether participants managed to synchronize with a fractal metronome and to determine the necessary amount of variability for participants to switch from anti-persistent to persistent inter-stride intervals. Participants did synchronize with the metronome despite its fractal randomness. The corresponding coefficient of variation of inter-beat intervals was fixed in Experiment 2, in which participants walked on a treadmill while being paced by non-isochronous metronomes with different scaling exponents. As expected, inter-stride intervals showed persistent correlations similar to self-paced walking only when cueing contained persistent correlations. Our results open up a new window to optimize rhythmic auditory cueing for gait stabilization by integrating fractal fluctuations in the inter-beat intervals.

  6. Persistent Fluctuations in Stride Intervals under Fractal Auditory Stimulation

    PubMed Central

    Marmelat, Vivien; Torre, Kjerstin; Beek, Peter J.; Daffertshofer, Andreas

    2014-01-01

    Stride sequences of healthy gait are characterized by persistent long-range correlations, which become anti-persistent in the presence of an isochronous metronome. The latter phenomenon is of particular interest because auditory cueing is generally considered to reduce stride variability and may hence be beneficial for stabilizing gait. Complex systems tend to match their correlation structure when synchronizing. In gait training, can one capitalize on this tendency by using a fractal metronome rather than an isochronous one? We examined whether auditory cues with fractal variations in inter-beat intervals yield similar fractal inter-stride interval variability as isochronous auditory cueing in two complementary experiments. In Experiment 1, participants walked on a treadmill while being paced by either an isochronous or a fractal metronome with different variation strengths between beats in order to test whether participants managed to synchronize with a fractal metronome and to determine the necessary amount of variability for participants to switch from anti-persistent to persistent inter-stride intervals. Participants did synchronize with the metronome despite its fractal randomness. The corresponding coefficient of variation of inter-beat intervals was fixed in Experiment 2, in which participants walked on a treadmill while being paced by non-isochronous metronomes with different scaling exponents. As expected, inter-stride intervals showed persistent correlations similar to self-paced walking only when cueing contained persistent correlations. Our results open up a new window to optimize rhythmic auditory cueing for gait stabilization by integrating fractal fluctuations in the inter-beat intervals. PMID:24651455

  7. Extraction of Stride Events From Gait Accelerometry During Treadmill Walking

    PubMed Central

    Lowry, Kristin A.; Bellanca, Jennica; Perera, Subashan; Redfern, Mark S.; Brach, Jennifer S.

    2016-01-01

    Objective: evaluating stride events can be valuable for understanding the changes in walking due to aging and neurological diseases. However, creating the time series necessary for this analysis can be cumbersome. In particular, finding heel contact and toe-off events which define the gait cycles accurately are difficult. Method: we proposed a method to extract stride cycle events from tri-axial accelerometry signals. We validated our method via data collected from 14 healthy controls, 10 participants with Parkinson’s disease, and 11 participants with peripheral neuropathy. All participants walked at self-selected comfortable and reduced speeds on a computer-controlled treadmill. Gait accelerometry signals were captured via a tri-axial accelerometer positioned over the L3 segment of the lumbar spine. Motion capture data were also collected and served as the comparison method. Results: our analysis of the accelerometry data showed that the proposed methodology was able to accurately extract heel and toe-contact events from both feet. We used t-tests, analysis of variance (ANOVA) and mixed models to summarize results and make comparisons. Mean gait cycle intervals were the same as those derived from motion capture, and cycle-to-cycle variability measures were within 1.5%. Subject group differences could be similarly identified using measures with the two methods. Conclusions: a simple tri-axial acceleromter accompanied by a signal processing algorithm can be used to capture stride events. Clinical impact: the proposed algorithm enables the assessment of stride events during treadmill walking, and is the first step toward the assessment of stride events using tri-axial accelerometers in real-life settings. PMID:27088063

  8. On the non-linear attachment characteristics of blood to bacterial cellulose/kaolin biomaterials.

    PubMed

    Véliz, Diosángeles Soto; Alam, Catharina; Toivola, Diana M; Toivakka, Martti; Alam, Parvez

    2014-04-01

    In this communication, we report a non-linear variation in the strength of blood attachment to bacterial cellulose/kaolin biomaterials as the fractions of bacterial cellulose to kaolin are increased. The changes observed for attachment strength are elucidated following both experimental and numerical investigations on both the biomaterial and the blood-biomaterial interface. Our research reveals that the non-linear strength of attachment of blood is related to topographical characteristics on the surface of the biomaterial, the maleability of the biomaterial and the intermolecular strength of attraction between clotted blood proteins (fibrinogen) with the cellulose/kaolin components of the biomaterial.

  9. Characteristics of Ultrasonic Linear Motor that Incorporates Two Transducers at an Acute Angle

    NASA Astrophysics Data System (ADS)

    Suzuki, Atsuyuki; Tsunoji, Masaki; Tsujino, Jiromaru

    2013-07-01

    In this study, we have developed an ultrasonic linear motor that incorporates two transducers at an acute angle. The two transducers are used to generate the vertical and horizontal vibration components. The complex vibration is excited using two electrical sources with a phase shift. Ultrasonic motors have unique characteristics such as silent motion and absence of magnetic noise. These characteristics are suitable for use in hospitals and so on. Therefore, we focus on developing actuators for use in a medical bed, specifically a bedsore prevention bed. A study of the vibration characteristics of the motor showed that the resonant frequencies of the transducers were appropriate, although the vibration amplitude of one transducer was less than that of the other. A study of the load characteristics showed that a no-load speed of 267 mm/s and a maximum thrust of 40 N were obtained.

  10. A New Linear Oscillatory Actuator with Variable Characteristics Using Two Sets of Coils

    PubMed Central

    Kitayama, Fumiya; Hirata, Katsuhiro; Niguchi, Noboru; Kobayashi, Masashi

    2016-01-01

    Nowadays, electromagnetic linear oscillatory actuators are used as vibration control devices because of their high controllability. However, there is a problem that thrust and vibration are small at a wide drive frequency range. In order to improve this problem, we propose a new linear oscillatory actuator that can easily change its own characteristics by using two sets of coils. Through finite element analysis, large vibration was observed at 100 Hz in a series connection, and large vibration and high thrust were observed at 70 Hz and 140 Hz in a parallel connection. From these results, we verified that the actuator had two different characteristics due to switchable connections, and could generate high thrust and large vibration by smaller currents at a wide drive frequency range. PMID:26999136

  11. A New Linear Oscillatory Actuator with Variable Characteristics Using Two Sets of Coils.

    PubMed

    Kitayama, Fumiya; Hirata, Katsuhiro; Niguchi, Noboru; Kobayashi, Masashi

    2016-03-15

    Nowadays, electromagnetic linear oscillatory actuators are used as vibration control devices because of their high controllability. However, there is a problem that thrust and vibration are small at a wide drive frequency range. In order to improve this problem, we propose a new linear oscillatory actuator that can easily change its own characteristics by using two sets of coils. Through finite element analysis, large vibration was observed at 100 Hz in a series connection, and large vibration and high thrust were observed at 70 Hz and 140 Hz in a parallel connection. From these results, we verified that the actuator had two different characteristics due to switchable connections, and could generate high thrust and large vibration by smaller currents at a wide drive frequency range.

  12. Evaluation of accuracy of linear regression models in predicting urban stormwater discharge characteristics.

    PubMed

    Madarang, Krish J; Kang, Joo-Hyon

    2014-06-01

    Stormwater runoff has been identified as a source of pollution for the environment, especially for receiving waters. In order to quantify and manage the impacts of stormwater runoff on the environment, predictive models and mathematical models have been developed. Predictive tools such as regression models have been widely used to predict stormwater discharge characteristics. Storm event characteristics, such as antecedent dry days (ADD), have been related to response variables, such as pollutant loads and concentrations. However it has been a controversial issue among many studies to consider ADD as an important variable in predicting stormwater discharge characteristics. In this study, we examined the accuracy of general linear regression models in predicting discharge characteristics of roadway runoff. A total of 17 storm events were monitored in two highway segments, located in Gwangju, Korea. Data from the monitoring were used to calibrate United States Environmental Protection Agency's Storm Water Management Model (SWMM). The calibrated SWMM was simulated for 55 storm events, and the results of total suspended solid (TSS) discharge loads and event mean concentrations (EMC) were extracted. From these data, linear regression models were developed. R(2) and p-values of the regression of ADD for both TSS loads and EMCs were investigated. Results showed that pollutant loads were better predicted than pollutant EMC in the multiple regression models. Regression may not provide the true effect of site-specific characteristics, due to uncertainty in the data.

  13. Effect of Stride Length Variation on Oxygen Uptake during Level and Positive Grade Treadmill Running.

    ERIC Educational Resources Information Center

    Heinert, Larry D.; And Others

    1988-01-01

    Investigation of 16 men's choices and uses of stride lengths during motorized treadmill running found that stride length variations combined with treadmill grade affected maximal oxygen uptake. (Author/CB)

  14. Effect of Stride Length Variation on Oxygen Uptake during Level and Positive Grade Treadmill Running.

    ERIC Educational Resources Information Center

    Heinert, Larry D.; And Others

    1988-01-01

    Investigation of 16 men's choices and uses of stride lengths during motorized treadmill running found that stride length variations combined with treadmill grade affected maximal oxygen uptake. (Author/CB)

  15. Hindlimb muscle anatomical mechanical advantage differs among joints and stride phases in basilisk lizards.

    PubMed

    Bergmann, Philip J; Hare-Drubka, Meredith

    2015-08-01

    The vertebrate musculoskeletal system is composed of skeletal levers powered by muscles. Effective mechanical advantage (EMA) and muscle properties influence organismal performance at various tasks. Anatomical mechanical advantage (AMA) is a proxy for EMA that facilitates the study of preserved specimens when many muscles or many species are of interest. AMA is the quotient of in-lever to out-lever length, and quantifies the force-velocity trade-off of a lever, where high AMAs translate into high force, low velocity levers. We studied AMAs, physiological cross-sectional areas (PCSAs), fiber lengths, and fiber widths for 20 hindlimb muscles of the lizard Basiliscus vittatus, moving the hip, knee, and ankle during both the stance and swing phases of the stride. We tested the hypotheses that muscles moving proximal limb joints, and those active during stance, would have characteristics that maximize force. We also tested whether adults had more force-optimized levers than juveniles to compensate for higher body mass. We found no differences between adults and juveniles, but found differences among joints and between stride phases. AMAs were lowest and PCSAs highest for the knee, and PCSA was higher for stance than swing muscles. Fiber width decreased distally, but did not differ between stride phases. Fiber length of stance muscles decreased distally and was highest for swing muscles of the knee. Our findings show that different muscle and lever characteristics allow the knee to be both force- and velocity-optimized, indicating its important role in locomotion. Copyright © 2015 Elsevier GmbH. All rights reserved.

  16. Stride parameters and hindlimb length in horses fatigued on a treadmill and at an endurance ride.

    PubMed

    Wickler, S J; Greene, H M; Egan, K; Astudillo, A; Dutto, D J; Hoyt, D F

    2006-08-01

    The relationship between fatigue and stride and/or muscle stiffness requires further study. To measure stride parameters in horses undergoing fatigue associated with running at submaximal speeds both on a treadmill and in an endurance ride. Stride frequencies and estimates of hindlimb stiffness would be decreased in fatigued horses. Horses were fatigued using 2 paradigms: run to exhaustion at a treadmill (4.5 m/sec, 6% incline) and finishing an 80 km endurance ride. Videos were digitised before and after fatigue and analysed for stride parameters: hind limb length, stride frequency, time of contact, step length, duty factor and stride length. In fatigued horses, stride durations were 5% longer (P = 0.007) resulting in lower stride frequencies (P = 0.016) and longer stride lengths (P = 0.006). The time of contacts (tc) for stance phase were not different (P = 0.108) nor was duty factor (tc/stride period, P = 0.457). Step length (speed x tc) and hindlimb lengths were also not different (P = 0.104, P = 0.8). For endurance horses, stride data for nonfatigued horses were consistent with data extrapolated to 4.5 m/sec from nonfatigued horses on the treadmill. Endurance horses slowed (P = 0.002) during the race from 4.55 to 4.03 m/sec and stride lengths were shorter. Despite a slower speed, other stride parameters were unchanged. Hindlimb length was shorter in fatigued horses. Horses fatigued on a treadmill and during the natural course of an endurance ride responded differently, biomechanically. On the treadmill, where speed is constrained, stride frequencies decreased and stride lengths increased. During one endurance ride, stride frequencies were the same, although speeds were substantially reduced. Limb length was shorter in fatigued endurance horses. It remains to be determined if these changes in mechanics are advantageous or disadvantageous in terms of energetics or injury. Further examination of endurance rides is also warranted.

  17. Studying the force characteristics of a high temperature superconducting linear synchronous motor

    NASA Astrophysics Data System (ADS)

    Zheng, Luhai; Jin, Jianxun

    2011-08-01

    A single-sided high temperature superconducting (HTS) linear synchronous motor (HTSLSM) with an HTS bulk magnet array as its secondary has been developed. A field-cooled magnetization system has also been developed to obtain the magnet array with alternate magnetic poles. In order to identify the performance and force characteristics of the HTSLSM, an equivalent 3D finite element analysis (FEA) model has been built up to analyze its field distributions and cogging force characteristics, and an experimental system has been constructed to measure its thrust and normal force characteristics. The traits of the thrust and the normal force have been extracted by comprehensive experiments, including the trends versus different exciting currents, different air gap lengths and variable magnetic poles. The analysis and experimental results are fundamental to the electromagnetic optimum design and control scheme evaluation for the HTSLSM.

  18. Changes in timing of muscle contractions and running economy with altered stride pattern during running.

    PubMed

    Connick, Mark J; Li, Francois-Xavier

    2014-01-01

    Large alterations to the preferred running stride decrease running economy, and shorter strides increase leg muscle activity. However, the effect of altered strides on the timing of leg muscle activation is not known. The aim of this study was to evaluate the impact of moderate alterations to the running stride on running economy and the timing of biceps femoris (BF), vastus lateralis (VL) and gastrocnemius (GAST) muscle contractions. The preferred stride pattern for eleven trained male runners was measured prior to a separate visit where participants ran for bouts of 5 min whilst synchronising foot contacts to a metronome signal which was tuned to (1) the preferred stride, and (2) frequencies which related to ± 8% and ± 4% of the preferred stride length. Running economy was measured at each stride pattern along with electromyography and three-dimensional kinematics to estimate onset and offset of muscle contractions for each muscle. Running economy was greatest at the preferred stride length. However, a quadratic fit to the data was optimised at a stride which was 2.9% shorter than preferred. Onset and offset of BF and VL muscle contractions occurred earlier with shorter than preferred strides. We detected no changes to the timing of muscle contractions with longer than preferred strides and no changes to GAST muscle contractions. The results suggest that runners optimise running economy with a stride length that is close to, but shorter than, the preferred stride, and that timing of BF and VL muscle contractions change with shorter than preferred strides. Copyright © 2013 Elsevier B.V. All rights reserved.

  19. An investigation of stride interval stationarity while listening to music or viewing television

    PubMed Central

    Sejdić, Ervin; Jeffery, Rebecca; Kroonenberg, Alanna Vanden; Chau, Tom

    2016-01-01

    In recent years, there has been considerable interest in the effects of auditory and visual distractions on pedestrian ambulation. A fundamental temporal characteristic of ambulation is the temporal fluctuation of the stride interval. In this paper, we investigate the stationarity of stride interval time series when people are exposed to different forms of auditory and visual distractions. An increase in nonstationary behavior may be suggestive of divided attention and more frequent central modulation of locomotion, both of which may have ramifications on pedestrian vigilance and responsiveness to environmental perturbations. One group of fifteen able-bodied (6 females) young adult participants completed a music protocol (overground walking with and without music). A second group of fifteen (7 females) did a television protocol (treadmill walking while watching TV with and without sound). Three walking trials, each 15 minutes in duration, were performed at each participant’s comfortable walking speed, with force sensitive resistors under the heel of each foot. Using the reverse arrangements test, the vast majority of time series were nonstationary, with a time-varying mean as the principal source of nonstationarity. Furthermore, the television trial with sound had the greatest number of nonstationarities followed by overground walking while listening to music. We discuss the possibility that these conditions measurably affect gait dynamics through a subconscious synchronization to external rhythms or a cyclic distraction followed by a period of increased conscious correction of gait timing. Our findings suggest that the regulation of stride timing is particularly susceptible to constant, time-evolving auditory stimuli, but that normal pacing can be restored quickly upon stimulus withdrawal. These kinds of sensory distractions should thus be carefully considered in studies of pedestrian ambulation. PMID:21820194

  20. An investigation of stride interval stationarity while listening to music or viewing television.

    PubMed

    Sejdić, Ervin; Jeffery, Rebecca; Vanden Kroonenberg, Alanna; Chau, Tom

    2012-06-01

    In recent years, there has been considerable interest in the effects of auditory and visual distractions on pedestrian ambulation. A fundamental temporal characteristic of ambulation is the temporal fluctuation of the stride interval. In this paper, we investigate the stationarity of stride interval time series when people are exposed to different forms of auditory and visual distractions. An increase in nonstationary behavior may be suggestive of divided attention and more frequent central modulation of locomotion, both of which may have ramifications on pedestrian vigilance and responsiveness to environmental perturbations. One group of fifteen able-bodied (6 females) young adult participants completed a music protocol (overground walking with and without music). A second group of fifteen (7 females) did a television protocol (treadmill walking while watching TV with and without sound). Three walking trials, each 15min in duration, were performed at each participant's comfortable walking speed, with force sensitive resistors under the heel of each foot. Using the reverse arrangements test, the vast majority of time series were nonstationary, with a time-varying mean as the principal source of nonstationarity. Furthermore, the television trial with sound had the greatest number of nonstationarities followed by overground walking while listening to music. We discuss the possibility that these conditions measurably affect gait dynamics through a subconscious synchronization to external rhythms or a cyclic distraction followed by a period of increased conscious correction of gait timing. Our findings suggest that the regulation of stride timing is particularly susceptible to constant, time-evolving auditory stimuli, but that normal pacing can be restored quickly upon stimulus withdrawal. These kinds of sensory distractions should thus be carefully considered in studies of pedestrian ambulation.

  1. Verifying performance characteristics of quantitative analytical systems: calibration verification, linearity, and analytical measurement range.

    PubMed

    Killeen, Anthony A; Long, Tom; Souers, Rhona; Styer, Patricia; Ventura, Christina B; Klee, George G

    2014-09-01

    Both the regulations in the Clinical Laboratory Improvement Amendments of 1988 (CLIA) and the checklists of the College of American Pathologists (CAP) Laboratory Accreditation Program require clinical laboratories to verify performance characteristics of quantitative test systems. Laboratories must verify performance claims when introducing an unmodified, US Food and Drug Administration-cleared or approved test system, and they must comply with requirements for periodic calibration and calibration verification for existing test systems. They must also periodically verify the analytical measurement range of many quantitative test systems. To provide definitions for many of the terms used in these regulations, to describe a set of basic analyses that laboratories may adapt to demonstrate compliance with both CLIA and the CAP Laboratory Accreditation Program checklists for performing calibration verification and for verifying the analytical measurement range of test systems, to review some of the recommended procedures for establishing performance goals, and to provide data illustrating the performance goals used in some of the CAP's calibration verification and linearity surveys. The CAP's calibration verification and linearity survey programs, the CLIA regulations, the Laboratory Accreditation Program requirements, and published literature were used to meet these objectives. Calibration verification and linearity and analytical measurement range verification should be performed using suitable materials with assessment of results using well-defined evaluation protocols. We describe the CAP's calibration verification and linearity programs that may be used for these purposes.

  2. Simulation of non-linear rf losses derived from characteristic Nb topography

    SciTech Connect

    Reece, Charles E.; Xu, Chen; Kelley, Michael

    2013-09-01

    A simplified model has been developed to simulate non-linear RF losses on Nb surfaces exclusively due to topographical enhancement of surface magnetic fields. If local sharp edges are small enough, at locations where local surface fields exceed Hc, small volumes of material may become normal conducting without thermal leading to quench. These small volumes of normal material yield increases in the effective surface resistance of the Nb. Using topographic data from typical BCP?d and EP?d fine grain niobium surfaces, we have simulated field-dependent losses and found that when extrapolated to resulting cavity performance, these losses correspond well to characteristic BCP/EP high field Q0 performance differences for fine grain Nb. We describe the structure of the model, its limitations, and the effects of this type of non-linear loss contribution on SRF cavities.

  3. Hospital- and patient-related characteristics determining maternity length of stay: a hierarchical linear model approach.

    PubMed

    Leung, K M; Elashoff, R M; Rees, K S; Hasan, M M; Legorreta, A P

    1998-03-01

    The purpose of this study was to identify factors related to pregnancy and childbirth that might be predictive of a patient's length of stay after delivery and to model variations in length of stay. California hospital discharge data on maternity patients (n = 499,912) were analyzed. Hierarchical linear modeling was used to adjust for patient case mix and hospital characteristics and to account for the dependence of outcome variables within hospitals. Substantial variation in length of stay among patients was observed. The variation was mainly attributed to delivery type (vaginal or cesarean section), the patient's clinical risk factors, and severity of complications (if any). Furthermore, hospitals differed significantly in maternity lengths of stay even after adjustment for patient case mix. Developing risk-adjusted models for length of stay is a complex process but is essential for understanding variation. The hierarchical linear model approach described here represents a more efficient and appropriate way of studying interhospital variations than the traditional regression approach.

  4. The linearized characteristics method and its application to practical nonlinear supersonic problems

    NASA Technical Reports Server (NTRS)

    Ferri, Antonio

    1952-01-01

    The methods of characteristics has been linearized by assuming that the flow field can be represented as a basic flow field determined by nonlinearized methods and a linearized superposed flow field that accounts for small changes of boundary conditions. The method has been applied to two-dimensional rotational flow where the basic flow is potential flow and to axially symmetric problems where conical flows have been used as the basic flows. In both cases the method allows the determination of the flow field to be simplified and the numerical work to be reduced to a few calculations. The calculations of axially symmetric flow can be simplified if tabulated values of some coefficients of the conical flow are obtained. The method has also been applied to slender bodies without symmetry and to some three-dimensional wing problems where two-dimensional flow can be used as the basic flow. Both problems were unsolved before in the approximation of nonlinear flow.

  5. Characteristics of the Linear Ultrasonic Motor using an Elliptical Shape Stator

    NASA Astrophysics Data System (ADS)

    Ho, Shine‑Tzong

    2006-07-01

    A prototype linear ultrasonic motor using normal vibration and tangential vibration modes of an elliptical shape stator was fabricated and studied in this research. The composite structure of the stator is formed by two multilayer piezoelectric actuators clamped in an elliptical elastic body. The geometry of the stator has been computed with the help of the finite element analysis. The dimensions of the stator’s structure were determined by making the two resonance frequencies close to each other. Two modes of normal and tangential vibration degenerate at the dimensional ratio of major axis and minor axis diameter equal to about 1.6 for coincidence of two resonance frequencies when the thickness is 6 mm and the width is 3 mm. The construction and some operational characteristics of the linear motor are presented. The maximum moving speed of the prototype was about 180 mm/s when applying 11 Vp driving voltage by using two signal driving method.

  6. Stride frequency and length adjustment in post-stroke individuals: influence on the margins of stability.

    PubMed

    Hak, Laura; Houdijk, Han; van der Wurff, Peter; Prins, Maarten R; Beek, Peter J; van Dieën, Jaap H

    2015-02-01

    To investigate whether post-stroke participants can walk at different combinations of stride frequency and stride length and how these adaptations affect the backward and medio-lateral margins of stability. Computer Assisted Rehabilitation Environment (CAREN). Ten post-stroke individuals. Six trials of 2 min walking on a treadmill at different combinations of stride frequency and stride length. Treadmill speed was set at the corresponding speed, and subjects received visual feedback about the required and actual stride length. Mean stride length and frequency and backward and medio-lateral margins of stability for each trial. Stroke patients were able to adjust step length when required, but had difficulty adjusting step frequency. When a stride frequency higher than self-selected stride frequency was imposed patients additionally needed to increase stride length in order to match the imposed treadmill speed. For trials at a high stride frequency, in particular, the increase in the backward and medio-lateral margins of stability was limited. In conclusion, training post-stroke individuals to increase stride frequency during walking might give them more opportunities to increase the margins of stability and consequently reduce fall risk.

  7. An inferential investigation into how stride length influences temporal parameters within the baseball pitching delivery.

    PubMed

    Crotin, Ryan L; Bhan, Shivam; Ramsey, Dan K

    2015-06-01

    Motion analyses of lower body mechanics offer new schemas to address injury prevention strategies among baseball pitchers, where the influence of stride length remains unknown. This study examined the temporal effect of stride length at constituent pitching events and phases. Nineteen competitive pitchers (15 collegiate, 4 high school) were randomly assigned to pitch two simulated, 80-pitch games at ±25% of their desired stride length. An integrated, three-dimensional motion capture system recorded each pitch. Paired t-tests were used to determine whether differences between stride conditions at respective events and within phases were significantly different. The results demonstrate the shorter strides mediated earlier onset of stride foot contact, reduced time in single support whereas double support intervals increased (p<.001). The opposite was observed with the longer strides. However, the acceleration phase, which comprises the highest throwing arm kinematics and kinetics, remained unchanged. The interaction between stride length, stride foot contact onsets, and time in single support is inferentially evidenced. The equivalent acceleration phases suggest stride length alone influenced time in single and double support by altering the onset of stride foot contact, which perhaps affects the mechanics in preparing the throwing arm for maximal external shoulder rotation.

  8. Linearly Tapered Slot Antenna Radiation Characteristics at Millimeter-Wave Frequencies

    NASA Technical Reports Server (NTRS)

    Simons, Rainee N.; Lee, Richard Q.

    1998-01-01

    An endfire travelling wave antenna, such as, a linearly tapered slot antenna (LTSA) is a viable alternative to a patch antenna at millimeter-wave frequencies because of its simple design and ease of fabrication. This paper presents the radiation characteristics of LTSA at higher millimeter-wave frequencies. The measured radiation patterns are observed to be well behaved and symmetric with the main beam in the endfire direction. The measured gain is about 10 dB. The LTSAs have potential wireless applications at 50 GHz, 77 GHz, and 94 GHz.

  9. Effect of stride frequency on thermoregulatory responses during endurance running in distance runners.

    PubMed

    Amano, Tatsuro; Ishitobi, Masaki; Ogura, Yukio; Inoue, Yoshimitsu; Koga, Shunsaku; Nishiyasu, Takeshi; Kondo, Narihiko

    2016-10-01

    Changing stride frequency may influence oxygen uptake and heart rate during running as a function of running economy and central command. This study investigated the influence of stride frequency manipulation on thermoregulatory responses during endurance running. Seven healthy endurance runners ran on a treadmill at a velocity of 15km/h for 60min in a controlled environmental chamber (ambient temperature 27°C and relative humidity 50%), and stride frequency was manipulated. Stride frequency was intermittently manipulated by increasing and decreasing frequency by 10% from the pre-determined preferred frequency. These periods of increase or decrease were separated by free frequency running in the order of free stride frequency, stride frequency manipulation (increase or decrease), free stride frequency, and stride frequency manipulation (increase or decrease) for 15min each. The increased and decreased stride frequencies were 110% and 91% of the free running frequency, respectively (196±6, 162±5, and 178±5steps/min, respectively, P<0.01). Compared to the control, stride frequency manipulation did not affect rectal temperature, heart rate, or the rate of perceived exhaustion during running. Whole-body sweat loss increased significantly when stride frequency was manipulated (1.48±0.11 and 1.57±0.11kg for control and manipulated stride frequencies, respectively, P<0.05), but stride frequency had a small effect on sweat loss overall (Cohen's d=0.31). A higher mean skin temperature was also observed under mixed frequency conditions compared to that in the control (P<0.05). While the precise mechanisms underlying these changes remain unknown (e.g. running economy or central command), our results suggest that manipulation of stride frequency does not have a large effect on sweat loss or other physiological variables, but does increase mean skin temperature during endurance running.

  10. Non-linear characteristics and long-range correlations in Asian stock markets

    NASA Astrophysics Data System (ADS)

    Jiang, J.; Ma, K.; Cai, X.

    2007-05-01

    We test several non-linear characteristics of Asian stock markets, which indicates the failure of efficient market hypothesis and shows the essence of fractal of the financial markets. In addition, by using the method of detrended fluctuation analysis (DFA) to investigate the long range correlation of the volatility in the stock markets, we find that the crossover phenomena exist in the results of DFA. Further, in the region of small volatility, the scaling behavior is more complicated; in the region of large volatility, the scaling exponent is close to 0.5, which suggests the market is more efficient. All these results may indicate the possibility of characteristic multifractal scaling behaviors of the financial markets.

  11. Dynamic Analysis of Resonance: Bifurcation Characteristics of Non-linear Parametric Systems

    NASA Astrophysics Data System (ADS)

    Hortel, M.; Škuderová, A.; Kratochvíl, C.; Houfek, M.

    The dynamic analysis is an important part of basic research of complex planetary transmission systems with split power flow. The bifurcation characteristics of the resonance courses especially for high-speed weakly and strongly non-linear parametric and in the damping time-heteronymous systems are highly sensitive to their parameters, i.e. to the quality and quantity of their bifurcation features and ambiguities. In the case of mass discretization, their analytical—numerical solution leads to complex integro-differential equations with solving kernels in the form of Green's resolventes and complex simulation models in MATLAB/Simulink. The case of one branch of the planetary transmission system with six degrees of freedom is analysed in terms of internal dynamics in this paper, i.e. the causes of the quantity and quality of resonance bifurcation curves and formation of ambiguity characteristics of relative motion in gear meshes.

  12. Technical characteristics can make the difference in a surgical linear stapler. Or not?

    PubMed

    Giaccaglia, Valentina; Antonelli, Maria Serena; Addario Chieco, Paola; Cocorullo, Gianfranco; Cavallini, Marco; Gulotta, Gaspare

    2015-07-01

    Anastomotic leak (AL) after gastrointestinal surgery is a severe complication associated with relevant short- and long-term sequelae. Most of the anastomosis are currently performed with a surgical stapler that is required to have appropriate characteristics to guarantee good performances. The aim of our study was to evaluate, in the laboratory, pressure resistance and tensile strength of anastomosis performed with different surgical linear staplers, available in the market. We have been studying three linear staplers, with diverse cartridges and staple heights, of three different companies, used for gastrointestinal anastomosis and gastric or intestinal closure. We performed 50 anastomosis for each device, with the pertinent different cartridges, on fresh pig intestine, for a total of 350 anastomosis, then injected saline solution and recorded the pressure that provokes a leak on the staple line. There were no statistically significant differences between the mean pressure necessary to induce an AL in the various instruments (P > 0.05). For studying the tensile strength, we performed a total of 350 anastomosis with the different linear staplers on a special strong paper (Tyvek), then recorded the maximal tensile force that could open the anastomosis. There were no statistically significant differences between the different staplers about the strength necessary to open the staple line (P > 0.05). we demonstrated that different linear staplers of three companies available in the market give comparable anastomotic pressure resistance and tensile strength. This might suggest that small dissimilarities between different devices are not involved, at least as major parameters, in AL etiology. Copyright © 2015 Elsevier Inc. All rights reserved.

  13. Characteristic-based non-linear simulation of large-scale standing-wave thermoacoustic engine.

    PubMed

    Abd El-Rahman, Ahmed I; Abdel-Rahman, Ehab

    2014-08-01

    A few linear theories [Swift, J. Acoust. Soc. Am. 84(4), 1145-1180 (1988); Swift, J. Acoust. Soc. Am. 92(3), 1551-1563 (1992); Olson and Swift, J. Acoust. Soc. Am. 95(3), 1405-1412 (1994)] and numerical models, based on low-Mach number analysis [Worlikar and Knio, J. Comput. Phys. 127(2), 424-451 (1996); Worlikar et al., J. Comput. Phys. 144(2), 199-324 (1996); Hireche et al., Canadian Acoust. 36(3), 164-165 (2008)], describe the flow dynamics of standing-wave thermoacoustic engines, but almost no simulation results are available that enable the prediction of the behavior of practical engines experiencing significant temperature gradient between the stack ends and thus producing large-amplitude oscillations. Here, a one-dimensional non-linear numerical simulation based on the method of characteristics to solve the unsteady compressible Euler equations is reported. Formulation of the governing equations, implementation of the numerical method, and application of the appropriate boundary conditions are presented. The calculation uses explicit time integration along with deduced relationships, expressing the friction coefficient and the Stanton number for oscillating flow inside circular ducts. Helium, a mixture of Helium and Argon, and Neon are used for system operation at mean pressures of 13.8, 9.9, and 7.0 bars, respectively. The self-induced pressure oscillations are accurately captured in the time domain, and then transferred into the frequency domain, distinguishing the pressure signals into fundamental and harmonic responses. The results obtained are compared with reported experimental works [Swift, J. Acoust. Soc. Am. 92(3), 1551-1563 (1992); Olson and Swift, J. Acoust. Soc. Am. 95(3), 1405-1412 (1994)] and the linear theory, showing better agreement with the measured values, particularly in the non-linear regime of the dynamic pressure response.

  14. Effect of aging on the stride pattern of veteran marathon runners.

    PubMed

    Conoboy, P; Dyson, R

    2006-07-01

    To investigate the stride pattern of different age groups of veteran runners in a marathon road race. This kinematic study investigated the stride pattern (stride length, stride period, velocity, stance time, and non-stance time) for 151 runners (78 men aged up to 75-80, 73 women aged up to 60-64) at the 7 mile point. Significant declines for men with aging were found for mean stride length (from 2.4 m at age 40-49 to 2.0 m at age 60+), velocity, and non-stance time (p<0.05), whereas stride period changed little. The findings indicate that the lower velocities of older runners are associated with shorter strides whereas cadence changes little. However, when a statistical adjustment was made for the variation in runners' velocity, it was found that older runners did not have a significantly shorter stride length at any given velocity. Although a shorter stride is the mechanical route by which older runners lose velocity, the shorter stride may not be the fundamental cause of the velocity reduction with age. This has implications for researchers and coaches when investigating and training veteran distance runners.

  15. Determining non-linear characteristics of a concentrating solar collector according to the experiment design

    NASA Astrophysics Data System (ADS)

    Nemś, M.; Kasperski, J.

    2016-09-01

    A linear concentrating solar air collector with internal multiple-fin array was built. The collector was designed as an air heater for the system of house heating with an all-year-round heat accumulation. In order to conduct transient type numerical simulations of the yearlong work cycle of the system, it was necessary to know the working characteristic of the solar collector. To determine the characteristics, some factors for experimental research were selected. The authors decided to conduct experimental research on the basis of fractional 3k factorial design for three factors. A set-up was built and then, a series of experiments were conducted according to the adopted experiment design. A working characteristic in the form of a quadratic polynomial was determined, and a diagram was prepared. The obtained results were then discussed. The obtained research method and the determined formula met the needs of further numerical modelling of the year-long work of the heating system containing the examined solar collector.

  16. Persistent and anti-persistent pattern in stride-to-stride variability of treadmill walking: influence of rhythmic auditory cueing.

    PubMed

    Terrier, Philippe; Dériaz, Olivier

    2012-12-01

    It has been observed that long time series of Stride Time (ST), Stride Length (SL) and Stride Speed (SS=SL/ST) exhibited statistical persistence (long-range auto-correlation) in overground walking. Rhythmic auditory cueing induced anti-persistent (or anti-correlated) patterns in ST series, while SL and SS remained persistent. On the other hand, it has been shown that SS became anti-persistent in treadmill walking, while ST and SL remained persistent. The aim of this study was to analyze the effect of the combination of treadmill walking (imposed speed) and auditory cueing (imposed cadence) on gait dynamics. Twenty middle-aged subjects performed 6×5 min walking trials at various imposed speeds on an instrumented treadmill. Freely chosen walking cadences were measured during the first three trials, and then imposed accordingly in the last three trials by using a metronome. Detrended fluctuation analysis (DFA) was performed on the times series of ST, SL, and SS. Treadmill induced anti-persistent dynamics in the time series of SS, but preserved the persistence of ST and SL. On the contrary, all the three parameters were anti-persistent under dual-constraints condition. Anti-persistent dynamics may be related to a tighter control: deviations are followed by a rapid over-correction, which produces oscillations around target values. Under single constraint condition, while SS is tightly regulated in order to follow the treadmill speed, redundancy between ST and SL would likely allow persistent pattern to occur. Conversely, under dual constraint conditions, the absence of redundancy among SL, ST and SS would explain the generalized anti-persistent pattern. Copyright © 2012 Elsevier B.V. All rights reserved.

  17. Characteristics of an 18 MV photon beam from a Therac 20 Medical Linear Accelerator

    SciTech Connect

    Patterson, M.S.; Shragge, P.C.

    1981-05-01

    The 18 MV photon beam characteristics of a Therac 20 Medical Linear Accelerator manufactured by Atomic Energy of Canada Ltd, are presented. Tissue phantom ratios (TPR's) and percent depth dose data are given; for a 10 x 10 cm field, the percent depth dose at a depth of 10 cm is 78.5 (SSD 100 cm). The relative dose factors (RDF'S) are given and are analyzed to elucidate the relative contributions from phantom scatter, collimator scatter, and backscatter from the top of the collimators into the monitor chambers. The effect of field size and depth on the penumbra is described. Crossplots of the beam at a depth of 5 cm indicate that the flattening filter could be improved; there are hot spots of 108% near the corners of 40 x 40 fields.

  18. Characteristics of an 18 MV photon beam from a Therac 20 Medical Linear Accelerator.

    PubMed

    Patterson, M S; Shragge, P C

    1981-01-01

    The 18 MV photon beam characteristics of a Therac 20 Medical Linear Accelerator manufactured by Atomic Energy of Canada Ltd, are presented. Tissue phantom ratios (TRP's) and percent depth dose data are given; for a 10 x 10 cm field, the percent depth dose at a depth of 10 cm is 78.5 (SSD 100 cm). The relative dose factors (RDF'S) are given and are analyzed to elucidate the relative contributions from phantom scatter, collimator scatter, and backscatter from the top of the collimators into the monitor chambers. The effect of field size and depth on the penumbra is described. Crossplots of the beam at a depth of 5 cm indicate that the flattening filter could be improved; there are hot spots of 108% near the corners of 40 x 40 fields.

  19. A seal test facility for the measurement of isotropic and anisotropic linear rotordynamic characteristics

    NASA Technical Reports Server (NTRS)

    Adams, M. L.; Yang, T.; Pace, S. E.

    1989-01-01

    A new seal test facility for measuring high-pressure seal rotor-dynamic characteristics has recently been made operational at Case Western Reserve University (CWRU). This work is being sponsored by the Electric Power Research Institute (EPRI). The fundamental concept embodied in this test apparatus is a double-spool-shaft spindle which permits independent control over the spin speed and the frequency of an adjustable circular vibration orbit for both forward and backward whirl. Also, the static eccentricity between the rotating and non-rotating test seal parts is easily adjustable to desired values. By accurately measuring both dynamic radial displacement and dynamic radial force signals, over a wide range of circular orbit frequency, one is able to solve for the full linear-anisotropic model's 12 coefficients rather than the 6 coefficients of the more restrictive isotropic linear model. Of course, one may also impose the isotropic assumption in reducing test data, thereby providing a valid qualification of which seal configurations are well represented by the isotropic model and which are not. In fact, as argued in reference (1), the requirement for maintaining a symmetric total system mass matrix means that the resulting isotropic model needs 5 coefficients and the anisotropic model needs 11 coefficients.

  20. Hospital- and patient-related characteristics determining maternity length of stay: a hierarchical linear model approach.

    PubMed Central

    Leung, K M; Elashoff, R M; Rees, K S; Hasan, M M; Legorreta, A P

    1998-01-01

    OBJECTIVES: The purpose of this study was to identify factors related to pregnancy and childbirth that might be predictive of a patient's length of stay after delivery and to model variations in length of stay. METHODS: California hospital discharge data on maternity patients (n = 499,912) were analyzed. Hierarchical linear modeling was used to adjust for patient case mix and hospital characteristics and to account for the dependence of outcome variables within hospitals. RESULTS: Substantial variation in length of stay among patients was observed. The variation was mainly attributed to delivery type (vaginal or cesarean section), the patient's clinical risk factors, and severity of complications (if any). Furthermore, hospitals differed significantly in maternity lengths of stay even after adjustment for patient case mix. CONCLUSIONS: Developing risk-adjusted models for length of stay is a complex process but is essential for understanding variation. The hierarchical linear model approach described here represents a more efficient and appropriate way of studying interhospital variations than the traditional regression approach. PMID:9518967

  1. Irradiation of intense characteristic x-rays from weakly ionized linear molybdenum plasma.

    PubMed

    Sato, Eiichi; Hayasi, Yasuomi; Germer, Rudolf; Tanaka, Etsuro; Mori, Hidezo; Kawai, Toshiaki; Obara, Haruo; Ichimaru, Toshio; Takayama, Kazuyoshi; Ido, Hideaki

    2003-01-01

    In the plasma flash x-ray generator, a high-voltage main condenser of approximately 200 nF is charged up to 55 kV by a power supply, and electric charges in the condenser are discharged to an x-ray tube after triggering the cathode electrode. The flash x-rays are then produced. The x-ray tube is a demountable triode that is connected to a turbo molecular pump with a pressure of approximately 1 mPa. As electron flows from the cathode electrode are roughly converged to a rod molybdenum target of 2.0 mm in diameter by the electric field in the x-ray tube, weakly ionized linear plasma, which consists of molybdenum ions and electrons, forms by target evaporation. At a charging voltage of 55 kV, the maximum tube voltage was almost equal to the charging voltage of the main condenser, and the peak current was about 20 kA. When the charging voltage was increased, the linear plasma formed, and the K-series characteristic x-ray intensities increased. The K lines were quite sharp and intense, and hardly any bremsstrahlung rays were detected. The x-ray pulse widths were approximately 700 ns, and the time-integrated x-ray intensity had a value of approximately 35 micro C/kg at 1.0 m from the x-ray source with a charging voltage of 50 kV.

  2. Characteristics of a dedicated linear accelerator-based stereotactic radiosurgery-radiotherapy unit.

    PubMed

    Das, I J; Downes, M B; Corn, B W; Curran, W J; Werner-Wasik, M; Andrews, D W

    1996-01-01

    A stereotactic radiosurgery and radiotherapy (SRS/SRT) system on a dedicated Varian Clinac-600SR linear accelerator with Brown-Roberts-Wells and Gill-Thomas-Cosman relocatable frames along with the Radionics (RSA) planning system is evaluated. The Clinac-600SR has a single 6-MV beam with the same beam characteristics as that of the mother unit, the Clinac-600C. The primary collimator is a fixed cone projecting to a 10-cm diameter at isocenter. The secondary collimator is a heavily shielded cylindrical collimator attached to the face plate of the primary collimator. The tertiary collimation consists of the actual treatment cones. The cone sizes vary from 12.5 to 40.0 mm diameter. The mechanical stability of the entire system was verified. The variations in isocenter position with table, gantry, and collimator rotation were found to be < 0.5 mm with a compounded accuracy of < or = 1.0 mm. The radiation leakage under the cones was < 1% measured at a depth of 5 cm in a phantom. The beam profiles of all cones in the x and y directions were within +/- 0.5 mm and match with the physical size of the cone. The dosimetric data such as tissue maximum ratio, off-axis ratio, and cone factor were taken using film, diamond detector, and ion chambers. The mechanical and dosimetric characteristics including dose linearity of this unit are presented and found to be suitable for SRS/SRT. The difficulty in absolute dose measurement for small cone is discussed.

  3. Hybrid discrete ordinates and characteristics method for solving the linear Boltzmann equation

    NASA Astrophysics Data System (ADS)

    Yi, Ce

    With the ability of computer hardware and software increasing rapidly, deterministic methods to solve the linear Boltzmann equation (LBE) have attracted some attention for computational applications in both the nuclear engineering and medical physics fields. Among various deterministic methods, the discrete ordinates method (SN) and the method of characteristics (MOC) are two of the most widely used methods. The SN method is the traditional approach to solve the LBE for its stability and efficiency. While the MOC has some advantages in treating complicated geometries. However, in 3-D problems requiring a dense discretization grid in phase space (i.e., a large number of spatial meshes, directions, or energy groups), both methods could suffer from the need for large amounts of memory and computation time. In our study, we developed a new hybrid algorithm by combing the two methods into one code, TITAN. The hybrid approach is specifically designed for application to problems containing low scattering regions. A new serial 3-D time-independent transport code has been developed. Under the hybrid approach, the preferred method can be applied in different regions (blocks) within the same problem model. Since the characteristics method is numerically more efficient in low scattering media, the hybrid approach uses a block-oriented characteristics solver in low scattering regions, and a block-oriented SN solver in the remainder of the physical model. In the TITAN code, a physical problem model is divided into a number of coarse meshes (blocks) in Cartesian geometry. Either the characteristics solver or the SN solver can be chosen to solve the LBE within a coarse mesh. A coarse mesh can be filled with fine meshes or characteristic rays depending on the solver assigned to the coarse mesh. Furthermore, with its object-oriented programming paradigm and layered code structure, TITAN allows different individual spatial meshing schemes and angular quadrature sets for each coarse

  4. Stride angle as a novel indicator of running economy in well-trained runners.

    PubMed

    Santos-Concejero, Jordan; Tam, Nicholas; Granados, Cristina; Irazusta, Jon; Bidaurrazaga-Letona, Iraia; Zabala-Lili, Jon; Gil, Susana M

    2014-07-01

    The main purpose of this study was to investigate the relationship between a novel biomechanical variable, the stride angle, and running economy (RE) in a homogeneous group of long-distance athletes. Twenty-five well-trained male runners completed 4-minute running stages on a treadmill at different set velocities. During the test, biomechanical variables such as stride angle, swing time, ground contact time, stride length, stride frequency, and the different sub-phases of ground contact were recorded using an optical measurement system. VO2 values at velocities below the lactate threshold were measured to calculate RE. Stride angle was negatively correlated with RE at every speed (p < 0.001, large effect sizes). Running economy was also negatively correlated with swing phase and positively correlated with ground contact time and running performance according to the best 10-km race time (p ≤ 0.05, moderate and large effect sizes). Last, stride angle was correlated with ground contact time at every speed (p < 0.001, large effect sizes). In conclusion, it seems that optimal execution of stride angle allows runners to minimize contact time during ground contact, whereby facilitating a better RE. Coaches and/or athletes may find stride angle a useful and easily obtainable measure to track and make alterations to running technique, because changes in stride angle may influence the energy cost of running and lead to improved performance.

  5. The effect of stride length on the dynamics of barefoot and shod running.

    PubMed

    Thompson, M A; Gutmann, A; Seegmiller, J; McGowan, C P

    2014-08-22

    A number of interventions and technique changes have been proposed to attempt to improve performance and reduce the number of running related injuries. Running shoes, barefoot running and alterations in spatio-temporal parameters (stride frequency and stride length) have been associated with significant kinematic and kinetic changes, which may have implications for performance and injury prevention. However, because footwear interventions have been shown to also affect spatio-temporal parameters, there is uncertainty regarding the origin of the kinematic and kinetic alterations. Therefore, the purpose of this study was to independently evaluate the effects of shoes and changes in stride length on lower extremity kinetics. Eleven individuals ran over-ground at stride lengths ± 5 and 10% of their preferred stride length, in both the barefoot and shod condition. Three-dimensional motion capture and force plate data were captured synchronously and used to compute lower extremity joint moments. We found a significant main effect of stride length on anterior-posterior and vertical GRFs, and sagittal plane knee and ankle moments in both barefoot and shod running. When subjects ran at identical stride lengths in the barefoot and shod conditions we did not observe differences for any of the kinetic variables that were measured. These findings suggest that barefoot running triggers a decrease in stride length, which could lead to a decrease in GRFs and sagittal plane joint moments. When evaluating barefoot running as a potential option to reduce injury, it is important to consider the associated change in stride length.

  6. Linear temporal characteristics of heart interbeat interval as an index of the pilot's perceived risk.

    PubMed

    Sharma, S

    2006-07-15

    The concept of adaptive automation is the first commendable step towards machine monitoring and support of the human operator behaviour and performance. Despite a large number of studies, the concept is still not sufficiently mature and more experimental studies are required to enable its application in the real world. As a small contribution in this direction, this experimental study made an effort to develop some techniques for online assessment of the pilot's perceived risk of the consequences resulting from their inability to execute a task adequately. Linear dynamical characteristics of 60 pilot's heart interbeat intervals were used for the assessment. Past research has shown that such 'perceived risk' influences the pilot's need for an automation aid. The preliminary results of this study suggested that the frequency and power of the heart interbeat interval dominant cycle, together with the characteristics of the energy contained in the power spectrum, can be sensitive indices of the level of perceived risk. The study techniques and preliminary results appear promising for incorporation into the algorithm of an intelligent online monitoring and alerting system on future aerospace vehicles to define the moments when the human supervisory controllers require an automation aid.

  7. Split-Cell, Linear Characteristic Transport Method for Unstructured Tetrahedral Meshes

    SciTech Connect

    Mathews, Kirk A.; Miller, Rodney L.; Brennan, Charles R.

    2000-10-15

    The linear characteristic (LC) method is extended to unstructured meshes of tetrahedral cells in three-dimensional Cartesian coordinates. For each ordinate in a discrete ordinates sweep, each cell is split into subcells along a line parallel to the ordinate. Direct affine transformations among appropriate oblique Cartesian coordinate systems for the faces and interior of each cell and subcell are used to simplify the characteristic transport through each subcell. This approach is straightforward and eliminates computationally expensive trigonometric functions. An efficient and well-conditioned technique for evaluating the required integral moments of exponential functions is presented. Various test problems are used to demonstrate (a) the approach to cubic convergence as the mesh is refined, (b) insensitivity to the details of irregular meshes, and (c) numerical robustness. These tests also show that meshes should represent volumes of regions with curved as well as planar boundaries exactly and that cells should have optical thicknesses throughout the mesh that are more or less equal. A hybrid Monte Carlo/discrete ordinates method, together with MCNP, is used to distinguish between error introduced by the angular and the spatial quadratures. We conclude that the LC method should be a practical and reliable scheme for these meshes, presuming that the cells are not optically too thick.

  8. Dynamic modeling and characteristics analysis of a modal-independent linear ultrasonic motor.

    PubMed

    Li, Xiang; Yao, Zhiyuan; Zhou, Shengli; Lv, Qibao; Liu, Zhen

    2016-12-01

    In this paper, an integrated model is developed to analyze the fundamental characteristics of a modal-independent linear ultrasonic motor with double piezoelectric vibrators. The energy method is used to model the dynamics of the two piezoelectric vibrators. The interface forces are coupled into the dynamic equations of the two vibrators and the moving platform, forming a whole machine model of the motor. The behavior of the force transmission of the motor is analyzed via the resulting model to understand the drive mechanism. In particular, the relative contact length is proposed to describe the intermittent contact characteristic between the stator and the mover, and its role in evaluating motor performance is discussed. The relations between the output speed and various inputs to the motor and the start-stop transients of the motor are analyzed by numerical simulations, which are validated by experiments. Furthermore, the dead-zone behavior is predicted and clarified analytically using the proposed model, which is also observed in experiments. These results are useful for designing servo control scheme for the motor.

  9. Analysis of HIV medication adherence in relation to person and treatment characteristics using hierarchical linear modeling.

    PubMed

    Halkitis, Perry; Palamar, Joseph; Mukherjee, Preetika

    2008-04-01

    The purpose of this investigation was to consider person characteristics, treatment level variables, and illicit drug use to help explain the HIV antiviral adherence patterns of a community-based, non-drug-treatment-seeking sample of men who have sex with men (MSM). Adherence data were gathered for 300 MSM eight times over the course of 1 year using electronic monitoring. Treatment and person level characteristics were assessed at baseline assessment using computer-administered surveys, and drug usage was established via a diagnostic inventory. These longitudinal data were analyzed via Hierarchical Linear Modeling. The sample was diverse in terms of age and race/ethnicity. Across the span of the year in which the participants were assessed, adherence rates were relatively stable and high (means: 82% to 90%) at each time point and remained relatively stable across the yearlong investigation. Lower adherence rates were evident among those who were drug users, black identified (in terms of race), older, and by pill burden. Individuals on HIV antiretroviral therapy demonstrated consistent although not optimal adherence rates when assessed during the course of a year. The significance of numerous person level factors such as age, race, and drug use suggest that adherence to treatment may in part be impacted by the circumstances that the individual brings to the treatment behavior, and suggests interventions that delve beyond the behavioral to consider and address life social and intrapersonal circumstances that may interfere with adherence behaviors.

  10. Measurement of Drive Characteristics of Linear Induction Motor with Experimental Equipment Implemented Disc-shaped Secondary Side

    NASA Astrophysics Data System (ADS)

    Morizane, Toshimitsu; Kimura, Noriyuki

    The ordinary experimental equipment has a long stroke or a large cylindrical rotating secondary side in order to measure the drive characteristics of Linear Induction Motor (LIM). In this paper, we propose the measurement method of the drive characteristics of LIM with the experimental equipment implemented a disc-shaped secondary side. This method makes the experimental equipment smaller in size. It has been shown that the drive characteristics of LIM can be successfully measured.

  11. Hierarchical linear modeling of FIM instrument growth curve characteristics after spinal cord injury.

    PubMed

    Warschausky, S; Kay, J B; Kewman, D G

    2001-03-01

    To examine the recovery of aspects of functional independence as a continuous process using growth curve analysis. Retrospective database review of functional outcome assessment data from inception cohort. Inpatient rehabilitation unit; community. A total of 142 subjects (79.6% men; age range, 18-77yr; mean age +/- standard deviation, 36.2 +/- 15.5yr) who were admitted to a rehabilitation unit between March 1986 and November 1994 with a minimum of 4 postinjury FIM assessments. Neurologic subgroups included 63 individuals with paraplegia, 36 with low tetraplegia, 24 with high tetraplegia, and 19 with incomplete injury. FIM instrument. Growth curve analyses with hierarchical linear modeling using a decelerating recovery function yielded a reliable model in which longer rehabilitation length of stay was associated with a more rapid rate of recovery but lower plateau. Neurologic injury category had expected effects on rate and degree of recovery. Level of impairment-specific results included an age effect in which older age was associated with lower level of plateau. In specific neurologic groups there was a significant gender effect, in which men made more rapid recovery than women, and a significant effect of level of education, in which higher education was associated with more rapid rate of recovery. Rate of FIM recovery was reliably modeled in the sample with incomplete injuries, but none of the demographic predictors was significant. Functional recovery can be modeled as a decelerating rather than simple linear function. The study of predictors of recovery characteristics, including rate of recovery and plateau, offers a valuable way of understanding rehabilitative needs and outcomes. Gender and education effects on the recovery process are intriguing and warrant further investigation.

  12. Youth Baseball Pitching Stride Length: Normal Values and Correlation With Field Testing.

    PubMed

    Fry, Karl E; Pipkin, Andrew; Wittman, Kelcie; Hetzel, Scott; Sherry, Marc

    Pitching biomechanical analysis has been recommended as an important component of performance, injury prevention, and rehabilitation. Normal values for youth pitching stride length have not been established, leading to application of normative values found among professional pitchers to youth pitchers. The average youth pitching stride length will be significantly less than that of college and professional pitchers. There will be a positive correlation between stride length, lower extremity power, balance, and pitching experience. Prospective cohort study. Level 3. Ninety-two youth baseball pitchers (aged 9-14 years) met the inclusion/exclusion criteria and completed the study. Stride length was recorded using a Dartfish video system over 3 maximal effort pitches. Both intra- and interrater reliability was calculated for the assessment of stride length. Double-leg vertical jump, single-leg stance time, leg length, weight, age, and pitching experience were also recorded. Mean (SD) stride length was 66.0% (7.1%) of height. Stride length was correlated ( P < 0.01) with vertical jump (0.38), pitching experience (0.36), and single-leg balance (0.28), with excellent intra- and interrater reliability (0.985 or higher). No significant correlations between stride length and body weight, leg length, or age existed. There was a significant difference between youth pitching stride length and the current published norms for older and more elite throwers. There was a positive correlation between stride length and lower extremity power, pitching experience, and single-leg balance. Two-dimensional analysis of stride length allows for the assessment of pitching biomechanics in a practical manner. These values can be used for return to pitching parameters after an injury and designing injury prevention and performance programs.

  13. Development and initial operating characteristics of the 20 megawatt linear plasma accelerator facility

    NASA Technical Reports Server (NTRS)

    Carter, A. F.; Weaver, W. R.; Mcfarland, D. R.; Wood, G. P.

    1971-01-01

    A 20-megawatt linear plasma accelerator facility, a steady flow, Faraday-type plasma accelerator facility for high velocity aerodynamic testing, was constructed, developed, and brought to an operational status. The accelerator has a 63.5-mm-square and 0.5-meter-long channel and utilizes nitrogen-seeded with 2 % mole fraction of cesium vapor. Modification of the original accelerator design characteristics and the improvements necessary to make the arc heater a suitable plasma source are described. The measured accelerator electrode current distribution and the electrode-wall potential distributions are given. The computed and the measured values are in good agreement. Measured pitot pressure indicates that an accelerator exit velocity of 9.2 km/sec, is obtained with 30 of the 36 electrode pairs powered and corresponds to a velocity increase to about 2 1/4 times the computed entrance velocity. The computed stagnation enthalpy at the accelerator exit is 92 MJ/kg, and the mass density corresponds to an altitude of about 58 km. The 92 MJ/kg stagnation enthalpy corresponds to a kinetic energy content at low temperature equivalent to a velocity of 13.6 km/sec.

  14. Amide-I characteristics of helical β-peptides by linear infrared measurement and computations.

    PubMed

    Zhao, Juan; Shi, Jipei; Wang, Jianping

    2014-01-09

    In this work, we have examined the amide-I characteristics of three β-peptide oligomers in typical helical conformations (two in 14-helix and one in 12/10-helix), solvated in water, methanol, and chloroform, respectively. Local-mode frequencies and their distributions were computed using a molecular-mechanics force field based frequency map that was constructed on the basis of molecular dynamics simulations. The local-mode frequencies were found to be determined primarily by peptide backbone and side chain, rather by solvent, suggesting their local structural sensitivities. Intermode vibrational couplings computed using a transition dipole scheme were found to be very sensitive to peptide conformation, with their signs and magnitudes varying periodically along the peptide chain. Linear infrared absorption spectra of the three peptides, simulated using a frequency-frequency time-correlation function method, were found to be in fair agreement with experimental results. Normalized potential energy distribution analysis indicated that the amide-I mode can delocalize over a few amide units. However, the IR band structure appears to be more sophisticated in helical β-peptides than in helical α-peptides.

  15. Assisted early mobility for hospitalized older veterans: preliminary data from the STRIDE program.

    PubMed

    Hastings, S Nicole; Sloane, Richard; Morey, Miriam C; Pavon, Juliessa M; Hoenig, Helen

    2014-11-01

    An important contributor to hospital-associated disability is immobility during hospitalization. Preliminary results from STRIDE, a clinical demonstration program of supervised walking for older adults admitted to the hospital with medical illness, are reported. The STRIDE program consisted of a targeted gait and balance assessment by a physical therapist, followed by daily walks supervised by a recreation therapy assistant for the duration of the hospital stay. To examine program effectiveness, STRIDE participants (n = 92) were compared with individuals referred but not enrolled (because of refusal or because program was at capacity, n = 35). Median length of stay was 4.7 days for STRIDE participants and 5.7 days for individuals receiving usual care (P = .31). There was one inpatient fall in each group (not associated with a STRIDE walk). Overall, 92% of STRIDE participants were discharged to home (rather than a skilled nursing facility (SNF)) compared to 74% of individuals receiving usual care (P = .007). Thirty-day emergency department visit rates and readmission rates were not significantly different between the two groups. STRIDE, a supervised walking program for hospitalized older adults, was feasible and safe, and program participants were less likely to be discharged to a SNF than a demographically similar comparison group. STRIDE is a promising interdisciplinary approach to promoting mobility and improving outcomes in hospitalized older adults. © 2014, Copyright the Authors Journal compilation © 2014, The American Geriatrics Society.

  16. Dynamic Characteristics Analysis of a Small-Sized Linear Oscillatory Actuator Employing the 3-D Finite Element Method

    NASA Astrophysics Data System (ADS)

    Shoji, Noritaka; Hirata, Katsuhiro; Ueyama, Kenji; Hashimoto, Eiichiro; Takagi, Takahiro

    Recently, linear oscillatory actuators have been used in a wide range of applications because of their advantages, such as high efficiency, simple structure, and easy control. Small linear oscillatory actuators are expected to be used in haptic devices and the vibration system of mobile phones. In this paper, we propose a new structure of a small linear oscillatory actuator. The static and dynamic characteristics of the actuator are calculated by the 3-D finite element method. The effectiveness of this method is shown by the comparison of the calculated results with the experimental results.

  17. Tracking Performance Changes With Running-Stride Variability When Athletes Are Functionally Overreached.

    PubMed

    Fuller, Joel T; Bellenger, Clint R; Thewlis, Dominic; Arnold, John; Thomson, Rebecca L; Tsiros, Margarita D; Robertson, Eileen Y; Buckley, Jonathan D

    2017-03-01

    Stride-to-stride fluctuations in running-stride interval display long-range correlations that break down in the presence of fatigue accumulated during an exhaustive run. The purpose of the study was to investigate whether long-range correlations in running-stride interval were reduced by fatigue accumulated during prolonged exposure to a high training load (functional overreaching) and were associated with decrements in performance caused by functional overreaching. Ten trained male runners completed 7 d of light training (LT7), 14 d of heavy training (HT14) designed to induce a state of functional overreaching, and 10 d of light training (LT10) in a fixed order. Running-stride intervals and 5-km time-trial (5TT) performance were assessed after each training phase. The strength of long-range correlations in running-stride interval was assessed at 3 speeds (8, 10.5, and 13 km/h) using detrended fluctuation analysis. Relative to performance post-LT7, time to complete the 5TT was increased after HT14 (+18 s; P < .05) and decreased after LT10 (-20 s; P = .03), but stride-interval long-range correlations remained unchanged at HT14 and LT10 (P > .50). Changes in stride-interval long-range correlations measured at a 10.5-km/h running speed were negatively associated with changes in 5TT performance (r -.46; P = .03). Runners who were most affected by the prolonged exposure to high training load (as evidenced by greater reductions in 5TT performance) experienced the greatest reductions in stride-interval long-range correlations. Measurement of stride-interval long-range correlations may be useful for monitoring the effect of high training loads on athlete performance.

  18. Theoretical and experimental investigations on the dynamic and thermodynamic characteristics of the linear compressor for the pulse tube cryocooler

    NASA Astrophysics Data System (ADS)

    Zhang, L.; Dang, H. Z.; Tan, J.; Bao, D.; Zhao, Y. B.; Qian, G. Z.

    2015-12-01

    Theoretical and experimental investigations on the dynamic and thermodynamic characteristics of a linear compressor incorporating the thermodynamic characteristics of the inertance tube pulse tube cold finger have been made. Both the compressor and cold finger are assumed as a one-dimensional thermodynamic model. The governing equations of the thermodynamic characteristics of the working gas are summarized, and the effects of the cooling performance on the working gas in the compression space are discussed. Based on the analysis of the working gas, the governing equations of the dynamic and thermodynamic characteristics of the compressor are deduced, and then the principles of achieving the optimal performance of the compressor are discussed in detail. Systematic experimental investigations are conducted on a developed moving-coil linear compressor which drives a pulse tube cold finger, which indicate the general agreement with the simulated results, and thus verify the rationality of the theoretical model and analyses.

  19. Self-optimization of Stride Length Among Experienced and Inexperienced Runners

    PubMed Central

    HUNTER, IAIN; LEE, KELLY; WARD, JARED; TRACY, JAMES

    2017-01-01

    Experienced runners appear to naturally select a stride length which is optimal for minimizing oxygen uptake. However, whether this ability is naturally built into the human body or whether it is learned through experience has not been previously tested. This study investigated whether inexperienced runners are as capable as experienced runners of self-optimizing stride length to minimize oxygen uptake. Thirty-three subjects (nineteen experienced and fourteen inexperienced) ran for twenty-minutes while preferred and economical stride lengths were measured. A t-test checked for differences between the experienced and inexperienced groups in the percent increase of oxygen uptake due to not running at the most economical stride length. No difference was found between groups with the increase in oxygen uptake due to not being optimized (p=0.47). The average percent increase in oxygen uptake above the most economical for inexperienced and experienced runners was 1.8% and 1.2% respectively. We concluded that inexperienced and experienced runners are equally capable of matching preferred stride length to economical stride length, thus athletes and coaches do not need to alter runner’s stride length when economy is the main concern. PMID:28515840

  20. Self-optimization of Stride Length Among Experienced and Inexperienced Runners.

    PubMed

    Hunter, Iain; Lee, Kelly; Ward, Jared; Tracy, James

    2017-01-01

    Experienced runners appear to naturally select a stride length which is optimal for minimizing oxygen uptake. However, whether this ability is naturally built into the human body or whether it is learned through experience has not been previously tested. This study investigated whether inexperienced runners are as capable as experienced runners of self-optimizing stride length to minimize oxygen uptake. Thirty-three subjects (nineteen experienced and fourteen inexperienced) ran for twenty-minutes while preferred and economical stride lengths were measured. A t-test checked for differences between the experienced and inexperienced groups in the percent increase of oxygen uptake due to not running at the most economical stride length. No difference was found between groups with the increase in oxygen uptake due to not being optimized (p=0.47). The average percent increase in oxygen uptake above the most economical for inexperienced and experienced runners was 1.8% and 1.2% respectively. We concluded that inexperienced and experienced runners are equally capable of matching preferred stride length to economical stride length, thus athletes and coaches do not need to alter runner's stride length when economy is the main concern.

  1. Stride search: A general algorithm for storm detection in high-resolution climate data

    DOE PAGES

    Bosler, Peter A.; Roesler, Erika L.; Taylor, Mark A.; ...

    2016-04-13

    This study discusses the problem of identifying extreme climate events such as intense storms within large climate data sets. The basic storm detection algorithm is reviewed, which splits the problem into two parts: a spatial search followed by a temporal correlation problem. Two specific implementations of the spatial search algorithm are compared: the commonly used grid point search algorithm is reviewed, and a new algorithm called Stride Search is introduced. The Stride Search algorithm is defined independently of the spatial discretization associated with a particular data set. Results from the two algorithms are compared for the application of tropical cyclonemore » detection, and shown to produce similar results for the same set of storm identification criteria. Differences between the two algorithms arise for some storms due to their different definition of search regions in physical space. The physical space associated with each Stride Search region is constant, regardless of data resolution or latitude, and Stride Search is therefore capable of searching all regions of the globe in the same manner. Stride Search's ability to search high latitudes is demonstrated for the case of polar low detection. Wall clock time required for Stride Search is shown to be smaller than a grid point search of the same data, and the relative speed up associated with Stride Search increases as resolution increases.« less

  2. Stride Search: a general algorithm for storm detection in high-resolution climate data

    NASA Astrophysics Data System (ADS)

    Bosler, Peter A.; Roesler, Erika L.; Taylor, Mark A.; Mundt, Miranda R.

    2016-04-01

    This article discusses the problem of identifying extreme climate events such as intense storms within large climate data sets. The basic storm detection algorithm is reviewed, which splits the problem into two parts: a spatial search followed by a temporal correlation problem. Two specific implementations of the spatial search algorithm are compared: the commonly used grid point search algorithm is reviewed, and a new algorithm called Stride Search is introduced. The Stride Search algorithm is defined independently of the spatial discretization associated with a particular data set. Results from the two algorithms are compared for the application of tropical cyclone detection, and shown to produce similar results for the same set of storm identification criteria. Differences between the two algorithms arise for some storms due to their different definition of search regions in physical space. The physical space associated with each Stride Search region is constant, regardless of data resolution or latitude, and Stride Search is therefore capable of searching all regions of the globe in the same manner. Stride Search's ability to search high latitudes is demonstrated for the case of polar low detection. Wall clock time required for Stride Search is shown to be smaller than a grid point search of the same data, and the relative speed up associated with Stride Search increases as resolution increases.

  3. Stride search: A general algorithm for storm detection in high-resolution climate data

    SciTech Connect

    Bosler, Peter A.; Roesler, Erika L.; Taylor, Mark A.; Mundt, Miranda R.

    2016-04-13

    This study discusses the problem of identifying extreme climate events such as intense storms within large climate data sets. The basic storm detection algorithm is reviewed, which splits the problem into two parts: a spatial search followed by a temporal correlation problem. Two specific implementations of the spatial search algorithm are compared: the commonly used grid point search algorithm is reviewed, and a new algorithm called Stride Search is introduced. The Stride Search algorithm is defined independently of the spatial discretization associated with a particular data set. Results from the two algorithms are compared for the application of tropical cyclone detection, and shown to produce similar results for the same set of storm identification criteria. Differences between the two algorithms arise for some storms due to their different definition of search regions in physical space. The physical space associated with each Stride Search region is constant, regardless of data resolution or latitude, and Stride Search is therefore capable of searching all regions of the globe in the same manner. Stride Search's ability to search high latitudes is demonstrated for the case of polar low detection. Wall clock time required for Stride Search is shown to be smaller than a grid point search of the same data, and the relative speed up associated with Stride Search increases as resolution increases.

  4. From normal to fast walking: Impact of cadence and stride length on lower extremity joint moments.

    PubMed

    Ardestani, Marzieh M; Ferrigno, Christopher; Moazen, Mehran; Wimmer, Markus A

    2016-05-01

    This study aimed to clarify the influence of various speeding strategies (i.e. adjustments of cadence and stride length) on external joint moments. This study investigated the gait of 52 healthy subjects who performed self-selected normal and fast speed walking trials in a motion analysis laboratory. Subjects were classified into three separate groups based on how they increased their speed from normal to fast walking: (i) subjects who increased their cadence, (ii) subjects who increased their stride length and (iii) subjects who simultaneously increased both stride length and cadence. Joint moments were calculated using inverse dynamics and then compared between normal and fast speed trials within and between three groups using spatial parameter mapping. Individuals who increased cadence, but not stride length, to walk faster did not experience a significant increase in the lower limb joint moments. Conversely, subjects who increased their stride length or both stride length and cadence, experienced a significant increase in all joint moments. Additionally, our findings revealed that increasing the stride length had a higher impact on joint moments in the sagittal plane than those in the frontal plane. However, both sagittal and frontal plane moments were still more responsive to the gait speed change than transverse plane moments. This study suggests that the role of speed in altering the joint moment patterns depends on the individual's speed-regulating strategy, i.e. an increase in cadence or stride length. Since the confounding effect of walking speed is a major consideration in human gait research, future studies may investigate whether stride length is the confounding variable of interest. Copyright © 2016 Elsevier B.V. All rights reserved.

  5. Effects of stride length and running mileage on a probabilistic stress fracture model.

    PubMed

    Edwards, W Brent; Taylor, David; Rudolphi, Thomas J; Gillette, Jason C; Derrick, Timothy R

    2009-12-01

    The fatigue life of bone is inversely related to strain magnitude. Decreasing stride length is a potential mechanism of strain reduction during running. If stride length is decreased, the number of loading cycles will increase for a given mileage. It is unclear if increased loading cycles are detrimental to skeletal health despite reductions in strain. To determine the effects of stride length and running mileage on the probability of tibial stress fracture. Ten male subjects ran overground at their preferred running velocity during two conditions: preferred stride length and 10% reduction in preferred stride length. Force platform and kinematic data were collected concurrently. A combination of experimental and musculoskeletal modeling techniques was used to determine joint contact forces acting on the distal tibia. Peak instantaneous joint contact forces served as inputs to a finite element model to estimate tibial strains during stance. Stress fracture probability for stride length conditions and three running mileages (3, 5, and 7 miles x d(-1)) were determined using a probabilistic model of bone damage, repair, and adaptation. Differences in stress fracture probability were compared between conditions using a 2 x 3 repeated-measures ANOVA. The main effects of stride length (P = 0.017) and running mileage (P = 0.001) were significant. Reducing stride length decreased the probability of stress fracture by 3% to 6%. Increasing running mileage increased the probability of stress fracture by 4% to 10%. Results suggest that strain magnitude plays a more important role in stress fracture development than the total number of loading cycles. Runners wishing to decrease their probability for tibial stress fracture may benefit from a 10% reduction in stride length.

  6. Head and Tibial Acceleration as a Function of Stride Frequency and Visual Feedback during Running

    PubMed Central

    Busa, Michael A.; Lim, Jongil; van Emmerik, Richard E. A.; Hamill, Joseph

    2016-01-01

    Individuals regulate the transmission of shock to the head during running at different stride frequencies although the consequences of this on head-gaze stability remain unclear. The purpose of this study was to examine if providing individuals with visual feedback of their head-gaze orientation impacts tibial and head accelerations, shock attenuation and head-gaze motion during preferred speed running at different stride frequencies. Fifteen strides from twelve recreational runners running on a treadmill at their preferred speed were collected during five stride frequencies (preferred, ±10% and ±20% of preferred) in two visual task conditions (with and without real-time visual feedback of head-gaze orientation). The main outcome measures were tibial and head peak accelerations assessed in the time and frequency domains, shock attenuation from tibia to head, and the magnitude and velocity of head-gaze motion. Decreasing stride frequency resulted in greater vertical accelerations of the tibia (p<0.01) during early stance and at the head (p<0.01) during early and late stance; however, for the impact portion the increase in head acceleration was only observed for the slowest stride frequency condition. Visual feedback resulted in reduced head acceleration magnitude (p<0.01) and integrated power spectral density in the frequency domain (p<0.01) in late stance, as well as overall of head-gaze motion (p<0.01). When running at preferred speed individuals were able to stabilize head acceleration within a wide range of stride frequencies; only at a stride frequency 20% below preferred did head acceleration increase. Furthermore, impact accelerations of the head and tibia appear to be solely a function of stride frequency as no differences were observed between feedback conditions. Increased visual task demands through head gaze feedback resulted in reductions in head accelerations in the active portion of stance and increased head-gaze stability. PMID:27271850

  7. Head and Tibial Acceleration as a Function of Stride Frequency and Visual Feedback during Running.

    PubMed

    Busa, Michael A; Lim, Jongil; van Emmerik, Richard E A; Hamill, Joseph

    2016-01-01

    Individuals regulate the transmission of shock to the head during running at different stride frequencies although the consequences of this on head-gaze stability remain unclear. The purpose of this study was to examine if providing individuals with visual feedback of their head-gaze orientation impacts tibial and head accelerations, shock attenuation and head-gaze motion during preferred speed running at different stride frequencies. Fifteen strides from twelve recreational runners running on a treadmill at their preferred speed were collected during five stride frequencies (preferred, ±10% and ±20% of preferred) in two visual task conditions (with and without real-time visual feedback of head-gaze orientation). The main outcome measures were tibial and head peak accelerations assessed in the time and frequency domains, shock attenuation from tibia to head, and the magnitude and velocity of head-gaze motion. Decreasing stride frequency resulted in greater vertical accelerations of the tibia (p<0.01) during early stance and at the head (p<0.01) during early and late stance; however, for the impact portion the increase in head acceleration was only observed for the slowest stride frequency condition. Visual feedback resulted in reduced head acceleration magnitude (p<0.01) and integrated power spectral density in the frequency domain (p<0.01) in late stance, as well as overall of head-gaze motion (p<0.01). When running at preferred speed individuals were able to stabilize head acceleration within a wide range of stride frequencies; only at a stride frequency 20% below preferred did head acceleration increase. Furthermore, impact accelerations of the head and tibia appear to be solely a function of stride frequency as no differences were observed between feedback conditions. Increased visual task demands through head gaze feedback resulted in reductions in head accelerations in the active portion of stance and increased head-gaze stability.

  8. Daily stride rate activity and heart rate response in children with cerebral palsy.

    PubMed

    Balemans, Astrid C J; van Wely, Leontien; Middelweerd, Anouk; van den Noort, Josien C; Becher, Jules G; Dallmeijer, Annet J

    2014-01-01

    To compare daily stride rate activity, daily exercise intensity, and heart rate intensity of stride rate in children with cerebral palsy with that of typically developing children. Forty-three children with cerebral palsy, walking without (Gross Motor Function Classification System (GMFCS) I and II) or with (GMFCS III) an aid and 27 typically developing children (age range 7-14 years) wore a StepWatch™ activity monitor and a heart rate monitor. Time spent and mean heart rate reserve at each stride rate activity level and time spent in each mean heart rate reserve zone was compared. Daily stride rate activity was lower in children with cerebral palsy (39%, 49% and 79% in GMFCS I, II and III, respectively) compared with typically developing children (p < 0.05), while there were no differences in time spent at different mean heart rate reserve zones. Mean heart rate reserve at all stride rate activity levels was not different between typically developing children, GMFCS I and II, while mean heart rate reserve was higher for GFMCS III at stride rates < 30 strides/min (p < 0.05). Stride rate activity levels reflect the effort of walking, in children with cerebral palsy who are walking without aids, similar to that of typically developing, whereas children with cerebral palsy using walking aids show higher effort of walking. Despite a lower stride rate activity in cerebral palsy, daily exercise intensity seems comparable, indicating that the StepWatch™ monitor and the heart rate monitor measure different aspects of physical activity.

  9. Select injury-related variables are affected by stride length and foot strike style during running.

    PubMed

    Boyer, Elizabeth R; Derrick, Timothy R

    2015-09-01

    Some frontal plane and transverse plane variables have been associated with running injury, but it is not known if they differ with foot strike style or as stride length is shortened. To identify if step width, iliotibial band strain and strain rate, positive and negative free moment, pelvic drop, hip adduction, knee internal rotation, and rearfoot eversion differ between habitual rearfoot and habitual mid-/forefoot strikers when running with both a rearfoot strike (RFS) and a mid-/forefoot strike (FFS) at 3 stride lengths. Controlled laboratory study. A total of 42 healthy runners (21 habitual rearfoot, 21 habitual mid-/forefoot) ran overground at 3.35 m/s with both a RFS and a FFS at their preferred stride lengths and 5% and 10% shorter. Variables did not differ between habitual groups. Step width was 1.5 cm narrower for FFS, widening to 0.8 cm as stride length shortened. Iliotibial band strain and strain rate did not differ between foot strikes but decreased as stride length shortened (0.3% and 1.8%/s, respectively). Pelvic drop was reduced 0.7° for FFS compared with RFS, and both pelvic drop and hip adduction decreased as stride length shortened (0.8° and 1.5°, respectively). Peak knee internal rotation was not affected by foot strike or stride length. Peak rearfoot eversion was not different between foot strikes but decreased 0.6° as stride length shortened. Peak positive free moment (normalized to body weight [BW] and height [h]) was not affected by foot strike or stride length. Peak negative free moment was -0.0038 BW·m/h greater for FFS and decreased -0.0004 BW·m/h as stride length shortened. The small decreases in most variables as stride length shortened were likely associated with the concomitant wider step width. RFS had slightly greater pelvic drop, while FFS had slightly narrower step width and greater negative free moment. Shortening one's stride length may decrease or at least not increase propensity for running injuries based on the variables

  10. Influence of Defects on Vibrational Characteristics of Linear Chains of Inert Gases Atoms Adsorbed on Carbon Nanobundles

    NASA Astrophysics Data System (ADS)

    Manzhelii, E. V.

    2016-11-01

    The study of vibrational characteristics of chains of rare gas atoms adsorbed in the grooves between nanotubes in nanobundles is reduced to the analyses of the phonon spectrum and the vibrational characteristics of linear chains of atoms in an external field. Atoms in the chain have three degrees of freedom. The analytical expressions for the vibrational characteristics of the atoms in the chain, depending on the ratio between the interatomic distance in the chain r and the equilibrium distance between atoms in the chain r_0 , are obtained. It is shown that at rlinear part of the temperature dependence of the heat capacity shifts to lower temperatures. The distance within only one pair of atoms is modified. It is the defect that can entail discrete states split off from the quasi-continuous spectrum band. The discrete levels with frequencies below the quasi-continuous spectrum band shift the linear part of the temperature dependence of the heat capacity to lower temperatures. The conditions for appearing of discrete frequency levels are obtained, and their characteristics are found.

  11. Influence of Defects on Vibrational Characteristics of Linear Chains of Inert Gases Atoms Adsorbed on Carbon Nanobundles

    NASA Astrophysics Data System (ADS)

    Manzhelii, E. V.

    2017-04-01

    The study of vibrational characteristics of chains of rare gas atoms adsorbed in the grooves between nanotubes in nanobundles is reduced to the analyses of the phonon spectrum and the vibrational characteristics of linear chains of atoms in an external field. Atoms in the chain have three degrees of freedom. The analytical expressions for the vibrational characteristics of the atoms in the chain, depending on the ratio between the interatomic distance in the chain r and the equilibrium distance between atoms in the chain r_0, are obtained. It is shown that at rlinear part of the temperature dependence of the heat capacity shifts to lower temperatures. The distance within only one pair of atoms is modified. It is the defect that can entail discrete states split off from the quasi-continuous spectrum band. The discrete levels with frequencies below the quasi-continuous spectrum band shift the linear part of the temperature dependence of the heat capacity to lower temperatures. The conditions for appearing of discrete frequency levels are obtained, and their characteristics are found.

  12. Characteristic Analysis and Trial Manufacture of Permanent-Magnetic Type Linear Generator

    NASA Astrophysics Data System (ADS)

    Takahara, Kenji; Ohsaki, Shingo; Itoh, Yuzo; Ohyama, Kazuhiro; Kawaguchi, Hideki

    This paper describes design and trial manufacture of the linear generator, which can convert any mechanical vibration of an automobile to electric energy. A mover, which includes permanent magnets, is linearly driven through a stator, by vibrations. Nd Fe-B magnets in the mover are placed as same magnetic poles face mutually, in order to make the change of magnetic flux in the coils of the stator. The coils are placed in the stator with same intervals of magnets. The coils are wound for the reverse to the next coil and they are connected series all. A magnetic material case covers the stator makes the magnetic flax is extended through the case and decrease canceling the flux in the coils of the stator. Numerical simulations calculated distribution of the magnetic field, electromotive force and driven power of the mover in order to determine the size of the linear generator. The linear generator and an experimental apparatus were produced on the basis of the simulation, and its performance was tested by experiments. The produced linear generator was confirmed to be useful as an onboard auxiliary power supply.

  13. Diffusion entropy analysis on the stride interval fluctuation of human gait

    NASA Astrophysics Data System (ADS)

    Cai, Shi-Min; Zhou, Pei-Ling; Yang, Hui-Jie; Zhou, Tao; Wang, Bing-Hong; Zhao, Fang-Cui

    2007-03-01

    In this paper, the diffusion entropy technique is applied to investigate the scaling behavior of stride interval fluctuations of human gait. The scaling behaviors of the stride interval of human walking at norm, slow, and fast rate are similar; with the scale-invariance exponents in the interval [0.663,0.955], of which the mean value is 0.821±0.011. Dynamical analysis of these stride interval fluctuations reveals a self-similar pattern: fluctuation at one time scale are statistically similar to those at multiple other time scales, at least over hundreds of steps, while the healthy subjects walk at their norm rate. The long-range correlations are observed during the spontaneous walking by removal of the trend in the time series with Fourier filter. These findings uncover that the fractal dynamics of stride interval fluctuation of human gait are normally intrinsic to the locomotor systems.

  14. Influence of contextual task constraints on preferred stride parameters and their variabilities during human walking.

    PubMed

    Ojeda, Lauro V; Rebula, John R; Kuo, Arthur D; Adamczyk, Peter G

    2015-10-01

    Walking is not always a free and unencumbered task. Everyday activities such as walking in pairs, in groups, or on structured walkways can limit the acceptable gait patterns, leading to motor behavior that differs from that observed in more self-selected gait. Such different contexts may lead to gait performance different than observed in typical laboratory experiments, for example, during treadmill walking. We sought to systematically measure the impact of such task constraints by comparing gait parameters and their variability during walking in different conditions over-ground, and on a treadmill. We reconstructed foot motion from foot-mounted inertial sensors, and characterized forward, lateral and angular foot placement while subjects walked over-ground in a straight hallway and on a treadmill. Over-ground walking was performed in three variations: with no constraints (self-selected, SS); while deliberately varying walking speed (self-varied, SV); and while following a toy pace car programmed to vary speed (externally-varied, EV). We expected that these conditions would exhibit a statistically similar relationship between stride length and speed, and between stride length and stride period. We also expected treadmill walking (TM) would differ in two ways: first, that variability in stride length and stride period would conform to a constant-speed constraint opposite in slope from the normal relationship; and second, that stride length would decrease, leading to combinations of stride length and speed not observed in over-ground conditions. Results showed that all over-ground conditions used similar stride length-speed relationships, and that variability in treadmill walking conformed to a constant-speed constraint line, as expected. Decreased stride length was observed in both TM and EV conditions, suggesting adaptations due to heightened awareness or to prepare for unexpected changes or problems. We also evaluated stride variability in constrained and

  15. Influence of contextual task constraints on preferred stride parameters and their variabilities during human walking

    PubMed Central

    Ojeda, Lauro V.; Rebula, John R.; Kuo, Arthur D.; Adamczyk, Peter G.

    2015-01-01

    Walking is not always a free and unencumbered task. Everyday activities such as walking in pairs, in groups, or on structured walkways can limit the acceptable gait patterns, leading to motor behavior that differs from that observed in more self-selected gait. Such different contexts may lead to gait performance different than observed in typical laboratory experiments, for example, during treadmill walking. We sought to systematically measure the impact of such task constraints by comparing gait parameters and their variability during walking in different conditions over-ground, and on a treadmill. We reconstructed foot motion from foot-mounted inertial sensors, and characterized forward, lateral and angular foot placement while subjects walked over-ground in a straight hallway and on a treadmill. Over-ground walking was performed in three variations: with no constraints (self-selected, SS); while deliberately varying walking speed (self-varied, SV); and while following a toy pace car programmed to vary speed (externally-varied, EV). We expected that these conditions would exhibit a statistically similar relationship between stride length and speed, and between stride length and stride period. We also expected treadmill walking (TM) would differ in two ways: first, that variability in stride length and stride period would conform to a constant-speed constraint opposite in slope from the normal relationship; and second, that stride length would decrease, leading to combinations of stride length and speed not observed in over-ground conditions. Results showed that all over-ground conditions used similar stride length-speed relationships, and that variability in treadmill walking conformed to a constant-speed constraint line, as expected. Decreased stride length was observed in both TM and EV conditions, suggesting adaptations due to heightened awareness or to prepare for unexpected changes or problems. We also evaluated stride variability in constrained and

  16. Perception of linear horizontal self-motion induced by peripheral vision /linearvection/ - Basic characteristics and visual-vestibular interactions

    NASA Technical Reports Server (NTRS)

    Berthoz, A.; Pavard, B.; Young, L. R.

    1975-01-01

    The basic characteristics of the sensation of linear horizontal motion have been studied. Objective linear motion was induced by means of a moving cart. Visually induced linear motion perception (linearvection) was obtained by projection of moving images at the periphery of the visual field. Image velocity and luminance thresholds for the appearance of linearvection have been measured and are in the range of those for image motion detection (without sensation of self motion) by the visual system. Latencies of onset are around 1 sec and short term adaptation has been shown. The dynamic range of the visual analyzer as judged by frequency analysis is lower than the vestibular analyzer. Conflicting situations in which visual cues contradict vestibular and other proprioceptive cues show, in the case of linearvection a dominance of vision which supports the idea of an essential although not independent role of vision in self motion perception.

  17. Perception of linear horizontal self-motion induced by peripheral vision /linearvection/ - Basic characteristics and visual-vestibular interactions

    NASA Technical Reports Server (NTRS)

    Berthoz, A.; Pavard, B.; Young, L. R.

    1975-01-01

    The basic characteristics of the sensation of linear horizontal motion have been studied. Objective linear motion was induced by means of a moving cart. Visually induced linear motion perception (linearvection) was obtained by projection of moving images at the periphery of the visual field. Image velocity and luminance thresholds for the appearance of linearvection have been measured and are in the range of those for image motion detection (without sensation of self motion) by the visual system. Latencies of onset are around 1 sec and short term adaptation has been shown. The dynamic range of the visual analyzer as judged by frequency analysis is lower than the vestibular analyzer. Conflicting situations in which visual cues contradict vestibular and other proprioceptive cues show, in the case of linearvection a dominance of vision which supports the idea of an essential although not independent role of vision in self motion perception.

  18. Does stride length influence metabolic cost and biomechanical risk factors for knee osteoarthritis in obese women?

    PubMed

    Russell, Elizabeth M; Braun, Barry; Hamill, Joseph

    2010-06-01

    Obesity is the primary modifiable risk factor for knee osteoarthritis. The goal of this study was to develop a walking protocol for obese individuals that supported weight loss while minimizing biomechanical risk factors for knee osteoarthritis. We tested the hypotheses that walking with short, quick strides at a preferred walking speed requires more energy expenditure in obese women and reduces biomechanical risk factors for knee osteoarthritis at foot-ground impact relative to walking at the preferred stride length. Ten obese (BMI=33.09(4.22)kg/m(2)) and 10 healthy-weight (BMI=22.66(0.86)kg/m(2)) women volunteered. V O(2) was measured while subjects walked on a treadmill at their preferred walking speed at a preferred stride length and a 15% shortened stride length (increased stride frequency). Peak impact shock, peak external knee adduction moment, and knee adduction angular impulse were measured during the two gait conditions. Decreasing stride length 15% significantly increased metabolic cost by 4.6% (P<0.01; effect size=0.24) and decreased the adduction angular impulse (P=0.046; effect size=0.203), but did not significantly affect the adduction moment (P=0.196; effect size=0.100) or impact shock (P=0.698; effect size=0.605). The small, but significant, increase in metabolic cost when walking with short, quick steps may be beneficial for weight reduction or maintenance in obese populations. The results of this study suggest that a 15% decrease in stride length is not sufficient to decrease the peak values of two of the biomechanical variables that may predispose obese women to knee osteoarthritis but does elicit benefits over the course of a stride. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

  19. Pelvic Rotation Effect on Human Stride Length: Releasing the Constraint of Obstetric Selection.

    PubMed

    Whitcome, Katherine K; Miller, E Elizabeth; Burns, Jessica L

    2017-04-01

    As human walking speed increases, pelvic step accounts for a greater percentage of total step length and is associated with an increase in amplitude of pelvic rotation. As a result, for any given speed individuals of varied pelvic width and leg length should differ in locomotor kinematics and energetic cost. Yet despite absolutely shorter legs and wider pelves relative to leg length in females, mass-specific cost of transport in walking does not differ by sex. Focusing on stride length as the major component of gait economy, we perform a quantitative analysis of temporal, spatial and rotational gait parameters using kinematic measurements obtained from 30 healthy adults walking at two comfortable speeds. We predicted that a larger component of stride length would derive from pelvic rotation in females and that a stride length model incorporating pelvic and limb kinematics would be a better predictor than a simple limb-based model. We found that pelvic rotation was greater in females at both speeds but reached significance only at the faster speed. A larger component of female stride length derived from pelvic rotation and the female hip translated farther than the male hip, but only when walking faster. The ModelLIMB and PELVIS was a better predictor of stride length than the limb only model and accurately predicted female stride length but not male stride length. Females exploit the breadth of their obstetric pelvis to obtain longer strides relative to leg length and perform at comfortable travel speeds with greater excursion angles than males. Anat Rec, 300:752-763, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  20. Walking at the preferred stride frequency maximizes local dynamic stability of knee motion.

    PubMed

    Russell, Daniel M; Haworth, Joshua L

    2014-01-03

    Healthy humans display a preference for walking at a stride frequency dependent on the inertial properties of their legs. Walking at preferred stride frequency (PSF) is predicted to maximize local dynamic stability, whereby sensitivity to intrinsic perturbations arising from natural variability inherent in biological motion is minimized. Previous studies testing this prediction have employed different variability measures, but none have directly quantified local dynamic stability by computing maximum finite-time Lyapunov exponent (λ(Max)), which quantifies the rate of divergence of nearby trajectories in state space. Here, ten healthy adults walked 45 m overground while sagittal motion of both knees was recorded via electrogoniometers. An auditory metronome prescribed 7 different frequencies relative to each individual's PSF (PSF; ±5, ±10, ±15 strides/min). Stride frequencies were performed under both freely adopted speed (FS) and controlled speed (CS: set at the speed of PSF trials) conditions. Local dynamic stability was maximal (λ(Max) was minimal) at the PSF, becoming less stable for higher and lower stride frequencies. This occurred under both FS and CS conditions, although controlling speed further reduced local dynamic stability at non-preferred stride frequencies. In contrast, measures of variability revealed effects of stride frequency and speed conditions that were distinct from λ(Max). In particular, movement regularity computed by approximate entropy (ApEn) increased for slower walking speeds, appearing to depend on speed rather than stride frequency. The cadence freely adopted by humans has the benefit of maximizing local dynamic stability, which can be interpreted as humans tuning to their resonant frequency of walking. © 2013 Elsevier Ltd. All rights reserved.

  1. [Study of spectrum preprocessing method when applying the characteristic spectrum linear inversion modeling to extract the mineral information].

    PubMed

    Wang, Fei; Lin, Qi-zhong; Wang, Qin-jun; Li, Shuai

    2011-05-01

    The rapid identification of the minerals in the field is crucial in the remote sensing geology study and mineral exploration. The characteristic spectrum linear inversion modeling is able to obtain the mineral information quickly in the field study. However, the authors found that there was significant difference among the results of the model using the different kinds of spectra of the same sample. The present paper mainly studied the continuum based fast Fourier transform processing (CFFT) method and the characteristic spectrum linear inversion modeling (CSLM). On one hand, the authors obtained the optimal preferences of the CFFT method when applying it to rock samples: setting the CFFT low-pass frequency to 150 Hz. On the other hand, through the evaluation and study of the results of CSLM using different spectra, the authors found that the ASD spectra which were denoised in the CFFT method could provide better results when using them to extract the mineral information in the field.

  2. Interacting linear and nonlinear characteristics produce population coding asymmetries between ON and OFF cells in the retina.

    PubMed

    Nichols, Zachary; Nirenberg, Sheila; Victor, Jonathan

    2013-09-11

    The early visual system is a model for understanding the roles of cell populations in parallel processing. Cells in this system can be classified according to their responsiveness to different stimuli; a prominent example is the division between cells that respond to stimuli of opposite contrasts (ON vs OFF cells). These two cell classes display many asymmetries in their physiological characteristics (including temporal characteristics, spatial characteristics, and nonlinear characteristics) that, individually, are known to have important roles in population coding. Here we describe a novel distinction between the information that ON and OFF ganglion cell populations carry in mouse--that OFF cells are able to signal motion information about both light and dark objects, while ON cells have a selective deficit at signaling the motion of dark objects. We found that none of the previously reported asymmetries in physiological characteristics could account for this distinction. We therefore analyzed its basis via a recently developed linear-nonlinear-Poisson model that faithfully captures input/output relationships for a broad range of stimuli (Bomash et al., 2013). While the coding differences between ON and OFF cell populations could not be ascribed to the linear or nonlinear components of the model individually, they had a simple explanation in the way that these components interact. Sensory transformations in other systems can likewise be described by these models, and thus our findings suggest that similar interactions between component properties may help account for the roles of cell classes in population coding more generally.

  3. The polarization-optical measuring method of linearity of radiant-power characteristic of the laser emission photodetectors

    NASA Astrophysics Data System (ADS)

    Baranov, M. S.; Khramov, V. N.; Chebanenko, R. A.

    2016-04-01

    The method of measurement of the power (lux-ampere) characteristic of photodetectors for work with the continuous laser sources of light which radiation has the linear polarization is developed and realized. The way offered in this work is approved on the basis of the FD-24K widespread photo diode. The received results quite correspond to passport data of this kind of photodetectors. Methods of statistical processing of results are applied.

  4. The influence of stride-length on plantar foot-pressures and joint moments.

    PubMed

    Allet, Lara; IJzerman, Herman; Meijer, Kenneth; Willems, Paul; Savelberg, Hans

    2011-07-01

    Joint moments have been acknowledged as key factors in understanding gait abnormalities. Gait velocity is further known to affect joint moments and foot pressures. Keeping gait velocity constant is thus a strategy to cancel out the influence of different preferred gait speed between groups. But even if gait velocity is controlled, individuals can choose different stride length-stride frequency combinations to cope with an imposed gait velocity. To understand the influence of stride frequency-stride length on joint moments and plantar pressures. Twenty healthy young adults had to cross an 8m walkway with a walking speed of 1.3ms(-1). The wooden walkway was equipped with a force and a pressure platform. While walking speed was kept constant each participant walked with five different imposed stride lengths (SL): preferred (SL0); with a decrease of 10% (SL-10); with a decrease of 20% (SL-20); with an increase of 10% (SL+10) and with an increase of 20% (SF+20). Ankle and knee joint moments significantly decreased with a decrease in SL. A significant (p<.05) lower peak pressure was achieved with a decreased SL under the heel, toes and midfoot. The results showed that a change in stride lengths alters both, joint moments and foot pressures with clinically interesting indications. Redistribution of joint moments in the elderly for example might rather result from decreased SL than from age. Copyright © 2011 Elsevier B.V. All rights reserved.

  5. Characteristics of linearly tapered slot antenna with CPW feed on high resistivity silicon

    NASA Technical Reports Server (NTRS)

    Simons, Rainee N.; Taub, Susan R.; Lee, Richard Q.

    1993-01-01

    A linearly tapered slot antenna (LTSA) has been fabricated on a high resistivity silicon substrate and tested at C-Band frequencies. The LTSA is electromagnetically coupled to a coplanar waveguide (CPW) feed. In this paper, the measured radiation patterns, gain, and return loss are presented and discussed.

  6. Gait variability and basal ganglia disorders: stride-to-stride variations of gait cycle timing in Parkinson's disease and Huntington's disease

    NASA Technical Reports Server (NTRS)

    Hausdorff, J. M.; Cudkowicz, M. E.; Firtion, R.; Wei, J. Y.; Goldberger, A. L.

    1998-01-01

    The basal ganglia are thought to play an important role in regulating motor programs involved in gait and in the fluidity and sequencing of movement. We postulated that the ability to maintain a steady gait, with low stride-to-stride variability of gait cycle timing and its subphases, would be diminished with both Parkinson's disease (PD) and Huntington's disease (HD). To test this hypothesis, we obtained quantitative measures of stride-to-stride variability of gait cycle timing in subjects with PD (n = 15), HD (n = 20), and disease-free controls (n = 16). All measures of gait variability were significantly increased in PD and HD. In subjects with PD and HD, gait variability measures were two and three times that observed in control subjects, respectively. The degree of gait variability correlated with disease severity. In contrast, gait speed was significantly lower in PD, but not in HD, and average gait cycle duration and the time spent in many subphases of the gait cycle were similar in control subjects, HD subjects, and PD subjects. These findings are consistent with a differential control of gait variability, speed, and average gait cycle timing that may have implications for understanding the role of the basal ganglia in locomotor control and for quantitatively assessing gait in clinical settings.

  7. Gait variability and basal ganglia disorders: stride-to-stride variations of gait cycle timing in Parkinson's disease and Huntington's disease

    NASA Technical Reports Server (NTRS)

    Hausdorff, J. M.; Cudkowicz, M. E.; Firtion, R.; Wei, J. Y.; Goldberger, A. L.

    1998-01-01

    The basal ganglia are thought to play an important role in regulating motor programs involved in gait and in the fluidity and sequencing of movement. We postulated that the ability to maintain a steady gait, with low stride-to-stride variability of gait cycle timing and its subphases, would be diminished with both Parkinson's disease (PD) and Huntington's disease (HD). To test this hypothesis, we obtained quantitative measures of stride-to-stride variability of gait cycle timing in subjects with PD (n = 15), HD (n = 20), and disease-free controls (n = 16). All measures of gait variability were significantly increased in PD and HD. In subjects with PD and HD, gait variability measures were two and three times that observed in control subjects, respectively. The degree of gait variability correlated with disease severity. In contrast, gait speed was significantly lower in PD, but not in HD, and average gait cycle duration and the time spent in many subphases of the gait cycle were similar in control subjects, HD subjects, and PD subjects. These findings are consistent with a differential control of gait variability, speed, and average gait cycle timing that may have implications for understanding the role of the basal ganglia in locomotor control and for quantitatively assessing gait in clinical settings.

  8. Manganite-based memristive heterojunction with tunable non-linear I-V characteristics.

    PubMed

    Lee, Hong-Sub; Park, Hyung-Ho; Rozenberg, M J

    2015-04-21

    A resistive random access memory (ReRAM) based on the memristive effect allows high-density integration through a cross-point array (CPA) structure. However, a significant common drawback of the CPA configuration is the crosstalk between cells. Here, we introduce a solution based on a novel heterojunction stack solely made of members of the perovskite manganite family Pr(1-x)Ca(x)MnO3 (PCMO) and CaMnO(3-δ) (CMO) which show electroforming-free bipolar resistive switching. The heterojunction consists of rectifying interfaces and shows a symmetrical and tunable non-linear current-voltage curve. The spectromicroscopic measurements support the scenario of specialized roles, with the memristive effect taking place at the active Al-PCMO interface via a redox mechanism, while non-linearity was achieved by adopting a rectifying double interface PCMO-CMO-PCMO.

  9. Characteristics of the photon beam from a new 25-MV linear accelerator

    SciTech Connect

    Aldrich, J.E.; Andrew, J.W.; Michaels, H.B.; O'Brien, P.F.

    1985-09-01

    The Therac 25 is a relatively compact therapy machine, the heart of which is a double-pass electron linear accelerator. The electron beam is injected into the accelerator at the treatment head end of the machine and is accelerated back down the arm to an energy of 13 MeV. At this end of the machine a magnet system reflects the beam back into the structure where it gains up to an additional 12 MeV of energy. After leaving the linear accelerator the beam is bent by an achromatic head magnet through 270 degrees to the treatment head. The machine produces eight electron beams and a 25-MV photon beam. In this work only the parameters of the photon beam are addressed based on measurements at the first two clinical sites. Percentage depth doses, tissue phantom ratios, and beam symmetry and stability are presented and discussed.

  10. A Monolithic CMOS Magnetic Hall Sensor with High Sensitivity and Linearity Characteristics.

    PubMed

    Huang, Haiyun; Wang, Dejun; Xu, Yue

    2015-10-27

    This paper presents a fully integrated linear Hall sensor by means of 0.8 μm high voltage complementary metal-oxide semiconductor (CMOS) technology. This monolithic Hall sensor chip features a highly sensitive horizontal switched Hall plate and an efficient signal conditioner using dynamic offset cancellation technique. An improved cross-like Hall plate achieves high magnetic sensitivity and low offset. A new spinning current modulator stabilizes the quiescent output voltage and improves the reliability of the signal conditioner. The tested results show that at the 5 V supply voltage, the maximum Hall output voltage of the monolithic Hall sensor microsystem, is up to ±2.1 V and the linearity of Hall output voltage is higher than 99% in the magnetic flux density range from ±5 mT to ±175 mT. The output equivalent residual offset is 0.48 mT and the static power consumption is 20 mW.

  11. Characteristics of the photon beam from a new 25-MV linear accelerator.

    PubMed

    Aldrich, J E; Andrew, J W; Michaels, H B; O'Brien, P F

    1985-01-01

    The Therac 25 is a relatively compact therapy machine, the heart of which is a double-pass electron linear accelerator. The electron beam is injected into the accelerator at the treatment head end of the machine and is accelerated back down the arm to an energy of 13 MeV. At this end of the machine a magnet system reflects the beam back into the structure where it gains up to an additional 12 MeV of energy. After leaving the linear accelerator the beam is bent by an achromatic head magnet through 270 degrees to the treatment head. The machine produces eight electron beams and a 25-MV photon beam. In this work only the parameters of the photon beam are addressed based on measurements at the first two clinical sites. Percentage depth doses, tissue phantom ratios, and beam symmetry and stability are presented and discussed.

  12. Stride-Time Variability and Fall Risk in Persons with Multiple Sclerosis

    PubMed Central

    Wajda, Douglas A.; Motl, Robert W.; Sosnoff, Jacob J.

    2015-01-01

    Gait variability is associated with falls in clinical populations. However, gait variability's link to falls in persons with Multiple Sclerosis (PwMS) is not well established. This investigation examined the relationship between stride-time variability, fall risk, and physiological fall risk factors in PwMS. 17 PwMS (62.8 ± 7.4 years) and 17 age-matched controls (62.8 ± 5.9 years) performed the 6-minute walk test. Stride-time was assessed with accelerometers attached to the participants' shanks. Stride-time variability was measured by interstride coefficient of variation (CV) of stride-time. The participant's fall risk was measured by the short form physiological profile assessment (PPA). A Spearman correlation analysis was used to determine the relationship between variables. Increased fall risk was strongly associated with increased stride-time CV in both PwMS (ρ = 0.71, p < 0.01) and the controls (ρ = 0.67, p < 0.01). Fall risk was not correlated with average stride-time (p > 0.05). In PwMS, stride-time CV was related to postural sway (ρ = 0.74, p < 0.01) while in the control group, it was related to proprioception (ρ = 0.61, p < 0.01) and postural sway (ρ = 0.78, p < 0.01). Current observations suggest that gait variability is maybe more sensitive marker of fall risk than average gait parameters in PwMS. It was also noted that postural sway may be potentially targeted to modify gait variability in PwMS. PMID:26843986

  13. Characteristics of electron beams from a new 25-MeV linear accelerator

    SciTech Connect

    O'Brien, P.; Michaels, H.B.; Aldrich, J.E.; Andrew, J.W.

    1985-11-01

    Clinically useful electron fields are produced on the Atomic Energy of Canada, Limited Therac 25 linear accelerator by computer-controlled scanning of the electron beam. Measurements were made to determine the properties of these electron fields. Central axis percentage depth dose and bremsstrahlung background were compared for these fields and for the fields from selected machines that use scattering foils. Dose calibrations were made in both water and polystyrene using the American Association of Physicists in Medicine Task Group 21 protocol. Measurements were made to determine the relative output factors, virtual source position, and the attenuation of the electron fields by lead.

  14. Tidal propagation and its non-linear characteristics in the Head Bay of Bengal

    NASA Astrophysics Data System (ADS)

    Rose, Linta; Bhaskaran, Prasad K.

    2017-03-01

    The Head Bay of Bengal is highly vulnerable to flooding events caused due to monsoons, cyclones and sea-level rise, owing to its funnel-like shape, high tidal range, presence of numerous river drainage systems, low-lying topography, and shallow bathymetry. Tides dominate the hydrodynamic behaviour and coastal processes in this region and its propagation is quite distinct. The present study uses ADCIRC hydrodynamic model customized for the Head Bay of Bengal, discretized using unstructured finite elements and validated against limited available observations in this data sparse region. The water-level elevations derived from ADCIRC simulation was used to understand the pattern of non-linear tidal propagation with respect to complex coastal geomorphology prevalent in this region. The study finds a marginal amplification of diurnal tide, nearly double amplification of semi-diurnal components, and existence of a degenerate amphidromic point near Meghna delta consistent with previous studies. The spatial and temporal variability of tidal spectral components were examined by applying the techniques of wavelet, harmonic, and time-series analysis at various locations. Maximum amplification of tides occurs at the head of the bay, along a zone enclosing the mouth of tidal inlets; and for regions northward, the tides decay with progressively increasing phase lags. The study signifies dominance of a forced fortnightly tide and tidal asymmetry leading to flood-dominance in the rivers Hooghly, Meghna, and Tetulia. The non-linear properties of tides have been elucidated, and their origin and spatio-temporal variability in these riverine systems were further investigated. Shallow depth and sharp depth gradients were discerned to be the important conditions for the origin of non-linear components. It has been deduced that non-linear tides are generated in regions where propagating tides are accumulated, and amplified in regions where they are funneled. A study of tidal energetics

  15. Characteristics of electron beams from a new 25-MeV linear accelerator.

    PubMed

    O'Brien, P; Michaels, H B; Aldrich, J E; Andrew, J W

    1985-01-01

    Clinically useful electron fields are produced on the Atomic Energy of Canada, Limited Therac 25 linear accelerator by computer-controlled scanning of the electron beam. Measurements were made to determine the properties of these electron fields. Central axis percentage depth dose and bremsstrahlung background were compared for these fields and for the fields from selected machines that use scattering foils. Dose calibrations were made in both water and polystyrene using the American Association of Physicists in Medicine Task Group 21 protocol. Measurements were made to determine the relative output factors, virtual source position, and the attenuation of the electron fields by lead.

  16. A study of passive and adaptive hydraulic engine mount systems with emphasis on non-linear characteristics

    NASA Astrophysics Data System (ADS)

    Kim, G.; Singh, R.

    1995-01-01

    Passive hydraulic mounts exhibit excitation frequency variant and deflection amplitude sensitive stiffness and damping properties. Such non-linear dynamic characteristics are examined by using analytical and experimental methods, both at the device level and within the context of a simplified vehicle model. A new lumped parameter non-linear mathematical model of the hydraulic mount is developed by simulating its decoupler switching mechanism and inertia track dynamics. The low frequency performance features and limitations of several passive mounts are made clear through the non-linear vehicle model simulation and comparable laboratory vibration tests. The high frequency performance problems of the passive hydraulic mount are identified by applying the quasi-linear analysis method. Based on these results, a new adaptive mount system is developed which exhibits broad bandwidth performance features up to 250 Hz. It implements an on-off damping control mode by using engine intake manifold vacuum and a microprocessor based solenoid valve controller. A laboratory bench set-up has already demonstrated its operational feasibility. Through analytical methods, it is observed that our adaptive mount provides superior dynamic performance to passive engine mounts and comparable performance to a small scale active mount over a wide frequency range, given the engine mounting resonance control, shock absorption and vibration isolation performance requirements. Although technical prospects of the proposed adaptive system appear promising, the in situperformance needs to be evaluated.

  17. Flow Structure and Turbulence Characteristics downstream of a Spanwise Suspended Linear Canopy through Laboratory Experiments

    NASA Astrophysics Data System (ADS)

    Qiao, Jundong; Delavan, Sarah

    2014-11-01

    Laboratory experiments were conducted to explore the mean flow structure and turbulence properties downstream of a spanwise suspended linear canopy in a 2-D open channel flow using the Particle Tracking Velocimetry technique. This canopy simulated the effect of one long-line structure of a mussel farm. Four experimental scenarios with the approach velocities 50, 80, 110, and 140 mm s-1 were under investigation. Three sub-layers formed downstream of the canopy. An internal canopy layer, where the time-averaged velocity decreases linearly with increasing distance downstream, a canopy mixing layer increasing in vertical extent with increasing distance downstream of the canopy, and an external canopy layer with higher velocity under the canopy, which may bring nutrients from the local ambient environment into this layer. The canopy turbulence results in upward momentum transport downstream of the canopy within a distance of 0.60 of the canopy depth and downward momentum transport beyond 1.20 of it. In the scenarios with relatively lower approach velocities 50 and 80 mm s1 , the wake turbulence results in upward momentum transport. The broader goal of this study is to offer guidelines for the design and site selection of more productive mussel farms. The results suggest that distance interval between the parallel long-lines in a mussel farm should be less than 0.6 times the height of a long-line dropper. Also, potential farm locations that are characterized with current velocity from 50 to 80 mm s1 are suggested.

  18. A Monolithic CMOS Magnetic Hall Sensor with High Sensitivity and Linearity Characteristics

    PubMed Central

    Huang, Haiyun; Wang, Dejun; Xu, Yue

    2015-01-01

    This paper presents a fully integrated linear Hall sensor by means of 0.8 μm high voltage complementary metal-oxide semiconductor (CMOS) technology. This monolithic Hall sensor chip features a highly sensitive horizontal switched Hall plate and an efficient signal conditioner using dynamic offset cancellation technique. An improved cross-like Hall plate achieves high magnetic sensitivity and low offset. A new spinning current modulator stabilizes the quiescent output voltage and improves the reliability of the signal conditioner. The tested results show that at the 5 V supply voltage, the maximum Hall output voltage of the monolithic Hall sensor microsystem, is up to ±2.1 V and the linearity of Hall output voltage is higher than 99% in the magnetic flux density range from ±5 mT to ±175 mT. The output equivalent residual offset is 0.48 mT and the static power consumption is 20 mW. PMID:26516864

  19. A non-Linear transport model for determining shale rock characteristics

    NASA Astrophysics Data System (ADS)

    Ali, Iftikhar; Malik, Nadeem

    2016-04-01

    Unconventional hydrocarbon reservoirs consist of tight porous rocks which are characterised by nano-scale size porous networks with ultra-low permeability [1,2]. Transport of gas through them is not well understood at the present time, and realistic transport models are needed in order to determine rock properties and for estimating future gas pressure distribution in the reservoirs. Here, we consider a recently developed non-linear gas transport equation [3], ∂p-+ U ∂p- = D ∂2p-, t > 0, (1) ∂t ∂x ∂x2 complimented with suitable initial and boundary conditions, in order to determine shale rock properties such as the permeability K, the porosity φ and the tortuosity, τ. In our new model, the apparent convection velocity, U = U(p,px), and the apparent diffusivity D = D(p), are both highly non-linear functions of the pressure. The model incorporate various flow regimes (slip, surface diffusion, transition, continuum) based upon the Knudsen number Kn, and also includes Forchchiemers turbulence correction terms. In application, the model parameters and associated compressibility factors are fully pressure dependent, giving the model more realism than previous models. See [4]. Rock properties are determined by solving an inverse problem, with model parameters adjustment to minimise the error between the model simulation and available data. It is has been found that the proposed model performs better than previous models. Results and details of the model will be presented at the conference. Corresponding author: namalik@kfupm.edu.sa and nadeem_malik@cantab.net References [1] Cui, X., Bustin, A.M. and Bustin, R., "Measurements of gas permeability and diffusivity of tight reservoir rocks: different approaches and their applications", Geofluids 9, 208-223 (2009). [2] Chiba R., Fomin S., Chugunov V., Niibori Y. and Hashida T., "Numerical Simulation of Non Fickian Diffusion and Advection in a Fractured Porous Aquifer", AIP Conference Proceedings 898, 75 (2007

  20. Quasi-linear velocity space diffusion of heavy cometary pickup ions on bispherical diffusion characteristics

    NASA Technical Reports Server (NTRS)

    Huddleston, D. E.; Coates, A. J.; Johnstone, A. D.

    1992-01-01

    We consider an ion transport equation describing the source, convection, adiabatic acceleration, and quasi-linear velocity diffusion of cometary pickup ions. The equation is solved numerically along solar wind plasma flow lines for the environment of Comet Halley, to obtain distributions at positions on the Giotto spacecraft trajectory which may be compared with observations. We obtain full two-dimensional (pitch angle and velocity) numerical distributions which show pitch angle scattering about the wave scattering centers at +/- V(A), where V(A) is the Alfven wave speed in the solar wind frame. Peak ion phase-space densities approximately follow the bispherical shell geometry. The energy distributions F(v) agree well with Giotto observations at lower v, but in the high-energy tail there is evidence possibly for the first-order Fermi acceleration mechanism taking place in the Comet Halley foreshock region.

  1. Characteristics of a Linearly Tapered Slot Antenna (LTSA) Conformed Longitudinally Around a Cylinder

    NASA Technical Reports Server (NTRS)

    Jordan, Jennifer L.; Ponchak, George E.; Tavassolian, Negar; Tentzeris, Manos M.

    2007-01-01

    The family of tapered slot antennas (TSA s) is suitable for numerous applications. Their ease of fabrication, wide bandwidth, and high gain make them desirable for military and commercial systems. Fabrication on thin, flexible substrates allows the TSA to be conformed over a given body, such as an aircraft wing or a piece of clothing for wearable networks. Previously, a Double Exponentially Tapered Slot Antenna (DETSA) was conformed around an exponential curvature, which showed that the main beam skewed towards the direction of curvature. This paper presents a Linearly Tapered Slot Antenna (LTSA) conformed longitudinally around a cylinder. Measured and simulated radiation patterns and the direction of maximum H co-polarization (Hco) as a function of the cylinder radius are presented.

  2. Integrating a Linear Signal Model with Groundwater and Rainfall time-series on the Characteristic Identification of Groundwater Systems

    NASA Astrophysics Data System (ADS)

    Chen, Yu-Wen; Wang, Yetmen; Chang, Liang-Cheng

    2017-04-01

    Groundwater resources play a vital role on regional supply. To avoid irreversible environmental impact such as land subsidence, the characteristic identification of groundwater system is crucial before sustainable management of groundwater resource. This study proposes a signal process approach to identify the character of groundwater systems based on long-time hydrologic observations include groundwater level and rainfall. The study process contains two steps. First, a linear signal model (LSM) is constructed and calibrated to simulate the variation of underground hydrology based on the time series of groundwater levels and rainfall. The mass balance equation of the proposed LSM contains three major terms contain net rate of horizontal exchange, rate of rainfall recharge and rate of pumpage and four parameters are required to calibrate. Because reliable records of pumpage is rare, the time-variant groundwater amplitudes of daily frequency (P ) calculated by STFT are assumed as linear indicators of puamage instead of pumpage records. Time series obtained from 39 observation wells and 50 rainfall stations in and around the study area, Pintung Plain, are paired for model construction. Second, the well-calibrated parameters of the linear signal model can be used to interpret the characteristic of groundwater system. For example, the rainfall recharge coefficient (γ) means the transform ratio between rainfall intention and groundwater level raise. The area around the observation well with higher γ means that the saturated zone here is easily affected by rainfall events and the material of unsaturated zone might be gravel or coarse sand with high infiltration ratio. Considering the spatial distribution of γ, the values of γ decrease from the upstream to the downstream of major rivers and also are correlated to the spatial distribution of grain size of surface soil. Via the time-series of groundwater levels and rainfall, the well-calibrated parameters of LSM have

  3. Project Stride: An Equine-Assisted Intervention to Reduce Symptoms of Social Anxiety in Young Women.

    PubMed

    Alfonso, Sarah V; Alfonso, Lauren A; Llabre, Maria M; Fernandez, M Isabel

    2015-01-01

    Although there is evidence supporting the use of equine-assisted activities to treat mental disorders, its efficacy in reducing signs and symptoms of social anxiety in young women has not been examined. We developed and pilot tested Project Stride, a brief, six-session intervention combining equine-assisted activities and cognitive-behavioral strategies to reduce symptoms of social anxiety. A total of 12 women, 18-29 years of age, were randomly assigned to Project Stride or a no-treatment control. Participants completed the Liebowitz Social Anxiety Scale at baseline, immediate-post, and 6 weeks after treatment. Project Stride was highly acceptable and feasible. Compared to control participants, those in Project Stride had significantly greater reductions in social anxiety scores from baseline to immediate-post [decrease of 24.8 points; t (9) = 3.40, P = .008)] and from baseline to follow-up [decrease of 31.8 points; t (9) = 4.12, P = .003)]. These findings support conducting a full-scale efficacy trial of Project Stride. Copyright © 2015 Elsevier Inc. All rights reserved.

  4. The effects of stride technique and pitch location on slo-pitch batting.

    PubMed

    Wu, Tom; Gervais, Pierre; Baudin, Pierre; Bouffard, Marcel

    2011-11-01

    In slo-pitch softball, the ball is delivered in an arc trajectory with a moderate velocity; hence, batters have time to adjust their stride technique based on the pitched ball location. The purpose of this study was to examine the influence of stride technique and pitched ball location on the mechanics of slo-pitch batting. A two-way ANOVA of two locations of pitch (inside and outside) x three strides (open, parallel, and closed) repeated measure study was conducted in this study. The results showed that the stride technique and pitched ball location did not have a consistent impact on the participants across different batting conditions, so the study recommends slo-pitch batters to explore different stride techniques when striking the ball. Further, to better understand the generalizability of the findings, the results indicated that participants were quite homogeneous as a group. Hence, coaches and educators may apply the findings from this study to other players with similar skill level.

  5. Prediction of Dynamic Stall Characteristics Using Advanced Non-Linear Panel Methods.

    DTIC Science & Technology

    1984-04-04

    three- dimensional method , incorporating the techniques that are being examined in the two-dimensional pilot code. r.• - t... . .. -..-. .°.- S °"°"° I...RD-Ai48 453 PREDICTION OF DYNAMIC STRLL CHARACTERISTICS USING 1/1 RDVRNCED NON-LINERR PAN..(U) ANALYTICAL METHODS INC REDMOND WA B MRSKEW ET AL. 84...1 2.0 micROCOPY RESOLUTION TEST CHART hAyl0#dM. @UAU M STAUIOAPOI A VOSR-TR 84.0 97 5 Analytical methods Report 8406 FINAL REPORT Tw. ’ PREDICITON OF

  6. Is it the intervention or the students? using linear regression to control for student characteristics in undergraduate STEM education research.

    PubMed

    Theobald, Roddy; Freeman, Scott

    2014-01-01

    Although researchers in undergraduate science, technology, engineering, and mathematics education are currently using several methods to analyze learning gains from pre- and posttest data, the most commonly used approaches have significant shortcomings. Chief among these is the inability to distinguish whether differences in learning gains are due to the effect of an instructional intervention or to differences in student characteristics when students cannot be assigned to control and treatment groups at random. Using pre- and posttest scores from an introductory biology course, we illustrate how the methods currently in wide use can lead to erroneous conclusions, and how multiple linear regression offers an effective framework for distinguishing the impact of an instructional intervention from the impact of student characteristics on test score gains. In general, we recommend that researchers always use student-level regression models that control for possible differences in student ability and preparation to estimate the effect of any nonrandomized instructional intervention on student performance.

  7. Is It the Intervention or the Students? Using Linear Regression to Control for Student Characteristics in Undergraduate STEM Education Research

    PubMed Central

    Theobald, Roddy; Freeman, Scott

    2014-01-01

    Although researchers in undergraduate science, technology, engineering, and mathematics education are currently using several methods to analyze learning gains from pre- and posttest data, the most commonly used approaches have significant shortcomings. Chief among these is the inability to distinguish whether differences in learning gains are due to the effect of an instructional intervention or to differences in student characteristics when students cannot be assigned to control and treatment groups at random. Using pre- and posttest scores from an introductory biology course, we illustrate how the methods currently in wide use can lead to erroneous conclusions, and how multiple linear regression offers an effective framework for distinguishing the impact of an instructional intervention from the impact of student characteristics on test score gains. In general, we recommend that researchers always use student-level regression models that control for possible differences in student ability and preparation to estimate the effect of any nonrandomized instructional intervention on student performance. PMID:24591502

  8. Output trends, characteristics, and measurements of three megavoltage radiotherapy linear accelerators.

    PubMed

    Hossain, Murshed

    2014-07-08

    The purpose of this study is to characterize and understand the long-term behavior of the output from megavoltage radiotherapy linear accelerators. Output trends of nine beams from three linear accelerators over a period of more than three years are reported and analyzed. Output, taken during daily warm-up, forms the basis of this study. The output is measured using devices having ion chambers. These are not calibrated by accredited dosimetry laboratory, but are baseline-compared against monthly output which is measured using calibrated ion chambers. We consider the output from the daily check devices as it is, and sometimes normalized it by the actual output measured during the monthly calibration of the linacs. The data show noisy quasi-periodic behavior. The output variation, if normalized by monthly measured "real' output, is bounded between ± 3%. Beams of different energies from the same linac are correlated with a correlation coefficient as high as 0.97, for one particular linac, and as low as 0.44 for another. These maximum and minimum correlations drop to 0.78 and 0.25 when daily output is normalized by the monthly measurements. These results suggest that the origin of these correlations is both the linacs and the daily output check devices. Beams from different linacs, independent of their energies, have lower correlation coefficient, with a maximum of about 0.50 and a minimum of almost zero. The maximum correlation drops to almost zero if the output is normalized by the monthly measured output. Some scatter plots of pairs of beam output from the same linac show band-like structures. These structures are blurred when the output is normalized by the monthly calibrated output. Fourier decomposition of the quasi-periodic output is consistent with a 1/f power law. The output variation appears to come from a distorted normal distribution with a mean of slightly greater than unity. The quasi-periodic behavior is manifested in the seasonally averaged output

  9. Output trends, characteristics, and measurements of three mega-voltage radiotherapy linear accelerators

    PubMed Central

    Hossain, Murshed

    2015-01-01

    The purpose of this study is to characterize and understand the long term behavior of the output from megavoltage radiotherapy linear accelerators. Output trends of nine beams from three linear accelerators over a period of more than three years are reported and analyzed. Output taken during daily warm-up forms the basis of this study. The output is measured using devices having ion-chambers. These are not calibrated by accredited dosimetry laboratory but are baseline compared against monthly output which are measured using calibrated ion-chambers. We consider the output from the daily check devices as it is and sometimes normalized them by the actual output measured during the monthly calibration of the Linacs. The data shows noisy quasi-periodic behavior. The output variation if normalized by monthly measured “real’ output, is bounded between ±3%. Beams of different energies from the same Linac are correlated with a correlation coefficient as high as 0.97 for one particular Linac and as low as 0.44 for another. These maximum and minimum correlations drop to 0.78 and 0.25 when daily output is normalized by the monthly measurements. These results suggest that the origin of these correlations are both the Linacs and the daily output check devices. Beams from different Linacs, independent of their energies, have lower correlation coefficient with a maximum of about 0.50 and a minimum of almost zero. The maximum correlation drops to almost zero if the output is normalized by the monthly measured output. Some scatter plots of pairs of beam-output from the same Linac show band-like structures. These structures are blurred when the output is normalized by the monthly calibrated output. Fourier decomposition of the quasi periodic output is consistent with a 1/f power law. The output variation appears to come from a distorted normal distribution with a mean of slightly greater than unity. The quasi-periodic behavior is manifested in the seasonally averaged output

  10. Comparison of dosimetric characteristics of Siemens virtual and physical wedges for ONCOR linear accelerator.

    PubMed

    Attalla, Ehab M; Abo-Elenein, H S; Ammar, H; El-Desoky, Ismail

    2010-07-01

    Dosimetric properties of virtual wedge (VW) and physical wedge (PW) in 6- and 10-MV photon beams from a Siemens ONCOR linear accelerator, including wedge factors, depth doses, dose profiles, peripheral doses, are compared. While there is a great difference in absolute values of wedge factors, VW factors (VWFs) and PW factors (PWFs) have a similar trend as a function of field size. PWFs have stronger depth dependence than VWF due to beam hardening in PW fields. VW dose profiles in the wedge direction, in general, match very well with those of PW, except in the toe area of large wedge angles with large field sizes. Dose profiles in the nonwedge direction show a significant reduction in PW fields due to off-axis beam softening and oblique filtration. PW fields have significantly higher peripheral doses than open and VW fields. VW fields have similar surface doses as the open fields, while PW fields have lower surface doses. Surface doses for both VW and PW increase with field size and slightly with wedge angle. For VW fields with wedge angles 45° and less, the initial gap up to 3 cm is dosimetrically acceptable when compared to dose profiles of PW. VW fields in general use less monitor units than PW fields.

  11. Characteristics of the fourth order resonance in high intensity linear accelerators

    NASA Astrophysics Data System (ADS)

    Jeon, D.; Hwang, Kyung Ryun

    2017-06-01

    For the 4σ = 360° space-charge resonance in high intensity linear accelerators, the emittance growth is surveyed for input Gaussian beams, as a function of the depressed phase advance per cell σ and the initial tune depression (σo - σ). For each data point, the linac lattice is designed such that the fourth order resonance dominates over the envelope instability. The data show that the maximum emittance growth takes place at σ ≈ 87° over a wide range of the tune depression (or beam current), which confirms that the relevant parameter for the emittance growth is σ and that for the bandwidth is σo - σ. An interesting four-fold phase space structure is observed that cannot be explained with the fourth order resonance terms alone. Analysis attributes this effect to a small negative sixth order detuning term as the beam is redistributed by the resonance. Analytical studies show that the tune increases monotonically for the Gaussian beam which prevents the resonance for σ > 90°. Frequency analysis indicates that the four-fold structure observed for input Kapchinskij-Vladmirskij beams when σ < 90°, is not the fourth order resonance but a fourth order envelope instability because the 1/4 = 90°/360° component is missing in the frequency spectrum.

  12. Recuperation of slow walking in de novo Parkinson's disease is more closely associated with increased cadence, rather than with expanded stride length.

    PubMed

    Kwon, Kyum-Yil; Lee, Hye Mi; Kang, Sung Hoon; Pyo, Seon Jong; Kim, Han Jun; Koh, Seong-Beom

    2017-07-01

    Gait characteristics in the early stages of Parkinson's disease (PD) have been less investigated so far. Moreover, the levodopa effect on gait in early PD remains to be further elucidated. We prospectively designed the study to examine gait dynamics and effect of dopaminergic treatment in patients with de novo PD. Spatiotemporal parameters were measured in healthy controls and drug naïve patients with PD, using computerized analysis with GAITRite system during usual gait. In PD group, motor symptoms and gait parameters were examined in both drug naive and levodopa 100mg trial conditions. Twenty four de novo PD patients and 27 healthy controls (matched for age, sex, and height) were selected for the study. Compared with the controls, patients with de novo PD showed the decrease in stride length, in both Med-OFF and Med-ON conditions. Notably, drug naïve patients with PD demonstrated slow walking velocity, whereas those with levodopa administration exhibited the increase of cadence by shortening stride time, which resulted in the improvement of gait speed. In addition, the stride length (gait hypokinesia) correlated with postural instability and gait difficulty subscore, but not with tremor, rigidity, bradykinesia, or total motor score. As a compensatory mechanism of slow walking, we found that the increment in cadence (frequency) is more important than the increment in stride length (amplitude) in gait dynamics in de novo PD. Additionally, the results may indicate that gait hypokinesia in PD could be regarded as one of axial symptoms. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. Stride search: A general algorithm for storm detection in high resolution climate data

    SciTech Connect

    Bosler, Peter Andrew; Roesler, Erika Louise; Taylor, Mark A.; Mundt, Miranda

    2015-09-08

    This article discusses the problem of identifying extreme climate events such as intense storms within large climate data sets. The basic storm detection algorithm is reviewed, which splits the problem into two parts: a spatial search followed by a temporal correlation problem. Two specific implementations of the spatial search algorithm are compared. The commonly used grid point search algorithm is reviewed, and a new algorithm called Stride Search is introduced. Stride Search is designed to work at all latitudes, while grid point searches may fail in polar regions. Results from the two algorithms are compared for the application of tropical cyclone detection, and shown to produce similar results for the same set of storm identification criteria. The time required for both algorithms to search the same data set is compared. Furthermore, Stride Search's ability to search extreme latitudes is demonstrated for the case of polar low detection.

  14. Stride search: A general algorithm for storm detection in high resolution climate data

    DOE PAGES

    Bosler, Peter Andrew; Roesler, Erika Louise; Taylor, Mark A.; ...

    2015-09-08

    This article discusses the problem of identifying extreme climate events such as intense storms within large climate data sets. The basic storm detection algorithm is reviewed, which splits the problem into two parts: a spatial search followed by a temporal correlation problem. Two specific implementations of the spatial search algorithm are compared. The commonly used grid point search algorithm is reviewed, and a new algorithm called Stride Search is introduced. Stride Search is designed to work at all latitudes, while grid point searches may fail in polar regions. Results from the two algorithms are compared for the application of tropicalmore » cyclone detection, and shown to produce similar results for the same set of storm identification criteria. The time required for both algorithms to search the same data set is compared. Furthermore, Stride Search's ability to search extreme latitudes is demonstrated for the case of polar low detection.« less

  15. Optic flow odometry operates independently of stride integration in carried ants.

    PubMed

    Pfeffer, Sarah E; Wittlinger, Matthias

    2016-09-09

    Cataglyphis desert ants are impressive navigators. When the foragers roam the desert, they employ path integration. For these ants, distance estimation is one key challenge. Distance information was thought to be provided by optic flow (OF)-that is, image motion experienced during travel-but this idea was abandoned when stride integration was discovered as an odometer mechanism in ants. We show that ants transported by nest mates are capable of measuring travel distance exclusively by the use of OF cues. Furthermore, we demonstrate that the information gained from the optic flowmeter cannot be transferred to the stride integrator. Our results suggest a dual information channel that allows the ants to measure distances by strides and OF cues, although both systems operate independently and in a redundant manner.

  16. GPS analysis of human locomotion: further evidence for long-range correlations in stride-to-stride fluctuations of gait parameters.

    PubMed

    Terrier, Philippe; Turner, Vincent; Schutz, Yves

    2005-02-01

    During free walking, gait is automatically adjusted to provide optimal mechanical output and minimal energy expenditure; gait parameters, such as cadence, fluctuate from one stride to the next around average values. It was described that this fluctuation exhibited long-range correlations and fractal-like patterns. In addition, it was suggested that these long-range correlations disappeared if the participant followed the beep of metronome to regulate his or her pace. Until now, these fractal fluctuations were only observed for stride interval, because no technique existed to adequately analyze an extended time of free walking. The aim of the present study was to measure walking speed (WS), step frequency (SF) and step length (SL) with high accuracy (<1 cm) satellite positioning method (global positioning system or GPS) in order to detect long-range correlations in the stride-to-stride fluctuations. Eight participants walked 30 min under free and constrained (metronome) conditions. Under free walking conditions, DFA (detrended fluctuation analysis) and surrogate data tests showed that the fluctuation of WS, SL and SF exhibited a fractal pattern (i.e., scaling exponent alpha: 0.5 < alpha < 1) in a large majority of participants (7/8). Under constrained conditions (metronome), SF fluctuations became significantly anti-correlated (alpha < 0.5) in all participants. However, the scaling exponent of SL and WS was not modified. We conclude that, when the walking pace is controlled by an auditory signal, the feedback loop between the planned movement (at supraspinal level) and the sensory inputs induces a continual shifting of SF around the mean (persistent anti-correlation), but with no effect on the fluctuation dynamics of the other parameters (SL, WS).

  17. Non-linear dynamic characteristics and optimal control of giant magnetostrictive film subjected to in-plane stochastic excitation

    NASA Astrophysics Data System (ADS)

    Zhu, Z. W.; Zhang, W. D.; Xu, J.

    2014-03-01

    The non-linear dynamic characteristics and optimal control of a giant magnetostrictive film (GMF) subjected to in-plane stochastic excitation were studied. Non-linear differential items were introduced to interpret the hysteretic phenomena of the GMF, and the non-linear dynamic model of the GMF subjected to in-plane stochastic excitation was developed. The stochastic stability was analysed, and the probability density function was obtained. The condition of stochastic Hopf bifurcation and noise-induced chaotic response were determined, and the fractal boundary of the system's safe basin was provided. The reliability function was solved from the backward Kolmogorov equation, and an optimal control strategy was proposed in the stochastic dynamic programming method. Numerical simulation shows that the system stability varies with the parameters, and stochastic Hopf bifurcation and chaos appear in the process; the area of the safe basin decreases when the noise intensifies, and the boundary of the safe basin becomes fractal; the system reliability improved through stochastic optimal control. Finally, the theoretical and numerical results were proved by experiments. The results are helpful in the engineering applications of GMF.

  18. Non-linear dynamic characteristics and optimal control of giant magnetostrictive film subjected to in-plane stochastic excitation

    SciTech Connect

    Zhu, Z. W.; Zhang, W. D. Xu, J.

    2014-03-15

    The non-linear dynamic characteristics and optimal control of a giant magnetostrictive film (GMF) subjected to in-plane stochastic excitation were studied. Non-linear differential items were introduced to interpret the hysteretic phenomena of the GMF, and the non-linear dynamic model of the GMF subjected to in-plane stochastic excitation was developed. The stochastic stability was analysed, and the probability density function was obtained. The condition of stochastic Hopf bifurcation and noise-induced chaotic response were determined, and the fractal boundary of the system's safe basin was provided. The reliability function was solved from the backward Kolmogorov equation, and an optimal control strategy was proposed in the stochastic dynamic programming method. Numerical simulation shows that the system stability varies with the parameters, and stochastic Hopf bifurcation and chaos appear in the process; the area of the safe basin decreases when the noise intensifies, and the boundary of the safe basin becomes fractal; the system reliability improved through stochastic optimal control. Finally, the theoretical and numerical results were proved by experiments. The results are helpful in the engineering applications of GMF.

  19. Effects of footwear and stride length on metatarsal strains and failure in running.

    PubMed

    Firminger, Colin R; Fung, Anita; Loundagin, Lindsay L; Edwards, W Brent

    2017-08-16

    The metatarsal bones of the foot are particularly susceptible to stress fracture owing to the high strains they experience during the stance phase of running. Shoe cushioning and stride length reduction represent two potential interventions to decrease metatarsal strain and thus stress fracture risk. Fourteen male recreational runners ran overground at a 5-km pace while motion capture and plantar pressure data were collected during four experimental conditions: traditional shoe at preferred and 90% preferred stride length, and minimalist shoe at preferred and 90% preferred stride length. Combined musculoskeletal - finite element modeling based on motion analysis and computed tomography data were used to quantify metatarsal strains and the probability of failure was determined using stress-life predictions. No significant interactions between footwear and stride length were observed. Running in minimalist shoes increased strains for all metatarsals by 28.7% (SD 6.4%; p<0.001) and probability of failure for metatarsals 2-4 by 17.3% (SD 14.3%; p≤0.005). Running at 90% preferred stride length decreased strains for metatarsal 4 by 4.2% (SD 2.0%; p≤0.007), and no differences in probability of failure were observed. Significant increases in metatarsal strains and the probability of failure were observed for recreational runners acutely transitioning to minimalist shoes. Running with a 10% reduction in stride length did not appear to be a beneficial technique for reducing the risk of metatarsal stress fracture, however the increased number of loading cycles for a given distance was not detrimental either. Copyright © 2017. Published by Elsevier Ltd.

  20. Validity and test-retest reliability of the Stride Analyzer in people with knee osteoarthritis.

    PubMed

    Beckwée, David; Degelaen, Marc; Eggermont, Matthias; Gonzalez-Rodriguez, Miguel; Lefeber, Nina; Vaes, Peter; Bautmans, Ivan; Swinnen, Eva

    2016-09-01

    Subjects with knee osteoarthritis walk differently compared to healthy subjects. Managing these gait alterations has been proven effective for reducing pain and increasing function. The Stride Analyzer is a low cost gait analysis tool but its clinimetric properties have not been investigated yet in subjects with symptomatic knee osteoarthritis. The aim of this study was to investigate the reliability and validity of the SA compared with the Gold standard (Vicon) in persons with knee OA. Fifteen subjects with symptomatic knee osteoarthritis were instructed to walk at a self-selected speed in a gait laboratory. Temporospatial (TS) gait parameters were recorded simultaneously by the Stride Analyzer and by a 16-camera-infrared optoelectronic motion capturing system (Vicon). Validity and test-retest reliability of the Stride Analyzer were examined by Bland-Altman plots, intra-class correlation coefficients (ICC) and the standard error of measurement (SEM). Test-retest analyses showed good agreement for all TS parameters with ICC values ranging from 0.805 (single limb support right) to 0.949 (velocity) and SEM% values ranging from 0.78% (stance phase right (% of gait cycle)) to 4.52% (double limb support right (% of gait cycle)). Good agreement between Stride Analyzer and Vicon was found for the following TS parameters: velocity (z=1.01), cadence (z=-0.85), stride length (z=1.63) and gait cycle (z=0.86). All other gait parameters showed lower ICC values (<0.689). Our results suggest that the Stride Analyzer can be used in the clinical field to perform gait analysis in subjects with symptomatic knee osteoarthritis. Copyright © 2016 Elsevier B.V. All rights reserved.

  1. Influence of stride frequency and length on running mechanics: a systematic review.

    PubMed

    Schubert, Amy G; Kempf, Jenny; Heiderscheit, Bryan C

    2014-05-01

    A high number of recreational runners sustain a running-related injury each year. To reduce injury risk, alterations in running form have been suggested. One simple strategy for running stride frequency or length has been commonly advocated. To characterize how running mechanics change when stride frequency and length are manipulated. In January 2012, a comprehensive search of PubMed, CINAHL Plus, SPORTDiscus, PEDro, and Cochrane was performed independently by 2 reviewers. A second search of the databases was repeated in June 2012 to ensure that no additional studies met the criteria after the initial search. Inclusion criteria for studies were an independent variable including manipulation of stride frequency or length at a constant speed with outcome measures of running kinematics or kinetics. Systematic review. Level 3. Two reviewers independently appraised each article using a modified version of the Quality Index, designed for assessing bias of nonrandomized studies. Ten studies met the criteria for this review. There was consistent evidence that increased stride rate resulted in decreased center of mass vertical excursion, ground reaction force, shock attenuation, and energy absorbed at the hip, knee, and ankle joints. All but 1 study had a limited number of participants, with several methodological differences existing among studies (eg, overground and treadmill running, duration of test conditions). Although speed was held constant during testing, it was individually self-selected or fixed. Most studies used only male participants. Despite procedural differences among studies, an increased stride rate (reduced stride length) appears to reduce the magnitude of several key biomechanical factors associated with running injuries.

  2. Peripheral neuropathy does not alter the fractal dynamics of stride intervals of gait.

    PubMed

    Gates, Deanna H; Dingwell, Jonathan B

    2007-03-01

    The purpose of this study was to determine the effect (if any) of significant sensory loss on the long-range correlations normally observed in the stride intervals of human gait. Fourteen patients with severe peripheral neuropathy and 12 gender-, age-, height-, and weight-matched nondiabetic controls participated. Subjects walked around an approximately 200-m open-level walkway for 10 min at their comfortable pace. Continuous knee joint kinematics were recorded and used to calculate a stride interval time series for each subject. Power spectral density and detrended fluctuation analyses were used to determine whether these stride intervals exhibited long-range correlations. If the loss of long-range correlations indicates deterioration of the central control of gait, then changes in peripheral sensation should have no effect. If instead the loss of long-range correlations is a consequence of a general inability to regulate gait cycle timing, then a similar loss should occur in patients with peripheral locomotor disorders. Both power spectral density analyses and detrended fluctuation analyses showed that temporal correlations in the stride times of neuropathic and control subjects were statistically identical (P = 0.954 and P = 0.974, respectively), despite slower gait speeds (P = 0.008) and increased stride time variability (P = 0.036) among the neuropathy patients. All subjects in both groups exhibited long-range correlations. These findings demonstrate that the normal long-range correlation structure of stride intervals is unaltered by significant peripheral sensory loss. This further supports the hypothesis that the central nervous system is involved in the regulation of long-range correlations.

  3. Biomechanical analysis of hoof landing and stride parameters in harness trotter horses running on different tracks of a sand beach (from wet to dry) and on an asphalt road.

    PubMed

    Chateau, H; Holden, L; Robin, D; Falala, S; Pourcelot, P; Estoup, P; Denoix, J-M; Crevier-Denoix, N

    2010-11-01

    Sandy beaches are often considered good training surfaces for trotter horses. However, their biomechanical effects on locomotion are insufficiently documented. Events at hoof impact have mostly been studied under laboratory conditions with accelerometers, but there is lack of data (acceleration, force, movement) on events occurring under every day practical conditions in the field. To investigate hoof landing and stride parameters on different tracks (from wet to dry) of a sand beach and on an asphalt road. The right front hoof of 4 trotter horses was equipped with a triaxial accelerometer and a dynamometric horseshoe. Acceleration and force recordings (10 kHz) were synchronised with a high speed movie (600 Hz). Horses were driven on a sand beach where 3 tracks of decreasing water content had been delimited (from the sea to the shore): firm wet sand (FWS), deep wet sand (DWS) and deep dry sand (DDS). Firm wet sand and DWS were compared at 25 km/h and DDS compared to an asphalt road at 15 km/h. Recordings (10 strides) were randomly repeated 3 times. Statistical differences were tested using a GLM procedure (P < 0.05). Main significant results were 1) a decrease in the amplitude of the vertical deceleration (and force) of the hoof during impact on a softer surface (about 59% between DWS and FWS and 95% between DDS and asphalt), 2) a decrease in the longitudinal braking deceleration (and force) on softer grounds (50% for DWS vs. FWS and 55% for DDS vs. asphalt), 3) a decrease in the stride length and an increase in the stride frequency on a softer surface. Drier sand surfaces reduce shock and impact forces during landing. For daily training, it should, however, be realised that improved damping characteristics are associated with a shorter stride length and a higher stride frequency. © 2010 EVJ Ltd.

  4. Linear Growth and Final Height Characteristics in Adolescent Females with Anorexia Nervosa

    PubMed Central

    Kochavi, Brigitte; Toledano, Anat; Segev, Sharon; Balawi, Fadel; Mitrany, Edith; Stein, Daniel

    2012-01-01

    Objective Growth retardation is an established complication of anorexia nervosa (AN). However, findings concerning final height of AN patients are inconsistent. The aim of this study was to assess these phenomena in female adolescent inpatients with AN. Methods We retrospectively studied all 211 female adolescent AN patients hospitalized in an inpatient eating disorders department from 1/1/1987 to 31/12/99. Height and weight were assessed at admission and thereafter routinely during hospitalization and follow-up. Final height was measured in 69 patients 2–10 years after discharge. Pre-morbid height data was available in 29 patients. Results Patients’ height standard deviation scores (SDS) on admission (−0.285±1.0) and discharge (−0.271±1.02) were significantly (p<0.001) lower than expected in normal adolescents. Patients admitted at age ≤13 years, or less than 1 year after menarche, were more severely growth-impaired than patients admitted at an older age, (p = 0.03). Final height SDS, available for 69 patients, was −0.258±1.04, significantly lower than expected in a normal population (p = 0.04), and was more severely compromised in patients who were admitted less than 1 year from their menarche. In a subgroup of 29 patients with complete growth data (pre-morbid, admission, discharge, and final adult height), the pre-morbid height SDS was not significantly different from the expected (−0.11±1.1), whereas heights at the other time points were significantly (p = 0.001) lower (−0.56±1.2, −0.52±1.2, and −0.6±1.2, respectively). Conclusions Our findings suggest that whereas the premorbid height of female adolescent AN patients is normal, linear growth retardation is a prominent feature of their illness. Weight restoration is associated with catch-up growth, but complete catch-up is often not achieved. PMID:23029058

  5. On the Characteristics of Coaxial-Type Microwave Excited Linear Plasma: a Simple Numerical Analysis

    NASA Astrophysics Data System (ADS)

    Chen, Longwei; Meng, Yuedong; Zuo, Xiao; Ren, Zhaoxing; Wu, Kenan; Wang, Shuai

    2015-05-01

    To unveil the characteristics and available propagation mechanism of coaxial-type microwave excited line-shape plasma, the effects of parameters including microwave power, working pressure, dielectric constant, and external magnetic field on the plasma distribution were numerically investigated by solving a coupled system of Maxwell's equations and continuity equations. Numerical results indicate that high microwave power, relatively high working pressure, low dielectric constant, and shaped magnetic field profiles will help produce a high-density and uniform plasma source. Exciting both ends by microwave contributed to the high-density and uniform plasma source as well. Possible mechanisms were analyzed by using the polarization model of low temperature plasma. The generation and propagation processes of the line-shape plasma mainly depend on the interaction of three aspects, i.e. the transmitted part, penetration part and absorptive part of the electromagnetic field. The numerical results were qualitatively consistent with available experimental results from literature. More elaborate descriptions of the three aspects and corresponding interactions among them need to be investigated further to improve the properties of the line-shape plasma. supported by National Natural Science Foundation of China (Nos. 11205201 and 61205139), and the Scientific Foundation of Ministry of Education of China (No. N130405008)

  6. Exploring the relationship between stride, stature and hand size for forensic assessment.

    PubMed

    Guest, Richard; Miguel-Hurtado, Oscar; Stevenage, Sarah; Black, Sue

    2017-08-26

    Forensic evidence often relies on a combination of accurately recorded measurements, estimated measurements from landmark data such as a subject's stature given a known measurement within an image, and inferred data. In this study a novel dataset is used to explore linkages between hand measurements, stature, leg length and stride. These three measurements replicate the type of evidence found in surveillance videos with stride being extracted from an automated gait analysis system. Through correlations and regression modelling, it is possible to generate accurate predictions of stature from hand size, leg length and stride length (and vice versa), and to predict leg and stride length from hand size with, or without, stature as an intermediary variable. The study also shows improved accuracy when a subject's sex is known a-priori. Our method and models indicate the possibility of calculating or checking relationships between a suspect's physical measurements, particularly when only one component is captured as an accurately recorded measurement. Copyright © 2017 The Author(s). Published by Elsevier Ltd.. All rights reserved.

  7. [Reduction of plantar peak pressure by limiting stride length in diabetic patients].

    PubMed

    Drerup, B; Kolling, Ch; Koller, A; Wetz, H H

    2004-09-01

    Plantar peak pressure is a diagnostically significant parameter for the evaluation of the risk of foot ulceration in patients with diabetic neuropathy. The prophylaxis and therapy of the diabetic foot therefore is to a large extent oriented on peak pressure, and is aimed at an extensive reduction in this parameter. This is mainly accomplished with protective footwear including shoe modifications and cushioning. In comparison, other approaches affecting the loading and motion pattern of the patient are of minor importance--as for example control of gait pattern. In this study we examined shortening of stride length as a possible measure in reducing plantar peak pressure during gait. In 17 diabetic patients without acute foot ulcerations, stride length was reduced to 33% of leg length using an elastic hobble. This led to a reduction in stride length of 23%. At the same time, the walking speed was significantly reduced by 27% and the cadence by 5.7%. As a consequence, the peak pressure was reduced in nearly all regions of the foot--except the small toes. In the metatarsal region peak pressure is reduced by 14.5%. Thus, a reduction in stride length offers the possibility of reducing plantar peak pressure as a supplementary measure in addition to orthopaedic footwear. However, at present clinical feasibility has not yet been established.

  8. Making Some Modest Strides: The Story of Downtown Elementary School (DES)

    ERIC Educational Resources Information Center

    Alenuma, Sidonia Jessie

    2009-01-01

    This paper discusses research, (its process and results), on an inner city school. It highlights the methods of data collection used in the research and discusses the findings. Methods of data collection include observation, interview and documentary information. Results indicate that the school in question is making modest strides, in terms of…

  9. Long-Range Correlations in Stride Intervals May Emerge from Non-Chaotic Walking Dynamics

    PubMed Central

    Ahn, Jooeun; Hogan, Neville

    2013-01-01

    Stride intervals of normal human walking exhibit long-range temporal correlations. Similar to the fractal-like behaviors observed in brain and heart activity, long-range correlations in walking have commonly been interpreted to result from chaotic dynamics and be a signature of health. Several mathematical models have reproduced this behavior by assuming a dominant role of neural central pattern generators (CPGs) and/or nonlinear biomechanics to evoke chaos. In this study, we show that a simple walking model without a CPG or biomechanics capable of chaos can reproduce long-range correlations. Stride intervals of the model revealed long-range correlations observed in human walking when the model had moderate orbital stability, which enabled the current stride to affect a future stride even after many steps. This provides a clear counterexample to the common hypothesis that a CPG and/or chaotic dynamics is required to explain the long-range correlations in healthy human walking. Instead, our results suggest that the long-range correlation may result from a combination of noise that is ubiquitous in biological systems and orbital stability that is essential in general rhythmic movements. PMID:24086274

  10. Point particle binary system with components of different masses in the linear regime of the characteristic formulation of general relativity

    NASA Astrophysics Data System (ADS)

    Cedeño M, C. E.; de Araujo, J. C. N.

    2016-05-01

    A study of binary systems composed of two point particles with different masses in the linear regime of the characteristic formulation of general relativity with a Minkowski background is provided. The present paper generalizes a previous study by Bishop et al. The boundary conditions at the world tubes generated by the particles's orbits are explored, where the metric variables are decomposed in spin-weighted spherical harmonics. The power lost by the emission of gravitational waves is computed using the Bondi News function. The power found is the well-known result obtained by Peters and Mathews using a different approach. This agreement validates the approach considered here. Several multipole term contributions to the gravitational radiation field are also shown.

  11. Propulsion and guidance simulation of HTS bulk linear synchronous motor taking into account /E-J characteristic

    NASA Astrophysics Data System (ADS)

    Yoshida, K.; Matsumoto, H.

    2003-10-01

    We have proposed a new linear synchronous motor (LSM) theory which is based on an idea of considering the pinning force as synchronizing one in using current-carrying-armature-winding instead of permanent magnets. We have carried out basic experiments on two-dimensional electromagnetic forces produced in HTS bulk within DC-magnetic-field. As a result, we found that HTS bulk magnet in a cooling case can be levitated and guided stably according to the flux conditions between bulk and DC magnet. HTS bulk LSM can produce propulsion, levitation and guidance forces from zero speed, and be used in many applications. This paper proposes HTS bulk LSM analyzed and designed taking into account E- J characteristic. The LSM can produce stable guidance force without control. The LSM propulsion and guidance motion can be simulated numerically only by a simple propulsion control, which is not only closed-loop control but also open-loop control.

  12. A Novel Approach to Determine Strides, Ice Contact, and Swing Phases During Ice Hockey Skating Using a Single Accelerometer.

    PubMed

    Stetter, Bernd J; Buckeridge, Erica; von Tscharner, Vinzenz; Nigg, Sandro R; Nigg, Benno M

    2016-02-01

    This study presents a new approach for automated identification of ice hockey skating strides and a method to detect ice contact and swing phases of individual strides by quantifying vibrations in 3D acceleration data during the blade-ice interaction. The strides of a 30-m forward sprinting task, performed by 6 ice hockey players, were evaluated using a 3D accelerometer fixed to a hockey skate. Synchronized plantar pressure data were recorded as reference data. To determine the accuracy of the new method on a range of forward stride patterns for temporal skating events, estimated contact times and stride times for a sequence of 5 consecutive strides was validated. Bland-Altman limits of agreement (95%) between accelerometer and plantar pressure derived data were less than 0.019 s. Mean differences between the 2 capture methods were shown to be less than 1 ms for contact and stride time. These results demonstrate the validity of the novel approach to determine strides, ice contact, and swing phases during ice hockey skating. This technology is accurate, simple, effective, and allows for in-field ice hockey testing.

  13. The effect of footwear and footfall pattern on running stride interval long-range correlations and distributional variability.

    PubMed

    Fuller, Joel T; Amado, Avelino; Emmerik, Richard E A van; Hamill, Joseph; Buckley, Jonathan D; Tsiros, Margarita D; Thewlis, Dominic

    2016-02-01

    The presence of long-range correlations (self-similarity) in the stride-to-stride fluctuations in running stride interval has been used as an indicator of a healthy adaptable system. Changes to footfall patterns when running with minimalist shoes could cause a less adaptable running gait. The purpose of this study was to investigate stride interval variability and the degree of self-similarity of stride interval in runners wearing minimalist and conventional footwear. Twenty-six trained habitual rearfoot footfall runners, unaccustomed to running in minimalist footwear, performed 6-min sub-maximal treadmill running bouts at 11, 13 and 15 km·h(-1) in minimalist and conventional shoes. Force sensitive resistors were placed in the shoes to quantify stride interval (time between successive foot contacts). Footfall position, stride interval mean and coefficient of variation (CV), were used to assess performance as a function of shoe type. Long-range correlations of stride interval were assessed using detrended fluctuation analysis (α). Mean stride interval was 1-1.3% shorter (P=0.02) and 27% of runners adopted a midfoot footfall (MFF) in the minimalist shoe. There was a significant shoe effect on α and shoe*speed*footfall interaction effect on CV (P<0.05). Runners that adopted a MFF in minimalist shoes, displayed reduced long-range correlations (P<0.05) and CV (P<0.06) in their running stride interval at the 15 km·h(-1) speed. The reduced variability and self-similarity observed for runners that changed to a MFF in the minimalist shoe may be suggestive of a system that is less flexible and more prone to injury.

  14. Application of linear free energy relationships to characterizing the sorptive characteristics of organic contaminants on organoclays from water.

    PubMed

    Zhu, Runliang; Chen, Wangxiang; Liu, Yun; Zhu, Jianxi; Ge, Fei; He, Hongping

    2012-09-30

    Linear free energy relationships (LFERs) were applied to investigate the sorptive characteristics of organic contaminants (OCs) on organoclays from water. Three cetyltrimethylammonium modified montmorillonites (C-Mts) were selected as representative organoclays. The sorption coefficients (logK(oc)) of OCs on the C-Mts were calculated according to the results of batch sorption experiments. Then the LFER equations for OC sorption on C-Mts from water were developed. The results of this study showed that compared with bulk water, water saturated C-Mts are more polarizable, less polar and cohesive, and have stronger H-bond acceptor capacities and weaker H-bond donor capacities. The primary driving forces for the sorption of OCs from water to C-Mts can be ascribed to the weaker cohesive characteristics of C-Mts as well as the stronger nonspecific Van der Waals interaction between OCs and C-Mts. With increasing CTMA loading amount, the interaction between OCs and C-Mts increases whereas the C-Mts become more cohesive. Consequently, the sorption capacity of C-Mts first increases with CTMA loading amount and then decreases with further increased loading amount.

  15. Surface and buildup dose characteristics for 6, 10, and 18 MV photons from an Elekta Precise linear accelerator.

    PubMed

    Klein, Eric E; Esthappan, Jacqueline; Li, Zuofeng

    2003-01-01

    Understanding head scatter characteristics of photon beams is vital to properly commission treatment planning (TP) algorithms. Simultaneously, having definitive surface and buildup region dosimetry is important to optimize bolus. The Elekta Precise linacs have unique beam flattening filter configurations for each photon beam (6, 10, and 18 MV) in terms of material and location. We performed a comprehensive set of surface and buildup dose measurements with a thin window parallel-plate (PP) chamber to examine effects of field size (FS), source-to-skin distance (SSD), and attenuating media. Relative ionization data were converted to fractional depth dose (FDD) after correcting for bias effects and using the Gerbi method to account for chamber characteristics. Data were compared with a similar vintage Varian linac. At short SSDs the surface and buildup dose characteristics were similar to published data for Varian and Elekta accelerators. The FDD at surface (FDD(0)) for 6, 10, and 18 MV photons was 0.171, 0.159, and 0.199, respectively, for a 15x15 cm2, 100 cm SSD field. A blocking tray increased FDD(0) to 0.200, 0.200, and 0.256, while the universal wedge decreased FDD(0) to 0.107, 0.124, and 0.176. FDD(0) increased linearly with FS (approximately 1.16%/cm). FDD(0) decreased exponentially for 10 and 18 MV with increasing SSD. However, the 6 MV FDD(0) actually increased slightly with increasing SSD. This is likely due to the unique distal flattening filter for 6 MV. The measured buildup curves have been used to optimize TP calculations and guide bolus decisions. Overall the FDD(0) and buildup doses were very similar to published data. Of interest were the relatively low 10 MV surface doses, and the 6 MV FDD(0)'s dependence on SSD.

  16. Feel your stride and find your preferred running speed

    PubMed Central

    Lussiana, Thibault; Gindre, Cyrille

    2016-01-01

    ABSTRACT There is considerable inter-individual variability in self-selected intensity or running speed. Metabolic cost per distance has been recognized as a determinant of this personal choice. As biomechanical parameters have been connected to metabolic cost, and as different running patterns exist, we can question their possible determinant roles in self-selected speed. We examined the self-selected speed of 15 terrestrial and 16 aerial runners, with comparable characteristics, on a 400 m track and assessed biomechanical parameters and ratings of pleasure/displeasure. The results revealed that aerial runners choose greater speeds associated with shorter contact time, longer flight time, and higher leg stiffness than terrestrial runners. Pleasure was negatively correlated with contact time and positively with leg stiffness in aerial runners and was negatively correlated with flight time in terrestrial runners. We propose the existence of an optimization system allowing the connection of running patterns at running speeds, and feelings of pleasure or displeasure. PMID:26700723

  17. Feel your stride and find your preferred running speed.

    PubMed

    Lussiana, Thibault; Gindre, Cyrille

    2015-12-23

    There is considerable inter-individual variability in self-selected intensity or running speed. Metabolic cost per distance has been recognized as a determinant of this personal choice. As biomechanical parameters have been connected to metabolic cost, and as different running patterns exist, we can question their possible determinant roles in self-selected speed. We examined the self-selected speed of 15 terrestrial and 16 aerial runners, with comparable characteristics, on a 400 m track and assessed biomechanical parameters and ratings of pleasure/displeasure. The results revealed that aerial runners choose greater speeds associated with shorter contact time, longer flight time, and higher leg stiffness than terrestrial runners. Pleasure was negatively correlated with contact time and positively with leg stiffness in aerial runners and was negatively correlated with flight time in terrestrial runners. We propose the existence of an optimization system allowing the connection of running patterns at running speeds, and feelings of pleasure or displeasure. © 2016. Published by The Company of Biologists Ltd.

  18. Increased gait variability may not imply impaired stride-to-stride control of walking in healthy older adults: Winner: 2013 Gait and Clinical Movement Analysis Society Best Paper Award.

    PubMed

    Dingwell, Jonathan B; Salinas, Mandy M; Cusumano, Joseph P

    2017-06-01

    Older adults exhibit increased gait variability that is associated with fall history and predicts future falls. It is not known to what extent this increased variability results from increased physiological noise versus a decreased ability to regulate walking movements. To "walk", a person must move a finite distance in finite time, making stride length (Ln) and time (Tn) the fundamental stride variables to define forward walking. Multiple age-related physiological changes increase neuromotor noise, increasing gait variability. If older adults also alter how they regulate their stride variables, this could further exacerbate that variability. We previously developed a Goal Equivalent Manifold (GEM) computational framework specifically to separate these causes of variability. Here, we apply this framework to identify how both young and high-functioning healthy older adults regulate stepping from each stride to the next. Healthy older adults exhibited increased gait variability, independent of walking speed. However, despite this, these healthy older adults also concurrently exhibited no differences (all p>0.50) from young adults either in how their stride variability was distributed relative to the GEM or in how they regulated, from stride to stride, either their basic stepping variables or deviations relative to the GEM. Using a validated computational model, we found these experimental findings were consistent with increased gait variability arising solely from increased neuromotor noise, and not from changes in stride-to-stride control. Thus, age-related increased gait variability likely precedes impaired stepping control. This suggests these changes may in turn precede increased fall risk. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. Linear and nonlinear characteristics of the runoff response to regional climate factors in the Qira River basin, Xinjiang, Northwest China.

    PubMed

    Xue, Jie; Gui, Dongwei

    2015-01-01

    The inland river watersheds of arid Northwest China represent an example of how, in recent times, climatic warming has increased the complexity of Earth's hydrological processes. In the present study, the linear and nonlinear characteristics of the runoff response to temperature and precipitation were investigated in the Qira River basin, located on the northern slope of the Kunlun Mountains. The results showed that average temperature on annual and seasonal scales has displayed a significantly increasing trend, but this has not been reflected in accumulated precipitation and runoff. Using path analysis, a positive link between precipitation and runoff was found both annually and in the summer season. Conversely, it was found that the impact of temperature on runoff has been negative since the 1960s, attributable to higher evaporation and infiltration in the Qira River basin. Over the past 50 years, abrupt changes in annual temperature, precipitation and runoff occurred in 1997, 1987 and 1995, respectively. Combined with analysis using the correlation dimension method, it was found that the temperature, precipitation and runoff, both annually and seasonally, possessed chaotic dynamic characteristics, implying that complex hydro-climatic processes must be introduced into other variables within models to describe the dynamics. In addition, as determined via rescaled range analysis, a consistent annual and seasonal decreasing trend in runoff under increasing temperature and precipitation conditions in the future should be taken into account. This work may provide a theoretical perspective that can be applied to the proper use and management of oasis water resources in the lower reaches of river basins like that of the Qira River.

  20. Linear and nonlinear characteristics of the runoff response to regional climate factors in the Qira River basin, Xinjiang, Northwest China

    PubMed Central

    Xue, Jie

    2015-01-01

    The inland river watersheds of arid Northwest China represent an example of how, in recent times, climatic warming has increased the complexity of Earth’s hydrological processes. In the present study, the linear and nonlinear characteristics of the runoff response to temperature and precipitation were investigated in the Qira River basin, located on the northern slope of the Kunlun Mountains. The results showed that average temperature on annual and seasonal scales has displayed a significantly increasing trend, but this has not been reflected in accumulated precipitation and runoff. Using path analysis, a positive link between precipitation and runoff was found both annually and in the summer season. Conversely, it was found that the impact of temperature on runoff has been negative since the 1960s, attributable to higher evaporation and infiltration in the Qira River basin. Over the past 50 years, abrupt changes in annual temperature, precipitation and runoff occurred in 1997, 1987 and 1995, respectively. Combined with analysis using the correlation dimension method, it was found that the temperature, precipitation and runoff, both annually and seasonally, possessed chaotic dynamic characteristics, implying that complex hydro-climatic processes must be introduced into other variables within models to describe the dynamics. In addition, as determined via rescaled range analysis, a consistent annual and seasonal decreasing trend in runoff under increasing temperature and precipitation conditions in the future should be taken into account. This work may provide a theoretical perspective that can be applied to the proper use and management of oasis water resources in the lower reaches of river basins like that of the Qira River. PMID:26244113

  1. Growth, spectral, linear and nonlinear optical characteristics of an efficient semiorganic acentric crystal: L-valinium L-valine chloride

    NASA Astrophysics Data System (ADS)

    Nageshwari, M.; Jayaprakash, P.; Kumari, C. Rathika Thaya; Vinitha, G.; Caroline, M. Lydia

    2017-04-01

    An efficient nonlinear optical semiorganic material L-valinium L-valine chloride (LVVCl) was synthesized and grown-up by means of slow evaporation process. Single crystal XRD evince that LVVCl corresponds to monoclinic system having acentric space group P21. The diverse functional groups existing in LVVCl were discovered with FTIR spectral investigation. The UV-Visible and photoluminescence spectrum discloses the optical and electronic properties respectively for the grown crystal. Several optical properties specifically extinction coefficient, reflectance, linear refractive index, electrical and optical conductivity were also determined. The SEM analysis was also carried out and it portrayed the surface morphology of LVVCl. The calculated value of laser damage threshold was 2.59 GW/cm2. The mechanical and dielectric property of LVVCl was investigated employing microhardness and dielectric studies. The second and third order nonlinear optical characteristics of LVVCl was characterized utilizing Kurtz Perry and Z scan technique respectively clearly suggest its suitability in the domain of optics and photonics.

  2. Nest-site characteristics and linear abundance of cliff-nesting American kestrels on San Clemente Island, California

    USGS Publications Warehouse

    Sullivan, Brian L.; Kershner, Eric L.; Finn, S.P.; Condon, Anne M.; Cooper, Douglass M.; Garcelon, David K.

    2003-01-01

    American Kestrels( Falco sparverius) are typically secondary-cavity nesters, and use of natural cliff cavities for nest sites is less-commonly reported. On San Clemente Island (SCI), California, however, American Kestrels nest primarily on cliffs in major canyons(93%), to a lesser extent on seacliffs(4%), as well as in man-made structures (3%). We located and mapped 99 American Kestrel territories on SCI, and recorded 11 nest-site characteristics at 40 cliff nests during 2001-02. Nest cliffs were typically fractured igneous rock with mean height of 16.1 m +_ 1.8 SE. Mean slope of nest cliffs was vertical (x=91 degrees). Nest cliffs and cavities were significantly oriented to the southeast, away from the prevailing wind direction(NW). In eight canyons, where we believe that we found all occupied American Kestrel territories, the mean linear abundance was 2.1 pairs/km, greater than most published estimates. Contrary to most previous studies, no American Kestrels nested in tree cavities despite their presence in SCI canyons. The absence of cavity-excavating breeding birds from the island likely restricts kestrels to nesting in naturally-formed cavities and man-made structures.

  3. Ventilatory responses when altering stride frequency at a constant oxygen uptake.

    PubMed

    McMurray, R G; Smith, L G

    1985-10-01

    Ten women completed a slow walk (SW), fast walk (FW) and a slow run (R) on a motor driven treadmill to evaluate the effect of varying stride frequency on ventilatory responses. The treadmill grade was adjusted during the walks such that the oxygen uptake was the same as during running at 0% grade. Stride frequencies averaged 59, 69 and 80 strides/min for the SW, FW and R, respectively. Oxygen uptake was similar for all three trials (1.78 L/min); as were heart frequencies (154.6 beats/min). Mean blood pressure was unaffected by changing stride frequency. Minute ventilation was similar for all three trials (ca. 47.3 L/min). Significant differences in respiratory frequency were observed (SW = 33.2, FW = 35.4, R = 37.2 breaths/min). Tidal volumes were significantly greater during the slow walk (1417 ml) than either the fast walk (1331 ml) or the run (1301 ml). CO2 output was significantly greater during the run compared to either of the walking trials. End-tidal CO2 was 38.6 mm Hg during the slow walk and was significantly reduced during the fast walk (36.3) and run (36.0). The results suggest the existence of a mild hypocapnia during the fast walk and running exercise. These results further suggest that variations in ventilatory patterns exist during walking and running that are not totally accountable by blood pressure or CO2 and may be related to extra-metabolic stimuli.

  4. The ergogenic effect of elastic therapeutic tape on stride and step length in fatigued runners.

    PubMed

    Ward, John; Sorrels, Kenneth; Coats, Jesse; Pourmoghaddam, Amir; Moskop, JoAnn; Ueckert, Kate; Glass, Amanda

    2014-12-01

    The purpose of this study was to determine if elastic therapeutic tape placed on anterior lower limbs would affect stride and step length in fatigued runners' gait. Forty-two healthy participants were equally divided into a kinesiology tape group (Rocktape) and a no-tape control group. Participants in both groups underwent a baseline running gait test at 6 mph without tape. After this, participants engaged in an exhaustive lower body fatigue protocol until they reached maximal volitional exhaustion. Participants were then randomized to 1 of 2 interventions: (1) Experimental group, which had kinesiology tape placed under tension on the anterior aspect of their lower limbs bilaterally from the upper thigh to just below the patella, or (2) Control group, which did not receive taping. All participants then engaged in a similar 6-mph running gait postanalysis. Participant's gait was analyzed for 90 seconds during each test iteration. Researchers used a 2-way repeated-measures analysis of variance considering fatigue (prefatigue, postfatigue) and group (tape, no-tape) as subject factors. After the fatigue protocol, the no-tape group demonstrated a significant decrease in step length of 14.2 mm (P = .041) and stride length of 29.4 mm (P = .043). The kinesiology tape group did not demonstrate a significant decline in these gait parameters. In this preliminary study, placing elastic therapeutic tape over the anterior lower limbs demonstrated short-term preservation of runner step length and stride length in a fatigued state.

  5. Stride Counting in Human Walking and Walking Distance Estimation Using Insole Sensors

    PubMed Central

    Truong, Phuc Huu; Lee, Jinwook; Kwon, Ae-Ran; Jeong, Gu-Min

    2016-01-01

    This paper proposes a novel method of estimating walking distance based on a precise counting of walking strides using insole sensors. We use an inertial triaxial accelerometer and eight pressure sensors installed in the insole of a shoe to record walkers’ movement data. The data is then transmitted to a smartphone to filter out noise and determine stance and swing phases. Based on phase information, we count the number of strides traveled and estimate the movement distance. To evaluate the accuracy of the proposed method, we created two walking databases on seven healthy participants and tested the proposed method. The first database, which is called the short distance database, consists of collected data from all seven healthy subjects walking on a 16 m distance. The second one, named the long distance database, is constructed from walking data of three healthy subjects who have participated in the short database for an 89 m distance. The experimental results show that the proposed method performs walking distance estimation accurately with the mean error rates of 4.8% and 3.1% for the short and long distance databases, respectively. Moreover, the maximum difference of the swing phase determination with respect to time is 0.08 s and 0.06 s for starting and stopping points of swing phases, respectively. Therefore, the stride counting method provides a highly precise result when subjects walk. PMID:27271634

  6. Complexity analysis of stride interval time series by threshold dependent symbolic entropy.

    PubMed

    Aziz, Wajid; Arif, Muhammad

    2006-09-01

    The stride interval of human gait fluctuates in complex fashion. It reflects the rhythm of the locomotor system. The temporal fluctuations in the stride interval provide us a non-invasive technique to evaluate the effects of neurological impairments on gait and its changes with age and disease. In this paper, we have used threshold dependent symbolic entropy, which is based on symbolic nonlinear time series analysis to study complexity of gait of control and neurodegenerative disease subjects. Symbolic entropy characterizes quantitatively the complexity even in time series having relatively few data points. We have calculated normalized corrected Shannon entropy (NCSE) of symbolic sequences extracted from stride interval time series. This measure of complexity showed significant difference between control and neurodegenerative disease subjects for a certain range of thresholds. We have also investigated complexity of physiological signal and randomized noisy data. In the study, we have found that the complexity of physiological signal was higher than that of random signals at short threshold values.

  7. Making Strides

    ERIC Educational Resources Information Center

    Roach, Ronald

    2008-01-01

    Since 1980, Dr. Linda Hayden has been able to bring innovation to Elizabeth City State University (ECSU) by seeking out and partnering with entities like the U.S. Navy and NASA. For years, these partnerships allowed faculty, students, and administrators in the computer science department and other departments to gain early exposure to cutting-edge…

  8. Making strides

    SciTech Connect

    Anderson, J.; Burr, M.T.

    1997-01-01

    Inge Fretheim, president of Amoco Power Resources Corp., was speaking to an audience of developers, finance executives and other power industry leader at the Fifth Annual Independent Energy Forum in New York City last October. {open_quotes}A deregulated framework should include market competition, not just private investment that the government defines,{close_quotes} he said. {open_quotes}Governments that only seek to increase the efficiency of power generation itself will not see the full benefits that the IPP industry can bring to the table.{close_quotes} The industry has made significant progress in many markets around the world in the past year, but a number of obstacles are still standing in developers` way. As Fretheim pointed out, in many cases project tender solicitations are too rigid to allow the competitive process to achieve its full potential. When companies are asked to bid on a pre-defined {open_quotes}box,{close_quotes} they are not able to bring their full palette of skills and resources to the canvas. Competitive bidding has during the past year become a favorite means of awarding project contracts in many countries around the world. This trend reflect the increasing state of competitiveness in the global power industry. New financing sources are emerging, but not enough to fill the gap. Numerous examples of the industry`s consolidation--including the Enron/Portland General merger. Southern Energy International`s purchase of Consolidated Electric Power Asia and Tractebel`s acquisition of CRSS Capital and several plants in the United States--point toward an industry of large, trans-border utility companies.

  9. Making Strides

    ERIC Educational Resources Information Center

    Jarrell, Andrea

    2013-01-01

    In the mad dash to complete the plethora of projects that lead up to the public launch of a campaign, it would be easy to start thinking of the kickoff as a goal in itself, but it's merely a mile marker in the marathon of a fundraising campaign that may last five to 10 years. Given that only a fraction of an institution's constituents may attend a…

  10. Making Strides

    ERIC Educational Resources Information Center

    Jarrell, Andrea

    2013-01-01

    In the mad dash to complete the plethora of projects that lead up to the public launch of a campaign, it would be easy to start thinking of the kickoff as a goal in itself, but it's merely a mile marker in the marathon of a fundraising campaign that may last five to 10 years. Given that only a fraction of an institution's constituents may attend a…

  11. Making Strides

    ERIC Educational Resources Information Center

    Roach, Ronald

    2008-01-01

    Since 1980, Dr. Linda Hayden has been able to bring innovation to Elizabeth City State University (ECSU) by seeking out and partnering with entities like the U.S. Navy and NASA. For years, these partnerships allowed faculty, students, and administrators in the computer science department and other departments to gain early exposure to cutting-edge…

  12. Effects of socks which improved foot sensation on velocity and stride length of elderly subjects crossing obstacles.

    PubMed

    Yoo, Won-Gyu

    2015-08-01

    [Purpose] We developed socks which improve foot sensation and investigated their effect on the velocity and stride length of elderly women crossing obstacles. [Subjects] Ten community-dwelling, elderly women who could walk independently were recruited. [Methods] We measured velocity and stride length using the GAITRite system while the participants crossed obstacles under three conditions: barefoot, wearing ordinary socks, and wearing the socks which improve foot sensation. [Results] Velocity and stride length in bare feet and when wearing the sense-improving socks increased significantly compared to their values when wearing standard socks. Velocity and stride length did not differ between the bare foot and improved sock conditions. [Conclusion] Wearing socks helps protect the foot, but can decrease foot sensory input. Therefore, the socks which improve foot sensation were useful for preventing falls and protecting the feet of the elderly women while they crossed obstacles.

  13. Environmental monitoring of linear alkylbenzene sulfonates and physicochemical characteristics of seawater in El-Mex Bay (Alexandria, Egypt).

    PubMed

    Okbah, M A; Ibrahim, A M A; Gamal, M N M

    2013-04-01

    In the present work, the influence of different physicochemical characteristics on the distribution of anionic detergents, linear alkylbenzene sulfonates (LAS), was studied. Surface and bottom water samples were collected from eight different sites from a small bay near the main sewage discharge of Alexandria City (El-Max Bay). The results showed great variations in the concentrations, as a function of the regional and seasonal variations. The study revealed that the pH values lie in the normal side, with a range of 8.0-8.5 inside the bay and 7.5-7.7 at El-Umum Drain effluent. Wide variations, observed between the surface and the bottom water of the bay, salinity, dissolved oxygen, oxidizable organic matter, total hardness, and total alkalinity, were scattered in the ranges (3.33-42.73 practical salinity unit), (0.42-8.27 mg O2/l), (0.12-10.49 mg/l), (1.39-8.99 mg/l), and (0.23-0.48 mg/l), respectively. The regional variations of LAS concentrations in the bay waters showed that the concentration decreased as the distance from the source of drainage water (El-Umum Drain). The seasonal average variations of LAS cleared out that summer and spring periods had the highest concentrations at surface (0.13 ± 0.04 mg LAS/l) and bottom (0.12 ± 0.10 mg LAS/l) layer, which is attributed to increase in population density and human activities. The inverse relationships between total LAS concentration and salinity, dissolved oxygen, and calcium ions concentration are r = -0.78, 0.50, and 0.67, respectively. This is related to the occurrence of the untreated wastewater containing detergents, the biodegradation rate of surfactants, and strong precipitation of LAS as Ca.

  14. The influence of minimalist footwear and stride length reduction on lower-extremity running mechanics and cumulative loading.

    PubMed

    Firminger, Colin R; Edwards, W Brent

    2016-12-01

    To examine the effects of shoe type and stride length reduction on lower-extremity running mechanics and cumulative loading. Within-subject with four conditions: (1) control shoe at preferred stride length; (2) control shoe at 90% preferred stride length; (3) minimalist shoe at preferred stride length; (4) minimalist shoe at 90% preferred stride length. Fourteen young healthy males ran overground at their preferred speed while motion capture, force platform, and plantar pressure data were collected. Peak moments, impulse, mechanical work, and cumulative impulse were calculated at the metatarsophalangeal, ankle, and knee joint, and compared between conditions using a 2×2 factor repeated measures ANOVA. In general, running in minimalist footwear increased measures of loading at the metatarsophalangeal joint and ankle joint (mean increases of 7.3% and 5.9%, respectively), but decreased measures of loading at the knee (mean decrease of 7.3%). Conversely, running with reduced stride length decreased single-stance measures of loading at the ankle and knee joint (ranging from -0.9% to -20.5%), though cumulative impulse was higher at the ankle and lower at the knee. Running in minimalist shoes increased loads at the metatarsophalangeal and ankle joint, which may explain some of the incidence of overuse injuries observed in minimalist shoe users. Decreased ankle loads at 90% preferred stride length were not necessarily sufficient to reduce cumulative loads when impulse and loading cycles were weighted equally. Knee loads decreased more when running at 90% preferred stride length (16.2% mean reduction) versus running in a minimalist shoe (7.3% mean reduction), but both load reduction mechanisms appeared to have an additive effect (22.2% mean reduction). Copyright © 2016 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

  15. Stride Segmentation during Free Walk Movements Using Multi-Dimensional Subsequence Dynamic Time Warping on Inertial Sensor Data

    PubMed Central

    Barth, Jens; Oberndorfer, Cäcilia; Pasluosta, Cristian; Schülein, Samuel; Gassner, Heiko; Reinfelder, Samuel; Kugler, Patrick; Schuldhaus, Dominik; Winkler, Jürgen; Klucken, Jochen; Eskofier, Björn M.

    2015-01-01

    Changes in gait patterns provide important information about individuals’ health. To perform sensor based gait analysis, it is crucial to develop methodologies to automatically segment single strides from continuous movement sequences. In this study we developed an algorithm based on time-invariant template matching to isolate strides from inertial sensor signals. Shoe-mounted gyroscopes and accelerometers were used to record gait data from 40 elderly controls, 15 patients with Parkinson’s disease and 15 geriatric patients. Each stride was manually labeled from a straight 40 m walk test and from a video monitored free walk sequence. A multi-dimensional subsequence Dynamic Time Warping (msDTW) approach was used to search for patterns matching a pre-defined stride template constructed from 25 elderly controls. F-measure of 98% (recall 98%, precision 98%) for 40 m walk tests and of 97% (recall 97%, precision 97%) for free walk tests were obtained for the three groups. Compared to conventional peak detection methods up to 15% F-measure improvement was shown. The msDTW proved to be robust for segmenting strides from both standardized gait tests and free walks. This approach may serve as a platform for individualized stride segmentation during activities of daily living. PMID:25789489

  16. Effect of stride length manipulation on symptoms of exercise-induced muscle damage and the repeated bout effect.

    PubMed

    Rowlands, A V; Eston, R G; Tilzey, C

    2001-05-01

    This study assessed the effects of stride length on symptoms of exercise-induced muscle damage after downhill running and whether the extent of the symptoms sustained in a repeated bout of downhill running are influenced by stride length manipulation in the first bout. Eighteen males aged 21.1 +/- 0.6 years (mean +/- s) were allocated to one of three groups for bout one: preferred stride frequency, overstride and understride. Bout two was performed 2 weeks later at the participants' preferred stride frequency. Maximal isometric force and perceived muscle soreness were assessed pre-test and 30 min, 24, 48 and 72 h post-exercise for each downhill run. Three-factor analyses of variance with repeated measures on time and bout were used for analysis. Results revealed a three-way interaction for soreness (F8,60 = 3.56, P < 0.05) and relative isometric strength (F5.0,37.8 = 3.2, P < 0.05). Post-hoc analyses revealed that, after bout one, the overstride group perceived most soreness and the understride group retained most strength. After the second bout, the overstride and preferred stride frequency groups perceived less soreness than the preferred stride frequency group in bout one. Strength retention was greater after bout two for all groups. In conclusion, strength retention after a repeated bout appears to be independent of the damage experienced in the initial bout of downhill running. However, understriding may provide least protection against soreness in a subsequent bout.

  17. Kernel-Smoothing Estimation of Item Characteristic Functions for Continuous Personality Items: An Empirical Comparison with the Linear and the Continuous-Response Models

    ERIC Educational Resources Information Center

    Ferrando, Pere J.

    2004-01-01

    This study used kernel-smoothing procedures to estimate the item characteristic functions (ICFs) of a set of continuous personality items. The nonparametric ICFs were compared with the ICFs estimated (a) by the linear model and (b) by Samejima's continuous-response model. The study was based on a conditioned approach and used an error-in-variables…

  18. Kernel-Smoothing Estimation of Item Characteristic Functions for Continuous Personality Items: An Empirical Comparison with the Linear and the Continuous-Response Models

    ERIC Educational Resources Information Center

    Ferrando, Pere J.

    2004-01-01

    This study used kernel-smoothing procedures to estimate the item characteristic functions (ICFs) of a set of continuous personality items. The nonparametric ICFs were compared with the ICFs estimated (a) by the linear model and (b) by Samejima's continuous-response model. The study was based on a conditioned approach and used an error-in-variables…

  19. A comparative analysis of spectral exponent estimation techniques for 1/f(β) processes with applications to the analysis of stride interval time series.

    PubMed

    Schaefer, Alexander; Brach, Jennifer S; Perera, Subashan; Sejdić, Ervin

    2014-01-30

    The time evolution and complex interactions of many nonlinear systems, such as in the human body, result in fractal types of parameter outcomes that exhibit self similarity over long time scales by a power law in the frequency spectrum S(f)=1/f(β). The scaling exponent β is thus often interpreted as a "biomarker" of relative health and decline. This paper presents a thorough comparative numerical analysis of fractal characterization techniques with specific consideration given to experimentally measured gait stride interval time series. The ideal fractal signals generated in the numerical analysis are constrained under varying lengths and biases indicative of a range of physiologically conceivable fractal signals. This analysis is to complement previous investigations of fractal characteristics in healthy and pathological gait stride interval time series, with which this study is compared. The results of our analysis showed that the averaged wavelet coefficient method consistently yielded the most accurate results. Class dependent methods proved to be unsuitable for physiological time series. Detrended fluctuation analysis as most prevailing method in the literature exhibited large estimation variances. The comparative numerical analysis and experimental applications provide a thorough basis for determining an appropriate and robust method for measuring and comparing a physiologically meaningful biomarker, the spectral index β. In consideration of the constraints of application, we note the significant drawbacks of detrended fluctuation analysis and conclude that the averaged wavelet coefficient method can provide reasonable consistency and accuracy for characterizing these fractal time series. Copyright © 2013 Elsevier B.V. All rights reserved.

  20. The Effect of Stride Length and Lateral Pelvic Tilt on Elbow Torque in Youth Baseball Pitchers.

    PubMed

    Tocci, Noah X; Howell, David R; Sugimoto, Dai; Dawkins, Corey; Whited, Amy; Bae, Donald

    2017-09-23

    High elbow torque during a pitch may contribute to injury risk. Our objective was to determine the pitch mechanics associated with elbow varus torque in youth baseball pitchers. Eighteen male youth pitchers (age = 15.5 ± 1.6 years) threw 3 fastballs and 3 change-ups from a windup position while undergoing 3-dimensional kinematic analysis. Independent variables included ball release point distance, stride length, lateral pelvic tilt, and ball velocity. Two multiple regression models, separated by pitch type (fastball, change-up) were used to determine the association of independent variables with peak varus torque at the elbow. Fastball and change-up regression models indicated that stride length (β = 0.301, p = .015; β = 0.46, p < .001, respectively) and lateral pelvic tilt (β = -0.50, p < .001; β = -0.25, p = .04, respectively) were significantly associated with peak elbow varus torque. During fastballs, pitch velocity was significantly associated with peak elbow varus torque (β = 0.38, p = .002), while release point distance was significantly associated with peak elbow varus torque during change-ups (β = -0.33, p = .015). Youth pitchers with longer strides and less lateral pelvic tilt demonstrated greater elbow torque regardless of pitch type, while the association of ball velocity and release point to elbow varus torque was dependent on pitch type.

  1. Gait dynamics in Pisa syndrome and Camptocormia: The role of stride length and hip kinematics.

    PubMed

    Tramonti, C; Di Martino, S; Unti, E; Frosini, D; Bonuccelli, U; Rossi, B; Ceravolo, R; Chisari, C

    2017-09-01

    This is an observational cross-sectional study evaluating gait dynamics in patients with Parkinson's Disease (PD) and severe postural deformities, PD without axial deviations and healthy subjects. Ten PS individuals with Pisa syndrome (PS) and nine subjects with Camptocormia (CC) performed 3-D Gait Analysis and were evaluated with walking and balance scales. Correlations with clinical and functional scales were investigated. Spatio-temporal and kinematic data were compared to ten PD subjects without postural deformities (PP) and ten healthy matched individuals (CG). Data obtained showed decreased walking velocity, stride and step length in PP, PS and CC groups compared to controls. The correlation analysis showed that stride and step length were associated with reduced functional abilities and disease severity in PS and CC groups. Kinematic data revealed marked reduction in range of movements (ROMs) at all lower-extremity joints in PS group. While, in CC group the main differences were pronounced in hip and knee joints. PS and CC groups presented a more pronounced reduction in hip articular excursion compared to PP subjects, revealing an increased hip flexion pattern during gait cycle. Moreover, the increased hip and knee flexion pattern adversely affected functional performance during walking tests. Results obtained provide evidence that step length, along with stride length, can be proposed as simple and clear indicators of disease severity and reduced functional abilities. The reduction of ROMs at hip joint represented an important mechanism contributing to decreased walking velocity, balance impairment and reduced gait performance in PD patients with postural deformities. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Running-specific, periodized strength training attenuates loss of stride length during intense endurance running.

    PubMed

    Esteve-Lanao, Jonathan; Rhea, Matthew R; Fleck, Steven J; Lucia, Alejandro

    2008-07-01

    The purpose of this study was to determine the effects of a running-specific, periodized strength training program (performed over the specific period [8 weeks] of a 16-week macrocycle) on endurance-trained runners' capacity to maintain stride length during running bouts at competitive speeds. Eighteen well-trained middle-distance runners completed the study (personal bests for 1500 and 5000 m of 3 minutes 57 seconds +/- 12 seconds and 15 minutes 24 seconds +/- 36 seconds). They were randomly assigned to each of the following groups (6 per group): periodized strength group, performing a periodized strength training program over the 8-week specific (intervention) period (2 sessions per week); nonperiodized strength group, performing the same strength training exercises as the periodized group over the specific period but with no week-to-week variations; and a control group, performing no strength training at all during the specific period. The percentage of loss in the stride length (cm)/speed (m.s) (SLS) ratio was measured by comparing the mean SLS during the first and third (last) group of the total repetitions, respectively, included in each of the interval training sessions performed at race speeds during the competition period that followed the specific period. Significant differences (p < 0.05) were found in mean percentage of SLS loss between the 3 study groups, with the periodized strength group showing no significant SLS change (0.36 +/- 0.95%) and the 2 other groups showing a moderate or high SLS loss (-1.22 +/- 1.5% and -3.05 +/- 1.2% for the nonperiodized strength and control groups, respectively). In conclusion, periodized, running-specific strength training minimizes the loss of stride length that typically occurs in endurance runners during fatiguing running bouts.

  3. The Ergogenic Effect of Elastic Therapeutic Tape on Stride and Step Length in Fatigued Runners

    PubMed Central

    Ward, John; Sorrels, Kenneth; Coats, Jesse; Pourmoghaddam, Amir; Moskop, JoAnn; Ueckert, Kate; Glass, Amanda

    2014-01-01

    Objective The purpose of this study was to determine if elastic therapeutic tape placed on anterior lower limbs would affect stride and step length in fatigued runners’ gait. Methods Forty-two healthy participants were equally divided into a kinesiology tape group (Rocktape) and a no-tape control group. Participants in both groups underwent a baseline running gait test at 6 mph without tape. After this, participants engaged in an exhaustive lower body fatigue protocol until they reached maximal volitional exhaustion. Participants were then randomized to 1 of 2 interventions: (1) Experimental group, which had kinesiology tape placed under tension on the anterior aspect of their lower limbs bilaterally from the upper thigh to just below the patella, or (2) Control group, which did not receive taping. All participants then engaged in a similar 6-mph running gait postanalysis. Participant’s gait was analyzed for 90 seconds during each test iteration. Researchers used a 2-way repeated-measures analysis of variance considering fatigue (prefatigue, postfatigue) and group (tape, no-tape) as subject factors. Results After the fatigue protocol, the no-tape group demonstrated a significant decrease in step length of 14.2 mm (P = .041) and stride length of 29.4 mm (P = .043). The kinesiology tape group did not demonstrate a significant decline in these gait parameters. Conclusions In this preliminary study, placing elastic therapeutic tape over the anterior lower limbs demonstrated short-term preservation of runner step length and stride length in a fatigued state. PMID:25435835

  4. INS/EKF-based stride length, height and direction intent detection for walking assistance robots.

    PubMed

    Brescianini, Dario; Jung, Jun-Young; Jang, In-Hun; Park, Hyun Sub; Riener, Robert

    2011-01-01

    We propose an algorithm used to obtain the information on stride length, height difference, and direction based on user's intent during walking. For exoskeleton robots used to assist paraplegic patients' walking, this information is used to generate gait patterns by themselves in on-line. To obtain this information, we attach an inertial measurement unit(IMU) on crutches and apply an extended kalman filter-based error correction method to reduce the phenomena of drift due to bias of the IMU. The proposed method is verifed in real walking scenarios including walking, climbing up-stairs, and changing direction of walking with normal. © 2011 IEEE

  5. Linear Elastic Waves

    NASA Astrophysics Data System (ADS)

    Revenough, Justin

    Elastic waves propagating in simple media manifest a surprisingly rich collection of phenomena. Although some can't withstand the complexities of Earth's structure, the majority only grow more interesting and more important as remote sensing probes for seismologists studying the planet's interior. To fully mine the information carried to the surface by seismic waves, seismologists must produce accurate models of the waves. Great strides have been made in this regard. Problems that were entirely intractable a decade ago are now routinely solved on inexpensive workstations. The mathematical representations of waves coded into algorithms have grown vastly more sophisticated and are troubled by many fewer approximations, enforced symmetries, and limitations. They are far from straightforward, and seismologists using them need a firm grasp on wave propagation in simple media. Linear Elastic Waves, by applied mathematician John G. Harris, responds to this need.

  6. Relationship of stride activity and participation in mobility-based life habits among children with cerebral palsy

    PubMed Central

    Bjornson, Kristie F.; Zhou, Chuan; Stevenson, Richard D.; Christakis, Dimitri

    2014-01-01

    Objective To date walking outcomes in cerebral palsy (CP) have been capacity-based (what a child does in structured setting). Physical activity performance (what a child really does in daily life) has been documented to influence the relationship of capacity-based gross motor measures to participation.(1) This study examines the relationship between walking performance and participation in mobility-related habits of daily life in children with CP. Design Cross-sectional prospective cohort study. Setting Regional pediatric specialty care centers Participants A cohort of 128 ambulatory children with CP ages 2–9 yrs, 41% female, and 49% having hemiplegia participated. Interventions Not Applicable. Main Outcome Measures Walking performance was quantified from a 5-day sample of StepWatch accelerometry data. Stride activity was summarized through the outcomes of average total strides/day (independent of intensity) and average number of strides/day at > 30 strides/minute (marker of intensity). Mobility-based participation was assessed by the Life Habits (Life-H) categories of Personal Care, Housing, Mobility, and Recreation. Regression models were developed controlling for gender, age, cognition, communication, pain, and body composition. Results Average total strides/day was positively associated with the Personal Care, Housing, Mobility, and Recreation Life-H categories (β = .34 to.41, p <.001). Average number of strides > 30 stride/min/day was associated with all categories (β = .54 to.60, p < .001). Conclusions Accelerometry-based walking activity performance is significantly associated with levels of participation in mobility-based life habits for ambulatory children with CP. Evaluation of other factors and the direction of relationships within the ICF is warranted to inform rehabilitation strategies. PMID:24231402

  7. Manipulating the stride length/stride velocity relationship of walking using a treadmill and rhythmic auditory cueing in non-disabled older individuals. A short-term feasibility study.

    PubMed

    Eikema, D J A; Forrester, L W; Whitall, J

    2014-09-01

    One target for rehabilitating locomotor disorders in older adults is to increase mobility by improving walking velocity. Combining rhythmic auditory cueing (RAC) and treadmill training permits the study of the stride length/stride velocity ratio (SL/SV), often reduced in those with mobility deficits. We investigated the use of RAC to increase velocity by manipulating the SL/SV ratio in older adults. Nine participants (6 female; age: 61.1 ± 8.8 years) walked overground on a gait mat at preferred and fast speeds. After acclimatization to comfortable speed on a treadmill, participants adjusted their cadence to match the cue for 3 min at 115% of preferred speed by either (a) increasing stride length only or (b) increasing stride frequency only. Following training, participants walked across the gait mat at preferred velocity without, and then with, RAC. Group analysis determined no immediate overground velocity increase, but reintroducing RAC did produce an increase in velocity after both conditions. Group and single subject analysis determined that the SL/SV ratio changed in the intended direction only in the stride length condition. We conclude that RAC is a powerful organizer of gait parameters, evidenced by its induced after-effects following short duration training. Copyright © 2014 Elsevier B.V. All rights reserved.

  8. Forces and mechanical energy fluctuations during diagonal stride roller skiing; running on wheels?

    PubMed

    Kehler, Alyse L; Hajkova, Eliska; Holmberg, Hans-Christer; Kram, Rodger

    2014-11-01

    Mechanical energy can be conserved during terrestrial locomotion in two ways: the inverted pendulum mechanism for walking and the spring-mass mechanism for running. Here, we investigated whether diagonal stride cross-country roller skiing (DIA) utilizes similar mechanisms. Based on previous studies, we hypothesized that running and DIA would share similar phase relationships and magnitudes of kinetic energy (KE), and gravitational potential energy (GPE) fluctuations, indicating elastic energy storage and return, as if roller skiing is like 'running on wheels'. Experienced skiers (N=9) walked and ran at 1.25 and 3 m s(-1), respectively, and roller skied with DIA at both speeds on a level dual-belt treadmill that recorded perpendicular and parallel forces. We calculated the KE and GPE of the center of mass from the force recordings. As expected, the KE and GPE fluctuated with an out-of-phase pattern during walking and an in-phase pattern during running. Unlike walking, during DIA, the KE and GPE fluctuations were in phase, as they are in running. However, during the glide phase, KE was dissipated as frictional heat and could not be stored elastically in the tendons, as in running. Elastic energy storage and return epitomize running and thus we reject our hypothesis. Diagonal stride cross-country skiing is a biomechanically unique movement that only superficially resembles walking or running.

  9. Effect of linear polymer additives on the electroosmotic characteristics of agarose gels in ultrathin-layer electrophoresis.

    PubMed

    Lengyel, T; Guttman, A

    1999-08-20

    Electroosmotic properties of agarose gels with low, medium, high and super high electroendosmosis (EEO) were evaluated based on the apparent electric field mediated mobility of a neutral, fluorescent marker under constant field strength using ultrathin-layer separation configuration. Electroosmotic flow mobility values were measured in different gel concentrations and also in the absence and the presence of various linear polymer additives. Under ultrathin-layer separation conditions, a slight decrease in electroosmotic flow mobility was observed with increasing agarose gel concentration of 1 to 3% for all agarose gels investigated. When linear polymer additives, such as linear polyacrylamide, hydroxyethyl cellulose or polyethylene oxide were added to 1% low electroendosmosis agarose gel, significant reduction of the electroosmotic flow properties were observed with increasing additive concentration. Effect of the intrinsic electroosmotic properties of the various electroendosmosis agaroses on the apparent mobilities and separation performance of double-stranded DNA fragments during automated ultrathin-layer agarose gel electrophoresis was also investigated.

  10. Stride-to-stride energy regulation for robust self-stability of a torque-actuated dissipative spring-mass hopper

    NASA Astrophysics Data System (ADS)

    Ankarali, M. Mert; Saranli, Uluç

    2010-09-01

    In this paper, we analyze the self-stability properties of planar running with a dissipative spring-mass model driven by torque actuation at the hip. We first show that a two-dimensional, approximate analytic return map for uncontrolled locomotion with this system under a fixed touchdown leg angle policy and an open-loop ramp torque profile exhibits only marginal self-stability that does not always persist for the exact system. We then propose a per-stride feedback strategy for the hip torque that explicitly compensates for damping losses, reducing the return map to a single dimension and substantially improving the robust stability of fixed points. Subsequent presentation of simulation evidence establishes that the predictions of this approximate model are consistent with the behavior of the exact plant model. We illustrate the relevance and utility of our model both through the qualitative correspondence of its predictions to biological data as well as its use in the design of a task-level running controller.

  11. Lizard tricks: overcoming conflicting requirements of speed versus climbing ability by altering biomechanics of the lizard stride.

    PubMed

    Clemente, Christofer J; Withers, Philip C; Thompson, Graham G; Lloyd, David

    2013-10-15

    Adaptations promoting greater performance in one habitat are thought to reduce performance in others. However, there are many examples of animals in which, despite habitat differences, such predicted differences in performance do not occur. One such example is the relationship between locomotory performance to habitat for varanid lizards. To explain the lack of difference in locomotor performance we examined detailed observations of the kinematics of each lizard's stride. Differences in kinematics were greatest between climbing and non-climbing species. For terrestrial lizards, the kinematics indicated that increased femur adduction, femur rotation and ankle angle all contributed positively to changes in stride length, but they were constrained for climbing species, probably because of biomechanical restrictions on the centre of mass height (to increase stability on vertical surfaces). Despite climbing species having restricted stride length, no differences have been previously reported in sprint speed between climbing and non-climbing varanids. This is best explained by climbing varanids using an alternative speed modulation strategy of varying stride frequency to avoid the potential trade-off of speed versus stability on vertical surfaces. Thus, by measuring the relevant biomechanics for lizard strides, we have shown how kinematic differences among species can mask performance differences typically associated with habitat variation.

  12. Prolonged cycling alters stride time variability and kinematics of a post-cycle transition run in triathletes.

    PubMed

    Connick, Mark J; Li, Francois-Xavier

    2015-02-01

    Previous studies have employed relatively short cycling protocols to investigate the effect of cycling on muscle activation and kinematics in running. The aim of this study was to investigate the effect of 3h of cycling on stride time variability (STV), stride length, tibialis anterior (TA) activation, and lower limb range of motion (ROM) in a transition run. Eight triathletes completed a run-cycle-run protocol. Data were collected from a pre-cycle run and a transition run after 3h of cycling. STV, stride length and ROM were assessed using three-dimensional motion analysis, and TA activation was recorded using surface electromyography. Results showed that compared with the pre-cycle run triathletes exhibited increased STV (Cohen's d=0.95) and shorter strides (d=0.15) in the transition run (p<0.05). TA activation and ROM did not change. After 10min of transition running, ankle and hip ROM significantly increased (d=0.40 and 0.41 respectively) compared to the beginning of the transition run (p<0.05) but no other changes were observed. The results suggest that locomotor control and kinematics in a transition run are affected by prolonged cycling and stride time variability is potentially a novel method of evaluating the immediate effect of prolonged cycling on the locomotor control of running. Copyright © 2014 Elsevier Ltd. All rights reserved.

  13. Effect of stride length on symptoms of exercise-induced muscle damage during a repeated bout of downhill running.

    PubMed

    Eston, R G; Lemmey, A B; McHugh, P; Byrne, C; Walsh, S E

    2000-08-01

    The purpose of this study was to assess the effects of changes in stride length on the symptoms of exercise-induced muscle damage (EIMD) during a repeated bout of downhill running in a group of 18 men and women. Muscle tenderness, plasma creatine kinase activity (CK) and maximal voluntary isometric force were measured before and after two downhill runs, with each run separated by 5 weeks. The first downhill run was at the preferred stride frequency (PSF). Participants were then randomly allocated to one of three sex-balanced groups with equal numbers of men and women: overstride (-8% PSF), understride (+8% PSF) and normal stride frequency for the second downhill run. Stride length had no effect (P>0.05) on muscle tenderness, CK or isometric peak force. Increases in muscle tenderness (P<0.001) and CK were lower (P<0.05) following the second downhill run, although there was no difference in the pattern and extent of the strength decrement between the two runs. There were also no differences (P>0.05) in muscle tenderness, CK or the relative strength loss between the men and the women. Results suggest that the symptoms of EIMD are unaffected by gender and small alterations to the normal stride pattern during constant velocity downhill running. The observation that muscle tenderness and CK were reduced following a repeated bout of similar eccentric exercise is consistent with the phenomenon known as the 'repeated bout effect' of muscle damage.

  14. Factors affecting the coefficient of variation of stride time of the elderly without falling history: a prospective study.

    PubMed

    Matsuda, Kensuke; Ikeda, Shou; Nakahara, Masami; Ikeda, Takuro; Okamoto, Ryuji; Kurosawa, Kazuo; Horikawa, Etuo

    2015-04-01

    [Purpose] The purpose of this study was to investigate the factors affecting the coefficient of variation (CV) of stride time in an exercise intervention for the elderly without falling history. [Subjects and Methods] The subjects were 42 elderly women who had participated in a care prevention program for 12 weeks. Stride time CV, motor function, movement ability, balance, Modified Falls Efficacy Scale (MFES) score, and Life-space Assessment (LSA) score before and after the intervention were examined for significant differences using the paired t-test. Multiple regression analysis was used to determine the factors that changed in the stride time CV. [Results] There were significant differences in muscle strength, sit-and-reach flexibility, the one-leg standing time (eyes open), the maximum walking speed, local stability of trunk acceleration, The Timed Up and Go Test (TUG-T), the MFES score, and the LSA score between the pre-intervention and post-intervention. Stepwise multiple regression analysis revealed that improvement of quadriceps muscle strength, sit-and-reach flexibility, the one-leg standing time, TUG-T, local stability of trunk acceleration (vertical direction) and MFES score were independent variables explaining the reduction in stride time CV. [Conclusion] The results was suggested that it might be possible to reduce the stride time CV by improving strength, flexibility and dynamic balance, and reducing fear of falls through interventions.

  15. Low-cost temperature sensor based on long-period fiber gratings with linear wavelength transmission characteristics

    NASA Astrophysics Data System (ADS)

    Yang, Ching Chung; Hsia, Chung Ho

    1998-06-01

    A hybrid fiber grating-based temperature sensor with simple demodulation scheme has been constructed. Temperature variation of 1 degree C could be linearly resolved in a 40 degree C range by directly measuring the transmission power through a long period fiber grating with a bandwidth of 6.5nm.

  16. Can Tai Chi training impact fractal stride time dynamics, an index of gait health, in older adults? Cross-sectional and randomized trial studies.

    PubMed

    Gow, Brian J; Hausdorff, Jeffrey M; Manor, Brad; Lipsitz, Lewis A; Macklin, Eric A; Bonato, Paolo; Novak, Vera; Peng, Chung-Kang; Ahn, Andrew C; Wayne, Peter M

    2017-01-01

    To determine if Tai Chi (TC) has an impact on long-range correlations and fractal-like scaling in gait stride time dynamics, previously shown to be associated with aging, neurodegenerative disease, and fall risk. Using Detrended Fluctuation Analysis (DFA), this study evaluated the impact of TC mind-body exercise training on stride time dynamics assessed during 10 minute bouts of overground walking. A hybrid study design investigated long-term effects of TC via a cross-sectional comparison of 27 TC experts (24.5 ± 11.8 yrs experience) and 60 age- and gender matched TC-naïve older adults (50-70 yrs). Shorter-term effects of TC were assessed by randomly allocating TC-naïve participants to either 6 months of TC training or to a waitlist control. The alpha (α) long-range scaling coefficient derived from DFA and gait speed were evaluated as outcomes. Cross-sectional comparisons using confounder adjusted linear models suggest that TC experts exhibited significantly greater long-range scaling of gait stride time dynamics compared with TC-naïve adults. Longitudinal random-slopes with shared baseline models accounting for multiple confounders suggest that the effects of shorter-term TC training on gait dynamics were not statistically significant, but trended in the same direction as longer-term effects although effect sizes were very small. In contrast, gait speed was unaffected in both cross-sectional and longitudinal comparisons. These preliminary findings suggest that fractal-like measures of gait health may be sufficiently precise to capture the positive effects of exercise in the form of Tai Chi, thus warranting further investigation. These results motivate larger and longer-duration trials, in both healthy and health-challenged populations, to further evaluate the potential of Tai Chi to restore age-related declines in gait dynamics. The randomized trial component of this study was registered at ClinicalTrials.gov (NCT01340365).

  17. Comparing Machine Learning Classifiers and Linear/Logistic Regression to Explore the Relationship between Hand Dimensions and Demographic Characteristics

    PubMed Central

    2016-01-01

    Understanding the relationship between physiological measurements from human subjects and their demographic data is important within both the biometric and forensic domains. In this paper we explore the relationship between measurements of the human hand and a range of demographic features. We assess the ability of linear regression and machine learning classifiers to predict demographics from hand features, thereby providing evidence on both the strength of relationship and the key features underpinning this relationship. Our results show that we are able to predict sex, height, weight and foot size accurately within various data-range bin sizes, with machine learning classification algorithms out-performing linear regression in most situations. In addition, we identify the features used to provide these relationships applicable across multiple applications. PMID:27806075

  18. Comparing Machine Learning Classifiers and Linear/Logistic Regression to Explore the Relationship between Hand Dimensions and Demographic Characteristics.

    PubMed

    Miguel-Hurtado, Oscar; Guest, Richard; Stevenage, Sarah V; Neil, Greg J; Black, Sue

    2016-01-01

    Understanding the relationship between physiological measurements from human subjects and their demographic data is important within both the biometric and forensic domains. In this paper we explore the relationship between measurements of the human hand and a range of demographic features. We assess the ability of linear regression and machine learning classifiers to predict demographics from hand features, thereby providing evidence on both the strength of relationship and the key features underpinning this relationship. Our results show that we are able to predict sex, height, weight and foot size accurately within various data-range bin sizes, with machine learning classification algorithms out-performing linear regression in most situations. In addition, we identify the features used to provide these relationships applicable across multiple applications.

  19. Linear analysis of signal and noise characteristics of a nonlinear CMOS active-pixel detector for mammography

    NASA Astrophysics Data System (ADS)

    Yun, Seungman; Kim, Ho Kyung; Han, Jong Chul; Kam, Soohwa; Youn, Hanbean; Cunningham, Ian A.

    2017-03-01

    The imaging properties of a complementary metal-oxide-semiconductor (CMOS) active-pixel photodiode array coupled to a thin gadolinium-based granular phosphor screen with a fiber-optic faceplate are investigated. It is shown that this system has a nonlinear response at low detector exposure levels (<10 mR), resulting in an over-estimation of the detective quantum efficiency (DQE) by a factor of two in some cases. Errors in performance metrics on this scale make it difficult to compare new technologies with established systems and predict performance benchmarks that can be achieved in practice and help understand performance bottlenecks. It is shown the CMOS response is described by a power-law model that can be used to linearize image data. Linearization removed an unexpected dependence of the DQE on detector exposure level.

  20. Contrasting characteristics of aqueous reactive species induced by cross-field and linear-field plasma jets

    NASA Astrophysics Data System (ADS)

    Xu, Han; Chen, Chen; Liu, Dingxin; Xu, Dehui; Liu, Zhijie; Wang, Xiaohua; Kong, Michael G.

    2017-06-01

    A comparative study on aqueous reactive species in deionized water treated by two types of plasma jets is presented. Classified by the direction of the electric field in the jet device, a linear-field jet and cross-field jet have been set up. Concentrations of several aqueous reactive species are measured quantitatively by chemical fluorescent assays and electron spin resonance spectrometer. Results show that these two-type plasma jets would generate approximately the same gaseous reactive species under the same discharge power, but the linear-field plasma jet is much more efficient at delivering those species to the remote deionized water. This leads to a much more aqueous short-lived species including OH and \\text{O}2- produced in water, which are mainly correlated to the solvation of gaseous short-lived species such as ions and electrons. Regarding the long-lived species of aqueous H2O2, the concentration grows faster when treated by the linear-field plasma jet in the initial stage, but after 10 min it is similar to that treated by the cross-field counterpart due to the vapor-liquid equilibrium. The aqueous peroxynitrite is also predicted to be produced as a result of the air inclusion in the feeding gas.

  1. Characteristics of 10 mm Multilayer L1-F2 Mode Vibrator and Application to a Linear Motor

    NASA Astrophysics Data System (ADS)

    Funakubo, Tomoki; Tomikawa, Yoshiro

    2003-05-01

    In the present paper we discuss a small-sized multilayer L1-F2 mode vibrator and its application to an ultrasonic linear motor. In an attempt to reduce both the size and the driving voltage of an L1-F2 mode vibrator, we constructed a multilayer L1-F2 mode vibrator whose inner electrodes are simply divided into two. Test results clarified that the multilayer L1-F2 mode vibrator exhibits two resonance modes; namely, a first longitudinal mode and a second flexural mode, and that an amplitude of vibration velocity is sufficiently large for application to a linear motor. Specific merits of our multilayer L1-F2 mode vibrator are that the driving voltage is low (5 Vrms), owing to multilayer construction, and that the vibrator is small (10 × 2.5 × 2 mm: W×H×D), owing to the simple construction of the inner electrodes. Additionally, the present study revealed that an ultrasonic linear motor using the multilayer L1-F2 mode vibrator exhibits superior performance in practical application.

  2. Effects of a stretching regime on stride length and range of motion in equine trot.

    PubMed

    Rose, Natasha S; Northrop, Alison J; Brigden, Charlotte V; Martin, Jaime H

    2009-07-01

    The aim of this study was to quantify the effects of two different 8-week stretching regimes on stride length (SL) and range of motion (ROM) in the equine trot. Eighteen horses were divided into three matched groups: a 6 days/week stretching regime (6DSR), a 3 days/week stretching regime (3DSR) and a control no-stretching regime (NSR). SL and ROM data were collected at weeks 0, 2, 4, 6 and 8 for trot in-hand. Stretching had no significant effect on SL. A number of significant differences were found in joint ROM between treatments in the shoulder, stifle and hock, suggesting some negative biomechanical effects of the 6DSR. Stretching daily may be too intensive and cause delayed onset of muscle soreness. Further examination of stretch frequency may establish its potential to enhance performance and welfare.

  3. Effect of treadmill versus overground running on the structure of variability of stride timing.

    PubMed

    Lindsay, Timothy R; Noakes, Timothy D; McGregor, Stephen J

    2014-04-01

    Gait timing dynamics of treadmill and overground running were compared. Nine trained runners ran treadmill and track trials at 80, 100, and 120% of preferred pace for 8 min. each. Stride time series were generated for each trial. To each series, detrended fluctuation analysis (DFA), power spectral density (PSD), and multiscale entropy (MSE) analysis were applied to infer the regime of control along the randomness-regularity axis. Compared to overground running, treadmill running exhibited a higher DFA and PSD scaling exponent, as well as lower entropy at non-preferred speeds. This indicates a more ordered control for treadmill running, especially at non-preferred speeds. The results suggest that the treadmill itself brings about greater constraints and requires increased voluntary control. Thus, the quantification of treadmill running gait dynamics does not necessarily reflect movement in overground settings.

  4. Velocity and stride parameters of world-class 400-meter athletes compared with less experienced runners.

    PubMed

    Hanon, Christine; Gajer, Bruno

    2009-03-01

    The purpose of this study was to determine, based on the time course of the velocity and stride pattern recorded in each 50-m segment of a 400-m competition, whether elite 400-m runners present the same pacing strategy as less successful athletes. Based on video data, 3 different levels of performance were analyzed: world-class, national, and regional levels for both sexes, with each of the 6 groups comprising 5 subjects. The peak velocity was reached by all athletes between the 50- and 100-m marks with mean values of 8.96 and 10.12 m.s for the 5 best women and men, respectively. Peak frequencies were observed in the second and third 50-m segments; peak values were 3.99 +/- 0.13 for the world-class women (WWC) and 4.12 +/- 0.19 for the men (MWC). A stride length of 2.29 +/- 0.04 was observed for the WWC and 2.53 +/- 0.08 for the MWC. The better athletes were able to achieve higher absolute and relative velocities (97.6 +/- 0.5 [MWC] and 96.3 +/- 0.7% [WWC] of their best performance for 200 m) at the 200-m mark compared with the lower-level athletes. Furthermore, the fatigue index was calculated as 22.99, 14.43, and 13.91% for the world-class, national, and regional levels, respectively. In summary, world-class runners adopt a more aggressive pacing strategy and demonstrate greater fatigue than the less experienced runners; this might indicate a greater mental commitment and/or a better capacity to run under fatigue.

  5. Influence of running stride frequency in heart rate variability analysis during treadmill exercise testing.

    PubMed

    Bailón, Raquel; Garatachea, Nuria; de la Iglesia, Ignacio; Casajús, Jose Antonio; Laguna, Pablo

    2013-07-01

    The analysis and interpretation of heart rate variability (HRV) during exercise is challenging not only because of the nonstationary nature of exercise, the time-varying mean heart rate, and the fact that respiratory frequency exceeds 0.4 Hz, but there are also other factors, such as the component centered at the pedaling frequency observed in maximal cycling tests, which may confuse the interpretation of HRV analysis. The objectives of this study are to test the hypothesis that a component centered at the running stride frequency (SF) appears in the HRV of subjects during maximal treadmill exercise testing, and to study its influence in the interpretation of the low-frequency (LF) and high-frequency (HF) components of HRV during exercise. The HRV of 23 subjects during maximal treadmill exercise testing is analyzed. The instantaneous power of different HRV components is computed from the smoothed pseudo-Wigner-Ville distribution of the modulating signal assumed to carry information from the autonomic nervous system, which is estimated based on the time-varying integral pulse frequency modulation model. Besides the LF and HF components, the appearance is revealed of a component centered at the running SF as well as its aliases. The power associated with the SF component and its aliases represents 22±7% (median±median absolute deviation) of the total HRV power in all the subjects. Normalized LF power decreases as the exercise intensity increases, while normalized HF power increases. The power associated with the SF does not change significantly with exercise intensity. Consideration of the running SF component and its aliases is very important in HRV analysis since stride frequency aliases may overlap with LF and HF components.

  6. Evaluating Linearly Interpolated Intercensal Estimates of Demographic and Socioeconomic Characteristics of U.S. Counties and Census Tracts 2001–2009

    PubMed Central

    Peterson, Christine E.; Miles, Jeremy N.; Shih, Regina A.

    2015-01-01

    The American Community Survey (ACS) multiyear estimation program has greatly advanced opportunities for studying change in the demographic and socioeconomic characteristics of U.S. communities. Challenges remain, however, for researchers studying years prior to the full implementation of the ACS or areas smaller than the thresholds for ACS annual estimates (i.e., small counties and census tracts). We evaluate intercensal estimates of the demographic and socioeconomic characteristics of U.S. counties and census tracts produced via linear interpolation between the 2000 census and both the 2010 census and 2005–2009 ACS. Discrepancies between interpolated estimates and reference estimates from the Population Estimates Program, the Small Area Income and Poverty Estimates, and ACS are calculated using several measures of error. Findings are discussed in relation to the potential for measurement error to bias longitudinal estimates of linearly interpolated neighborhood change, and alternative intercensal estimation models are discussed, including those that may better capture non-linear trends in economic conditions over the 21st century. PMID:26527053

  7. Hierarchical Linear Modeling of Passage Reading Fluency Growth as a Function of Student Characteristics. Technical Report # 0922

    ERIC Educational Resources Information Center

    Tindal, Gerald; Nese, Joseph F.; Alonzo, Julie

    2009-01-01

    All students from grades 3 through 8 were tested in the fall, winter, and spring of 2009 on passage reading fluency (PRF) measures from easyCBM [R]. Student characteristics were analyzed for influence on reading growth. The results showed the negative effects from being a male or a student of color, coming from an economically disadvantaged…

  8. Investigation of Non Linear Aerodynamic Characteristics of Slender Bodies at High Incidence, in Subsonic and Transonic Speeds.

    DTIC Science & Technology

    1980-12-01

    the calculation of the longitudinal aerodynamic characteristics of bodies at incidence including the separation of symmetric vortices, in sub - sonic...direction cosines of the vector normal to an elemental panel N number of sub -divigions, axi.al directionc -V - N number of sub -divisions, circumferential...summarizes the research performed under Grant No. DAERO- 78-G-119 during the period September ist 1978 to September 30th, 1980. Many modern aircraft and

  9. Increased delivery stride length places greater loads on the ankle joint in elite male cricket fast bowlers.

    PubMed

    Spratford, Wayne; Hicks, Amy

    2014-01-01

    The purpose of this study was to investigate the effect stride length has on ankle biomechanics of the leading leg with reference to the potential risk of injury in cricket fast bowlers. Ankle joint kinematic and kinetic data were collected from 51 male fast bowlers during the stance phase of the final delivery stride. The bowling cohort comprised national under-19, first class and international-level athletes. Bowlers were placed into either Short, Average or Long groups based on final stride length, allowing statistical differences to be measured. A multivariate analysis of variance with a Bonferroni post-hoc correction (α = 0.05) revealed significant differences between peak plantarflexion angles (Short-Long P = 0.005, Average and Long P = 0.04) and negative joint work (Average-Long P = 0.026). This study highlighted that during fast bowling the ankle joint of the leading leg experiences high forces under wide ranges of movement. As stride length increases, greater amounts of negative work and plantarflexion are experienced. These increases place greater loads on the ankle joint and move the foot into positions that make it more susceptible to injuries such as posterior impingement syndrome.

  10. Effects of different frequencies of rhythmic auditory cueing on the stride length, cadence, and gait speed in healthy young females.

    PubMed

    Yu, Lili; Zhang, Qi; Hu, Chunying; Huang, Qiuchen; Ye, Miao; Li, Desheng

    2015-02-01

    [Purpose] The aim of this study was to explore the effects of different frequencies of rhythmic auditory cueing (RAC) on stride length, cadence, and gait speed in healthy young females. The findings of this study might be used as clinical guidance of physical therapy for choosing the suitable frequency of RAC. [Subjects] Thirteen healthy young females were recruited in this study. [Methods] Ten meters walking tests were measured in all subjects under 4 conditions with each repeated 3 times and a 3-min seated rest period between repetitions. Subjects first walked as usual and then were asked to listen carefully to the rhythm of a metronome and walk with 3 kinds of RAC (90%, 100%, and 110% of the mean cadence). The three frequencies (90%, 100%, and 110%) of RAC were randomly assigned. Gait speed, stride length, and cadence were calculated, and a statistical analysis was performed using the SPSS (version 17.0) computer package. [Results] The gait speed and cadence of 90% RAC walking showed significant decreases compared with normal walking and 100% and 110% RAC walking. The stride length, cadence, and gait speed of 110% RAC walking showed significant increases compared with normal walking and 90% and 100% RAC walking. [Conclusion] Our results showed that 110% RAC was the best of the 3 cueing frequencies for improvement of stride length, cadence, and gait speed in healthy young females.

  11. Influence of footwear and equipment on stride length and range of motion of ankle, knee and hip joint.

    PubMed

    Schulze, Christoph; Lindner, Tobias; Woitge, Sandra; Schulz, Katharina; Finze, Susanne; Mittelmeier, Wolfram; Bader, Rainer

    2014-01-01

    Footwear and equipment worn by military personnel is of importance for them to be able to meet the physical demands specific to their profession daily activities. The aim of the present study was to investigate by means of gait analysis how army-provided footwear and equipment influence the range of motion of hip, knee and ankle joints as well as stride length. Thirty-two soldiers were subjected to gait analysis on a treadmill by way of video recordings and goniometric measurements. The stride length increased when military shoes are worn. We found no influence on stride length in connection to increased loading. The weight of the shoes represents the decisive factor. Neither shoes nor equipment changed the range of motion of the knee joint. Weight of equipment affected range of motion of the hip joint. The range of motion of the upper and lower ankle joints was mainly influenced by the properties of the shoes. Military footwear and weight of equipment influence stride length and range of motion of joints of the lower extremities in a specific way. Shape of material is the decisive factor.

  12. Analysis and Classification of Stride Patterns Associated with Children Development Using Gait Signal Dynamics Parameters and Ensemble Learning Algorithms

    PubMed Central

    Wu, Meihong; Liao, Lifang; Luo, Xin; Ye, Xiaoquan; Yao, Yuchen; Chen, Pinnan; Shi, Lei; Huang, Hui

    2016-01-01

    Measuring stride variability and dynamics in children is useful for the quantitative study of gait maturation and neuromotor development in childhood and adolescence. In this paper, we computed the sample entropy (SampEn) and average stride interval (ASI) parameters to quantify the stride series of 50 gender-matched children participants in three age groups. We also normalized the SampEn and ASI values by leg length and body mass for each participant, respectively. Results show that the original and normalized SampEn values consistently decrease over the significance level of the Mann-Whitney U test (p < 0.01) in children of 3–14 years old, which indicates the stride irregularity has been significantly ameliorated with the body growth. The original and normalized ASI values are also significantly changing when comparing between any two groups of young (aged 3–5 years), middle (aged 6–8 years), and elder (aged 10–14 years) children. Such results suggest that healthy children may better modulate their gait cadence rhythm with the development of their musculoskeletal and neurological systems. In addition, the AdaBoost.M2 and Bagging algorithms were used to effectively distinguish the children's gait patterns. These ensemble learning algorithms both provided excellent gait classification results in terms of overall accuracy (≥90%), recall (≥0.8), and precision (≥0.8077). PMID:27034952

  13. Is walking a random walk? Evidence for long-range correlations in stride interval of human gait.

    PubMed

    Hausdorff, J M; Peng, C K; Ladin, Z; Wei, J Y; Goldberger, A L

    1995-01-01

    Complex fluctuations of unknown origin appear in the normal gait pattern. These fluctuations might be described as being 1) uncorrelated white noise, 2) short-range correlations, or 3) long-range correlations with power-law scaling. To test these possibilities, the stride interval of 10 healthy young men was measured as they walked for 9 min at their usual rate. From these time series, we calculated scaling indexes by using a modified random walk analysis and power spectral analysis. Both indexes indicated the presence of long-range self-similar correlations extending over hundreds of steps; the stride interval at any time depended on the stride interval at remote previous times, and this dependence decayed in a scale-free (fractallike) power-law fashion. These scaling indexes were significantly different from those obtained after random shuffling of the original time series, indicating the importance of the sequential ordering of the stride interval. We demonstrate that conventional models of gait generation fail to reproduce the observed scaling behavior and introduce a new type of central pattern generator model that successfully accounts for the experimentally observed long-range correlations.

  14. Is walking a random walk? Evidence for long-range correlations in stride interval of human gait

    NASA Technical Reports Server (NTRS)

    Hausdorff, Jeffrey M.; Peng, C.-K.; Ladin, Zvi; Wei, Jeanne Y.; Goldberger, Ary L.

    1995-01-01

    Complex fluctuation of unknown origin appear in the normal gait pattern. These fluctuations might be described as being (1) uncorrelated white noise, (2) short-range correlations, or (3) long-range correlations with power-law scaling. To test these possibilities, the stride interval of 10 healthy young men was measured as they walked for 9 min at their usual rate. From these time series we calculated scaling indexes by using a modified random walk analysis and power spectral analysis. Both indexes indicated the presence of long-range self-similar correlations extending over hundreds of steps; the stride interval at any time depended on the stride interval at remote previous times, and this dependence decayed in a scale-free (fractallike) power-law fashion. These scaling indexes were significantly different from those obtained after random shuffling of the original time series, indicating the importance of the sequential ordering of the stride interval. We demonstrate that conventional models of gait generation fail to reproduce the observed scaling behavior and introduce a new type of central pattern generator model that sucessfully accounts for the experimentally observed long-range correlations.

  15. Is walking a random walk? Evidence for long-range correlations in stride interval of human gait

    NASA Technical Reports Server (NTRS)

    Hausdorff, Jeffrey M.; Peng, C.-K.; Ladin, Zvi; Wei, Jeanne Y.; Goldberger, Ary L.

    1995-01-01

    Complex fluctuation of unknown origin appear in the normal gait pattern. These fluctuations might be described as being (1) uncorrelated white noise, (2) short-range correlations, or (3) long-range correlations with power-law scaling. To test these possibilities, the stride interval of 10 healthy young men was measured as they walked for 9 min at their usual rate. From these time series we calculated scaling indexes by using a modified random walk analysis and power spectral analysis. Both indexes indicated the presence of long-range self-similar correlations extending over hundreds of steps; the stride interval at any time depended on the stride interval at remote previous times, and this dependence decayed in a scale-free (fractallike) power-law fashion. These scaling indexes were significantly different from those obtained after random shuffling of the original time series, indicating the importance of the sequential ordering of the stride interval. We demonstrate that conventional models of gait generation fail to reproduce the observed scaling behavior and introduce a new type of central pattern generator model that sucessfully accounts for the experimentally observed long-range correlations.

  16. Metabolic Cost of Stride Rate, Resistance, and Combined Use of Arms and Legs on the Elliptical Trainer

    ERIC Educational Resources Information Center

    Mier, Constance M.; Feito, Yuri

    2006-01-01

    We measured the effects of stride rate, resistance, and combined arm-leg use on energy expenditure during elliptical trainer exercise and assessed the accuracy of the manufacturer's energy expenditure calculations. Twenty-six men and women (M age = 29 years, SD = 8; M body weight = 73.0 kg, SD = 15.2) participated. Twenty-two participants…

  17. Analysis and Classification of Stride Patterns Associated with Children Development Using Gait Signal Dynamics Parameters and Ensemble Learning Algorithms.

    PubMed

    Wu, Meihong; Liao, Lifang; Luo, Xin; Ye, Xiaoquan; Yao, Yuchen; Chen, Pinnan; Shi, Lei; Huang, Hui; Wu, Yunfeng

    2016-01-01

    Measuring stride variability and dynamics in children is useful for the quantitative study of gait maturation and neuromotor development in childhood and adolescence. In this paper, we computed the sample entropy (SampEn) and average stride interval (ASI) parameters to quantify the stride series of 50 gender-matched children participants in three age groups. We also normalized the SampEn and ASI values by leg length and body mass for each participant, respectively. Results show that the original and normalized SampEn values consistently decrease over the significance level of the Mann-Whitney U test (p < 0.01) in children of 3-14 years old, which indicates the stride irregularity has been significantly ameliorated with the body growth. The original and normalized ASI values are also significantly changing when comparing between any two groups of young (aged 3-5 years), middle (aged 6-8 years), and elder (aged 10-14 years) children. Such results suggest that healthy children may better modulate their gait cadence rhythm with the development of their musculoskeletal and neurological systems. In addition, the AdaBoost.M2 and Bagging algorithms were used to effectively distinguish the children's gait patterns. These ensemble learning algorithms both provided excellent gait classification results in terms of overall accuracy (≥90%), recall (≥0.8), and precision (≥0.8077).

  18. Metabolic Cost of Stride Rate, Resistance, and Combined Use of Arms and Legs on the Elliptical Trainer

    ERIC Educational Resources Information Center

    Mier, Constance M.; Feito, Yuri

    2006-01-01

    We measured the effects of stride rate, resistance, and combined arm-leg use on energy expenditure during elliptical trainer exercise and assessed the accuracy of the manufacturer's energy expenditure calculations. Twenty-six men and women (M age = 29 years, SD = 8; M body weight = 73.0 kg, SD = 15.2) participated. Twenty-two participants…

  19. A comparative analysis of spectral exponent estimation techniques for 1/fβ processes with applications to the analysis of stride interval time series

    PubMed Central

    Schaefer, Alexander; Brach, Jennifer S.; Perera, Subashan; Sejdić, Ervin

    2013-01-01

    Background The time evolution and complex interactions of many nonlinear systems, such as in the human body, result in fractal types of parameter outcomes that exhibit self similarity over long time scales by a power law in the frequency spectrum S(f) = 1/fβ. The scaling exponent β is thus often interpreted as a “biomarker” of relative health and decline. New Method This paper presents a thorough comparative numerical analysis of fractal characterization techniques with specific consideration given to experimentally measured gait stride interval time series. The ideal fractal signals generated in the numerical analysis are constrained under varying lengths and biases indicative of a range of physiologically conceivable fractal signals. This analysis is to complement previous investigations of fractal characteristics in healthy and pathological gait stride interval time series, with which this study is compared. Results The results of our analysis showed that the averaged wavelet coefficient method consistently yielded the most accurate results. Comparison with Existing Methods: Class dependent methods proved to be unsuitable for physiological time series. Detrended fluctuation analysis as most prevailing method in the literature exhibited large estimation variances. Conclusions The comparative numerical analysis and experimental applications provide a thorough basis for determining an appropriate and robust method for measuring and comparing a physiologically meaningful biomarker, the spectral index β. In consideration of the constraints of application, we note the significant drawbacks of detrended fluctuation analysis and conclude that the averaged wavelet coefficient method can provide reasonable consistency and accuracy for characterizing these fractal time series. PMID:24200509

  20. Impact of stride-coupled gaze shifts of walking blowflies on the neuronal representation of visual targets

    PubMed Central

    Kress, Daniel; Egelhaaf, Martin

    2014-01-01

    During locomotion animals rely heavily on visual cues gained from the environment to guide their behavior. Examples are basic behaviors like collision avoidance or the approach to a goal. The saccadic gaze strategy of flying flies, which separates translational from rotational phases of locomotion, has been suggested to facilitate the extraction of environmental information, because only image flow evoked by translational self-motion contains relevant distance information about the surrounding world. In contrast to the translational phases of flight during which gaze direction is kept largely constant, walking flies experience continuous rotational image flow that is coupled to their stride-cycle. The consequences of these self-produced image shifts for the extraction of environmental information are still unclear. To assess the impact of stride-coupled image shifts on visual information processing, we performed electrophysiological recordings from the HSE cell, a motion sensitive wide-field neuron in the blowfly visual system. This cell has been concluded to play a key role in mediating optomotor behavior, self-motion estimation and spatial information processing. We used visual stimuli that were based on the visual input experienced by walking blowflies while approaching a black vertical bar. The response of HSE to these stimuli was dominated by periodic membrane potential fluctuations evoked by stride-coupled image shifts. Nevertheless, during the approach the cell’s response contained information about the bar and its background. The response components evoked by the bar were larger than the responses to its background, especially during the last phase of the approach. However, as revealed by targeted modifications of the visual input during walking, the extraction of distance information on the basis of HSE responses is much impaired by stride-coupled retinal image shifts. Possible mechanisms that may cope with these stride-coupled responses are discussed

  1. Impact of stride-coupled gaze shifts of walking blowflies on the neuronal representation of visual targets.

    PubMed

    Kress, Daniel; Egelhaaf, Martin

    2014-01-01

    During locomotion animals rely heavily on visual cues gained from the environment to guide their behavior. Examples are basic behaviors like collision avoidance or the approach to a goal. The saccadic gaze strategy of flying flies, which separates translational from rotational phases of locomotion, has been suggested to facilitate the extraction of environmental information, because only image flow evoked by translational self-motion contains relevant distance information about the surrounding world. In contrast to the translational phases of flight during which gaze direction is kept largely constant, walking flies experience continuous rotational image flow that is coupled to their stride-cycle. The consequences of these self-produced image shifts for the extraction of environmental information are still unclear. To assess the impact of stride-coupled image shifts on visual information processing, we performed electrophysiological recordings from the HSE cell, a motion sensitive wide-field neuron in the blowfly visual system. This cell has been concluded to play a key role in mediating optomotor behavior, self-motion estimation and spatial information processing. We used visual stimuli that were based on the visual input experienced by walking blowflies while approaching a black vertical bar. The response of HSE to these stimuli was dominated by periodic membrane potential fluctuations evoked by stride-coupled image shifts. Nevertheless, during the approach the cell's response contained information about the bar and its background. The response components evoked by the bar were larger than the responses to its background, especially during the last phase of the approach. However, as revealed by targeted modifications of the visual input during walking, the extraction of distance information on the basis of HSE responses is much impaired by stride-coupled retinal image shifts. Possible mechanisms that may cope with these stride-coupled responses are discussed.

  2. A Comparison of Stride Length and Lower Extremity Kinematics during Barefoot and Shod Running in Well Trained Distance Runners

    PubMed Central

    Francis, Peter; Ledingham, James; Clarke, Sarah; Collins, DJ; Jakeman, Philip

    2016-01-01

    Stride length, hip, knee and ankle angles were compared during barefoot and shod running on a treadmill at two speeds. Nine well-trained (1500m time: 3min:59.80s ± 14.7 s) male (22 ±3 years; 73 ±9 kg; 1.79 ±0.4 m) middle distance (800 m – 5,000 m) runners performed 2 minutes of running at 3.05 m·s-1 and 4.72 m·s-1 on an treadmill. This approach allowed continuous measurement of lower extremity kinematic data and calculation of stride length. Statistical analysis using a 2X2 factorial ANOVA revealed speed to have a main effect on stride length and hip angle and footwear to have a main effect on hip angle. There was a significant speed*footwear interaction for knee and ankle angles. Compared to shod running at the lower speed (3.05 m·s-1), well trained runners have greater hip, knee and ankle angles when running barefoot. Runners undertake a high volume (~75%) of training at lower intensities and therefore knowledge of how barefoot running alters running kinematics at low and high speeds may be useful to the runner. Key points Barefoot and shod kinematics are examined in competitive track runners with a mean 1500m personal best of 3:59:80. Previous literature has not investigated competitive track runners. Compared to amateur runners, competitive track runners demonstrate a smaller reduction in stride length during barefoot running at ~3 m·s-1. There is no difference in stride length or lower extremity kinematics when running at 4.72 m·s-1. Given that competitive runners spend a large (~75%) amount of time training at lower speeds, interventions which favourably alter running kinematics may be advantageous for the prevention of injury. PMID:27803620

  3. Variations in stride length and running economy in male novice runners subsequent to a seven-week training program.

    PubMed

    Bailey, S P; Messier, S P

    1991-06-01

    The purposes of this investigation were to document the changes in stride length of college-age male novice runners (n = 13) who were allowed of freely choose their stride length throughout a 7-week training period (FCSL), and to compare subsequent changes in running economy to those observed in a similar group of runners (n = 13) that ran for 7 weeks with constant stride lengths equivalent to their initially chosen stride lengths (CSL). Subjects trained 3 days per week for approximately 7 weeks (22 training bouts). Each training bout consisted of a minute warmup (60% VO2max) and a 15-minute run at a speed equivalent to 80% of the subjects' initial VO2max. Absolute stride length (ASL), heart rate (HR), and ratings of perceived exertion (RPE) were measured during the 12th and 20th minute of exercise. Relative and absolute submaximal VO2 were measured during the 4th and 22nd training bout. No significant differences in percent change in ASL were found between the groups or across the weeks of training at the 12th or 20th minute of exercise; however, there was a significant difference (p less than or equal to .05) between the groups during the 4th week of training. No significant differences were found between the groups in relative or absolute submaximal VO2. Relative submaximal VO2 at the 12th minute of exercise decreased significantly following the training period in both the FCSL (-3.38%) and CSL (-4.32%) groups. Absolute submaximal VO2 did not change significantly following the training period.(ABSTRACT TRUNCATED AT 250 WORDS)

  4. Propagation and stability characteristics of a 500-m-long laser-based fiducial line for high-precision alignment of long-distance linear accelerators.

    PubMed

    Suwada, Tsuyoshi; Satoh, Masanori; Telada, Souichi; Minoshima, Kaoru

    2013-09-01

    A laser-based alignment system with a He-Ne laser has been newly developed in order to precisely align accelerator units at the KEKB injector linac. The laser beam was first implemented as a 500-m-long fiducial straight line for alignment measurements. We experimentally investigated the propagation and stability characteristics of the laser beam passing through laser pipes in vacuum. The pointing stability at the last fiducial point was successfully obtained with the transverse displacements of ±40 μm level in one standard deviation by applying a feedback control. This pointing stability corresponds to an angle of ±0.08 μrad. This report contains a detailed description of the experimental investigation for the propagation and stability characteristics of the laser beam in the laser-based alignment system for long-distance linear accelerators.

  5. A longitudinal linear model of patient characteristics to predict failure to attend an inner-city chronic pain clinic

    PubMed Central

    Shaparin, N; White, RS; Andreae, MH; Hall, CB; Kaufman, AG

    2014-01-01

    Patients often fail to attend appointments in chronic pain clinics for unknown reasons. We hypothesized that certain patient characteristics predict failure to attend scheduled appointments pointing to systematic barriers to access chronic pain services for certain underserved populations. We collected retrospective data from a longitudinal observational cohort of patients at an academic pain clinic in Newark, New Jersey. To examine the effect of demographic factors on appointment status, we fit a marginal logistic regression using generalized estimating equations with exchangeable correlation. 1394 patients with 3488 total encounters between January 1, 2006 and December 31, 2009 were included. Spanish spoken as a primary language (alternatively Hispanic or other race) and living between five and ten miles from the clinic were associated with reduced odds of arriving for an appointment; making an appointment for a particular complaint such as cancer pain or back pain, an interventional pain procedure scheduled in connection with the appointment, unemployed status, and continuity of care (as measured by office visit number) were associated with increased odds of arriving. Spanish spoken as primary language and distance to the pain clinic predicted failure to attend a scheduled appointment in our cohort. If these constitute systematic barriers to access, they may be amendable to targeted interventions. Perspective We identified certain patient characteristics, specifically Spanish spoken as primary language and geographic distance from the clinic, that predict failure to attend an inner-city chronic pain clinic. These identified barriers to access chronic pain services may be modifiable by simple cost effective interventions. PMID:24747766

  6. A molecular dynamics study on thin film liquid boiling characteristics under rapid linear boundary heating: Effect of liquid film thickness

    NASA Astrophysics Data System (ADS)

    Rabbi, Kazi Fazle; Tamim, Saiful Islam; Faisal, A. H. M.; Mukut, K. M.; Hasan, Mohammad Nasim

    2017-06-01

    This study is a molecular dynamics investigation of phase change phenomena i.e. boiling of thin liquid films subjected to rapid linear heating at the boundary. The purpose of this study is to understand the phase change heat transfer phenomena at nano scale level. In the simulation, a thin film of liquid argon over a platinum surface has been considered. The simulation domain herein is a three-phase system consisting of liquid and vapor argon atoms placed over a platinum wall. Initially the whole system is brought to an equilibrium state at 90 K and then the temperature of the bottom wall is increased to a higher temperature (250K) within a finite time interval. Four different liquid argon film thicknesses have been considered (3 nm, 4 nm, 5 nm and 6 nm) in this study. The boundary heating rate (40×109 K/s) is kept constant in all these cases. Variation in system temperature, pressure, net evaporation number, spatial number density of the argon region with time for different film thickness have been demonstrated and analyzed. The present study indicates that the pattern of phase transition may be significantly different (i.e. evaporation or explosive boiling) depending on the liquid film thickness. Among the four cases considered in the present study, explosive boiling has been observed only for the liquid films of 5nm and 6nm thickness, while for the other cases, evaporation take place.

  7. Hierarchical linear modeling of California Verbal Learning Test--Children's Version learning curve characteristics following childhood traumatic head injury.

    PubMed

    Warschausky, Seth; Kay, Joshua B; Chi, PaoLin; Donders, Jacobus

    2005-03-01

    California Verbal Learning Test-Children's Version (CVLT-C) indices have been shown to be sensitive to the neurocognitive effects of traumatic brain injury (TBI). The effects of TBI on the learning process were examined with a growth curve analysis of CVLT-C raw scores across the 5 learning trials. The sample with history of TBI comprised 86 children, ages 6-16 years, at a mean of 10.0 (SD=19.5) months postinjury; 37.2% had severe injury, 27.9% moderate, and 34.9% mild. The best-fit model for verbal learning was with a quadratic function. Greater TBI severity was associated with lower rate of acquisition and more gradual deceleration in the rate of acquisition. Intelligence test index scores, previously shown to be sensitive to severity of TBI, were positively correlated with rate of acquisition. Results provide evidence that the CVLT-C learning slope is not a simple linear function and further support for specific effects of TBI on verbal learning. ((c) 2005 APA, all rights reserved).

  8. A Bayesian Hierarchical Non-Linear Regression Model in Receiver Operating Characteristic Analysis of Clustered Continuous Diagnostic Data

    PubMed Central

    Zou, Kelly H.; O’Malley, A. James

    2005-01-01

    Receiver operating characteristic (ROC) analysis is a useful evaluative method of diagnostic accuracy. A Bayesian hierarchical nonlinear regression model for ROC analysis was developed. A validation analysis of diagnostic accuracy was conducted using prospective multi-center clinical trial prostate cancer biopsy data collected from three participating centers. The gold standard was based on radical prostatectomy to determine local and advanced disease. To evaluate the diagnostic performance of PSA level at fixed levels of Gleason score, a normality transformation was applied to the outcome data. A hierarchical regression analysis incorporating the effects of cluster (clinical center) and cancer risk (low, intermediate, and high) was performed, and the area under the ROC curve (AUC) was estimated. PMID:16161801

  9. PROGRAM VSAERO: A computer program for calculating the non-linear aerodynamic characteristics of arbitrary configurations: User's manual

    NASA Technical Reports Server (NTRS)

    Maskew, B.

    1982-01-01

    VSAERO is a computer program used to predict the nonlinear aerodynamic characteristics of arbitrary three-dimensional configurations in subsonic flow. Nonlinear effects of vortex separation and vortex surface interaction are treated in an iterative wake-shape calculation procedure, while the effects of viscosity are treated in an iterative loop coupling potential-flow and integral boundary-layer calculations. The program employs a surface singularity panel method using quadrilateral panels on which doublet and source singularities are distributed in a piecewise constant form. This user's manual provides a brief overview of the mathematical model, instructions for configuration modeling and a description of the input and output data. A listing of a sample case is included.

  10. Combined linear polarization and angular distribution measurements of x-rays for precise determination of multipole-mixing in characteristic transitions of high-Z systems

    NASA Astrophysics Data System (ADS)

    Weber, G.; Bräuning, H.; Surzhykov, A.; Brandau, C.; Fritzsche, S.; Geyer, S.; Grisenti, R. E.; Hagmann, S.; Hahn, C.; Hess, R.; Hess, S.; Kozhuharov, C.; Kühnel, M.; Märtin, R.; Petridis, N.; Spillmann, U.; Trotsenko, S.; Winters, D. F. A.; Stöhlker, Th

    2015-07-01

    By applying novel-type position sensitive x-ray detectors as Compton polarimeters we recently performed a study of the linear polarization of Lyman-{{α }1} radiation following radiative electron capture into initially bare uranium ions. It was found that a model-independent determination of the ratio of the E1 and M2 transition amplitudes, and consequently of the corresponding transition rates, is feasible by combining the linear polarization data with a measurement of the angular distribution of the emitted radiation. In this work a detailed description of the underlying experimental technique for combined measurements of the linear polarization and the angular distribution of characteristic transitions in high-Z ions is presented. Special emphasis is given to the application of two, two-dimensional position-sensitive x-ray detectors for Compton polarimetry of hard x-rays. Moreover, we demonstrate the polarimeter efficiency of such detector systems can be significantly improved if events, where the charge is spread over neighboring segments, are reconstructed to be used in the polarization analysis.

  11. Stimulant Reduction Intervention using Dosed Exercise (STRIDE) - CTN 0037: Study protocol for a randomized controlled trial

    PubMed Central

    2011-01-01

    Background There is a need for novel approaches to the treatment of stimulant abuse and dependence. Clinical data examining the use of exercise as a treatment for the abuse of nicotine, alcohol, and other substances suggest that exercise may be a beneficial treatment for stimulant abuse, with direct effects on decreased use and craving. In addition, exercise has the potential to improve other health domains that may be adversely affected by stimulant use or its treatment, such as sleep disturbance, cognitive function, mood, weight gain, quality of life, and anhedonia, since it has been shown to improve many of these domains in a number of other clinical disorders. Furthermore, neurobiological evidence provides plausible mechanisms by which exercise could positively affect treatment outcomes. The current manuscript presents the rationale, design considerations, and study design of the National Institute on Drug Abuse (NIDA) Clinical Trials Network (CTN) CTN-0037 Stimulant Reduction Intervention using Dosed Exercise (STRIDE) study. Methods/Design STRIDE is a multisite randomized clinical trial that compares exercise to health education as potential treatments for stimulant abuse or dependence. This study will evaluate individuals diagnosed with stimulant abuse or dependence who are receiving treatment in a residential setting. Three hundred and thirty eligible and interested participants who provide informed consent will be randomized to one of two treatment arms: Vigorous Intensity High Dose Exercise Augmentation (DEI) or Health Education Intervention Augmentation (HEI). Both groups will receive TAU (i.e., usual care). The treatment arms are structured such that the quantity of visits is similar to allow for equivalent contact between groups. In both arms, participants will begin with supervised sessions 3 times per week during the 12-week acute phase of the study. Supervised sessions will be conducted as one-on-one (i.e., individual) sessions, although other

  12. STRIDES: Galaxy Evolution over Cosmic Time from new samples of Gravitationally Lensed Quasars

    NASA Astrophysics Data System (ADS)

    Agnello, Adriano; Treu, Tommaso

    2015-08-01

    When a quasar is gravitationally lensed by a galaxy, its multiple images show light-curves that are offset by awell defined time delay, which depends on the mass profile of the lens and on cosmological distances to the lens and the source. By measuring the time-delay and accurately modelling the deflector's mass profile, this provides one-step measurements of cosmological distances to objects at redshift $z\\sim1,$ whence the cosmological parameters (primarily $H_0$). One can turn this argument around and learn about galaxies instead, or even perform a joint (and less biased) inference. The joint modelling of the lens, the source structure and time-variability implies that the DM halos of lens galaxies at z~0.4-1 and the source properties of quasars and their hosts at z~1-2are inferred, besides information on cosmology that is complementary to other low-redshift probes such as SN Ia and BAO.A large (N~100) sample of lensed quasars will be transformative in this sense, as these systems are rare on the sky.I will describe our STRIDES[*] searches in the Dark Energy Survey, aiming at 120 previously unknown lensed quasars brighter than i=21. Candidates have been selected with a variety of data mining techniques and flagged for follow-up (on spectroscopy, high-resolution imaging and lightcurve variability), which will take place in the following months. I will also cover recent modelling development of already monitored lenses within our collaboration, including a sharp multi-band reconstruction of the sources and use of stellar kinematics to ensure unbiased uncertainties on the lens mass profiles.This will lead to: (i) percent-level uncertainties on cosmological parameters(ii) insight on the coevolution of quasars and their host galaxies throughout cosmic time, up to z~2(iii) a quantative description of dark matter density profiles and the substructure content in massive galaxies up to z~1.[*] strides.physics.ucsb.edu

  13. Stimulant reduction intervention using dosed exercise (STRIDE) - CTN 0037: study protocol for a randomized controlled trial.

    PubMed

    Trivedi, Madhukar H; Greer, Tracy L; Grannemann, Bruce D; Church, Timothy S; Somoza, Eugene; Blair, Steven N; Szapocznik, Jose; Stoutenberg, Mark; Rethorst, Chad; Warden, Diane; Ring, Kolette M; Walker, Robrina; Morris, David W; Kosinski, Andrzej S; Kyle, Tiffany; Marcus, Bess; Crowell, Becca; Oden, Neal; Nunes, Edward

    2011-09-19

    There is a need for novel approaches to the treatment of stimulant abuse and dependence. Clinical data examining the use of exercise as a treatment for the abuse of nicotine, alcohol, and other substances suggest that exercise may be a beneficial treatment for stimulant abuse, with direct effects on decreased use and craving. In addition, exercise has the potential to improve other health domains that may be adversely affected by stimulant use or its treatment, such as sleep disturbance, cognitive function, mood, weight gain, quality of life, and anhedonia, since it has been shown to improve many of these domains in a number of other clinical disorders. Furthermore, neurobiological evidence provides plausible mechanisms by which exercise could positively affect treatment outcomes. The current manuscript presents the rationale, design considerations, and study design of the National Institute on Drug Abuse (NIDA) Clinical Trials Network (CTN) CTN-0037 Stimulant Reduction Intervention using Dosed Exercise (STRIDE) study. STRIDE is a multisite randomized clinical trial that compares exercise to health education as potential treatments for stimulant abuse or dependence. This study will evaluate individuals diagnosed with stimulant abuse or dependence who are receiving treatment in a residential setting. Three hundred and thirty eligible and interested participants who provide informed consent will be randomized to one of two treatment arms: Vigorous Intensity High Dose Exercise Augmentation (DEI) or Health Education Intervention Augmentation (HEI). Both groups will receive TAU (i.e., usual care). The treatment arms are structured such that the quantity of visits is similar to allow for equivalent contact between groups. In both arms, participants will begin with supervised sessions 3 times per week during the 12-week acute phase of the study. Supervised sessions will be conducted as one-on-one (i.e., individual) sessions, although other participants may be exercising

  14. Method for generating linear current-field characteristics and eliminating charging delay in no-insulation superconducting magnets

    NASA Astrophysics Data System (ADS)

    Kim, Seokho; Hahn, Seungyong; Kim, Kwangmin; Larbalestier, David

    2017-03-01

    No-insulation (NI) rare-earth barium copper oxide (REBCO) magnets are promising for high field or high temperature superconducting magnets because they simplify quench protection. However, the turn-to-turn leakage current path induced by the absence of insulation introduces nonlinearities into the magnetic fieldcurrent characteristic and significant delay in reaching the desired field. This paper shows that active feedback control can mitigate both the nonlinearity and the charging delay. To verify our approach, simulations and tests were performed with an NI REBCO magnet made of 13 double-pancake coils. A proportional and integral (PI) feedback control of the power supply was adopted which allowed determination of the appropriate PI gains using dynamic simulations of the equivalent circuit of the NI magnet. Feedback control tests were then performed in liquid nitrogen at 77 K. The time to reach 99.5% of the target magnetic field to become essentially steady-state was reduced by more than 2000 times from 850 s without control to 0.4 s with control. The results demonstrate a potential that one of the most significant perceived disadvantages of an NI magnet can essentially be removed by active feedback control of the power supply current.

  15. Temperature-Dependent Non-linear Resistive Switching Characteristics and Mechanism Using a New W/WO3/WOx/W Structure.

    PubMed

    Chakrabarti, Somsubhra; Samanta, Subhranu; Maikap, Siddheswar; Rahaman, Sheikh Ziaur; Cheng, Hsin-Ming

    2016-12-01

    Post-metal annealing temperature-dependent forming-free resistive switching memory characteristics, Fowler-Nordheim (F-N) tunneling at low resistance state, and after reset using a new W/WO3/WOx/W structure have been investigated for the first time. Transmission electron microscope image shows a polycrystalline WO3/WOx layer in a device with a size of 150 × 150 nm(2). The composition of WO3/WOx is confirmed by X-ray photo-electron spectroscopy. Non-linear bipolar resistive switching characteristics have been simulated using space-charge limited current (SCLC) conduction at low voltage, F-N tunneling at higher voltage regions, and hopping conduction during reset, which is well fitted with experimental current-voltage characteristics. The barrier height at the WOx/W interface for the devices annealed at 500 °C is lower than those of the as-deposited and annealed at 400 °C (0.63 vs. 1.03 eV). An oxygen-vacant conducting filament with a diameter of ~34 nm is formed/ruptured into the WO3/WOx bilayer owing to oxygen ion migration under external bias as well as barrier height changes for high-resistance to low-resistance states. In addition, the switching mechanism including the easy method has been explored through the current-voltage simulation. The devices annealed at 500 °C have a lower operation voltage, lower barrier height, and higher non-linearity factor, which are beneficial for selector-less crossbar memory arrays.

  16. Temperature-Dependent Non-linear Resistive Switching Characteristics and Mechanism Using a New W/WO3/WOx/W Structure

    NASA Astrophysics Data System (ADS)

    Chakrabarti, Somsubhra; Samanta, Subhranu; Maikap, Siddheswar; Rahaman, Sheikh Ziaur; Cheng, Hsin-Ming

    2016-09-01

    Post-metal annealing temperature-dependent forming-free resistive switching memory characteristics, Fowler-Nordheim (F-N) tunneling at low resistance state, and after reset using a new W/WO3/WOx/W structure have been investigated for the first time. Transmission electron microscope image shows a polycrystalline WO3/WOx layer in a device with a size of 150 × 150 nm2. The composition of WO3/WOx is confirmed by X-ray photo-electron spectroscopy. Non-linear bipolar resistive switching characteristics have been simulated using space-charge limited current (SCLC) conduction at low voltage, F-N tunneling at higher voltage regions, and hopping conduction during reset, which is well fitted with experimental current-voltage characteristics. The barrier height at the WOx/W interface for the devices annealed at 500 °C is lower than those of the as-deposited and annealed at 400 °C (0.63 vs. 1.03 eV). An oxygen-vacant conducting filament with a diameter of ~34 nm is formed/ruptured into the WO3/WOx bilayer owing to oxygen ion migration under external bias as well as barrier height changes for high-resistance to low-resistance states. In addition, the switching mechanism including the easy method has been explored through the current-voltage simulation. The devices annealed at 500 °C have a lower operation voltage, lower barrier height, and higher non-linearity factor, which are beneficial for selector-less crossbar memory arrays.

  17. Reliability and validity of the Myotest® for measuring running stride kinematics.

    PubMed

    Gindre, Cyrille; Lussiana, Thibault; Hebert-Losier, Kim; Morin, Jean-Benoit

    2016-01-01

    Accelerometer-based systems are often used to quantify human movement. This study's aim was to assess the reliability and validity of the Myotest® accelerometer-based system for measuring running stride kinematics. Twenty habitual runners ran two 60 m trials at 12, 15, 18 and 21 km·h(-1). Contact time, aerial time and step frequency parameters from six consecutive running steps of each trial were extracted using Myotest® data. Between-trial reproducibility of measures was determined by comparing kinematic parameters from the two runs performed at the same speed. Myotest® measures were compared against photocell-based (Optojump Next®) and high-frequency video data to establish concurrent validity. The Myotest®-derived parameters were highly reproducible between trials at all running speeds (intra-class correlation coefficient (ICC): 0.886 to 0.974). Compared to the photo-cell and high-speed video-based measures, the mean contact times from the Myotest® were 34% shorter and aerial times were 64% longer. Only step frequency was comparable between systems and demonstrated high between-system correlation (ICC ≥ 0.857). The Myotest® is a practical portable device that is reliable for measuring contact time, aerial time and step frequency during running. In terms of validity, it provides accurate step frequency measures but underestimates contact time and overestimates aerial time compared to photocell- and optical-based systems.

  18. Weight Maintenance Following the STRIDE Weight Loss and Lifestyle Intervention for Individuals taking Antipsychotic Medications

    PubMed Central

    Green, Carla A.; Yarborough, Bobbi Jo H.; Leo, Michael C.; Stumbo, Scott P.; Perrin, Nancy A.; Nichols, Gregory A.; Stevens, Victor J.

    2015-01-01

    Objective Individuals taking antipsychotic medications have increased risk of obesity-related early morbidity/mortality. This report presents weight maintenance results from a successful weight loss and behavioral lifestyle change program developed for people taking antipsychotic medications. Design and Methods STRIDE was a 2-arm, randomized controlled trial. Intervention participants attended weekly group meetings for 6 months, then monthly group meetings for 6 months. Assessments were completed at baseline, 6, 12, and 24 months. Results At 24-months, intervention participants lost 3.7% of baseline weight and control participants 2.1%, a non-significant difference. Fasting glucose results followed a similar pattern. There was a statistically significant difference, however, for fasting insulin—the intervention group’s levels decreased between the end of the intensive intervention (at 6 months) and 24 months (10.1 to 7.91μU/mL); control participants’ levels increased (11.66 to 12.92μU/mL) during this period. There were also fewer medical hospitalizations among intervention participants (5.7%) than controls (21.1%; Χ2=8.47, p=0.004) during the 12 to 24-month post-intervention maintenance period. Conclusions Weight-change differences between arms diminished following the intervention period, though fasting insulin levels continued to improve. Reduced hospitalizations suggest that weight loss, even with regain, may have long-term positive benefits for people taking antipsychotic medications and may reduce costs. PMID:26334929

  19. Stride-Cycle Influences on Goal-Directed Head Movements Made During Walking

    NASA Technical Reports Server (NTRS)

    Peters, Brian T.; vanEmmerik, Richard E. A.; Bloomberg, Jacob J.

    2006-01-01

    Horizontal head movements were studied in six subjects as they made rapid horizontal gaze adjustments while walking. The aim of the present research was to determine if gait-cycle events alter the head movement response to a visual target acquisition task. Gaze shifts of approximately 40deg were elicited by a step change in the position of a visual target from a central location to a second location in the left or right horizontal periphery. The timing of the target position change was constrained to occur at 25,50,75 and 100% of the stride cycle. The trials were randomly presented as the subjects walked on a treadmill at their preferred speed (range: 1.25 to 1.48 m/s, mean: 1.39 +/- 0.09 m/s ) . Analyses focused on the movement onset latencies of the head and eyes and on the peak velocity and saccade amplitude of the head movement response. A comparison of the group means indicated that the head movement onset lagged the eye onset (262 ms versus 252 ms). The head and eye movement onset latencies were not affected by either the direction of the target change nor the point in the gait cycle during which the target relocation occurred. However, the presence of an interaction between the gait cycle events and the direction of the visual target shift indicates that the peak head saccade velocity and head saccade amplitude are affected by the natural head oscillations that occur while walking.

  20. Optimizing Strided Remote Memory Access Operations on the Quadrics QsNetII Network Interconnect

    SciTech Connect

    Nieplocha, Jarek; Tipparaju, Vinod; Krishnan, Manoj Kumar

    2006-11-02

    This paper describes and evaluates protocols for optimizing strided non-contiguous communication on the Quadrics QsNetII high-performance network interconnect. Most of previous related studies focused primarily on NIC-based or host-based protocols. This paper discusses merits for using both approaches and tries to determine for types and data sizes in the communication operations these protocols should be used. We focus on the Quadrics QsNetII-II network which offers powerful communication processors on the network interface card (NIC) and practical and flexible opportunities for exploiting them in context of user. Furthermore, the paper focuses on non-contiguous data remote memory access (RMA) transfers and performs the evaluation in context of standalone communication and application microbenchmarks. In comparison to the vendor provided noncontiguous interfaces, proposed approach achieved very significant performance improvement in context of microbenchmarks as well as application kernels- dense matrix multiplication and the Co-Array Fortran version of the NAS BT parallel benchmark. For example, for NAS BT Class B 54 % improvement in overall communication time and a 42% improvement in matrix multiplication was achieved for 64 processes.

  1. Weight maintenance following the STRIDE lifestyle intervention for individuals taking antipsychotic medications.

    PubMed

    Green, Carla A; Yarborough, Bobbi Jo H; Leo, Michael C; Stumbo, Scott P; Perrin, Nancy A; Nichols, Gregory A; Stevens, Victor J

    2015-10-01

    Individuals taking antipsychotic medications have increased risk of obesity-related early morbidity/mortality. This report presents weight maintenance results from a successful weight loss and behavioral lifestyle change program developed for people taking antipsychotic medications. STRIDE was a two-arm randomized controlled trial. Intervention participants attended weekly group meetings for 6 months, then monthly group meetings for 6 months. Assessments were completed at baseline and at 6, 12, and 24 months. At 24 months, intervention participants lost 3.7% of baseline weight and control participants 2.1%, a non-significant difference. Fasting glucose results followed a similar pattern. There was a statistically significant difference, however, for fasting insulin-the intervention group's levels decreased between the end of the intensive intervention (at 6 months) and 24 months (10.1-7.91 μU/mL); control participants' levels increased (11.66 to 12.92 μU/mL) during this period. There were also fewer medical hospitalizations among intervention participants (5.7%) than controls (21.1%; χ(2) = 8.47, P = 0.004) during the 12- to 24-month post-intervention maintenance period. Weight change differences between arms diminished following the intervention period, though fasting insulin levels continued to improve. Reduced hospitalizations suggest that weight loss, even with regain, may have long-term positive benefits for people taking antipsychotic medications and may reduce costs. © 2015 The Obesity Society.

  2. Stride cycle influences on goal-directed head movements made during walking.

    PubMed

    Peters, Brian T; van Emmerik, Richard E A; Bloomberg, Jacob J

    2006-08-01

    Horizontal head movements were studied in six subjects as they made rapid horizontal gaze adjustments while walking. The aim of the present research was to determine if gait cycle events alter the head movement response to a visual target acquisition task. Gaze shifts of approximately 40 degrees were elicited by a step change in the position of a visual target from a central location to a second location in the left or right horizontal periphery. The timing of the target position change was constrained to occur at 25%, 50%, 75% and 100% of the stride cycle. The trials were randomly presented as the subjects walked on a treadmill at their preferred speed (range: 1.25-1.48 m/s, mean: 1.39+/-0.09 m/s). Analyses focused on the movement onset latencies of the head and eyes and on the peak velocity and saccade amplitude of the head movement response. The head and eye movement onset latencies were not affected by either the direction of the target change or the point in the gait cycle during which the target relocation occurred. However, the presence of an interaction between the gait cycle events and the direction of the visual target shift for both the amplitude and peak velocity of the head movement response indicates that the head movement responses to visual target changes can be influenced by the phase of the gait cycle during which the target relocation takes place.

  3. Measurement of stride parameters using a wearable GPS and inertial measurement unit.

    PubMed

    Tan, Huiling; Wilson, Alan M; Lowe, John

    2008-01-01

    Both GPS and inertial measurement units (IMUs) have been extensively used in biomechanical studies. Expensive high accuracy GPS units can provide information about intrastride speed and position, but their application is limited by their size and cost. Single and double integration of acceleration from IMU provides information about short-term fluctuations in speed and position, but suffers from integration error over a longer period of time. The integration of GPS and IMU has been widely used in large and expensive units designed for survey and vehicle navigation. Here we propose a data fusion scheme, which is a Kalman filter based complementary filter and enhances the frequency response of the GPS and IMU used alone. We also report the design of a small (28 g) low cost GPS/IMU unit. Its accuracy after post-processing with the proposed data fusion scheme for determining average speed and intrastride variation was compared to a traditional high cost survey GPS. The low cost unit achieved an accuracy of 0.15 ms(-1) (s.d.) for horizontal speed in cycling and human running across a speed range of 3-10 ms(-1). The stride frequency and vertical displacement calculated based on measurements from the low cost GPS/IMU units had an s.d. of 0.08 Hz and 0.02 m respectively, compared to measurements from high performance OEM4 GPS units.

  4. The excitation and characteristic frequency of the long-period volcanic event: An approach based on an inhomogeneous autoregressive model of a linear dynamic system

    USGS Publications Warehouse

    Nakano, M.; Kumagai, H.; Kumazawa, M.; Yamaoka, K.; Chouet, B.A.

    1998-01-01

    We present a method to quantify the source excitation function and characteristic frequencies of long-period volcanic events. The method is based on an inhomogeneous autoregressive (AR) model of a linear dynamic system, in which the excitation is assumed to be a time-localized function applied at the beginning of the event. The tail of an exponentially decaying harmonic waveform is used to determine the characteristic complex frequencies of the event by the Sompi method. The excitation function is then derived by operating an AR filter constructed from the characteristic frequencies to the entire seismogram of the event, including the inhomogeneous part of the signal. We apply this method to three long-period events at Kusatsu-Shirane Volcano, central Japan, whose waveforms display simple decaying monochromatic oscillations except for the beginning of the events. We recover time-localized excitation functions lasting roughly 1 s at the start of each event and find that the estimated functions are very similar to each other at all the stations of the seismic network for each event. The phases of the characteristic oscillations referred to the estimated excitation function fall within a narrow range for almost all the stations. These results strongly suggest that the excitation and mode of oscillation are both dominated by volumetric change components. Each excitation function starts with a pronounced dilatation consistent with a sudden deflation of the volumetric source which may be interpreted in terms of a choked-flow transport mechanism. The frequency and Q of the characteristic oscillation both display a temporal evolution from event to event. Assuming a crack filled with bubbly water as seismic source for these events, we apply the Van Wijngaarden-Papanicolaou model to estimate the acoustic properties of the bubbly liquid and find that the observed changes in the frequencies and Q are consistently explained by a temporal change in the radii of the bubbles

  5. The effect of rider weight and additional weight in Icelandic horses in tölt: part II. Stride parameters responses.

    PubMed

    Gunnarsson, V; Stefánsdóttir, G J; Jansson, A; Roepstorff, L

    2017-09-01

    This study investigated the effects of rider weight in the BW ratio (BWR) range common for Icelandic horses (20% to 35%), on stride parameters in tölt in Icelandic horses. The kinematics of eight experienced Icelandic school horses were measured during an incremental exercise test using a high-speed camera (300 frames/s). Each horse performed five phases (642 m each) in tölt at a BWR between rider (including saddle) and horse starting at 20% (BWR20) and increasing to 25% (BWR25), 30% (BWR30), 35% (BWR35) and finally 20% (BWR20b) was repeated. One professional rider rode all horses and weight (lead) was added to saddle and rider as needed. For each phase, eight strides at speed of 5.5 m/s were analyzed for stride duration, stride frequency, stride length, duty factor (DF), lateral advanced placement, lateral advanced liftoff, unipedal support (UPS), bipedal support (BPS) and height of front leg action. Stride length became shorter (Y=2.73-0.004x; P0.05). In conclusion, increased BWR decreased stride length and increased DF proportionally to the same extent in all limbs, whereas BPS increased at the expense of decreased UPS. These changes can be expected to decrease tölt quality when subjectively evaluated according to the breeding goals for the Icelandic horse. However, beat, symmetry and height of front leg lifting were not affected by BWR.

  6. Recommended number of strides for automatic assessment of gait symmetry and regularity in above-knee amputees by means of accelerometry and autocorrelation analysis

    PubMed Central

    2012-01-01

    Background Symmetry and regularity of gait are essential outcomes of gait retraining programs, especially in lower-limb amputees. This study aims presenting an algorithm to automatically compute symmetry and regularity indices, and assessing the minimum number of strides for appropriate evaluation of gait symmetry and regularity through autocorrelation of acceleration signals. Methods Ten transfemoral amputees (AMP) and ten control subjects (CTRL) were studied. Subjects wore an accelerometer and were asked to walk for 70 m at their natural speed (twice). Reference values of step and stride regularity indices (Ad1 and Ad2) were obtained by autocorrelation analysis of the vertical and antero-posterior acceleration signals, excluding initial and final strides. The Ad1 and Ad2 coefficients were then computed at different stages by analyzing increasing portions of the signals (considering both the signals cleaned by initial and final strides, and the whole signals). At each stage, the difference between Ad1 and Ad2 values and the corresponding reference values were compared with the minimum detectable difference, MDD, of the index. If that difference was less than MDD, it was assumed that the portion of signal used in the analysis was of sufficient length to allow reliable estimation of the autocorrelation coefficient. Results All Ad1 and Ad2 indices were lower in AMP than in CTRL (P < 0.0001). Excluding initial and final strides from the analysis, the minimum number of strides needed for reliable computation of step symmetry and stride regularity was about 2.2 and 3.5, respectively. Analyzing the whole signals, the minimum number of strides increased to about 15 and 20, respectively. Conclusions Without the need to identify and eliminate the phases of gait initiation and termination, twenty strides can provide a reasonable amount of information to reliably estimate gait regularity in transfemoral amputees. PMID:22316184

  7. An exploratory clustering approach for extracting stride parameters from tracking collars on free-ranging wild animals.

    PubMed

    Dewhirst, Oliver P; Roskilly, Kyle; Hubel, Tatjana Y; Jordan, Neil R; Golabek, Krystyna A; McNutt, J Weldon; Wilson, Alan M

    2017-02-01

    Changes in stride frequency and length with speed are key parameters in animal locomotion research. They are commonly measured in a laboratory on a treadmill or by filming trained captive animals. Here, we show that a clustering approach can be used to extract these variables from data collected by a tracking collar containing a GPS module and tri-axis accelerometers and gyroscopes. The method enables stride parameters to be measured during free-ranging locomotion in natural habitats. As it does not require labelled data, it is particularly suitable for use with difficult to observe animals. The method was tested on large data sets collected from collars on free-ranging lions and African wild dogs and validated using a domestic dog. © 2017. Published by The Company of Biologists Ltd.

  8. Gait dynamics in Parkinson's disease: common and distinct behavior among stride length, gait variability, and fractal-like scaling.

    PubMed

    Hausdorff, Jeffrey M

    2009-06-01

    Parkinson's disease (PD) is a common, debilitating neurodegenerative disease. Gait disturbances are a frequent cause of disability and impairment for patients with PD. This article provides a brief introduction to PD and describes the gait changes typically seen in patients with this disease. A major focus of this report is an update on the study of the fractal properties of gait in PD, the relationship between this feature of gait and stride length and gait variability, and the effects of different experimental conditions on these three gait properties. Implications of these findings are also briefly described. This update highlights the idea that while stride length, gait variability, and fractal scaling of gait are all impaired in PD, distinct mechanisms likely contribute to and are responsible for the regulation of these disparate gait properties.

  9. Gait dynamics in Parkinson's disease: Common and distinct behavior among stride length, gait variability, and fractal-like scaling

    NASA Astrophysics Data System (ADS)

    Hausdorff, Jeffrey M.

    2009-06-01

    Parkinson's disease (PD) is a common, debilitating neurodegenerative disease. Gait disturbances are a frequent cause of disability and impairment for patients with PD. This article provides a brief introduction to PD and describes the gait changes typically seen in patients with this disease. A major focus of this report is an update on the study of the fractal properties of gait in PD, the relationship between this feature of gait and stride length and gait variability, and the effects of different experimental conditions on these three gait properties. Implications of these findings are also briefly described. This update highlights the idea that while stride length, gait variability, and fractal scaling of gait are all impaired in PD, distinct mechanisms likely contribute to and are responsible for the regulation of these disparate gait properties.

  10. Linear integrated circuits

    NASA Astrophysics Data System (ADS)

    Young, T.

    This book is intended to be used as a textbook in a one-semester course at a variety of levels. Because of self-study features incorporated, it may also be used by practicing electronic engineers as a formal and thorough introduction to the subject. The distinction between linear and digital integrated circuits is discussed, taking into account digital and linear signal characteristics, linear and digital integrated circuit characteristics, the definitions for linear and digital circuits, applications of digital and linear integrated circuits, aspects of fabrication, packaging, and classification and numbering. Operational amplifiers are considered along with linear integrated circuit (LIC) power requirements and power supplies, voltage and current regulators, linear amplifiers, linear integrated circuit oscillators, wave-shaping circuits, active filters, DA and AD converters, demodulators, comparators, instrument amplifiers, current difference amplifiers, analog circuits and devices, and aspects of troubleshooting.

  11. Effects of flunixin on cardiorespiratory, plasma lactate and stride length responses to intense treadmill exercise in Standardbred trotters.

    PubMed

    Kallings, P; Persson, S G B; Essén-Gustavsson, B

    2010-11-01

    Since nonsteroidal anti-inflammatory drugs, such as flunixin, on account of their anti-inflammatory and analgesic properties, are used in both racing and equestrian sport horses, the question has been raised as to whether these drugs affect the physiological responses to exercise and thus performance potential. The aims of this investigation were to study the effects of flunixin on cardiorespiratory, metabolic and locomotor parameters in horses during intense treadmill exercise. Six Standardbred trotters underwent an incremental treadmill exercise test to fatigue, without drug and then after administration of flunixin meglumine (1.1 mg/kg bwt i.m.). Heart rate (HR), oxygen uptake and stride length were measured and venous blood samples drawn repeatedly during the test. Heart rates were found to be significantly higher at submaximal speeds, while the velocity causing a HR of 200 beats/min was significantly decreased after treatment with flunixin. Maximal HR and plasma lactate concentration 5 min after exercise were unchanged after medication. Flunixin caused higher plasma lactate concentrations at all speeds and the lactate threshold was decreased, compared with baseline values. Oxygen uptake levelled off at the highest velocities and did not change after flunixin treatment. Stride length was increased after treatment, although not at the highest velocities. The increased HR and lactate responses to exercise after flunixin treatment indicate that it does influence physiological responses, but does not improve the performance potential of clinically healthy horses. However, the lengthened stride during submaximal exercise after medication could imply undetected subclinical lameness, masked in some of the horses, i.e. they have performed with a longer stride at the cost of a higher heart rate and an increased lactate concentration. © 2010 EVJ Ltd.

  12. Determining if muscle activity is related to preferred stride frequency during running in the water and on land.

    PubMed

    Masumoto, Kenji; Bailey, Joshua P; Mercer, John A

    2015-12-01

    To determine if muscle activity is related to preferred stride frequency (PSF) during deep water running (DWR) and treadmill running on dry land (TMR). Subjects (n = 11; 26.2 ± 4.4 years) completed TMR and DWR at their mode-specific preferred stride frequency (PSF mode). They also ran at stride frequencies which were lower and higher than the PSF mode (i.e., PSF mode ± 5, 10, and 15 %). Muscle activity from the rectus femoris (RF), biceps femoris (BF), tibialis anterior (TA), and gastrocnemius (GL), SF, and rating of perceived exertion (RPE) were measured. The PSF mode during DWR was significantly lower than that of TMR (i.e., 49.9 ± 11.0 versus 81.9 ± 4.8 strides/min, P < 0.0001). Additionally, muscle activity from the RF, TA, and GL during DWR was significantly lower than during TMR at respective PSF mode (~83.6 % decrease, P < 0.0001). However, RPE while running at the PSF mode during DWR and TMR was similar. During DWR, the RF, TA, and GL muscle activity was not different between PSF mode and any other SF conditions (P > 0.0005). During TMR, there was no significant difference in the RF and GL muscle activity between PSF mode and any other SF conditions during TMR (P > 0.0005). During DWR, subjects selected a lower PSF than during TMR even though RPE was the same. It was also determined that the relationship between muscle activity and changes in SF relative to the PSF mode was unique during DWR and TMR.

  13. Effect of fatigue on stride pattern continuously measured by an accelerometric gait recorder in middle distance runners.

    PubMed

    Le Bris, R; Billat, V; Auvinet, B; Chaleil, D; Hamard, L; Barrey, E

    2006-06-01

    The purpose of this study was to analyze the continuous changes in stride patterns of athletes running at speed elicited VO(2max). Six male sub-elite middle-distance runners carried out a constant track running test to exhaustion (time to exhaustion: 409+/-71 s) at their maximal aerobic speed (17.4+/-1.1 km.h(-1)). The body accelerations were measured with a triaxial accelerometer fixed at the low back. A set of variables was computed from the accelerometer output: stride frequency, stride symmetry and regularity, signal energies and impulses in each axis and the integral of the total acceleration vector. An ANOVA with repeated measures was performed to test the changes of these variables during the three times: the onset point, midway point and end point of exercise. The following changes were observed: the regularity index which describes the similarity of crania-caudal movements over successive strides, decreased significantly between the start and the end of the test (309.9 to 274.5; P<0.05). During the same time, the media-lateral impulse (4.69%BW.s to 5.71%BW.s; P<0.001; BW: body weight) and signal energy (1.40 G(2).s to 2.06 G(2).s; P<0.001; G=9.81 m.s(-2)) increased significantly. The changes in medio-lateral axis (increase of energy expenditure which is not useful for propulsion) and in the regularity index (modifications in the temporal-spatial periodicity of the running cycle) could be considered as early alterations of running pattern when the athletes got fatigued.

  14. Repeated sprint ability and stride kinematics are altered following an official match in national-level basketball players.

    PubMed

    Delextrat, A; Baliqi, F; Clarke, N

    2013-04-01

    The aim of the study was to investigate the effects of playing an official national-level basketball match on repeated sprint ability (RSA) and stride kinematics. Nine male starting basketball players (22.8±2.2 years old, 191.3±5.8 cm, 88±10.3 kg, 12.3±4.6% body fat) volunteered to take part. Six repetitions of maximal 4-s sprints were performed on a non-motorised treadmill, separated by 21-s of passive recovery, before and immediately after playing an official match. Fluid loss, playing time, and the frequencies of the main match activities were recorded. The peak, mean, and performance decrement for average and maximal speed, acceleration, power, vertical and horizontal forces, and stride parameters were calculated over the six sprints. Differences between pre- and post-match were assessed by student t-tests. Significant differences between pre- and post-tests were observed in mean speed (-3.3%), peak and mean horizontal forces (-4.3% and -17.4%), peak and mean vertical forces (-3.4% and -3.7%), contact time (+7.3%), stride duration (+4.6%) and stride frequency (-4.0%), (P<0.05). In addition, the variation in several RSA parameters, such as peak and mean speed, peak and mean acceleration, mean power, and peak and mean vertical force were significantly correlated to fluid loss and sprint, jump and shuffle frequencies (P<0.05). These results highlight that the impairment in repeated sprint ability depends on the specific activities performed, and that replacing fluid loss through sweating during a match is crucial.

  15. Dosimetric characteristics of a newly designed grid block for megavoltage photon radiation and its therapeutic advantage using a linear quadratic model

    SciTech Connect

    Meigooni, Ali S.; Dou Kai; Meigooni, Navid J.; Gnaster, Michael; Awan, Shahid; Dini, Sharifeh; Johnson, Ellis L.

    2006-09-15

    Grid radiation therapy with megavoltage x-ray beam has been proven to be an effective technique for management of large, bulky malignant tumors. The clinical advantage of GRID therapy, combined with conventional radiation therapy, has been demonstrated using a prototype GRID block [Mohiuddin, Curtis, Grizos, and Komarnicky, Cancer 66, 114-118 (1990)]. Recently, a new GRID block design with improved dosimetric properties has become commercially available from Radiation Product Design, Inc. (Albertive, MN). This GRID collimator consists of an array of focused apertures in a cerrobend block arranged in a hexagonal pattern having a circular cross-section with a diameter and center-to-center spacing of 14.3 and 21.1 mm, respectively, in the plane of isocenter. In this project, dosimetric characteristics of the newly redesigned GRID block have been investigated for a Varian 21EX linear accelerator (Varian Associates, Palo Alto, CA). These determinations were performed using radiographic films, thermoluminescent dosimeters in Solid Water trade mark sign phantom materials, and an ionization chamber in water. The output factor, percentage depth dose, beam profiles, and isodose distributions of the GRID radiation as a function of field size and beam energy have been measured using both 6 and 18 MV x-ray beams. In addition, the therapeutic advantage obtained from this treatment modality with the new GRID block design for a high, single fraction of dose has been calculated using the linear quadratic model with {alpha}/{beta} ratios for typical tumor and normal cells. These biological characteristics of the new GRID block design will also be presented.

  16. A Comparison of Stride Length and Lower Extremity Kinematics during Barefoot and Shod Running in Well Trained Distance Runners.

    PubMed

    Francis, Peter; Ledingham, James; Clarke, Sarah; Collins, D J; Jakeman, Philip

    2016-09-01

    Stride length, hip, knee and ankle angles were compared during barefoot and shod running on a treadmill at two speeds. Nine well-trained (1500m time: 3min:59.80s ± 14.7 s) male (22 ±3 years; 73 ±9 kg; 1.79 ±0.4 m) middle distance (800 m - 5,000 m) runners performed 2 minutes of running at 3.05 m·s(-1) and 4.72 m·s(-1) on an treadmill. This approach allowed continuous measurement of lower extremity kinematic data and calculation of stride length. Statistical analysis using a 2X2 factorial ANOVA revealed speed to have a main effect on stride length and hip angle and footwear to have a main effect on hip angle. There was a significant speed*footwear interaction for knee and ankle angles. Compared to shod running at the lower speed (3.05 m·s(-1)), well trained runners have greater hip, knee and ankle angles when running barefoot. Runners undertake a high volume (~75%) of training at lower intensities and therefore knowledge of how barefoot running alters running kinematics at low and high speeds may be useful to the runner.

  17. Influence of speed variation and age on ground reaction forces and stride parameters of children's normal gait.

    PubMed

    Diop, M; Rahmani, A; Belli, A; Gautheron, V; Geyssant, A; Cottalorda, J

    2005-10-01

    The aim of this study was to assess the influence of both age and speed on ground reaction forces and temporal parameters during normal gait in children. Fifteen children aged 4-6 years (group 1), 16 aged 6-8 years (group 2), and 16 aged 8-10 years (group 3) walked at 2.7 km/h, 3.6 km/h, and 4.5 km/h on a treadmill. For each child thirty successive steps were recorded. The influence of speed and age on normalized gait parameters was examined with two-way analysis of variance. The first vertical peak force (Fz1) and all the antero-posterior forces of group 1 were higher than those of the other groups for the three speeds. The minimum vertical force (Fz2), the second vertical peak force (Fz3), and the duration of stride and stance were significantly higher in groups 2 and 3. For all the groups, Fz1 and all the antero-posterior forces increased with the speed while Fz2, stride, stance, and double-stance duration decreased. Fz3 was not influenced by speed variation. The results of this study show that age and walking speed influence ground reaction forces and stride time parameters in 4- to 10-year-old children.

  18. Improving lifestyle interventions for people with serious mental illnesses: Qualitative results from the STRIDE study

    PubMed Central

    Yarborough, Bobbi Jo H.; Stumbo, Scott P.; Yarborough, Micah T.; Young, Thomas J.; Green, Carla A.

    2015-01-01

    Objective Individuals with serious mental illnesses are disproportionately affected by overweight and obesity. Understanding the factors that facilitate or hinder lifestyle change in this population could lead to better interventions and improved health outcomes. Methods A subset of intervention and usual-care participants (n = 84) in the STRIDE randomized trial were interviewed at 3, 9, and 18 months, yielding 101 interviews (some were interviewed more than once). Participants had a mean age of 48.1 (SD = 10.1); 64% were female. Participants had diagnoses of schizophrenia or schizoaffective disorder (41%), bipolar disorder (20%), affective psychoses (37%) or PTSD (2%). Interviews were transcribed verbatim, coded using Atlas.ti, and analyzed for common themes. Results Barriers to behavior change were similar to those described for the general population, including lack of support from significant others, the lure of unhealthy foods, and poor weather impeding exercise. Additional challenges included the effects of psychiatric symptoms, or consequences of symptoms (i.e., social isolation), on ability to make and sustain lifestyle changes. We found a strong preference for ongoing, group-based support to foster a sense of accountability which motivated and helped to sustain behavior changes. Conclusions and implications for practice Individuals with serious mental illnesses encounter many of the same barriers to weight loss seen in the general population, but they may be more vulnerable to additional obstacles. Lifestyle change interventions for this population should help participants develop the ability to iteratively cope with fluctuating mood and subsequent changes in motivation to eat healthfully and exercise regularly. PMID:26214184

  19. Effects of loading and size on maximum power output and gait characteristics in geckos.

    PubMed

    Irschick, Duncan J; Vanhooydonck, Bieke; Herrel, Anthony; Andronescu, Anemone

    2003-11-01

    Stride length, stride frequency and power output are all factors influencing locomotor performance. Here, we first test whether mass-specific power output limits climbing performance in two species of geckos (Hemidactylus garnoti and Gekko gecko) by adding external loads to their bodies. We then test whether body size has a negative effect on mass-specific power output. Finally, we test whether loading affects kinematics in both gecko species. Lizards were induced to run vertically on a smooth wooden surface with loads of 0-200% of body mass (BM) in H. garnoti and 0-100% BM in G. gecko. For each stride, we calculated angular and linear kinematics (e.g. trunk angle, stride length), performance (maximum speed) and mean mass-specific power output per stride. The addition of increasingly large loads caused an initial increase in maximum mass-specific power output in both species, but for H. garnoti, mass-specific power output remained constant at higher loads (150% and 200% BM), even though maximum velocity declined. This result, in combination with the fact that stride frequency showed no evidence of leveling off as speed increased in either species, suggests that power limits maximum speed. In addition, the large gecko (G. gecko) produced significantly less power than the smaller H. garnoti, despite the fact that both species ran at similar speeds. This difference disappeared, however, when we recalculated power output based on higher maximum speeds for unloaded G. gecko moving vertically obtained by other researchers. Finally, the addition of external loads did not affect speed modulation in either species: both G. gecko and H. garnoti increase speed primarily by increasing stride frequency, regardless of loading condition. For a given speed, both species take shorter but more strides with heavier loads, but for a given load, G. gecko attains similar speeds to H. garnoti by taking longer but fewer strides.

  20. Microtubule-driven nuclear movements and linear elements as meiosis-specific characteristics of the fission yeasts Schizosaccharomyces versatilis and Schizosaccharomyces pombe.

    PubMed

    Svoboda, A; Bähler, J; Kohli, J

    1995-11-01

    Meiotic prophase in Schizosaccharomyces pombe is characterized by striking nuclear movements and the formation of linear elements along chromosomes instead of tripartite synaptonemal complexes. We analysed the organization of nuclei and microtubules in cells of fission yeasts undergoing sexual differentiation. S. japonicus var. versatilis and S. pombe cells were studied in parallel, taking advantage of the better cytology in S. versatilis. During conjugation, microtubules were directed towards the mating projection. These microtubules seem to lead the haploid nuclei together in the zygote by interaction with the spindle pole bodies at the nuclear periphery. After karyogamy, arrays of microtubules emanating from the spindle pole body of the diploid nucleus extended to both cell poles. The same differentiated microtubule configuration was elaborated upon induction of azygotic meiosis in S. pombe. The cyclic movements of the elongated nuclei between the cell poles is reflected by a dynamic and coordinated shortening and lengthening of the two microtubule arrays. When the nucleus was at a cell end, one array was short while the other bridged the whole cell length. Experiments with inhibitors showed that microtubules are required for karyogamy and for the elongated shape and movement of nuclei during meiotic prophase. In both fission yeasts the SPBs and nucleoli are at the leading ends of the moving nuclei. Astral and cytoplasmic microtubules were also prominent during meiotic divisions and sporulation. We further show that in S. versatilis the linear elements formed during meiotic prophase are similar to those in S. pombe. Tripartite synaptonemal complexes were never detected. Taken together, these findings suggest that S. pombe and S. versatilis share basic characteristics in the organization of microtubules and the structure and behaviour of nuclei during their meiotic cell cycle. The prominent differentiations of microtubules and nuclei may be involved in the

  1. Linear variability of gait according to socioeconomic status in elderly

    PubMed Central

    2016-01-01

    Aim: To evaluate the linear variability of comfortable gait according to socioeconomic status in community-dwelling elderly. Method: For this cross-sectional observational study 63 self- functioning elderly were categorized according to the socioeconomic level on medium-low (n= 33, age 69.0 ± 5.0 years) and medium-high (n= 30, age 71.0 ± 6.0 years). Each participant was asked to perform comfortable gait speed for 3 min on an 40 meters elliptical circuit, recording in video five strides which were transformed into frames, determining the minimum foot clearance, maximum foot clearance and stride length. The intra-group linear variability was calculated by the coefficient of variation in percent. Results: The trajectory parameters variability is not different according to socioeconomic status with a 30% (range= 15-55%) for the minimum foot clearance and 6% (range= 3-8%) in maximum foot clearance. Meanwhile, the stride length consistently was more variable in the medium-low socioeconomic status for the overall sample (p= 0.004), female (p= 0.041) and male gender (p= 0.007), with values near 4% ​​(range = 2.5-5.0%) in the medium-low and 2% (range = 1.5-3.5%) in the medium-high. Conclusions: The intra-group linear variability is consistently higher and within reference parameters for stride length during comfortable gait for elderly belonging to medium-low socioeconomic status. This might be indicative of greater complexity and consequent motor adaptability. PMID:27546931

  2. Linear variability of gait according to socioeconomic status in elderly.

    PubMed

    Medina González, Paul

    2016-06-30

    To evaluate the linear variability of comfortable gait according to socioeconomic status in community-dwelling elderly. For this cross-sectional observational study 63 self- functioning elderly were categorized according to the socioeconomic level on medium-low (n= 33, age 69.0 ± 5.0 years) and medium-high (n= 30, age 71.0 ± 6.0 years). Each participant was asked to perform comfortable gait speed for 3 min on an 40 meters elliptical circuit, recording in video five strides which were transformed into frames, determining the minimum foot clearance, maximum foot clearance and stride length. The intra-group linear variability was calculated by the coefficient of variation in percent. The trajectory parameters variability is not different according to socioeconomic status with a 30% (range= 15-55%) for the minimum foot clearance and 6% (range= 3-8%) in maximum foot clearance. Meanwhile, the stride length consistently was more variable in the medium-low socioeconomic status for the overall sample (p= 0.004), female (p= 0.041) and male gender (p= 0.007), with values near 4% ​​(range = 2.5-5.0%) in the medium-low and 2% (range = 1.5-3.5%) in the medium-high. The intra-group linear variability is consistently higher and within reference parameters for stride length during comfortable gait for elderly belonging to medium-low socioeconomic status. This might be indicative of greater complexity and consequent motor adaptability.

  3. Non-linear direct multi-scale image enhancement based on the luminance and contrast masking characteristics of the human visual system.

    PubMed

    Nercessian, Shahan C; Panetta, Karen A; Agaian, Sos S

    2013-09-01

    Image enhancement is a crucial pre-processing step for various image processing applications and vision systems. Many enhancement algorithms have been proposed based on different sets of criteria. However, a direct multi-scale image enhancement algorithm capable of independently and/or simultaneously providing adequate contrast enhancement, tonal rendition, dynamic range compression, and accurate edge preservation in a controlled manner has yet to be produced. In this paper, a multi-scale image enhancement algorithm based on a new parametric contrast measure is presented. The parametric contrast measure incorporates not only the luminance masking characteristic, but also the contrast masking characteristic of the human visual system. The formulation of the contrast measure can be adapted for any multi-resolution decomposition scheme in order to yield new human visual system-inspired multi-scale transforms. In this article, it is exemplified using the Laplacian pyramid, discrete wavelet transform, stationary wavelet transform, and dual-tree complex wavelet transform. Consequently, the proposed enhancement procedure is developed. The advantages of the proposed method include: 1) the integration of both the luminance and contrast masking phenomena; 2) the extension of non-linear mapping schemes to human visual system inspired multi-scale contrast coefficients; 3) the extension of human visual system-based image enhancement approaches to the stationary and dual-tree complex wavelet transforms, and a direct means of; 4) adjusting overall brightness; and 5) achieving dynamic range compression for image enhancement within a direct multi-scale enhancement framework. Experimental results demonstrate the ability of the proposed algorithm to achieve simultaneous local and global enhancements.

  4. Linearizing the joint torque characteristics of an electric direct-drive robot for high performance control of in-contact operations

    SciTech Connect

    Muir, P.F.

    1992-01-01

    Many robot control algorithms for high performance in-contact operations including hybrid force/position, stiffness control and impedance control approaches require the command of the joint torques. However, most commercially available robots do not provide joint torque command capabilities. The joint command at the user level is typically position or velocity and at the control developer level is voltage current, or pulse-width, and the torque generated is a nonlinear function of the command and joint position. To enable the application of high performance in-contact control algorithms to commercially available robots, and thereby facilitate technology transfer from the robot control research community to commercial applications, a practical methodology has been developed to linearize the torque characteristics of electric motor-amplifier combinations. A four degree-of-freedom Adept 2 robot, having pulse-width modulation amplifiers and both variable reluctance and brushless DC motors, is converted to operate from joint torque commands to demonstrate the methodology. The average percentage torque deviation over the command and position ranges is reduced from as much as 76% to below 5% for the direct-drive joints 1, 2 and 4 and is cut by one half in the remaining ball-screw driven joint 3. 16 refs., 16 figs., 2 tabs.

  5. Responsiveness and Release Characteristic of Semi-IPN Hydrogels Consisting of Nano-Sized Clay Crosslinked Poly(Dimethylaminoethyl Methacrylate) and Linear Carboxymethyl Chitosan.

    PubMed

    Chen, Yi; Peng, Chang; Lu, Yanbing; Liu, Wenyong; Xu, Weijian

    2015-01-01

    PH and temperature double responsive semi-IPN hydrogels consisting of poly(dimethylaminoethyl methacrylate) (PDMAEMA) network crosslinked by nano-sized inorganic clay and linear carboxymethyl chitosan (CMCS) were synthesized by in situ, free radical polymerization in aqueous solution. The effect of the mass and carboxymethyl substitution of CMCS on the responsiveness, swelling/deswelling and drug release characteristic of gels were investigated. Comparing to the gels without CMCS, the resulting gels (named as C-NC gels) showed similar LCST and temperature response behavior. However, with the increase of added CMCS, the swelling ratio of gels decreased considerably around the isoelectric point (IEP) of CMCS, while increased in both strong acidic and alkaline condition. The deswelling rate was improved significantly when the content of CMCS is high. In drug load and release test by using theophylline as target, the C-NC gels exhibited an excellent load ability and controlled-release in simulated human intestinal and stomachic condition. Additionally, all properties of gels were affected by the DS of added CMCS due to the different ratio and interaction of negative and positive ions in gels.

  6. Effect of non-linearity of a predictor on the shape and magnitude of its receiver-operating-characteristic curve in predicting a binary outcome.

    PubMed

    Ho, Kwok M

    2017-08-31

    Area under a receiver-operating-characteristic (AUROC) curve is widely used in medicine to summarize the ability of a continuous predictive marker to predict a binary outcome. This study illustrated how a U-shaped or inverted U-shaped continuous predictor would affect the shape and magnitude of its AUROC curve in predicting a binary outcome by comparing the ROC curves of the worst first 24-hour arterial pH values of 9549 consecutive critically ill patients in predicting hospital mortality before and after centering the predictor by its mean or median. A simulation dataset with an inverted U-shaped predictor was used to assess how this would affect the shape and magnitude of the AUROC curve. An asymmetrical U-shaped relationship between pH and hospital mortality, resulting in an inverse-sigmoidal ROC curve, was observed. The AUROC substantially increased after centering the predictor by its mean (0.611 vs 0.722, difference = 0.111, 95% confidence interval [CI] 0.087-0.135), and was further improved after centering by its median (0.611 vs 0.745, difference = 0.133, 95%CI 0.110-0.157). A sigmoidal-shaped ROC curve was observed for an inverted U-shaped predictor. In summary, a non-linear predictor can result in a biphasic-shaped ROC curve; and centering the predictor can reduce its bias towards null predictive ability.

  7. The operational implications of donor behaviors following enrollment in STRIDE (Strategies to Reduce Iron Deficiency in blood donors).

    PubMed

    Cable, Ritchard G; Birch, Rebecca J; Spencer, Bryan R; Wright, David J; Bialkowski, Walter; Kiss, Joseph E; Rios, Jorge; Bryant, Barbara J; Mast, Alan E

    2017-07-13

    Donor behaviors in STRIDE (Strategies to Reduce Iron Deficiency), a trial to reduce iron deficiency, were examined. Six hundred ninety-two frequent donors were randomized to receive either 19 or 38 mg iron for 60 days or an educational letter based on their predonation ferritin. Compliance with assigned pills, response to written recommendations, change in donation frequency, and future willingness to take iron supplements were examined. Donors who were randomized to receive iron pills had increased red blood cell donations and decreased hemoglobin deferrals compared with controls or with pre-STRIDE donations. Donors who were randomized to receive educational letters had fewer hemoglobin deferrals compared with controls. Of those who received a letter advising of low ferritin levels with recommendations to take iron supplements or delay future donations, 57% reported that they initiated iron supplementation, which was five times as many as those who received letters lacking a specific recommendation. The proportion reporting delayed donation was not statistically different (32% vs. 20%). Of donors who were assigned pills, 58% reported taking them "frequently," and forgetting was the primary reason for non-compliance. Approximately 80% of participants indicated that they would take iron supplements if provided by the center. Donors who were assigned iron pills had acceptable compliance, producing increased red blood cell donations and decreased low hemoglobin deferrals compared with controls or with pre-STRIDE rates. The majority of donors assigned to an educational letter took action after receiving a low ferritin result, with more donors choosing to take iron than delay donation. Providing donors with information on iron status with personalized recommendations was an effective alternative to directly providing iron supplements. © 2017 AABB.

  8. Test-retest reliability of stride time variability while dual tasking in healthy and demented adults with frontotemporal degeneration

    PubMed Central

    2011-01-01

    Background Although test-retest reliability of mean values of spatio-temporal gait parameters has been assessed for reliability while walking alone (i.e., single tasking), little is known about the test-retest reliability of stride time variability (STV) while performing an attention demanding-task (i.e., dual tasking). The objective of this study was to examine immediate test-retest reliability of STV while single and dual tasking in cognitively healthy older individuals (CHI) and in demented patients with frontotemporal degeneration (FTD). Methods Based on a cross-sectional design, 69 community-dwelling CHI (mean age 75.5 ± 4.3; 43.5% women) and 14 demented patients with FTD (mean age 65.7 ± 9.8 years; 6.7% women) walked alone (without performing an additional task; i.e., single tasking) and while counting backward (CB) aloud starting from 50 (i.e., dual tasking). Each subject completed two trials for all the testing conditions. The mean value and the coefficient of variation (CoV) of stride time while walking alone and while CB at self-selected walking speed were measured using GAITRite® and SMTEC® footswitch systems. Results ICC of mean value in CHI under both walking conditions were higher than ICC of demented patients with FTD and indicated perfect reliability (ICC > 0.80). Reliability of mean value was better while single tasking than dual tasking in CHI (ICC = 0.96 under single-task and ICC = 0.86 under dual-task), whereas it was the opposite in demented patients (ICC = 0.65 under single-task and ICC = 0.81 under dual-task). ICC of CoV was slight to poor whatever the group of participants and the walking condition (ICC < 0.20), except while dual tasking in demented patients where it was fair (ICC = 0.34). Conclusions The immediate test-retest reliability of the mean value of stride time in single and dual tasking was good in older CHI as well as in demented patients with FTD. In contrast, the variability of stride time was low in both groups of

  9. A comparison of energy consumption between the use of a walking frame, crutches and a Stride-on rehabilitation scooter.

    PubMed

    Patel, Nimesh; Batten, Timothy; Roberton, Andrew; Enki, Doyo; Wansbrough, Guy; Davis, James

    2016-08-01

    Following foot and ankle surgery, patients may be required to mobilise non-weight bearing, requiring a walking aid such as crutches, walking frame or a Stride-on rehabilitation scooter, which aims to reduce the amount of work required. The energy consumption of mobilising using a Stride-on scooter has not previously been investigated, and we aim to establish this. Ten healthy volunteers (5 males:5 females) aged 20-40 years mobilised independently, then with each mobility device for 3min at 1km/h on a treadmill, with rest periods, whilst undergoing Cardio-Pulmonary Exercise Testing (CPET). Oxygen consumption (VO2), carbon dioxide excretion (VCO2), minute ventilation (MV), respiratory rate (RR) and pulse (HR) were measured at baseline, and after 3min of walking, without and with all 3 devices. Wilcoxon signed rank test was carried out to calculate significance with non-parametric values with Bonferroni correction. Three-point crutch mobilisation demonstrated significant increases in VO2 (0.7L), VCO2 (0.7L), MV (16.7L/min), pulse (24.8bpm) and RR (11.4breaths/min) compared to walking (p<0.05). Mobilisation with a frame produced significant (p<0.05) increases compared to walking; VO2 (0.7L), VCO2 (0.7L), MV (18.3L/min), pulse (35.9bpm), and RR (11.7breaths/min). Tests using the Stride-on demonstrated no significant increase compared to walking with regards to VO2 (0.1L; p=0.959), VCO2 (0.2L; p=0.332), pulse (10.1bpm; p=0.575), and RR (4.7breaths/min; p=0.633). The MV was significantly higher compared to walking (4.3L/min; p<0.05). Energy required for unit distance ambulation with a Stride-on device is similar to walking, and significantly lower than with a walking frame in single legged stance and three-point crutch mobilisation. This justifies its use as part of routine practice aiding early mobilisation of patients requiring restricted weight bearing or single legged weight bearing, especially in those with reduced cardio-pulmonary reserve as it is less

  10. Wearing the F-Scan mobile in-shoe pressure measurement system alters gait characteristics during running.

    PubMed

    Kong, Pui W; De Heer, Hendrik

    2009-01-01

    This study investigated the influence of wearing an F-Scan mobile in-shoe pressure measurement system on running characteristics. Six subjects ran on a treadmill at three speeds (3.5 ms(-1), 4.5 ms(-1) and 5.4 ms(-1)) with and without wearing the F-Scan system while kinematic data were collected at 240 Hz using a motion capture system. Six gait cycles were selected for analysis, with touchdown and toe-off visually identified based on foot markers displacement. Spatio-temporal gait parameters including stride frequency, stride length, stride length relative to height, and stance time were determined. A 2x3 ANOVA with repeated measures (alpha=0.05) was performed to identify differences in each gait parameter between running with and without the F-Scan system at different speeds. Wearing the F-Scan system did not affect the stance time but lead to an increase in stride frequency (P<0.05) and a decrease in stride length (P<0.05) and relative stride length (P<0.05). As speed increased, stance time decreased while stride frequency, stride length and relative stride length increased (all P<0.001). These results imply that wearing the F-Scan system alters gait characteristics and therefore data obtained may not represent those in a real life setting, at least in the case of running. One should take into account the potential risk of the movement of interest being altered when interpreting data obtained while subjects were wearing the F-Scan system. Future instrumentation should minimize the potential influence a measurement device may have on natural movement.

  11. Toward goal-oriented robotic gait training: The effect of gait speed and stride length on lower extremity joint torques.

    PubMed

    McGrath, Robert L; Pires-Fernandes, Margaret; Knarr, Brian; Higginson, Jill S; Sergi, Fabrizio

    2017-07-01

    Robot-assisted gait training is becoming increasingly common to support recovery of walking function after neurological injury. How to formulate controllers capable of promoting desired features in gait, i.e. goals, is complicated by the limited understanding of the human response to robotic input. A possible method to formulate controllers for goal-oriented gait training is based on the analysis of the joint torques applied by healthy subjects to modulate such goals. The objective of this work is to understand how sagittal plane joint torque is affected by two important gait parameters: gait speed (GS) and stride length (SL). We here present the results obtained from healthy subjects walking on a treadmill at different speeds, and asked to modulate stride length via visual feedback. Via principal component analysis, we extracted the global effects of the two factors on the peak-to-peak amplitude of joint torques. Next, we used a torque pulse approximation analysis to determine optimal timing and amplitude of torque pulses that approximate the SL-specific difference in joint torque profiles measured at different values of GS. Our results show a strong effect of GS on the torque profiles in all joints considered. In contrast, SL mostly affects the torque produced at the knee joint at early and late stance, with smaller effects on the hip and ankle joints. Our analysis generated a set of torque assistance profiles that will be experimentally tested using gait training robots.

  12. Tiger beetles pursue prey using a proportional control law with a delay of one half-stride

    PubMed Central

    Haselsteiner, Andreas F.; Gilbert, Cole; Wang, Z. Jane

    2014-01-01

    Tiger beetles are fast diurnal predators capable of chasing prey under closed-loop visual guidance. We investigated this control system using statistical analyses of high-speed digital recordings of beetles chasing a moving prey dummy in a laboratory arena. Correlation analyses reveal that the beetle uses a proportional control law in which the angular position of the prey relative to the beetle's body axis drives the beetle's angular velocity with a delay of about 28 ms. The proportionality coefficient or system gain, 12 s−1, is just below critical damping. Pursuit simulations using the derived control law predict angular orientation during pursuits with a residual error of about 7°. This is of the same order of magnitude as the oscillation imposed by the beetle's alternating tripod gait, which was not factored into the control law. The system delay of 28 ms equals a half-stride period, i.e. the time between the touch down of alternating tripods. Based on these results, we propose a physical interpretation of the observed control law: to turn towards its prey, the beetle on average exerts a sideways force proportional to the angular position of the prey measured a half-stride earlier. PMID:24718454

  13. A semiparametric negative binomial generalized linear model for modeling over-dispersed count data with a heavy tail: Characteristics and applications to crash data.

    PubMed

    Shirazi, Mohammadali; Lord, Dominique; Dhavala, Soma Sekhar; Geedipally, Srinivas Reddy

    2016-06-01

    Crash data can often be characterized by over-dispersion, heavy (long) tail and many observations with the value zero. Over the last few years, a small number of researchers have started developing and applying novel and innovative multi-parameter models to analyze such data. These multi-parameter models have been proposed for overcoming the limitations of the traditional negative binomial (NB) model, which cannot handle this kind of data efficiently. The research documented in this paper continues the work related to multi-parameter models. The objective of this paper is to document the development and application of a flexible NB generalized linear model with randomly distributed mixed effects characterized by the Dirichlet process (NB-DP) to model crash data. The objective of the study was accomplished using two datasets. The new model was compared to the NB and the recently introduced model based on the mixture of the NB and Lindley (NB-L) distributions. Overall, the research study shows that the NB-DP model offers a better performance than the NB model once data are over-dispersed and have a heavy tail. The NB-DP performed better than the NB-L when the dataset has a heavy tail, but a smaller percentage of zeros. However, both models performed similarly when the dataset contained a large amount of zeros. In addition to a greater flexibility, the NB-DP provides a clustering by-product that allows the safety analyst to better understand the characteristics of the data, such as the identification of outliers and sources of dispersion.

  14. The Effect of Modification Methods on the Performance Characteristics of Composites Based on a Linear Low-Density Polyethylene and Natural Hemp Fibers

    NASA Astrophysics Data System (ADS)

    Kajaks, J.; Zelca, Z.; Kukle, S.

    2015-11-01

    Influence of the content of hemp fibers (harvested in 2012) and their modification methods (treatment with boiling water, sodium hydroxide, and acetic anhydride) and addition of an interfacial modifier, maleated polyethylene (MAPE), on the performance characteristics (tensile strength, modulus, elongation at break, microhardness, and water resistance) of composites based on a linear low-density polyethylene (LLDPE) was investigated. The results obtained are compared with data found earlier for the same type of hemp fibers, but harvested in 2011. It is shown that optimum content of untreated hemp fibers in the LLDPE matrix is 30 wt.% and optimum length of the fibers is less than 1 mm. An increase in the content of hemp fibers (to 30 wt.%) raised the tensile strength and modulus of the composites, but reduced their elasticity and deformation ability. Simultaneously, the microhardness of the composite materials grew. Pretreating the fibers with sodium hydroxide improved the mechanical properties of the composites only slightly, but treating with acetic anhydride allowed us to elevate the content of the fibers up to 40 and 50 wt.%. The best results were achieved by addition of 50 wt.% MAPE, when the tensile modulus increased by about 47% and the tensile strength by 27% as compared with those of composites with fibers pretreated by other methods. To estimate the processing possibilities of the composites, the melt flow index (MFI) was determined. It is established that the pretreatment of the fibers significantly affects the numerical values of MFI. For example, upon treatment with acetic anhydride, a sufficiently high fluidity of the composites was retained even at a 50 wt.% content of fibers. The lowest fluidity was observed for composites with alkali-pretreated hemp fibers. The surface microhardness decreased upon their chemical pretreatment. The highest microhardness showed composites with 30 wt.% untreated fibers. The chemical pretreatment considerably raised the

  15. Non-linear Electrical Characteristics of ZnO Modified by Trioxides Sb2O3, Bi2O3, Fe2O3, Al2O3 and La2O3

    NASA Astrophysics Data System (ADS)

    Mekap, Anita; Das, Piyush R.; Choudhary, R. N. P.

    2016-08-01

    The non-linear behavior of polycrystalline-ZnO-based voltage-dependent resistors is considered in the present study. A high-temperature solid-state reaction route was used to synthesize polycrystalline samples of ZnO modified by small amounts of the trioxides Sb2O3, Bi2O3, Fe2O3, etc. in various proportions. X-ray diffraction and scanning electron microscopy techniques were used to study the structural and microstructural characteristics of modified ZnO. Detailed studies of non-linear phenomena of the I-V characteristics, dielectric permittivity ( ɛ r), impedance ( Z), etc. of the samples have provided many interesting results. All the samples exhibited dielectric anomaly. Non-linear variation in polarization with electric field for all the samples was observed. Moreover, significant non-linearity in the I-V characteristics was observed in the breakdown region of all the samples at room temperature. The non-linear coefficient ( α) in different cases, i.e. for I- V, ɛ r- f, ɛ r- T, and ɛ r- Z, was calculated and found to be appreciable. The frequency dependence of ac conductivity suggests that the material obeys Jonscher's universal power law.

  16. Linear Accelerators

    NASA Astrophysics Data System (ADS)

    Sidorin, Anatoly

    2010-01-01

    In linear accelerators the particles are accelerated by either electrostatic fields or oscillating Radio Frequency (RF) fields. Accordingly the linear accelerators are divided in three large groups: electrostatic, induction and RF accelerators. Overview of the different types of accelerators is given. Stability of longitudinal and transverse motion in the RF linear accelerators is briefly discussed. The methods of beam focusing in linacs are described.

  17. Linear Accelerators

    SciTech Connect

    Sidorin, Anatoly

    2010-01-05

    In linear accelerators the particles are accelerated by either electrostatic fields or oscillating Radio Frequency (RF) fields. Accordingly the linear accelerators are divided in three large groups: electrostatic, induction and RF accelerators. Overview of the different types of accelerators is given. Stability of longitudinal and transverse motion in the RF linear accelerators is briefly discussed. The methods of beam focusing in linacs are described.

  18. Reliability of the long-range power-law correlations obtained from the bilateral stride intervals in asymptomatic volunteers whilst treadmill walking.

    PubMed

    Pierrynowski, Michael Raymond; Gross, Anita; Miles, Melissa; Galea, Victoria; McLaughlin, Laurie; McPhee, Colleen

    2005-08-01

    Stride intervals measured during steady-state walking are irregular. These stride interval fluctuations are not random but exhibit long-range power-law correlation (alpha) such that a given stride interval is 'influenced' by earlier variations in the stride intervals. To estimate alpha, one requires a minute long sequence of right or left side stride interval data. However, to obtain a reliable alpha point estimate, the minimal stride sequence length is unknown. Additionally, it is unknown if the right and left side alpha are equivalent. In this study, the within-day and the right and left side reliabilities of alpha point estimates were examined in 23 volunteers performing three 8-min treadmill walks. In addition, eight volunteers were retested on three additional days to estimate between-day reliability. The standard error of measurement (S.E.M.) and the within- and between-day intraclass correlation (ICC) values, and their 95% confidence intervals, each calculated using the combined right and left leg 8-min alpha estimates were acceptable [0.047 (0.044-0.051); 0.914 (0.882-0.932) and 0.769 (0.689-0.815), respectively]. The left alpha (0.688 +/- 0.93) was greater than the right alpha (0.664 +/- 0.094), albeit this finding was underpowered (0.55). The alpha point estimates obtained from the full 8-min walks provided minimal S.E.M. and maximal within- and between-day ICCs. However, the minimal S.E.M. was statistically indistinguishable from the 6- and 7-min walk durations and all of the within-day and between-day ICCs were similar except for the 3- and 8-min between-day ICCs. This study suggests that data from four 3 min, three 6 min or two 8 min walk duration trials provide reliable alpha point estimates from a short series of short treadmill walks.

  19. A transdisciplinary approach to the selection of moderators of an exercise promotion intervention: baseline data and rationale for Colorado STRIDE.

    PubMed

    Magnan, Renee E; Nilsson, Renea; Marcus, Bess H; Ciccolo, Joseph T; Bryan, Angela D

    2013-02-01

    A transdisciplinary approach incorporating biological, psychological, behavioral, and genetic factors was taken to better identify proposed moderators of the effectiveness of an intervention to increase physical activity. This paper illustrates how theory-based individual difference variables can be integrated into a complex randomized controlled trial. The transdisciplinary framework guiding the selection of moderators, the COSTRIDE intervention study and sample, and the relationships among baseline variables are provided. Participants were non-active individuals randomly assigned to either the STRIDE exercise or health-and-wellness contact control condition. Structural equation modeling was utilized to demonstrate that relationships among baseline variables confirm hypothesized relationships in the transdisciplinary framework. Preliminary data from COSTRIDE suggest that interventions among sedentary individuals may be more effective if a broader range of factors influencing physical activity are considered.

  20. A transdisciplinary approach to the selection of moderators of an exercise promotion intervention: Baseline data and rationale for Colorado STRIDE

    PubMed Central

    Magnan, Renee E.; Nilsson, Renea; Marcus, Bess H.; Ciccolo, Joseph T.; Bryan, Angela D.

    2015-01-01

    Background A transdisciplinary approach incorporating biological, psychological, behavioral, and genetic factors was taken to better identify proposed moderators of the effectiveness of an intervention to increase physical activity. This paper illustrates how theory-based individual difference variables can be integrated into a complex randomized controlled trial. The transdisciplinary framework guiding the selection of moderators, the COSTRIDE intervention study and sample, and the relationships among baseline variables are provided. Methods Participants were non-active individuals randomly assigned to either the STRIDE exercise or health-and-wellness contact control condition. Results Structural equation modeling was utilized to demonstrate that relationships among baseline variables confirm hypothesized relationships in the transdisciplinary framework. Conclusions Preliminary data from COSTRIDE suggest that interventions among sedentary individuals may be more effective if a broader range of factors influencing physical activity are considered. Trial Registration clinicaltrials.gov NCT01091857 PMID:22083142

  1. Non-linear dynamics of human locomotion: effects of rhythmic auditory cueing on local dynamic stability

    PubMed Central

    Terrier, Philippe; Dériaz, Olivier

    2013-01-01

    It has been observed that times series of gait parameters [stride length (SL), stride time (ST), and stride speed (SS)], exhibit long-term persistence and fractal-like properties. Synchronizing steps with rhythmic auditory stimuli modifies the persistent fluctuation pattern to anti-persistence. Another non-linear method estimates the degree of resilience of gait control to small perturbations, i.e., the local dynamic stability (LDS). The method makes use of the maximal Lyapunov exponent, which estimates how fast a non-linear system embedded in a reconstructed state space (attractor) diverges after an infinitesimal perturbation. We propose to use an instrumented treadmill to simultaneously measure basic gait parameters (time series of SL, ST, and SS from which the statistical persistence among consecutive strides can be assessed), and the trajectory of the center of pressure (from which the LDS can be estimated). In 20 healthy participants, the response to rhythmic auditory cueing (RAC) of LDS and of statistical persistence [assessed with detrended fluctuation analysis (DFA)] was compared. By analyzing the divergence curves, we observed that long-term LDS (computed as the reverse of the average logarithmic rate of divergence between the 4th and the 10th strides downstream from nearest neighbors in the reconstructed attractor) was strongly enhanced (relative change +73%). That is likely the indication of a more dampened dynamics. The change in short-term LDS (divergence over one step) was smaller (+3%). DFA results (scaling exponents) confirmed an anti-persistent pattern in ST, SL, and SS. Long-term LDS (but not short-term LDS) and scaling exponents exhibited a significant correlation between them (r = 0.7). Both phenomena probably result from the more conscious/voluntary gait control that is required by RAC. We suggest that LDS and statistical persistence should be used to evaluate the efficiency of cueing therapy in patients with neurological gait disorders. PMID

  2. Walking training with cueing of cadence improves walking speed and stride length after stroke more than walking training alone: a systematic review.

    PubMed

    Nascimento, Lucas R; de Oliveira, Camila Quel; Ada, Louise; Michaelsen, Stella M; Teixeira-Salmela, Luci F

    2015-01-01

    After stroke, is walking training with cueing of cadence superior to walking training alone in improving walking speed, stride length, cadence and symmetry? Systematic review with meta-analysis of randomised or controlled trials. Adults who have had a stroke. Walking training with cueing of cadence. Four walking outcomes were of interest: walking speed, stride length, cadence and symmetry. This review included seven trials involving 211 participants. Because one trial caused substantial statistical heterogeneity, meta-analyses were conducted with and without this trial. Walking training with cueing of cadence improved walking speed by 0.23 m/s (95% CI 0.18 to 0.27, I(2)=0%), stride length by 0.21 m (95% CI 0.14 to 0.28, I(2)=18%), cadence by 19 steps/minute (95% CI 14 to 23, I(2)=40%), and symmetry by 15% (95% CI 3 to 26, random effects) more than walking training alone. This review provides evidence that walking training with cueing of cadence improves walking speed and stride length more than walking training alone. It may also produce benefits in terms of cadence and symmetry of walking. The evidence appears strong enough to recommend the addition of 30 minutes of cueing of cadence to walking training, four times a week for 4 weeks, in order to improve walking in moderately disabled individuals with stroke. PROSPERO (CRD42013005873). Copyright © 2014 Australian Physiotherapy Association. Published by Elsevier B.V. All rights reserved.

  3. Combined effect of CYP2B6 and NAT2 genotype on plasma efavirenz exposure during rifampin-based antituberculosis therapy in the STRIDE study.

    PubMed

    Luetkemeyer, Anne F; Rosenkranz, Susan L; Lu, Darlene; Grinsztejn, Beatriz; Sanchez, Jorge; Ssemmanda, Michael; Sanne, Ian; McIlleron, Helen; Havlir, Diane V; Haas, David W

    2015-06-15

    In STRIDE, slow metabolizer CYP2B6 and NAT2 genotypes were each associated with increased plasma efavirenz concentrations during antituberculosis therapy. Concentrations were greater on therapy than off therapy in 58% with CYP2B6 and 93% with NAT2 slow metabolizer genotypes. Individuals with slow metabolizer genotypes in both genes had markedly elevated concentrations.

  4. LINEAR ACCELERATOR

    DOEpatents

    Christofilos, N.C.; Polk, I.J.

    1959-02-17

    Improvements in linear particle accelerators are described. A drift tube system for a linear ion accelerator reduces gap capacity between adjacent drift tube ends. This is accomplished by reducing the ratio of the diameter of the drift tube to the diameter of the resonant cavity. Concentration of magnetic field intensity at the longitudinal midpoint of the external sunface of each drift tube is reduced by increasing the external drift tube diameter at the longitudinal center region.

  5. Longitudinal aerodynamic characteristics of a wing-winglet model designed at M = 0.8, C sub L = 0.4 using linear aerodynamic theory

    NASA Technical Reports Server (NTRS)

    Kuhlman, J. M.

    1983-01-01

    Wind tunnel test results have been presented herein for a subsonic transport type wing fitted with winglets. Wind planform was chosen to be representative of wings used on current jet transport aircraft, while wing and winglet camber surfaces were designed using two different linear aerodynamic design methods. The purpose of the wind tunnel investigation was to determine the effectiveness of these linear aerodynamic design computer codes in designing a non-planar transport configuration which would cruise efficiently. The design lift coefficient was chosen to be 0.4, at a design Mach number of 0.8. Force and limited pressure data were obtained for the basic wing, and for the wing fitted with the two different winglet designs, at Mach numbers of 0.60, 0.70, 0.75 and 0.80 over an angle of attack range of -2 to +6 degrees, at zero sideslip. The data have been presented without analysis to expedite publication.

  6. Steps toward improving diet and exercise for cancer survivors (STRIDE): a quasi-randomised controlled trial protocol.

    PubMed

    Frensham, Lauren J; Zarnowiecki, Dorota M; Parfitt, Gaynor; Stanley, Rebecca M; Dollman, James

    2014-06-13

    Cancer survivorship rates have increased in developed countries largely due to population ageing and improvements in cancer care. Survivorship is a neglected phase of cancer treatment and is often associated with adverse physical and psychological effects. There is a need for broadly accessible, non-pharmacological measures that may prolong disease-free survival, reduce or alleviate co-morbidities and enhance quality of life. The aim of the Steps TowaRd Improving Diet and Exercise (STRIDE) study is to evaluate the effectiveness of an online-delivered physical activity intervention for increasing walking in cancer survivors living in metropolitan and rural areas of South Australia. This is a quasi-randomised controlled trial. The intervention period is 12-weeks with 3-month follow-up. The trial will be conducted at a university setting and community health services in South Australia. Participants will be insufficiently active and aged 18 years or older. Participants will be randomly assigned to either the intervention or control group. All participants will receive a pedometer but only the intervention group will have access to the STRIDE website where they will report steps, affect and ratings of perceived exertion (RPE) during exercise daily. Researchers will use these variables to individualise weekly step goals to increase walking.The primary outcome measure is steps per day. The secondary outcomes are a) health measures (anthropometric and physiological), b) dietary habits (consumption of core foods and non-core foods) and c) quality of life (QOL) including physical, psychological and social wellbeing. Measures will be collected at baseline, post-intervention and 3-month follow-up. This protocol describes the implementation of a trial using an online resource to assist cancer survivors to become more physically active. It is an innovative tool that uses ratings of perceived exertion and daily affect to create individualised step goals for cancer survivors. The

  7. Kinematic characteristics of Andalusian, Arabian and Anglo-Arabian horses: a comparative study.

    PubMed

    Cano, M R; Vivo, J; Miró, F; Morales, J L; Galisteo, A M

    2001-10-01

    The aim of this study was to compare the kinematic trot characteristics of three different breeds of horse: Andalusian (AN, n = 15), Arabian (AR, n = 7) and Anglo-Arabian (AA, n = 5) using standard computer-assisted videography (25 Hz). Linear, temporal and angular parameters in fore- and hind limbs were analysed in six randomly selected strides per horse. Normalised angle-time diagrams along the complete stride were obtained for all joints angles in each breed and specific kinematic characteristics were detected graphically. AA horses displayed longer swing durations in both limbs ans a shorter angular range of motion (ARM) in scapula and pelvis inclination and in shoulder, hip and forelimb retraction-protraction angles. At lift off, stifle and tarsal joint angles were more flexed. In general, only small differences were observed in AR horse kinematics when compared with the other 2 breeds. AN horses presented negative overtracking length, which was positive in AR and AA. In AN horses the elbow and carpal joints were more flexed at the moment of maximal elevation, elbow and fore-fetlock joints also exhibited a larger ARM due to a smaller angle at maximal flexion. In the hind limbs, tarsal, hind fetlock and retraction-protraction angles presented a larger ARM in AN horses due to greater maximal flexion in the tarsal and hind fetlock joints. Fore- and hind fetlocks were also more flexed in horses from this breed. In conclusion, differences between kinematic variables at the trot were observed in the three breeds studied here, mainly in forelimb joints. The most outstanding feature was the greater forelimb flexion recorded in AN horses than in the other breeds which is consistent with the elevated movements in this breed. In AA horses, the ARM of proximal joints involved in retraction protraction in both fore- and hind limbs was smaller. All the differences observed highlighted the idiosyncratic nature of the trot in each breed; this may influence the functional

  8. Determining the Primary Endpoint for a Stimulant Abuse Trial: Lessons Learned from STRIDE (CTN 0037)

    PubMed Central

    Trivedi, Madhukar H.; Greer, Tracy L.; Potter, Jennifer Sharpe; Grannemann, Bruce D.; Nunes, Edward V.; Rethorst, Chad; Warden, Diane; Ring, Kolette M.; Somoza, Eugene

    2012-01-01

    Background No consensus is available for identifying the best primary outcome for substance abuse trials. While abstinence is the most desirable outcome for substance use interventions, a wide variety of other endpoints have been used to evaluate efficacy trials. Objectives This report provides a framework for determining an optimal primary endpoint and the relevant measurement approach for substance use disorder treatment trials. The framework was developed based on a trial for stimulant abuse using exercise as an augmentation treatment, delivered within the NIDA Clinical Trials Network. The use of a common primary endpoint across trials will facilitate comparisons of treatment efficacy. Methods Primary endpoint options in existing substance abuse studies were evaluated. This evaluation included surveys of the literature for endpoints and measurement approaches, followed by assessment of endpoint choices against study design issues, population characteristics, tests of sensitivity and tests of clinical meaningfulness. Conclusion We concluded that the best current choice for a primary endpoint is percent days abstinent, as measured by the Time Line Follow Back (TLFB) interview conducted three times a week with recall aided by a take-home Substance Use Diary. To further improve the accuracy of the self-reported drug use, an algorithm will be applied to reconcile the results from the TLFB with the results of qualitative urine drug screens. Scientific Significance There is a need for a standardized endpoint in this field to allow for comparison across treatment studies, and we suggest that the recommended endpoint be considered for use in this field. PMID:21854276

  9. The human vestibulo-ocular reflex during linear locomotion

    NASA Technical Reports Server (NTRS)

    Moore, S. T.; Hirasaki, E.; Raphan, T.; Cohen, B.

    2001-01-01

    During locomotion, there is a translation and compensatory rotation of the head in both the vertical and horizontal planes. During moderate to fast walking (100 m/min), vertical head translation occurs at the frequency of stepping (2 Hz) and generates peak linear acceleration of 0.37 g. Lateral head translation occurs at the stride frequency (1 Hz) and generates peak linear acceleration of 0.1 g. Peak head pitch and yaw angular velocities are approximately 17 degrees/s. The frequency and magnitude of these head movements are within the operational range of both the linear and angular vestibulo-ocular reflex (IVOR and aVOR). Vertical eye movements undergo a phase reversal from near to far targets. When viewing a far (>1 m) target, vertical eye velocity is typical of an aVOR response; that is, it is compensatory for head pitch. At close viewing distances (<1 m), vertical eye velocity is in phase with head pitch and is compensatory for vertical head translation, suggesting that the IVOR predominantly generates the eye movement response. Horizontal head movements during locomotion occur at the stride frequency of 1 Hz, where the IVOR gain is low. Horizontal eye movements are compensatory for head yaw at all viewing distances and are likely generated by the aVOR.

  10. The human vestibulo-ocular reflex during linear locomotion

    NASA Technical Reports Server (NTRS)

    Moore, S. T.; Hirasaki, E.; Raphan, T.; Cohen, B.

    2001-01-01

    During locomotion, there is a translation and compensatory rotation of the head in both the vertical and horizontal planes. During moderate to fast walking (100 m/min), vertical head translation occurs at the frequency of stepping (2 Hz) and generates peak linear acceleration of 0.37 g. Lateral head translation occurs at the stride frequency (1 Hz) and generates peak linear acceleration of 0.1 g. Peak head pitch and yaw angular velocities are approximately 17 degrees/s. The frequency and magnitude of these head movements are within the operational range of both the linear and angular vestibulo-ocular reflex (IVOR and aVOR). Vertical eye movements undergo a phase reversal from near to far targets. When viewing a far (>1 m) target, vertical eye velocity is typical of an aVOR response; that is, it is compensatory for head pitch. At close viewing distances (<1 m), vertical eye velocity is in phase with head pitch and is compensatory for vertical head translation, suggesting that the IVOR predominantly generates the eye movement response. Horizontal head movements during locomotion occur at the stride frequency of 1 Hz, where the IVOR gain is low. Horizontal eye movements are compensatory for head yaw at all viewing distances and are likely generated by the aVOR.

  11. Effect of 3 Weeks Use of Compression Garments on Stride and Impact Shock during a Fatiguing Run.

    PubMed

    Lucas-Cuevas, A G; Priego-Quesada, J I; Aparicio, I; Giménez, J V; Llana-Belloch, S; Pérez-Soriano, P

    2015-10-01

    Excessive and prolonged exposure to impact acceleration during running is associated with increased injury rate. Acute use of compressive garments has been speculated to improve attenuation. However, it is unknown how longer interventions of compressive garments influence attenuation in running. 40 runners trained with compressive and placebo stockings for 3 weeks. Perception of comfort, stride parameters (rate, length) and impact acceleration (head and tibial peak acceleration, magnitude, acceleration rate and attenuation) were measured every 5 min during a fatigue run (30 min at 80% of the individual's maximal aerobic speed). Compressive stockings reduced tibial peak acceleration and magnitude compared to placebo stockings at every minute (p<0.05) except for the initial measurement (p>0.05). Moreover, compressive stockings led to a lower rate of increase in tibial peak acceleration (14%, p<0.005) and magnitude (16%, p<0.001) as a result of the development of fatigue compared to placebo stockings (24% and 26% increase, p=0.014 and p=0.003, respectively). Similar perception of comfort was reported for both garments. Training with compressive stockings for 3 weeks reduced impact acceleration and the rate of increase in acceleration compared to placebo stockings. These findings suggest that compressive stockings may play a protective role by reducing impact accelerations during running. © Georg Thieme Verlag KG Stuttgart · New York.

  12. Sustaining the stride of health agenda beyond 2015 in post mdgs scenario: a projected roadmap for the developing countries.

    PubMed

    Shaikh, Babar Tasneem

    2014-01-01

    As the world is reaching toward 2015, the echoes of MDGs are becoming louder. Results with regard to achievements of the targets set globally, show mixed results. Very understandably, the developing countries will miss most of the targets by far, and the attributed reasons are obvious. Dearth of resources-financial and human, evidence for decision making, infrastructure, meaningful collaboration with developed countries, and overall governance of the health sector are some of the pitfalls on 2000-2015 screen. Nonetheless, international commitments are sending positive vibes and message that glass is half full. Countries must keep the pace and sustain the stride of MDGs agenda, with an appraised roadmap, of course. Poverty, natural and man-made disasters, and slow socio-economic development, and some incongruous technologies are the challenges en route. A holistic approach is the need of the time, and therefore this paper presents a strategic framework drawn from the WHO's proposed health systems building blocks, which might, help the developing countries and fragile health systems to turn around the state of affairs.

  13. Generalized two-dimensional (2D) linear system analysis metrics (GMTF, GDQE) for digital radiography systems including the effect of focal spot, magnification, scatter, and detector characteristics

    PubMed Central

    Kuhls-Gilcrist, Andrew T.; Gupta, Sandesh K.; Bednarek, Daniel R.; Rudin, Stephen

    2010-01-01

    The MTF, NNPS, and DQE are standard linear system metrics used to characterize intrinsic detector performance. To evaluate total system performance for actual clinical conditions, generalized linear system metrics (GMTF, GNNPS and GDQE) that include the effect of the focal spot distribution, scattered radiation, and geometric unsharpness are more meaningful and appropriate. In this study, a two-dimensional (2D) generalized linear system analysis was carried out for a standard flat panel detector (FPD) (194-micron pixel pitch and 600-micron thick CsI) and a newly-developed, high-resolution, micro-angiographic fluoroscope (MAF) (35-micron pixel pitch and 300-micron thick CsI). Realistic clinical parameters and x-ray spectra were used. The 2D detector MTFs were calculated using the new Noise Response method and slanted edge method and 2D focal spot distribution measurements were done using a pin-hole assembly. The scatter fraction, generated for a uniform head equivalent phantom, was measured and the scatter MTF was simulated with a theoretical model. Different magnifications and scatter fractions were used to estimate the 2D GMTF, GNNPS and GDQE for both detectors. Results show spatial non-isotropy for the 2D generalized metrics which provide a quantitative description of the performance of the complete imaging system for both detectors. This generalized analysis demonstrated that the MAF and FPD have similar capabilities at lower spatial frequencies, but that the MAF has superior performance over the FPD at higher frequencies even when considering focal spot blurring and scatter. This 2D generalized performance analysis is a valuable tool to evaluate total system capabilities and to enable optimized design for specific imaging tasks. PMID:21243038

  14. Characteristics of recursive backstepping algorithm and active damping of oscillations in feedback linearization for electromechanical system with extended stability analysis and perturbation rejection.

    PubMed

    Anand, V; Narendran, R

    2016-09-01

    In this paper, a technique for estimation of state variables and control of a class of electromechanical system is proposed. Initially, an attempt is made on rudimentary pole placement technique for the control of rotor position and angular velocity profiles of Permanent Magnet Stepper Motor. Later, an alternative approach is analyzed using feedback linearization method to reduce the error in tracking performances. A damping control scheme was additionally incorporated into the feedback linearization system in order to nullify the persistent oscillations present in the system. Furthermore, a robust backstepping controller with high efficacy is put forth to enhance the overall performance and to carry out disturbance rejection. The predominant advantage of this control technique is that it does not require the DQ Transformation of the motor dynamics. A Lyapunov candidate was employed to ensure global asymptotical stability criterion. Also, a nonlinear observer is presented to estimate the unknown states namely load torque and rotor angular velocity, even under load uncertainty conditions. Finally, the performances of all the aforementioned control schemes and estimation techniques are compared and analyzed extensively through simulation.

  15. Gait dynamics in Parkinson’s disease: Common and distinct behavior among stride length, gait variability, and fractal-like scaling

    PubMed Central

    Hausdorff, Jeffrey M.

    2009-01-01

    Parkinson’s disease (PD) is a common, debilitating neurodegenerative disease. Gait disturbances are a frequent cause of disability and impairment for patients with PD. This article provides a brief introduction to PD and describes the gait changes typically seen in patients with this disease. A major focus of this report is an update on the study of the fractal properties of gait in PD, the relationship between this feature of gait and stride length and gait variability, and the effects of different experimental conditions on these three gait properties. Implications of these findings are also briefly described. This update highlights the idea that while stride length, gait variability, and fractal scaling of gait are all impaired in PD, distinct mechanisms likely contribute to and are responsible for the regulation of these disparate gait properties. PMID:19566273

  16. Assessing Stride Variables and Vertical Stiffness with GPS-Embedded Accelerometers: Preliminary Insights for the Monitoring of Neuromuscular Fatigue on the Field.

    PubMed

    Buchheit, Martin; Gray, Andrew; Morin, Jean-Benoit

    2015-12-01

    The aim of the present study was to examine the ability of a GPS-imbedded accelerometer to assess stride variables and vertical stiffness (K), which are directly related to neuromuscular fatigue during field-based high-intensity runs. The ability to detect stride imbalances was also examined. A team sport player performed a series of 30-s runs on an instrumented treadmill (6 runs at 10, 17 and 24 km·h(-1)) with or without his right ankle taped (aimed at creating a stride imbalance), while wearing on his back a commercially-available GPS unit with an embedded 100-Hz tri-axial accelerometer. Contact (CT) and flying (FT) time, and K were computed from both treadmill and accelerometers (Athletic Data Innovations) data. The agreement between treadmill (criterion measure) and accelerometer-derived data was examined. We also compared the ability of the different systems to detect the stride imbalance. Biases were small (CT and K) and moderate (FT). The typical error of the estimate was trivial (CT), small (K) and moderate (FT), with nearly perfect (CT and K) and large (FT) correlations for treadmill vs. accelerometer. The tape induced very large increase in the right - left foot ∆ in CT, FT and K measured by the treadmill. The tape effect on CT and K ∆ measured with the accelerometers were also very large, but of lower magnitude than with the treadmill. The tape effect on accelerometer-derived ∆ FT was unclear. Present data highlight the potential of a GPS-embedded accelerometer to assess CT and K during ground running. Key pointsGPS-embedded tri-axial accelerometers may be used to assess contact time and vertical stiffness during ground running.These preliminary results open new perspective for the field monitoring of neuromuscular fatigue and performance in run-based sports.

  17. Assessing Stride Variables and Vertical Stiffness with GPS-Embedded Accelerometers: Preliminary Insights for the Monitoring of Neuromuscular Fatigue on the Field

    PubMed Central

    Buchheit, Martin; Gray, Andrew; Morin, Jean-Benoit

    2015-01-01

    The aim of the present study was to examine the ability of a GPS-imbedded accelerometer to assess stride variables and vertical stiffness (K), which are directly related to neuromuscular fatigue during field-based high-intensity runs. The ability to detect stride imbalances was also examined. A team sport player performed a series of 30-s runs on an instrumented treadmill (6 runs at 10, 17 and 24 km·h-1) with or without his right ankle taped (aimed at creating a stride imbalance), while wearing on his back a commercially-available GPS unit with an embedded 100-Hz tri-axial accelerometer. Contact (CT) and flying (FT) time, and K were computed from both treadmill and accelerometers (Athletic Data Innovations) data. The agreement between treadmill (criterion measure) and accelerometer-derived data was examined. We also compared the ability of the different systems to detect the stride imbalance. Biases were small (CT and K) and moderate (FT). The typical error of the estimate was trivial (CT), small (K) and moderate (FT), with nearly perfect (CT and K) and large (FT) correlations for treadmill vs. accelerometer. The tape induced very large increase in the right - left foot ∆ in CT, FT and K measured by the treadmill. The tape effect on CT and K ∆ measured with the accelerometers were also very large, but of lower magnitude than with the treadmill. The tape effect on accelerometer-derived ∆ FT was unclear. Present data highlight the potential of a GPS-embedded accelerometer to assess CT and K during ground running. Key points GPS-embedded tri-axial accelerometers may be used to assess contact time and vertical stiffness during ground running. These preliminary results open new perspective for the field monitoring of neuromuscular fatigue and performance in run-based sports PMID:26664264

  18. Automated stride assistance device improved the gait parameters and energy cost during walking of healthy middle-aged females but not those of young controls.

    PubMed

    Otsuki, Risa; Matsumoto, Hiromi; Ueki, Masaru; Uehara, Kazutake; Nozawa, Nobuko; Osaki, Mari; Hagino, Hiroshi

    2016-12-01

    [Purpose] The aim of this study was to clarify the effects of an automated stride assistance device on gait parameters and energy cost during walking performed by healthy middle-aged and young females. [Subjects and Methods] Ten middle-aged females and 10 young females were recruited as case and control participants, respectively. The participants walked for 3 minutes continuously under two different experimental conditions: with the device and without the device. Walking distance, mean walking speed, mean step length, cadence, walk ratio and the physiological cost index during the 3-minutes walk were measured. [Results] When walking with the stride assistance device, the step length and walk ratio of the middle-aged group were significantly higher than without it. Also, during walking without assistance from the device, the physiological cost index of the middle-aged group significantly increased; whereas during walking with assistance, there was no change. The intergroup comparison in the middle-aged group showed the physiological cost index was lower under the experimental condition with assistance provided, as opposed to the condition without the provision of assistance. [Conclusion] The results of this study show that the stride assistance device improved the gait parameters of the middle-aged group but not those of young controls.

  19. Most suitable mother wavelet for the analysis of fractal properties of stride interval time series via the average wavelet coefficient method.

    PubMed

    Zhang, Zhenwei; VanSwearingen, Jessie; Brach, Jennifer S; Perera, Subashan; Sejdić, Ervin

    2017-01-01

    Human gait is a complex interaction of many nonlinear systems and stride intervals exhibiting self-similarity over long time scales that can be modeled as a fractal process. The scaling exponent represents the fractal degree and can be interpreted as a "biomarker" of relative diseases. The previous study showed that the average wavelet method provides the most accurate results to estimate this scaling exponent when applied to stride interval time series. The purpose of this paper is to determine the most suitable mother wavelet for the average wavelet method. This paper presents a comparative numerical analysis of 16 mother wavelets using simulated and real fractal signals. Simulated fractal signals were generated under varying signal lengths and scaling exponents that indicate a range of physiologically conceivable fractal signals. The five candidates were chosen due to their good performance on the mean square error test for both short and long signals. Next, we comparatively analyzed these five mother wavelets for physiologically relevant stride time series lengths. Our analysis showed that the symlet 2 mother wavelet provides a low mean square error and low variance for long time intervals and relatively low errors for short signal lengths. It can be considered as the most suitable mother function without the burden of considering the signal length. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. Impact of leg length and body mass on the stride length and gait speed of infants with normal motor development: a longitudinal study.

    PubMed

    Rodriguez, Emmanuelle B; Chagas, Paula S C; Silva, Paula L P; Kirkwood, Renata N; Mancini, Marisa C

    2013-01-01

    Gait acquisition is supported by changes in the neuromusculoskeletal system of the child. Changes in the dimensions of the body structures resulting from the growth of the child partly explain gait improvement in the first year of life. To evaluate whether changes in body mass and leg length modulate the effect of independent gait practice (experience) on gait speed and stride length. Thirty-two infants with normal development were monitored monthly from the acquisition of independent gait until six months post-acquisition. Longitudinal evaluations included measurements of the body mass and leg length of each child. Temporospatial variables of gait (speed and stride length) were documented using the Qualisys Pro-reflex(r) system. The data were analyzed using multilevel regression models, with a significance level of α=0.05. An effect of the practice time on speed (p<0.0001) and stride length (p<0.0001) was observed. The change in leg length had a marginal effect on the rate of gait speed change: children whose leg growth was faster showed a higher rate of speed change (p=0.07). No other effects of anthropometric parameters were observed. The results suggest that the practice time promotes the improvement of the gait pattern of infants in the first year of life. However, the effects of the leg length and body weight of infants on the benefit of practice time remain undefined.

  1. Automated stride assistance device improved the gait parameters and energy cost during walking of healthy middle-aged females but not those of young controls

    PubMed Central

    Otsuki, Risa; Matsumoto, Hiromi; Ueki, Masaru; Uehara, Kazutake; Nozawa, Nobuko; Osaki, Mari; Hagino, Hiroshi

    2016-01-01

    [Purpose] The aim of this study was to clarify the effects of an automated stride assistance device on gait parameters and energy cost during walking performed by healthy middle-aged and young females. [Subjects and Methods] Ten middle-aged females and 10 young females were recruited as case and control participants, respectively. The participants walked for 3 minutes continuously under two different experimental conditions: with the device and without the device. Walking distance, mean walking speed, mean step length, cadence, walk ratio and the physiological cost index during the 3-minutes walk were measured. [Results] When walking with the stride assistance device, the step length and walk ratio of the middle-aged group were significantly higher than without it. Also, during walking without assistance from the device, the physiological cost index of the middle-aged group significantly increased; whereas during walking with assistance, there was no change. The intergroup comparison in the middle-aged group showed the physiological cost index was lower under the experimental condition with assistance provided, as opposed to the condition without the provision of assistance. [Conclusion] The results of this study show that the stride assistance device improved the gait parameters of the middle-aged group but not those of young controls. PMID:28174452

  2. Effect of Different Training Methods on Stride Parameters in Speed Maintenance Phase of 100m Sprint Runningmel.

    PubMed

    Cetin, Emel; Hindistan, Ibrahim Ethem; Ozkaya, Yasar Gul

    2017-04-27

    This study examined the effects of two different training methods relevant to sloping surface on stride parameters in speed maintenance phase of 100 m sprint running. Twenty recreationally active students were assigned into one of three groups: combined training (Com), horizontal training (H), and control (C) group. Com group performed uphill and downhill training on a sloping surface with an angle of 4°, while H group trained on a horizontal surface, 3 days a week for 8 weeks. Speed maintenance and deceleration phases were divided into distances with 10m intervals, and running time (t), running velocity (RV), step frequency (SF) and step length (SL) were measured at pre-, and post-exercise period. After 8-weeks of training program, t was shortened by 3.97% in Com group, and 2.37% in H group. RV also increased for totally 100m of running distance by 4,13% and 2,35% in Com, and H groups, respectively. At the speed maintenance phase, although t and maximal RV (RVmax) found to be statistically unaltered during overall phase, t was found to be decreased, and RVmax was preceded by 10m in distance in both training groups. SL was increased at 60-70m, and SF was decreased at 70-80m in H group. SL was increased with concomitant decrease in SF at 80-90m in Com group. Both training groups were maintained the RVmax with a great percentage at the speed maintenance phase. In conclusion, although both training methods resulted an increase in running time and RV, Com training method was more prominently effective method in improving RV, and this improvement was originated from the positive changes in SL during the speed maintaining phase.

  3. Continuous use of textured insole improve plantar sensation and stride length of people with Parkinson's disease: A pilot study.

    PubMed

    Lirani-Silva, Ellen; Vitório, Rodrigo; Barbieri, Fabio Augusto; Orcioli-Silva, Diego; Simieli, Lucas; Gobbi, Lilian Teresa Bucken

    2017-09-18

    Findings involving the acute benefits of textured insoles on gait in people with Parkinson's disease (PD) are still controversial. To our best acknowledge, the continuous use of textured insoles on gait in people with PD has not been investigated yet. The aim of this pilot study was to obtain preliminary data of the effects of textured insoles on gait and plantar sensation in people with PD after one-week intervention and one-week follow-up period. Nineteen patients with PD were distributed into two groups: experimental group and control group. Initially, the plantar sensation was assessed through Semmes-Weinstein Monofilaments. Then, participants performed 5 trials of walking (without insoles) at a self-selected speed. Gait data were collected using an optoelectronic system. Plantar sensation and gait assessments were repeated in three moments: before and after one-week wearing the group-specific insoles, and after one week wearing conventional insoles (follow-up). The textured insole had half-sphere elevations placed in the distal phalanx of the hallux, heads of metatarsophalangeal joints and heel. Results revealed that the use of textured insole for one week improved plantar sensation and stride length. However, only benefits on plantar sensation were maintained after the follow-up period. Our results suggest that the continuous use of textured insoles for one week benefits plantar sensation and gait in patients with PD. These results support the hypothesis that enhanced somatosensory feedback to the sensory system result in an improved motor output of gait. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. Striding through Time

    ERIC Educational Resources Information Center

    Clary, Renee; Wandersee, James

    2014-01-01

    The "Next Generation Science Standards" (NGSS) focus attention on integrating engineering and math in science instruction. The dinosaur trackway project described in this article shows that it is possible to assign engineering applications to students in disciplines other than physics and to integrate math and engineering applications in…

  5. Striding through Time

    ERIC Educational Resources Information Center

    Clary, Renee; Wandersee, James

    2014-01-01

    The "Next Generation Science Standards" (NGSS) focus attention on integrating engineering and math in science instruction. The dinosaur trackway project described in this article shows that it is possible to assign engineering applications to students in disciplines other than physics and to integrate math and engineering applications in…

  6. LINEAR ACCELERATOR

    DOEpatents

    Colgate, S.A.

    1958-05-27

    An improvement is presented in linear accelerators for charged particles with respect to the stable focusing of the particle beam. The improvement consists of providing a radial electric field transverse to the accelerating electric fields and angularly introducing the beam of particles in the field. The results of the foregoing is to achieve a beam which spirals about the axis of the acceleration path. The combination of the electric fields and angular motion of the particles cooperate to provide a stable and focused particle beam.

  7. Linear Clouds

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Context image for PIA03667 Linear Clouds

    These clouds are located near the edge of the south polar region. The cloud tops are the puffy white features in the bottom half of the image.

    Image information: VIS instrument. Latitude -80.1N, Longitude 52.1E. 17 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  8. Wideband Linear Phase Modulator

    NASA Technical Reports Server (NTRS)

    Mysoor, Narayan R.; Mueller, Robert O.

    1994-01-01

    Phase modulator for transmission in X band provides large phase deviation that remains nearly linear with voltage over relatively wide range. Operates with low loss over wide frequency band and with stable characteristics over wide temperature range. Phase modulator contains two varactor-diode phase shifters coupled via circulators. Separate drive circuit applies modulating voltages to varactor diodes. Modulation voltages vary in accordance with input to drive circuit.

  9. Characteristics of myeloid differentiation and maturation pathway derived from human hematopoietic stem cells exposed to different linear energy transfer radiation types.

    PubMed

    Monzen, Satoru; Yoshino, Hironori; Kasai-Eguchi, Kiyomi; Kashiwakura, Ikuo

    2013-01-01

    Exposure of hematopoietic stem/progenitor cells (HSPCs) to ionizing radiation causes a marked suppression of mature functional blood cell production in a linear energy transfer (LET)- and/or dose-dependent manner. However, little information about LET effects on the proliferation and differentiation of HSPCs has been reported. With the aim of characterizing the effects of different types of LET radiations on human myeloid hematopoiesis, in vitro hematopoiesis in Human CD34(+) cells exposed to carbon-ion beams or X-rays was compared. Highly purified CD34(+) cells exposed to each form of radiation were plated onto semi-solid culture for a myeloid progenitor assay. The surviving fractions of total myeloid progenitors, colony-forming cells (CFC), exposed to carbon-ion beams were significantly lower than of those exposed to X-rays, indicating that CFCs are more sensitive to carbon-ion beams (D(0) = 0.65) than to X-rays (D(0) = 1.07). Similar sensitivities were observed in granulocyte-macrophage and erythroid progenitors, respectively. However, the sensitivities of mixed-type progenitors to both radiation types were similar. In liquid culture for 14 days, no significant difference in total numbers of mononuclear cells was observed between non-irradiated control culture and cells exposed to 0.5 Gy X-rays, whereas 0.5 Gy carbon-ion beams suppressed cell proliferation to 4.9% of the control, a level similar to that for cells exposed to 1.5 Gy X-rays. Cell surface antigens associated with terminal maturation, such as CD13, CD14, and CD15, on harvest from the culture of X-ray-exposed cells were almost the same as those from the non-irradiated control culture. X-rays increased the CD235a(+) erythroid-related fraction, whereas carbon-ion beams increased the CD34(+)CD38(-) primitive cell fraction and the CD13(+)CD14(+/-)CD15(-) fraction. These results suggest that carbon-ion beams inflict severe damage on the clonal growth of myeloid HSPCs, although the intensity of cell surface

  10. Characteristics of Myeloid Differentiation and Maturation Pathway Derived from Human Hematopoietic Stem Cells Exposed to Different Linear Energy Transfer Radiation Types

    PubMed Central

    Monzen, Satoru; Yoshino, Hironori; Kasai-Eguchi, Kiyomi; Kashiwakura, Ikuo

    2013-01-01

    Exposure of hematopoietic stem/progenitor cells (HSPCs) to ionizing radiation causes a marked suppression of mature functional blood cell production in a linear energy transfer (LET)- and/or dose-dependent manner. However, little information about LET effects on the proliferation and differentiation of HSPCs has been reported. With the aim of characterizing the effects of different types of LET radiations on human myeloid hematopoiesis, in vitro hematopoiesis in Human CD34+ cells exposed to carbon-ion beams or X-rays was compared. Highly purified CD34+ cells exposed to each form of radiation were plated onto semi-solid culture for a myeloid progenitor assay. The surviving fractions of total myeloid progenitors, colony-forming cells (CFC), exposed to carbon-ion beams were significantly lower than of those exposed to X-rays, indicating that CFCs are more sensitive to carbon-ion beams (D0 = 0.65) than to X-rays (D0 = 1.07). Similar sensitivities were observed in granulocyte-macrophage and erythroid progenitors, respectively. However, the sensitivities of mixed-type progenitors to both radiation types were similar. In liquid culture for 14 days, no significant difference in total numbers of mononuclear cells was observed between non-irradiated control culture and cells exposed to 0.5 Gy X-rays, whereas 0.5 Gy carbon-ion beams suppressed cell proliferation to 4.9% of the control, a level similar to that for cells exposed to 1.5 Gy X-rays. Cell surface antigens associated with terminal maturation, such as CD13, CD14, and CD15, on harvest from the culture of X-ray-exposed cells were almost the same as those from the non-irradiated control culture. X-rays increased the CD235a+ erythroid-related fraction, whereas carbon-ion beams increased the CD34+CD38− primitive cell fraction and the CD13+CD14+/−CD15− fraction. These results suggest that carbon-ion beams inflict severe damage on the clonal growth of myeloid HSPCs, although the intensity of cell surface

  11. Linear and Nonlinear Optical Properties of Photoresponsive [60]Fullerene Hybrid Triads and Tetrads with Dual NIR Two-Photon Absorption Characteristics

    PubMed Central

    Jeon, Seaho; Haley, Joy; Flikkema, Jonathan; Nalla, Venkatram; Wang, Min; Sfeir, Matthew; Tan, Loon-Seng; Cooper, Thomas; Ji, Wei; Hamblin, Michael R.; Chiang, Long Y.

    2013-01-01

    Two C60-(antenna)x analogous compounds having branched hybrid triad C60(>DPAF-C18)(>CPAF-C2M) and tetrad C60(>DPAF-C18)(>CPAF-C2M)2 nanostructures were synthesized and characterized. The structural design was intended to facilitate the ultrafast fs intramolecular energy-transfer from photoexcited C60[>1(DPAF)*-C18](>CPAF-C2M)1or2 or C60(>DPAF-C18)[>1(CPAF)*-C2M]1or2 to the C60> cage moiety upon two-photon pumping at either 780 or 980 nm, respectively. The latter nanostructure showed approximately equal extinction coefficients of optical absorption over 400–550 nm that corresponds to near-IR two-photon based excitation wavelengths at 780–1100 nm for broadband nonlinear optical (NLO) applications. Aside from their enhanced two-photon absorption (2PA) activity at 780 nm, we also demonstrated ultrafast photo-responses at 980 nm showing 2PA cross-section (σ2) values of 995–1100 GM for the hybrid tetrad. These σ2 values were correlated to the observed good efficiency in reducing fs light-transmittance down to 35% at the light intensity of 110 GW/cm2. Accordingly, 2PA characteristics of these nanostructures at multiple NIR wavelengths provided support for their suitability in uses as broadband NLO nanomaterials at 600–1100 nm that includes the 2PA ability of two antenna, DPAF (700–850 nm) and CPAF (850–1100 nm), and the fullerene cage at shorter wavelengths (600–700 nm). PMID:24163713

  12. Linear Thyratron.

    DTIC Science & Technology

    1987-07-31

    2-2 Phase I LT Switching Characteristics for Cold Cathode. 2-8 6-1 Surface Flashover Strength (ky/cm). 6-11 6-2 Baffle Attenuation Coefficient and... surface flashover strength (pulsed) in air and vacuum for a variety of candidate insulator materials are listed in Table 6-1. 6.4 TIE CONTROL GRID SLOT...thyratron body-insulator-control grid triple point illustrated in Figure 2-5. The flashover propapagated to the top section of the anode. 2-1 OPTICAL PO/Z

  13. A study of the effect of in-line and perpendicular magnetic fields on beam characteristics of electron guns in medical linear accelerators

    SciTech Connect

    Constantin, Dragos E.; Fahrig, Rebecca; Keall, Paul J.

    2011-07-15

    Purpose: Using magnetic resonance imaging (MRI) for real-time guidance during radiotherapy is an active area of research and development. One aspect of the problem is the influence of the MRI scanner, modeled here as an external magnetic field, on the medical linear accelerator (linac) components. The present work characterizes the behavior of two medical linac electron guns with external magnetic fields for in-line and perpendicular orientations of the linac with respect to the MRI scanner. Methods: Two electron guns, Litton L-2087 and Varian VTC6364, are considered as representative models for this study. Emphasis was placed on the in-line design approach in which case the MRI scanner and the linac axes of symmetry coincide and assumes no magnetic shielding of the linac. For the in-line case, the magnetic field from a 0.5 T open MRI (GE Signa SP) magnet with a 60 cm gap between its poles was computed and used in full three dimensional (3D) space charge simulations, whereas for the perpendicular case the magnetic field was constant. Results: For the in-line configuration, it is shown that the electron beam is not deflected from the axis of symmetry of the gun and the primary beam current does not vanish even at very high values of the magnetic field, e.g., 0.16 T. As the field strength increases, the primary beam current has an initial plateau of constant value after which its value decreases to a minimum corresponding to a field strength of approximately 0.06 T. After the minimum is reached, the current starts to increase slowly. For the case when the beam current computation is performed at the beam waist position the initial plateau ends at 0.016 T for Litton L-2087 and at 0.012 T for Varian VTC6364. The minimum value of the primary beam current is 27.5% of the initial value for Litton L-2087 and 22.9% of the initial value for Varian VTC6364. The minimum current is reached at 0.06 and 0.062 T for Litton L-2087 and Varian VTC6364, respectively. At 0.16 T the

  14. A study of the effect of in-line and perpendicular magnetic fields on beam characteristics of electron guns in medical linear accelerators.

    PubMed

    Constantin, Dragoş E; Fahrig, Rebecca; Keall, Paul J

    2011-07-01

    Using magnetic resonance imaging (MRI) for real-time guidance during radiotherapy is an active area of research and development. One aspect of the problem is the influence of the MRI scanner, modeled here as an external magnetic field, on the medical linear accelerator (linac) components. The present work characterizes the behavior of two medical linac electron guns with external magnetic fields for in-line and perpendicular orientations of the linac with respect to the MRI scanner. Two electron guns, Litton L-2087 and Varian VTC6364, are considered as representative models for this study. Emphasis was placed on the in-line design approach in which case the MRI scanner and the linac axes of symmetry coincide and assumes no magnetic shielding of the linac. For the in-line case, the magnetic field from a 0.5 T open MRI (GE Signa SP) magnet with a 60 cm gap between its poles was computed and used in full three dimensional (3D) space charge simulations, whereas for the perpendicular case the magnetic field was constant. For the in-line configuration, it is shown that the electron beam is not deflected from the axis of symmetry of the gun and the primary beam current does not vanish even at very high values of the magnetic field, e.g., 0.16 T. As the field strength increases, the primary beam current has an initial plateau of constant value after which its value decreases to a minimum corresponding to a field strength of approximately 0.06 T. After the minimum is reached, the current starts to increase slowly. For the case when the beam current computation is performed at the beam waist position the initial plateau ends at 0.016 T for Litton L-2087 and at 0.012 T for Varian VTC6364. The minimum value of the primary beam current is 27.5% of the initial value for Litton L-2087 and 22.9% of the initial value for Varian VTC6364. The minimum current is reached at 0.06 and 0.062 T for Litton L-2087 and Varian VTC6364, respectively. At 0.16 T the beam current increases to 40

  15. A study of the effect of in-line and perpendicular magnetic fields on beam characteristics of electron guns in medical linear accelerators

    PubMed Central

    Constantin, Dragoş E.; Fahrig, Rebecca; Keall, Paul J.

    2011-01-01

    Purpose: Using magnetic resonance imaging (MRI) for real-time guidance during radiotherapy is an active area of research and development. One aspect of the problem is the influence of the MRI scanner, modeled here as an external magnetic field, on the medical linear accelerator (linac) components. The present work characterizes the behavior of two medical linac electron guns with external magnetic fields for in-line and perpendicular orientations of the linac with respect to the MRI scanner. Methods: Two electron guns, Litton L-2087 and Varian VTC6364, are considered as representative models for this study. Emphasis was placed on the in-line design approach in which case the MRI scanner and the linac axes of symmetry coincide and assumes no magnetic shielding of the linac. For the in-line case, the magnetic field from a 0.5 T open MRI (GE Signa SP) magnet with a 60 cm gap between its poles was computed and used in full three dimensional (3D) space charge simulations, whereas for the perpendicular case the magnetic field was constant. Results: For the in-line configuration, it is shown that the electron beam is not deflected from the axis of symmetry of the gun and the primary beam current does not vanish even at very high values of the magnetic field, e.g., 0.16 T. As the field strength increases, the primary beam current has an initial plateau of constant value after which its value decreases to a minimum corresponding to a field strength of approximately 0.06 T. After the minimum is reached, the current starts to increase slowly. For the case when the beam current computation is performed at the beam waist position the initial plateau ends at 0.016 T for Litton L-2087 and at 0.012 T for Varian VTC6364. The minimum value of the primary beam current is 27.5% of the initial value for Litton L-2087 and 22.9% of the initial value for Varian VTC6364. The minimum current is reached at 0.06 and 0.062 T for Litton L-2087 and Varian VTC6364, respectively. At 0.16 T the

  16. Changes in spring-mass model characteristics during repeated running sprints.

    PubMed

    Girard, Olivier; Micallef, Jean-Paul; Millet, Grégoire P

    2011-01-01

    This study investigated fatigue-induced changes in spring-mass model characteristics during repeated running sprints. Sixteen active subjects performed 12 × 40 m sprints interspersed with 30 s of passive recovery. Vertical and anterior-posterior ground reaction forces were measured at 5-10 m and 30-35 m and used to determine spring-mass model characteristics. Contact (P < 0.001), flight (P < 0.05) and swing times (P < 0.001) together with braking, push-off and total stride durations (P < 0.001) lengthened across repetitions. Stride frequency (P < 0.001) and push-off forces (P < 0.05) decreased with fatigue, whereas stride length (P = 0.06), braking (P = 0.08) and peak vertical forces (P = 0.17) changes approached significance. Center of mass vertical displacement (P < 0.001) but not leg compression (P > 0.05) increased with time. As a result, vertical stiffness decreased (P < 0.001) from the first to the last repetition, whereas leg stiffness changes across sprint trials were not significant (P > 0.05). Changes in vertical stiffness were correlated (r > 0.7; P < 0.001) with changes in stride frequency. When compared to 5-10 m, most of ground reaction force-related parameters were higher (P < 0.05) at 30-35 m, whereas contact time, stride frequency, vertical and leg stiffness were lower (P < 0.05). Vertical stiffness deteriorates when 40 m run-based sprints are repeated, which alters impact parameters. Maintaining faster stride frequencies through retaining higher vertical stiffness is a prerequisite to improve performance during repeated sprinting.

  17. Estimation of stride length in level walking using an inertial measurement unit attached to the foot: a validation of the zero velocity assumption during stance.

    PubMed

    Peruzzi, A; Della Croce, U; Cereatti, A

    2011-07-07

    In a variety of applications, inertial sensors are used to estimate spatial parameters by double integrating over time their coordinate acceleration components. In human movement applications, the drift inherent to the accelerometer signals is often reduced by exploiting the cyclical nature of gait and under the hypothesis that the velocity of the sensor is zero at some point in stance. In this study, the validity of the latter hypothesis was investigated by determining the minimum velocity of progression of selected points of the foot and shank during the stance phase of the gait cycle while walking at three different speeds on level ground. The errors affecting the accuracy of the stride length estimation resulting from assuming a zero velocity at the beginning of the integration interval were evaluated on twenty healthy subjects. Results showed that the minimum velocity of the selected points on the foot and shank increased as gait speed increased. Whereas the average minimum velocity of the foot locations was lower than 0.011 m/s, the velocity of the shank locations were up to 0.049 m/s corresponding to a percent error of the stride length equal to 3.3%. The preferable foot locations for an inertial sensor resulted to be the calcaneus and the lateral aspect of the rearfoot. In estimating the stride length, the hypothesis that the velocity of the sensor can be set to zero sometimes during stance is acceptable only if the sensor is attached to the foot. Copyright © 2011 Elsevier Ltd. All rights reserved.

  18. Magnetic field cycling effect on the non-linear current-voltage characteristics and magnetic field induced negative differential resistance in α-Fe{sub 1.64}Ga{sub 0.36}O{sub 3} oxide

    SciTech Connect

    Bhowmik, R. N. Vijayasri, G.

    2015-06-15

    We have studied current-voltage (I-V) characteristics of α-Fe{sub 1.64}Ga{sub 0.36}O{sub 3}, a typical canted ferromagnetic semiconductor. The sample showed a transformation of the I-V curves from linear to non-linear character with the increase of bias voltage. The I-V curves showed irreversible features with hysteresis loop and bi-stable electronic states for up and down modes of voltage sweep. We report positive magnetoresistance and magnetic field induced negative differential resistance as the first time observed phenomena in metal doped hematite system. The magnitudes of critical voltage at which I-V curve showed peak and corresponding peak current are affected by magnetic field cycling. The shift of the peak voltage with magnetic field showed a step-wise jump between two discrete voltage levels with least gap (ΔV{sub P}) 0.345(± 0.001) V. The magnetic spin dependent electronic charge transport in this new class of magnetic semiconductor opens a wide scope for tuning large electroresistance (∼500-700%), magnetoresistance (70-135 %) and charge-spin dependent conductivity under suitable control of electric and magnetic fields. The electric and magnetic field controlled charge-spin transport is interesting for applications of the magnetic materials in spintronics, e.g., magnetic sensor, memory devices and digital switching.

  19. Magnetic field cycling effect on the non-linear current-voltage characteristics and magnetic field induced negative differential resistance in α-Fe1.64Ga0.36O3 oxide

    NASA Astrophysics Data System (ADS)

    Bhowmik, R. N.; Vijayasri, G.

    2015-06-01

    We have studied current-voltage (I-V) characteristics of α-Fe1.64Ga0.36O3, a typical canted ferromagnetic semiconductor. The sample showed a transformation of the I-V curves from linear to non-linear character with the increase of bias voltage. The I-V curves showed irreversible features with hysteresis loop and bi-stable electronic states for up and down modes of voltage sweep. We report positive magnetoresistance and magnetic field induced negative differential resistance as the first time observed phenomena in metal doped hematite system. The magnitudes of critical voltage at which I-V curve showed peak and corresponding peak current are affected by magnetic field cycling. The shift of the peak voltage with magnetic field showed a step-wise jump between two discrete voltage levels with least gap (ΔVP) 0.345(± 0.001) V. The magnetic spin dependent electronic charge transport in this new class of magnetic semiconductor opens a wide scope for tuning large electroresistance (˜500-700%), magnetoresistance (70-135 %) and charge-spin dependent conductivity under suitable control of electric and magnetic fields. The electric and magnetic field controlled charge-spin transport is interesting for applications of the magnetic materials in spintronics, e.g., magnetic sensor, memory devices and digital switching.

  20. Trunk motion and gait characteristics of pregnant women when walking: report of a longitudinal study with a control group.

    PubMed

    Gilleard, Wendy L

    2013-03-20

    A longitudinal repeated measures design over pregnancy and post-birth, with a control group would provide insight into the mechanical adaptations of the body under conditions of changing load during a common female human lifespan condition, while minimizing the influences of inter human differences. The objective was to investigate systematic changes in the range of motion for the pelvic and thoracic segments of the spine, the motion between these segments (thoracolumbar spine) and temporospatial characteristics of step width, stride length and velocity during walking as pregnancy progresses and post-birth. Nine pregnant women were investigated when walking along a walkway at a self-selected velocity using an 8 camera motion analysis system on four occasions throughout pregnancy and once post birth. A control group of twelve non-pregnant nulliparous women were tested on three occasions over the same time period. The existence of linear trends for change was investigated. As pregnancy progresses there was a significant linear trend for increase in step width (p = 0.05) and a significant linear trend for decrease in stride length (p = 0.05). Concurrently there was a significant linear trend for decrease in the range of motion of the pelvic segment (p = 0.03) and thoracolumbar spine (p = 0.01) about a vertical axis (side to side rotation), and the pelvic segment (p = 0.04) range of motion around an anterio-posterior axis (side tilt). Post-birth, step width readapted whereas pelvic (p = 0.02) and thoracic (p < 0.001) segment flexion-extension range of motion decreased and increased respectively. The magnitude of all changes was greater than that accounted for with natural variability with re testing. As pregnancy progressed and post-birth there were significant linear trends seen in biomechanical changes when walking at a self-determined natural speed that were greater than that accounted for by natural variability with repeated testing. Not

  1. Automated mapping of pharmacy orders from two electronic health record systems to RxNorm within the STRIDE clinical data warehouse.

    PubMed

    Hernandez, Penni; Podchiyska, Tanya; Weber, Susan; Ferris, Todd; Lowe, Henry

    2009-11-14

    The Stanford Translational Research Integrated Database Environment (STRIDE) clinical data warehouse integrates medication information from two Stanford hospitals that use different drug representation systems. To merge this pharmacy data into a single, standards-based model supporting research we developed an algorithm to map HL7 pharmacy orders to RxNorm concepts. A formal evaluation of this algorithm on 1.5 million pharmacy orders showed that the system could accurately assign pharmacy orders in over 96% of cases. This paper describes the algorithm and discusses some of the causes of failures in mapping to RxNorm.

  2. Relationship between Biomechanical Characteristics of Spinal Manipulation and Neural Responses in an Animal Model: Effect of Linear Control of Thrust Displacement versus Force, Thrust Amplitude, Thrust Duration, and Thrust Rate.

    PubMed

    Reed, William R; Cao, Dong-Yuan; Long, Cynthia R; Kawchuk, Gregory N; Pickar, Joel G

    2013-01-01

    High velocity low amplitude spinal manipulation (HVLA-SM) is used frequently to treat musculoskeletal complaints. Little is known about the intervention's biomechanical characteristics that determine its clinical benefit. Using an animal preparation, we determined how neural activity from lumbar muscle spindles during a lumbar HVLA-SM is affected by the type of thrust control and by the thrust's amplitude, duration, and rate. A mechanical device was used to apply a linear increase in thrust displacement or force and to control thrust duration. Under displacement control, neural responses during the HVLA-SM increased in a fashion graded with thrust amplitude. Under force control neural responses were similar regardless of the thrust amplitude. Decreasing thrust durations at all thrust amplitudes except the smallest thrust displacement had an overall significant effect on increasing muscle spindle activity during the HVLA-SMs. Under force control, spindle responses specifically and significantly increased between thrust durations of 75 and 150 ms suggesting the presence of a threshold value. Thrust velocities greater than 20-30 mm/s and thrust rates greater than 300 N/s tended to maximize the spindle responses. This study provides a basis for considering biomechanical characteristics of an HVLA-SM that should be measured and reported in clinical efficacy studies to help define effective clinical dosages.

  3. Linearly tapered slot antenna impedance characteristics

    NASA Technical Reports Server (NTRS)

    Simons, Rainee N.; Lee, Richard Q.

    1995-01-01

    The paper presents for the first time an experimental technique to de-embed the input impedance of a LTSA from the measured reflection coefficient. The results show that the input impedance is dependent on the semi-flare angle and the length of the LTSA. The Re(Z(sub in)) is large when the electrical length of the LTSA is small and is on the order of few thousand ohms. However for an electrically large LTSA the Re(Z(sub in)) is in the range of 55 to 130 ohms. These results have potential applications in the design of broad band impedance matching networks for LTSA.

  4. Active assistive forced exercise provides long-term improvement to gait velocity and stride length in patients bilaterally affected by Parkinson's disease.

    PubMed

    Stuckenschneider, T; Helmich, I; Raabe-Oetker, A; Froböse, I; Feodoroff, B

    2015-10-01

    Forced exercise training presents a valid method of improving symptoms of Parkinson's disease such as rigor, dyskinesia and gait dysfunctions. Brain imaging data suggest that use of active assistive forced exercise could improve Parkinsonian symptoms more effectively than passive assistive forced exercise. However, the long-term effects of active versus passive assistive forced exercise on the symptoms of Parkinson's disease are unknown. Here, 24 patients showing bilateral effects of Parkinson's disease underwent a 12 week intervention of either passive or active assistive forced exercise. We analyzed tremor scores, gait patterns, and scores on the Unified Parkinson's Disease Rating Scale-III from three timepoints--before beginning the intervention, upon completion of the intervention, and twelve weeks after completion of the intervention. Participation in both passive and active assistive forced exercise increased gait velocity (0.5 km/h), swing phase (2%), monopedal stance phase (2%), elongated stride length (11 cm) and decreased double stance phase (4%). However, with participation in active assistive forced exercise, postural and kinetic tremor were also reduced and gait velocity and stride length were increased long-term. Given these findings, we conclude that future treatment for patients bilaterally affected by Parkinson's disease should carefully consider the type of assistive forced exercise intervention to be used. Copyright © 2015 Elsevier B.V. All rights reserved.

  5. Linear and angular control of circular walking in healthy older adults and subjects with cerebellar ataxia.

    PubMed

    Goodworth, Adam D; Paquette, Caroline; Jones, Geoffrey Melvill; Block, Edward W; Fletcher, William A; Hu, Bin; Horak, Fay B

    2012-05-01

    Linear and angular control of trunk and leg motion during curvilinear navigation was investigated in subjects with cerebellar ataxia and age-matched control subjects. Subjects walked with eyes open around a 1.2-m circle. The relationship of linear to angular motion was quantified by determining the ratios of trunk linear velocity to trunk angular velocity and foot linear position to foot angular position. Errors in walking radius (the ratio of linear to angular motion) also were quantified continuously during the circular walk. Relative variability of linear and angular measures was compared using coefficients of variation (CoV). Patterns of variability were compared using power spectral analysis for the trunk and auto-covariance analysis for the feet. Errors in radius were significantly increased in patients with cerebellar damage as compared to controls. Cerebellar subjects had significantly larger CoV of feet and trunk in angular, but not linear, motion. Control subjects also showed larger CoV in angular compared to linear motion of the feet and trunk. Angular and linear components of stepping differed in that angular, but not linear, foot placement had a negative correlation from one stride to the next. Thus, walking in a circle was associated with more, and a different type of, variability in angular compared to linear motion. Results are consistent with increased difficulty of, and role of the cerebellum in, control of angular trunk and foot motion for curvilinear locomotion.

  6. Gait analysis of slope walking: a study on step length, stride width, time factors and deviation in the center of pressure.

    PubMed

    Kawamura, K; Tokuhiro, A; Takechi, H

    1991-06-01

    Determination was made of step length, stride width, time factors and deviation in the center of pressure during up- and downslope walking in 17 healthy men between the ages of 19 and 34 using a force plate. Slope inclinations were set at 3, 6, 9 and 12 degrees. At 12 degrees, walking speed, the product of step length and cadence, decreased significantly (p less than 0.01) in both up- and downslope walking. The most conspicuous phenomenon in upslope walking was in cadence. The steeper the slope, the smaller was the cadence. The most conspicuous phenomenon in downslope walking was in step length. The steeper the slope, the shorter was the step length.

  7. Linear immunoglobulin A bullous dermatosis.

    PubMed

    Fortuna, Giulio; Marinkovich, M Peter

    2012-01-01

    Linear immunoglobulin A (IgA) bullous dermatosis, also known as linear IgA disease, is an autoimmune mucocutaneous disorder characterized by subepithelial bullae, with IgA autoantibodies directed against several different antigens in the basement membrane zone. Its immunopathologic characteristic resides in the presence of a continuous linear IgA deposit along the basement membrane zone, which is clearly visible on direct immunofluorescence. This disorder shows different clinical features and distribution when adult-onset of linear IgA disease is compared with childhood-onset. Diagnosis is achieved via clinical, histopathologic, and immunopathologic examinations. Two common therapies are dapsone and sulfapyridine, which reduce the inflammatory response and achieve disease remission in a variable period of time.

  8. Men and Women from the STRIDE Clinical Trial: An Assessment of Stimulant Abstinence Symptom Severity at Residential Treatment Entry

    PubMed Central

    Chartier, Karen G.; Sanchez, Katherine; Killeen, Therese K.; Burrow, Allison; Carmody, Thomas; Greer, Tracy L.; Trivedi, Madhukar H.

    2016-01-01

    Background and Objectives Gender-specific factors associated with stimulant abstinence severity were examined in a stimulant abusing or dependent residential treatment sample (N=302). Method Bivariate statistics tested gender differences in stimulant abstinence symptoms, measured by participant-reported experiences of early withdrawal. Multivariate linear regression examined gender and other predictors of stimulant abstinence symptom severity. Results Women compared to men reported greater stimulant abstinence symptom severity. Anxiety disorders and individual anxiety-related abstinence symptoms accounted for this difference. African American race/ethnicity was predictive of lower stimulant abstinence severity. Discussion and Conclusions Women were more sensitive to anxiety-related stimulant withdrawal symptoms. Scientific Significance Clinics that address anxiety-related abstinence symptoms, which more commonly occur in women, may improve treatment outcome. PMID:25694201

  9. Men and women from the STRIDE clinical trial: An assessment of stimulant abstinence symptom severity at residential treatment entry.

    PubMed

    Chartier, Karen G; Sanchez, Katherine; Killeen, Therese K; Burrow, Allison; Carmody, Thomas; Greer, Tracy L; Trivedi, Madhukar H

    2015-06-01

    Gender-specific factors associated with stimulant abstinence severity were examined in a stimulant abusing or dependent residential treatment sample (N = 302). Bivariate statistics tested gender differences in stimulant abstinence symptoms, measured by participant-reported experiences of early withdrawal. Multivariate linear regression examined gender and other predictors of stimulant abstinence symptom severity. Women compared to men reported greater stimulant abstinence symptom severity. Anxiety disorders and individual anxiety-related abstinence symptoms accounted for this difference. African American race/ethnicity was predictive of lower stimulant abstinence severity. Women were more sensitive to anxiety-related stimulant withdrawal symptoms. Clinics that address anxiety-related abstinence symptoms, which more commonly occur in women, may improve treatment outcome. © American Academy of Addiction Psychiatry.

  10. Morphologic and kinematic characteristics of elite sprinters.

    PubMed

    Coh, M; Milanović, D; Kampmiller, T

    2001-12-01

    The purpose of the study was to ascertain the basic morphologic and kinematic characteristics of elite sprinters. The sample included 24 sprinters, with times over a 100 m distance between 10.21 s and 11.19 s. Morphologic characteristics of the sprinters were measured with a test battery of 17 measures, obtained according to the methodology prescribed by the International Biologic Programme (IBP). The kinematic variables were obtained from a flying start 20 m run and a 20 m run with a low start, with the technology of a contact carpet (ERGO TESTER-Bosco). Stride frequency and length, duration of contact and flight phases were registered. Time parameters were measured with a system of infrared photocells (BROWER Timing System). T-test showed that elite sprinters do not differ significantly in morphologic characteristics (p > 0.05) from the 100 m results point of view. However, statistically significant differences were obtained in starting acceleration and maximal velocity. The most important kinematic parameters for generating differences between the elite sprinters are contact time and stride frequency.

  11. Linear control of the spectral characteristics of wavelength-selective components with a high-index tapered thin-film planar waveguide and a single-mode half-coupler.

    PubMed

    Das, A K; Hussain, A

    1999-04-20

    A simple system of linearly tunable fiber-film wavelength-dependent components is demonstrated that includes a linearly tapered high-index thin-film planar waveguide (PWG) evanescently coupled by a single-mode-fiber half-coupler. We present experimental and theoretical results for the linear tuning of spectral responses such as coupled power, resonance position (lambda0), and fiber output-light polarization through position shifting of the linearly tapered PWG, in the direction of the propagating light in the fiber, over the half-coupler block. We achieved almost linear control of the spectral response by changing the temperature of mixture-of-oils and overlay-doped poly(methyl methacrylate) PWG's when the refractive index of the system decreases with temperature. The variation in thickness of the tapered film is along the direction of the interaction length of the system. Linear tapered PWG's that comprised a mixture of oils, BK7 glass, and overlay-doped PMMA with high refractive indices were fabricated that could operate the device at lower and higher modes. We investigated the dependence of tuning lambda0 on the PWG mode. Tuning by shifting of a linear tapered PWG over a fiber half-block is mode dependent, whereas tuning by changing the refractive index of a uniform PWG is mode independent. Wavelength shift Deltalambda0 is found to decrease with an increase in the resonant PWG mode number m for linearly tapered PWG's. A fiber-to-asymmetric linear tapered-PWG coupler, which maintains the taper slope to within a specific limit, can function as a linearly tunable polarizer for the light in the fiber.

  12. [Linear lichen planopilaris of the face].

    PubMed

    Cañadas, Nadia G; Luna, Paula C; Etcheverry, Mauro D; Nocito, Mabel J; Castellanos Posse, Maria L; Marchesi, Carolina; Garuti, Romina A; Carmona Cuello, Lucía E; Carabajal, Graciela; Mazzini, Miguel A

    2010-07-15

    Linear lichen planopilaris of the face is a rare variant of lichen plano- pilaris. Asymptomatic follicular papules in a linear configuration are the characteristic clinical features. The incidence is still unknown, but there are a few cases reported exclusively in male adults. We present the case of a fourteen-year-old girl with linear lichen planopilaris of the face. Improvement was obtained with the use of tacrolimus 0.03 percent ointment.

  13. Kinematic characteristics of gait in middle-aged adults during level walking.

    PubMed

    Wu, Yu; Wang, Yin-Zhi; Xiao, Fei; Gu, Dong-Yun

    2014-01-01

    Middle-aged people have shown a high fall incidence and degeneration in gait stability, while few studies concern that. This study aimed to assess the kinematic characteristics of gait in middle-aged people compared with younger and older ones during level walking, and to find sensitive indicators to characterize degenerated gait stability in middle-aged people. 13 middle-aged (mean age=52.1 years), with 13 older (mean age=74.8 years) and 13 young (mean age=23.3 years) healthy adults participated in this study. We assessed following gait parameters of the subjects during their level walking: 1) temporal-spatial gait parameters: normalized gait velocity, stride length, step length and their variability; 2) gait stability parameters: acceleration root mean square (RMS) of COM and its variability; and instantaneous COM-COP inclination angles. Compared with young and older subjects, middle-aged adults showed no significant difference in temporal-spatial gait parameters and their stride-to-stride variability (P>0.050); Compared with young subjects, middle-aged adults showed a significant higher value in medial-lateral (ML) direction of acceleration RMS of COM (P=0.038) and its stride-to-stride variability (P=0.030), as well as in COM-COP inclination angle (P=0.003). There was no significant difference in the above two parameters of gait stability between middle-aged and older subjects (P>0.050). Results illustrated that middle-aged subjects showed similar degenerated pattern in gait stability as the older ones in ML direction. Gait stability parameters, including ML acceleration of COM and its variability, as well as ML COM-COP inclination angle may help to characterize this degenerated gait stability. It's necessary for us to develop early interventions for middle-aged adults to prevent falls during walking.

  14. Linear Back-Drive Differentials

    NASA Technical Reports Server (NTRS)

    Waydo, Peter

    2003-01-01

    Linear back-drive differentials have been proposed as alternatives to conventional gear differentials for applications in which there is only limited rotational motion (e.g., oscillation). The finite nature of the rotation makes it possible to optimize a linear back-drive differential in ways that would not be possible for gear differentials or other differentials that are required to be capable of unlimited rotation. As a result, relative to gear differentials, linear back-drive differentials could be more compact and less massive, could contain fewer complex parts, and could be less sensitive to variations in the viscosities of lubricants. Linear back-drive differentials would operate according to established principles of power ball screws and linear-motion drives, but would utilize these principles in an innovative way. One major characteristic of such mechanisms that would be exploited in linear back-drive differentials is the possibility of designing them to drive or back-drive with similar efficiency and energy input: in other words, such a mechanism can be designed so that a rotating screw can drive a nut linearly or the linear motion of the nut can cause the screw to rotate. A linear back-drive differential (see figure) would include two collinear shafts connected to two parts that are intended to engage in limited opposing rotations. The linear back-drive differential would also include a nut that would be free to translate along its axis but not to rotate. The inner surface of the nut would be right-hand threaded at one end and left-hand threaded at the opposite end to engage corresponding right- and left-handed threads on the shafts. A rotation and torque introduced into the system via one shaft would drive the nut in linear motion. The nut, in turn, would back-drive the other shaft, creating a reaction torque. Balls would reduce friction, making it possible for the shaft/nut coupling on each side to operate with 90 percent efficiency.

  15. Making strides and meeting challenges in pediatric allogeneic hematopoietic cell transplantation clinical trials in the United States: Past, present and future.

    PubMed

    Satwani, Prakash; Kahn, Justine; Jin, Zhezhen

    2015-11-01

    Over the past 20years, the field of pediatric allogeneic hematopoietic cell transplantation has made ground-breaking strides in the successful treatment of patients with both malignant and non-malignant diseases. As the field advances, so does the need for high-quality studies including randomized controlled trials, aimed at answering clinically important questions about optimizing care and outcomes of children undergoing alloHCT. In an effort to actively address emerging clinical questions, three main cooperative groups in the U.S. have joined forces to develop and implement multiple clinical trials for pediatric alloHCT patients. These groups include the Blood and Marrow Transplant Clinical Trials Network, the Children's Oncology Group and the Pediatric Blood and Marrow Transplant Consortium. Though the field of stem cell transplantation continues to advance, conducting clinical trials in the pediatric population is a unique challenge and as a result, optimal outcomes have yet to be reached in this population. Because of the limited number of pediatric transplant patients at each institution in the U.S., trials aimed at answering important clinical questions still struggle to accrue acceptable numbers of patients in an appropriate amount of time and thus gathering statistically useful data has posed a challenge for the field. In an effort to mitigate some of the challenges associated with obtaining statistically and clinically meaningful information about pediatric alloHCT, the implementation of new cooperative group trials is active and ongoing.

  16. Plantarflexor muscle and spatiotemporal gait characteristics of children with hemiplegic cerebral palsy: an observational study.

    PubMed

    Crosbie, Jack; Alhusaini, Adel A A; Dean, Catherine M; Shepherd, Roberta B

    2012-01-01

    The study investigated associations between the active and passive mechanical properties of the calf muscle in children with cerebral palsy and the spatiotemporal features of their gait on both level ground and over stairs. 26 children with hemiplegic cerebral palsy (age 4 - 10 years) walked barefoot across a level ten metre pathway and a staircase. Walking speed, stride length and cadence were calculated and spasticity, maximum isometric strength, stiffness and hysteresis of the affected side calf muscle measured. Multiple linear regression was used to determine the associations among variables. Walking speed and stride length were significantly associated with dorsiflexor muscle strength and the stiffness of the calf muscle, while stair ascent and descent speeds were significantly and inversely related to the amount of hysteresis displayed by the calf muscle. Passive mechanical properties of the calf muscle are influential in gait performance in these children.

  17. Linear Accelerator (LINAC)

    MedlinePlus

    ... equipment? How is safety ensured? What is this equipment used for? A linear accelerator (LINAC) is the ... Therapy (SBRT) . top of page How does the equipment work? The linear accelerator uses microwave technology (similar ...

  18. Electrothermal linear actuator

    NASA Technical Reports Server (NTRS)

    Derr, L. J.; Tobias, R. A.

    1969-01-01

    Converting electric power into powerful linear thrust without generation of magnetic fields is accomplished with an electrothermal linear actuator. When treated by an energized filament, a stack of bimetallic washers expands and drives the end of the shaft upward.

  19. Powerful Electromechanical Linear Actuator

    NASA Technical Reports Server (NTRS)

    Cowan, John R.; Myers, William N.

    1994-01-01

    Powerful electromechanical linear actuator designed to replace hydraulic actuator. Cleaner, simpler, and needs less maintenance. Features rotary-to-linear-motion converter with antibacklash gearing and position feedback via shaft-angle resolvers, which measure rotary motion.

  20. A linear programming manual

    NASA Technical Reports Server (NTRS)

    Tuey, R. C.

    1972-01-01

    Computer solutions of linear programming problems are outlined. Information covers vector spaces, convex sets, and matrix algebra elements for solving simultaneous linear equations. Dual problems, reduced cost analysis, ranges, and error analysis are illustrated.

  1. Linear Accelerator (LINAC)

    MedlinePlus

    ... equipment? How is safety ensured? What is this equipment used for? A linear accelerator (LINAC) is the ... Therapy (SBRT) . top of page How does the equipment work? The linear accelerator uses microwave technology (similar ...

  2. Linear shaped charge

    DOEpatents

    Peterson, David; Stofleth, Jerome H.; Saul, Venner W.

    2017-07-11

    Linear shaped charges are described herein. In a general embodiment, the linear shaped charge has an explosive with an elongated arrowhead-shaped profile. The linear shaped charge also has and an elongated v-shaped liner that is inset into a recess of the explosive. Another linear shaped charge includes an explosive that is shaped as a star-shaped prism. Liners are inset into crevices of the explosive, where the explosive acts as a tamper.

  3. IR Linearity Monitor

    NASA Astrophysics Data System (ADS)

    Hilbert, Bryan

    2012-10-01

    These observations will be used to monitor the signal non-linearity of the IR channel, as well as to update the IR channel non-linearity calibration reference file. The non-linearity behavior of each pixel in the detector will be investigated through the use of full frame and subarray flat fields, while the photometric behavior of point sources will be studied using observations of 47 Tuc. This is a continuation of the Cycle 19 non-linearity monitor, program 12696.

  4. IR linearity monitor

    NASA Astrophysics Data System (ADS)

    Hilbert, Bryan

    2013-10-01

    These observations will be used to monitor the signal non-linearity of the IR channel, as well as to update the IR channel non-linearity calibration reference file. The non-linearity behavior of each pixel in the detector will be investigated through the use of full frame and subarray flat fields, while the photometric behavior of point sources will be studied using observations of 47 Tuc. This is a continuation of the Cycle 20 non-linearity monitor, program 13079.

  5. Linear Rogowski coil.

    PubMed

    Nassisi, V; Delle Side, D

    2017-02-01

    Nowadays, the employment and development of fast current pulses require sophisticated systems to perform measurements. Rogowski coils are used to diagnose cylindrical shaped beams; therefore, they are designed and built with a toroidal structure. Recently, to perform experiments of radiofrequency biophysical stresses, flat transmission lines have been developed. Therefore, in this work we developed a linear Rogowski coil to detect current pulses inside flat conductors. The system is first approached by means of transmission line theory. We found that, if the pulse width to be diagnosed is comparable with the propagation time of the signal in the detector, it is necessary to impose a uniform current as input pulse, or to use short coils. We further analysed the effect of the resistance of the coil and the influence of its magnetic properties. As a result, the device we developed is able to record pulses lasting for some hundreds of nanoseconds, depending on the inductance, load impedance, and resistance of the coil. Furthermore, its response is characterized by a sub-nanosecond rise time (∼100 ps). The attenuation coefficient depends mainly on the turn number of the coil, while the fidelity of the response depends both on the magnetic core characteristics and on the current distribution along the plane conductors.

  6. Linear Rogowski coil

    NASA Astrophysics Data System (ADS)

    Nassisi, V.; Delle Side, D.

    2017-02-01

    Nowadays, the employment and development of fast current pulses require sophisticated systems to perform measurements. Rogowski coils are used to diagnose cylindrical shaped beams; therefore, they are designed and built with a toroidal structure. Recently, to perform experiments of radiofrequency biophysical stresses, flat transmission lines have been developed. Therefore, in this work we developed a linear Rogowski coil to detect current pulses inside flat conductors. The system is first approached by means of transmission line theory. We found that, if the pulse width to be diagnosed is comparable with the propagation time of the signal in the detector, it is necessary to impose a uniform current as input pulse, or to use short coils. We further analysed the effect of the resistance of the coil and the influence of its magnetic properties. As a result, the device we developed is able to record pulses lasting for some hundreds of nanoseconds, depending on the inductance, load impedance, and resistance of the coil. Furthermore, its response is characterized by a sub-nanosecond rise time (˜100 ps). The attenuation coefficient depends mainly on the turn number of the coil, while the fidelity of the response depends both on the magnetic core characteristics and on the current distribution along the plane conductors.

  7. Linear-Algebra Programs

    NASA Technical Reports Server (NTRS)

    Lawson, C. L.; Krogh, F. T.; Gold, S. S.; Kincaid, D. R.; Sullivan, J.; Williams, E.; Hanson, R. J.; Haskell, K.; Dongarra, J.; Moler, C. B.

    1982-01-01

    The Basic Linear Algebra Subprograms (BLAS) library is a collection of 38 FORTRAN-callable routines for performing basic operations of numerical linear algebra. BLAS library is portable and efficient source of basic operations for designers of programs involving linear algebriac computations. BLAS library is supplied in portable FORTRAN and Assembler code versions for IBM 370, UNIVAC 1100 and CDC 6000 series computers.

  8. Improved Electrohydraulic Linear Actuators

    NASA Technical Reports Server (NTRS)

    Hamtil, James

    2002-01-01

    A product line of improved electrohydraulic linear actuators has been developed. These actuators are designed especially for use in actuating valves in rocket-engine test facilities. They are also adaptable to similar industrial uses. Advantageous features of the electrohydraulic linear actuators with respect to shortcomings of prior electrohydraulic linear actuators are described.

  9. Linear-Algebra Programs

    NASA Technical Reports Server (NTRS)

    Lawson, C. L.; Krogh, F. T.; Gold, S. S.; Kincaid, D. R.; Sullivan, J.; Williams, E.; Hanson, R. J.; Haskell, K.; Dongarra, J.; Moler, C. B.

    1982-01-01

    The Basic Linear Algebra Subprograms (BLAS) library is a collection of 38 FORTRAN-callable routines for performing basic operations of numerical linear algebra. BLAS library is portable and efficient source of basic operations for designers of programs involving linear algebriac computations. BLAS library is supplied in portable FORTRAN and Assembler code versions for IBM 370, UNIVAC 1100 and CDC 6000 series computers.

  10. Optimal design of linear and non-linear dynamic vibration absorbers

    NASA Astrophysics Data System (ADS)

    Jordanov, I. N.; Cheshankov, B. I.

    1988-05-01

    An efficient numerical method is applied to obtain optimal parameters for both linear and non-linear damped dynamic vibration absorbers. The minimization of the vibration response has been carried out for damped as well as undamped force excited primary systems with linear and non-linear spring characteristics. Comparison is made with the optimum absorber parameters that are determined by using Den Hartog's classical results in the linear case. Six optimization criteria by which the response is minimized over narrow and broad frequency bands are examined. Pareto optimal solutions of the multi-objective decision making problem are obtained.

  11. Linearization of digital derived rate algorithm for use in linear stability analysis

    NASA Technical Reports Server (NTRS)

    Graham, R. E.; Porada, T. W.

    1985-01-01

    The digital derived rate (DDR) algorithm is used to calculate the rate of rotation of the Centaur upper-stage rocket. The DDR is highly nonlinear algorithm, and classical linear stability analysis of the spacecraft cannot be performed without linearization. The performance of this rate algorithm is characterized by a gain and phase curve that drop off at the same frequency. This characteristic is desirable for many applications. A linearization technique for the DDR algorithm is investigated. The linearization method is described. Examples of the results of the linearization technique are illustrated, and the effects of linearization are described. A linear digital filter may be used as a substitute for performing classical linear stability analyses, while the DDR itself may be used in time response analysis.

  12. Linear Controllers for Turbulent Boundary Layers

    NASA Astrophysics Data System (ADS)

    Lim, Junwoo; Kim, John; Kang, Sung-Moon; Speyer, Jason

    2000-11-01

    Several recent studies have shown that controllers based on a linear system theory work surprisingly well in turbulent flows, suggesting that a linear mechanism may play an important role even in turbulent flows. It has been also shown that non-normality of the linearized Navier-Stokes equations is an essential characteristic in the regeneration of near-wall turbulence structures in turbulent boundary layers. A few controllers designed to reduce the role of different linear mechanisms, including that to minimize the non-normality of the linearized Navier-Stokes equations, have been developed and applied to a low Reynolds nubmer turbulent channel flow. A reduced-order model containing the most controllable and observables modes is derived for each system. Other existing control schemes, such as Choi et al's opposition control, have been examined from the point of a linear system control. Further discussion on controller design, such as choice of cost function and other control parameters, will be presented.

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

    PubMed Central

    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 muscular contraction at a variety of speeds. The model was first verified by predicting gaits for living human subjects, and comparing costs, stride lengths and speeds to experimentally determined values for the same subjects. Subsequent simulations for A. afarensis yield estimates of the range of walking speeds from 0.6 to 1.3 m s−1 at a cost of 7.0 J kg−1 m−1 for the lowest speeds, falling to 5.8 J kg−1 m−1 at 1.0 m s−1, and rising to 6.2 J kg−1 m−1 at the maximum speed achieved. Speeds previously estimated for the makers of the Laetoli footprint trails (0.56 or 0.64 m s−1 for Trail 1, 0.72 or 0.75 m s−1 for Trail 2/3) may have been underestimated, substantially so for Trail 2/3, with true values in excess of 0.7 and 1.0 m s−1, respectively. The predictions conflict with suggestions that A. afarensis used a ‘shuffling’ gait, indicating rather that the species was a fully competent biped. PMID:16849203

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

    PubMed

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

    2005-12-22

    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 muscular contraction at a variety of speeds. The model was first verified by predicting gaits for living human subjects, and comparing costs, stride lengths and speeds to experimentally determined values for the same subjects. Subsequent simulations for A. afarensis yield estimates of the range of walking speeds from 0.6 to 1.3 m s-1 at a cost of 7.0 J kg-1 m-1 for the lowest speeds, falling to 5.8 J kg-1 m-1 at 1.0 m s-1, and rising to 6.2 J kg-1 m-1 at the maximum speed achieved. Speeds previously estimated for the makers of the Laetoli footprint trails (0.56 or 0.64 m s-1 for Trail 1, 0.72 or 0.75 m s-1 for Trail 2/3) may have been underestimated, substantially so for Trail 2/3, with true values in excess of 0.7 and 1.0 m s-1, respectively. The predictions conflict with suggestions that A. afarensis used a 'shuffling' gait, indicating rather that the species was a fully competent biped.

  15. Using Linear Agarose Channels to Study Drosophila Larval Crawling Behavior.

    PubMed

    Sun, Xiao; Heckscher, Ellie S

    2016-11-26

    Drosophila larval crawling is emerging as a powerful model to study neural control of sensorimotor behavior. However, larval crawling behavior on flat open surfaces is complex, including: pausing, turning, and meandering. This complexity in the repertoire of movement hinders detailed analysis of the events occurring during a single crawl stride cycle. To overcome this obstacle, linear agarose channels were made that constrain larval behavior to straight, sustained, rhythmic crawling. In principle, because agarose channels and the Drosophila larval body are both optically clear, the movement of larval structures labeled by genetically-encoded fluorescent probes can be monitored in intact, freely-moving larvae. In the past, larvae were placed in linear channels and crawling at the level of whole organism, segment, and muscle were analyzed(1). In the future, larvae crawling in channels can be used for calcium imaging to monitor neuronal activity. Moreover, these methods can be used with larvae of any genotype and with any researcher-designed channel. Thus the protocol presented below is widely applicable for studies using the Drosophila larva as a model to understand motor control.

  16. Making Strides with Educational Data

    ERIC Educational Resources Information Center

    Golden, Michael

    2005-01-01

    The Pennsylvania Department of Education (PDE) is working with local education agencies throughout the Commonwealth to create a culture of teaching and learning in every school that is student-centered, data-informed, personalized, and results-focused. Each of these elements have been supported seamlessly by systems, resources, technology, and…

  17. Striding Towards Better Physical Therapy

    NASA Technical Reports Server (NTRS)

    2003-01-01

    This paper presents a discussion on a new rehabilitative device that promises to improve physical therapy for patients working to regain the ability to walk after facing traumatic injuries or a degenerative illness. Produced by Enduro Medical Technology, of East Hartford, Connecticut, the Secure Ambulation Module (S.A.M.) creates a stable and secure environment for patients as they stand during ambulation therapy.

  18. Linear collider: a preview

    SciTech Connect

    Wiedemann, H.

    1981-11-01

    Since no linear colliders have been built yet it is difficult to know at what energy the linear cost scaling of linear colliders drops below the quadratic scaling of storage rings. There is, however, no doubt that a linear collider facility for a center of mass energy above say 500 GeV is significantly cheaper than an equivalent storage ring. In order to make the linear collider principle feasible at very high energies a number of problems have to be solved. There are two kinds of problems: one which is related to the feasibility of the principle and the other kind of problems is associated with minimizing the cost of constructing and operating such a facility. This lecture series describes the problems and possible solutions. Since the real test of a principle requires the construction of a prototype I will in the last chapter describe the SLC project at the Stanford Linear Accelerator Center.

  19. Linear mass actuator

    NASA Technical Reports Server (NTRS)

    Holloway, Sidney E., III (Inventor); Crossley, Edward A., Jr. (Inventor); Jones, Irby W. (Inventor); Miller, James B. (Inventor); Davis, C. Calvin (Inventor); Behun, Vaughn D. (Inventor); Goodrich, Lewis R., Sr. (Inventor)

    1992-01-01

    A linear mass actuator includes an upper housing and a lower housing connectable to each other and having a central passageway passing axially through a mass that is linearly movable in the central passageway. Rollers mounted in the upper and lower housings in frictional engagement with the mass translate the mass linearly in the central passageway and drive motors operatively coupled to the roller means, for rotating the rollers and driving the mass axially in the central passageway.

  20. Fault tolerant linear actuator

    DOEpatents

    Tesar, Delbert

    2004-09-14

    In varying embodiments, the fault tolerant linear actuator of the present invention is a new and improved linear actuator with fault tolerance and positional control that may incorporate velocity summing, force summing, or a combination of the two. In one embodiment, the invention offers a velocity summing arrangement with a differential gear between two prime movers driving a cage, which then drives a linear spindle screw transmission. Other embodiments feature two prime movers driving separate linear spindle screw transmissions, one internal and one external, in a totally concentric and compact integrated module.

  1. Linear phase compressive filter

    DOEpatents

    McEwan, Thomas E.

    1995-01-01

    A phase linear filter for soliton suppression is in the form of a laddered series of stages of non-commensurate low pass filters with each low pass filter having a series coupled inductance (L) and a reverse biased, voltage dependent varactor diode, to ground which acts as a variable capacitance (C). L and C values are set to levels which correspond to a linear or conventional phase linear filter. Inductance is mapped directly from that of an equivalent nonlinear transmission line and capacitance is mapped from the linear case using a large signal equivalent of a nonlinear transmission line.

  2. Linear phase compressive filter

    DOEpatents

    McEwan, T.E.

    1995-06-06

    A phase linear filter for soliton suppression is in the form of a laddered series of stages of non-commensurate low pass filters with each low pass filter having a series coupled inductance (L) and a reverse biased, voltage dependent varactor diode, to ground which acts as a variable capacitance (C). L and C values are set to levels which correspond to a linear or conventional phase linear filter. Inductance is mapped directly from that of an equivalent nonlinear transmission line and capacitance is mapped from the linear case using a large signal equivalent of a nonlinear transmission line. 2 figs.

  3. Recombineering linear BACs.

    PubMed

    Chen, Qingwen; Narayanan, Kumaran

    2015-01-01

    Recombineering is a powerful genetic engineering technique based on homologous recombination that can be used to accurately modify DNA independent of its sequence or size. One novel application of recombineering is the assembly of linear BACs in E. coli that can replicate autonomously as linear plasmids. A circular BAC is inserted with a short telomeric sequence from phage N15, which is subsequently cut and rejoined by the phage protelomerase enzyme to generate a linear BAC with terminal hairpin telomeres. Telomere-capped linear BACs are protected against exonuclease attack both in vitro and in vivo in E. coli cells and can replicate stably. Here we describe step-by-step protocols to linearize any BAC clone by recombineering, including inserting and screening for presence of the N15 telomeric sequence, linearizing BACs in vivo in E. coli, extracting linear BACs, and verifying the presence of hairpin telomere structures. Linear BACs may be useful for functional expression of genomic loci in cells, maintenance of linear viral genomes in their natural conformation, and for constructing innovative artificial chromosome structures for applications in mammalian and plant cells.

  4. Linear Corrugating - Final Technical Report

    SciTech Connect

    Lloyd Chapman

    2000-05-23

    Linear Corrugating is a process for the manufacture of corrugated containers in which the flutes of the corrugated medium are oriented in the Machine Direction (MD) of the several layers of paper used. Conversely, in the conventional corrugating process the flutes are oriented at right angles to the MD in the Cross Machine Direction (CD). Paper is stronger in MD than in CD. Therefore, boxes made using the Linear Corrugating process are significantly stronger-in the prime strength criteria, Box Compression Test (BCT) than boxes made conventionally. This means that using Linear Corrugating boxes can be manufactured to BCT equaling conventional boxes but containing 30% less fiber. The corrugated container industry is a large part of the U.S. economy, producing over 40 million tons annually. For such a large industry, the potential savings of Linear Corrugating are enormous. The grant for this project covered three phases in the development of the Linear Corrugating process: (1) Production and evaluation of corrugated boxes on commercial equipment to verify that boxes so manufactured would have enhanced BCT as proposed in the application; (2) Production and evaluation of corrugated boxes made on laboratory equipment using combined board from (1) above but having dual manufactures joints (glue joints). This box manufacturing method (Dual Joint) is proposed to overcome box perimeter limitations of the Linear Corrugating process; (3) Design, Construction, Operation and Evaluation of an engineering prototype machine to form flutes in corrugating medium in the MD of the paper. This operation is the central requirement of the Linear Corrugating process. Items I and II were successfully completed, showing predicted BCT increases from the Linear Corrugated boxes and significant strength improvement in the Dual Joint boxes. The Former was constructed and operated successfully using kraft linerboard as the forming medium. It was found that tensile strength and stretch

  5. An Instructional Note on Linear Programming--A Pedagogically Sound Approach.

    ERIC Educational Resources Information Center

    Mitchell, Richard

    1998-01-01

    Discusses the place of linear programming in college curricula and the advantages of using linear-programming software. Lists important characteristics of computer software used in linear programming for more effective teaching and learning. (ASK)

  6. [Gait characteristics of women with fibromyalgia: a premature aging pattern].

    PubMed

    Góes, Suelen M; Leite, Neiva; de Souza, Ricardo M; Homann, Diogo; Osiecki, Ana C V; Stefanello, Joice M F; Rodacki, André L F

    2014-01-01

    Fibromyalgia is a condition which involves chronic pain. Middle-aged individuals with fibromyalgia seem to exhibit changes in gait pattern, which may prematurely expose them to a gait pattern which resembles that found in the elderly population. To determine the 3D spatial (linear and angular) gait parameters of middle-aged women with fibromyalgia and compare to elderly women without this condition. 25 women (10 in the fibromyalgia group and 15 in the elderly group) volunteered to participate in the study. Kinematics was performed using an optoelectronic system, and linear and angular kinematic variables were determined. There was no difference in walking speed, stride length, cadence, hip, knee and ankle joints range of motion between groups, except the pelvic rotation, in which the fibromyalgia group showed greater rotation (P<0.05) compared to the elderly group. Also, there was a negative correlation with pelvic rotation and gluteus pain (r = -0.69; P<0.05), and between pelvic obliquity and greater trochanter pain (r = -0.69; P<0.05) in the fibromyalgia group. Middle-aged women with fibromyalgia showed gait pattern resemblances to elderly, women, which is characterized by reduced lower limb ROM, stride length and walking speed. Copyright © 2014 Elsevier Editora Ltda. All rights reserved.

  7. Fast feedback for linear colliders

    SciTech Connect

    Hendrickson, L.; Adolphsen, C.; Allison, S.; Gromme, T.; Grossberg, P.; Himel, T.; Krauter, K.; MacKenzie, R.; Minty, M.; Sass, R.

    1995-05-01

    A fast feedback system provides beam stabilization for the SLC. As the SLC is in some sense a prototype for future linear colliders, this system may be a prototype for future feedbacks. The SLC provides a good base of experience for feedback requirements and capabilities as well as a testing ground for performance characteristics. The feedback system controls a wide variety of machine parameters throughout the SLC and associated experiments, including regulation of beam position, angle, energy, intensity and timing parameters. The design and applications of the system are described, in addition to results of recent performance studies.

  8. Linear Equations: Equivalence = Success

    ERIC Educational Resources Information Center

    Baratta, Wendy

    2011-01-01

    The ability to solve linear equations sets students up for success in many areas of mathematics and other disciplines requiring formula manipulations. There are many reasons why solving linear equations is a challenging skill for students to master. One major barrier for students is the inability to interpret the equals sign as anything other than…

  9. Powerful Electromechanical Linear Actuator

    NASA Technical Reports Server (NTRS)

    Cowan, John R.; Myers, William N.

    1994-01-01

    Powerful electromechanical linear actuator designed to replace hydraulic actuator that provides incremental linear movements to large object and holds its position against heavy loads. Electromechanical actuator cleaner and simpler, and needs less maintenance. Two principal innovative features that distinguish new actuator are use of shaft-angle resolver as source of position feedback to electronic control subsystem and antibacklash gearing arrangement.

  10. Linearization of Robot Manipulators

    NASA Technical Reports Server (NTRS)

    Kreutz, Kenneth

    1987-01-01

    Four nonlinear control schemes equivalent. Report discusses theory of nonlinear feedback control of robot manipulator, emphasis on control schemes making manipulator input and output behave like decoupled linear system. Approach, called "exact external linearization," contributes efforts to control end-effector trajectories, positions, and orientations.

  11. SLAC Linear Collider

    SciTech Connect

    Richter, B.

    1985-12-01

    A report is given on the goals and progress of the SLAC Linear Collider. The status of the machine and the detectors are discussed and an overview is given of the physics which can be done at this new facility. Some ideas on how (and why) large linear colliders of the future should be built are given.

  12. Linear force device

    NASA Technical Reports Server (NTRS)

    Clancy, John P.

    1988-01-01

    The object of the invention is to provide a mechanical force actuator which is lightweight and manipulatable and utilizes linear motion for push or pull forces while maintaining a constant overall length. The mechanical force producing mechanism comprises a linear actuator mechanism and a linear motion shaft mounted parallel to one another. The linear motion shaft is connected to a stationary or fixed housing and to a movable housing where the movable housing is mechanically actuated through actuator mechanism by either manual means or motor means. The housings are adapted to releasably receive a variety of jaw or pulling elements adapted for clamping or prying action. The stationary housing is adapted to be pivotally mounted to permit an angular position of the housing to allow the tool to adapt to skewed interfaces. The actuator mechanisms is operated by a gear train to obtain linear motion of the actuator mechanism.

  13. Linear models: permutation methods

    USGS Publications Warehouse

    Cade, B.S.; Everitt, B.S.; Howell, D.C.

    2005-01-01

    Permutation tests (see Permutation Based Inference) for the linear model have applications in behavioral studies when traditional parametric assumptions about the error term in a linear model are not tenable. Improved validity of Type I error rates can be achieved with properly constructed permutation tests. Perhaps more importantly, increased statistical power, improved robustness to effects of outliers, and detection of alternative distributional differences can be achieved by coupling permutation inference with alternative linear model estimators. For example, it is well-known that estimates of the mean in linear model are extremely sensitive to even a single outlying value of the dependent variable compared to estimates of the median [7, 19]. Traditionally, linear modeling focused on estimating changes in the center of distributions (means or medians). However, quantile regression allows distributional changes to be estimated in all or any selected part of a distribution or responses, providing a more complete statistical picture that has relevance to many biological questions [6]...

  14. A Linear Bicharacteristic FDTD Method

    NASA Technical Reports Server (NTRS)

    Beggs, John H.

    2001-01-01

    The linear bicharacteristic scheme (LBS) was originally developed to improve unsteady solutions in computational acoustics and aeroacoustics [1]-[7]. It is a classical leapfrog algorithm, but is combined with upwind bias in the spatial derivatives. This approach preserves the time-reversibility of the leapfrog algorithm, which results in no dissipation, and it permits more flexibility by the ability to adopt a characteristic based method. The use of characteristic variables allows the LBS to treat the outer computational boundaries naturally using the exact compatibility equations. The LBS offers a central storage approach with lower dispersion than the Yee algorithm, plus it generalizes much easier to nonuniform grids. It has previously been applied to two and three-dimensional freespace electromagnetic propagation and scattering problems [3], [6], [7]. This paper extends the LBS to model lossy dielectric and magnetic materials. Results are presented for several one-dimensional model problems, and the FDTD algorithm is chosen as a convenient reference for comparison.

  15. Linear Coding of Voice Onset Time

    PubMed Central

    Frye, Richard E.; Fisher, Janet McGraw; Coty, Alexis; Zarella, Melissa; Liederman, Jacqueline; Halgren, Eric

    2008-01-01

    Voice-onset time (VOT) provides an important auditory cue for recognizing spoken consonant-vowel syllables. Although changes in the neuromagnetic response to consonant-vowel syllables with different VOT have been examined, such experiments have only manipulated VOT with respect to voicing. We utilized the characteristics of a previously developed asymmetric VOT continuum (Liederman et al., 2005) to determine if changes in the prominent M100 neuromagnetic response were linearly modulated by VOT. Eight right-handed English-speaking, normally developing participants performed a VOT discrimination task during a whole-head neuromagnetic recording. The M100 was identified in the gradiometers overlying the right and left temporal cortices and single dipoles were fit to each M100 waveform. A repeated measures analysis of variance with post-hoc contrast test for linear trend was used to determine whether characteristics of the M100 were linearly modulated by VOT. The morphology of the M100 gradiometer waveform and the peak latency of the dipole waveform were linearly modulated by VOT. This modulation was much greater in the left, as compared to the right, hemisphere. The M100 dipole moved in a linear fashion as VOT increased in both hemispheres, but along different axes in each hemisphere. This study suggests that VOT may linearly modulate characteristics of the M100, predominately in the left hemisphere, and suggests that the VOT of consonant-vowel syllables, instead of, or in addition to, voicing, should be examined in future experiments. PMID:17714009

  16. Linear ubiquitination in immunity.

    PubMed

    Shimizu, Yutaka; Taraborrelli, Lucia; Walczak, Henning

    2015-07-01

    Linear ubiquitination is a post-translational protein modification recently discovered to be crucial for innate and adaptive immune signaling. The function of linear ubiquitin chains is regulated at multiple levels: generation, recognition, and removal. These chains are generated by the linear ubiquitin chain assembly complex (LUBAC), the only known ubiquitin E3 capable of forming the linear ubiquitin linkage de novo. LUBAC is not only relevant for activation of nuclear factor-κB (NF-κB) and mitogen-activated protein kinases (MAPKs) in various signaling pathways, but importantly, it also regulates cell death downstream of immune receptors capable of inducing this response. Recognition of the linear ubiquitin linkage is specifically mediated by certain ubiquitin receptors, which is crucial for translation into the intended signaling outputs. LUBAC deficiency results in attenuated gene activation and increased cell death, causing pathologic conditions in both, mice, and humans. Removal of ubiquitin chains is mediated by deubiquitinases (DUBs). Two of them, OTULIN and CYLD, are constitutively associated with LUBAC. Here, we review the current knowledge on linear ubiquitination in immune signaling pathways and the biochemical mechanisms as to how linear polyubiquitin exerts its functions distinctly from those of other ubiquitin linkage types.

  17. Piecewise Linear Slope Estimation.

    PubMed

    Ingle, A N; Sethares, W A; Varghese, T; Bucklew, J A

    2014-11-01

    This paper presents a method for directly estimating slope values in a noisy piecewise linear function. By imposing a Markov structure on the sequence of slopes, piecewise linear fitting is posed as a maximum a posteriori estimation problem. A dynamic program efficiently solves this by traversing a linearly growing trellis. The alternating maximization algorithm (a kind of pseudo-EM method) is used to estimate the model parameters from data and its convergence behavior is analyzed. Ultrasound shear wave imaging is presented as a primary application. The algorithm is general enough for applicability in other fields, as suggested by an application to the estimation of shifts in financial interest rate data.

  18. Piecewise Linear Slope Estimation

    PubMed Central

    Sethares, W. A.; Bucklew, J. A.

    2015-01-01

    This paper presents a method for directly estimating slope values in a noisy piecewise linear function. By imposing a Markov structure on the sequence of slopes, piecewise linear fitting is posed as a maximum a posteriori estimation problem. A dynamic program efficiently solves this by traversing a linearly growing trellis. The alternating maximization algorithm (a kind of pseudo-EM method) is used to estimate the model parameters from data and its convergence behavior is analyzed. Ultrasound shear wave imaging is presented as a primary application. The algorithm is general enough for applicability in other fields, as suggested by an application to the estimation of shifts in financial interest rate data. PMID:26229417

  19. Optimal Linear Control.

    DTIC Science & Technology

    1979-12-01

    OPTIMAL LINEAR CONTROL C.A. HARVEY M.G. SAFO NOV G. STEIN J.C. DOYLE HONEYWELL SYSTEMS & RESEARCH CENTER j 2600 RIDGWAY PARKWAY j [ MINNEAPOLIS...RECIPIENT’S CAT ALC-’ W.IMIJUff’? * J~’ CR2 15-238-4F TP P EI)ŕll * (~ Optimal Linear Control ~iOGRPR UBA m a M.G Lnar o Con_ _ _ _ _ _ R PORT__ _ _ I RE...Characterizations of optimal linear controls have been derived, from which guides for selecting the structure of the control system and the weights in

  20. Linear magnetic bearing

    NASA Technical Reports Server (NTRS)

    Studer, P. A. (Inventor)

    1983-01-01

    A linear magnetic bearing system having electromagnetic vernier flux paths in shunt relation with permanent magnets, so that the vernier flux does not traverse the permanent magnet, is described. Novelty is believed to reside in providing a linear magnetic bearing having electromagnetic flux paths that bypass high reluctance permanent magnets. Particular novelty is believed to reside in providing a linear magnetic bearing with a pair of axially spaced elements having electromagnets for establishing vernier x and y axis control. The magnetic bearing system has possible use in connection with a long life reciprocating cryogenic refrigerator that may be used on the space shuttle.

  1. Spatio-temporal gait characteristics of level and vertical locomotion in a ground-dwelling and a climbing gecko.

    PubMed

    Zaaf, A; Van Damme, R; Herrel, A; Aerts, P

    2001-04-01

    The effects of incline (vertical versus horizontal) on spatio-temporal gait characteristics (stride and step length, frequency, duty factor, degree of sprawling) were measured over a range of speeds in a ground-dwelling (Eublepharis macularius) and a climbing (Gekko gecko) species of gecko. Surprisingly, the climbing species also performs very well when moving on the horizontal substratum. In the present experiments, climbing speeds ranged from 0.6 to 1.2 m s(-1), whereas speeds for level locomotion were between 0.6 and 1.8 m s(-1). In contrast, the vertical climbing capacities of the ground-dweller are limited (speeds below 0.1 m s(-1 )versus level speeds between 0.2 and 1.1 m s(-1)). In general, we demonstrate that very little adjustment in gait characteristics is made by either species when they are forced to move on their non-habitual substratum. Moreover, gait characteristics differ little between the species despite the clear differences in ecological niche. Higher level or climbing speeds are realized mainly (or exclusively in the case of level locomotion in G. gecko) by increasing stride frequency. Stride lengths and duty factors vary with speed in the ground-dweller, but not in the climbing species. Step length and the degree of sprawling are speed-independent (except for hind-limb sprawling in G. gecko on the level). It is argued that this common strategy suits climbing (fixed spatial variables, no floating phases) rather than level locomotion.

  2. Linear Boom Actuator

    NASA Technical Reports Server (NTRS)

    Koch, E. F.

    1985-01-01

    Actuator stabilizes spacecraft spin by varying length of support struts that hold spacecraft booms. Variation changes spin axis and controls wobble. Linear actuator controls spacecraft wobble applicable in rotating systems on Earth.

  3. Isolated linear blaschkoid psoriasis.

    PubMed

    Nasimi, M; Abedini, R; Azizpour, A; Nikoo, A

    2016-10-01

    Linear psoriasis (LPs) is considered a rare clinical presentation of psoriasis, which is characterized by linear erythematous and scaly lesions along the lines of Blaschko. We report the case of a 20-year-old man who presented with asymptomatic linear and S-shaped erythematous, scaly plaques on right side of his trunk. The plaques were arranged along the lines of Blaschko with a sharp demarcation at the midline. Histological examination of a skin biopsy confirmed the diagnosis of psoriasis. Topical calcipotriol and betamethasone dipropionate ointments were prescribed for 2 months. A good clinical improvement was achieved, with reduction in lesion thickness and scaling. In patients with linear erythematous and scaly plaques along the lines of Blaschko, the diagnosis of LPs should be kept in mind, especially in patients with asymptomatic lesions of late onset. © 2016 British Association of Dermatologists.

  4. Linear Resonance Cooler.

    DTIC Science & Technology

    1985-04-01

    for a Stirling cycle cryocooler . 26 * .*o .. * COMPRESSOR MOTOR FORCE VERSUS ROTOR AXIAL POSITION COMPRESSOR P-V DIAGRAM *COMPRESSOR MOTOR COMPRESSOR...potential. However, the limited test program has demonstrated the application of linear motor drive technology to a Stirling cycle cryocooler design. L...Ace-ss Ion& For flTIC TAB - TABLE OF CONTENTS TITLE IPAGE - 2. DETAILED DESIGN OF LINEAR RESONANCE CRYOCOOLER ......... 3 2.2 Expander

  5. Linear system theory

    NASA Technical Reports Server (NTRS)

    Callier, Frank M.; Desoer, Charles A.

    1991-01-01

    The aim of this book is to provide a systematic and rigorous access to the main topics of linear state-space system theory in both the continuous-time case and the discrete-time case; and the I/O description of linear systems. The main thrusts of the work are the analysis of system descriptions and derivations of their properties, LQ-optimal control, state feedback and state estimation, and MIMO unity-feedback systems.

  6. Linear system theory

    NASA Technical Reports Server (NTRS)

    Callier, Frank M.; Desoer, Charles A.

    1991-01-01

    The aim of this book is to provide a systematic and rigorous access to the main topics of linear state-space system theory in both the continuous-time case and the discrete-time case; and the I/O description of linear systems. The main thrusts of the work are the analysis of system descriptions and derivations of their properties, LQ-optimal control, state feedback and state estimation, and MIMO unity-feedback systems.

  7. Inertial Linear Actuators

    NASA Technical Reports Server (NTRS)

    Laughlin, Darren

    1995-01-01

    Inertial linear actuators developed to suppress residual accelerations of nominally stationary or steadily moving platforms. Function like long-stroke version of voice coil in conventional loudspeaker, with superimposed linear variable-differential transformer. Basic concept also applicable to suppression of vibrations of terrestrial platforms. For example, laboratory table equipped with such actuators plus suitable vibration sensors and control circuits made to vibrate much less in presence of seismic, vehicular, and other environmental vibrational disturbances.

  8. The cost of linearization

    NASA Astrophysics Data System (ADS)

    Morel, Danielle; Levy, William B.

    2006-03-01

    Information processing in the brain is metabolically expensive and energy usage by the different components of the nervous system is not well understood. In a continuing effort to explore the costs and constraints of information processing at the single neuron level, dendritic processes are being studied. More specifically, the role of various ion channel conductances is explored in terms of integrating dendritic excitatory synaptic input. Biophysical simulations of dendritic behavior show that the complexity of voltage-dependent, non-linear dendritic conductances can produce simplicity in the form of linear synaptic integration. Over increasing levels of synaptic activity, it is shown that two types of voltage-dependent conductances produce linearization over a limited range. This range is determined by the parameters defining the ion channel and the 'passive' properties of the dendrite. A persistent sodium and a transient A-type potassium channel were considered at steady-state transmembrane potentials in the vicinity of and hyperpolarized to the threshold for action potential initiation. The persistent sodium is seen to amplify and linearize the synaptic input over a short range of low synaptic activity. In contrast, the A-type potassium channel has a broader linearization range but tends to operate at higher levels of synaptic bombardment. Given equivalent 'passive' dendritic properties, the persistent sodium is found to be less costly than the A-type potassium in linearizing synaptic input.

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

    PubMed

    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. Superconducting linear actuator

    NASA Technical Reports Server (NTRS)

    Johnson, Bruce; Hockney, Richard

    1993-01-01

    Special actuators are needed to control the orientation of large structures in space-based precision pointing systems. Electromagnetic actuators that presently exist are too large in size and their bandwidth is too low. Hydraulic fluid actuation also presents problems for many space-based applications. Hydraulic oil can escape in space and contaminate the environment around the spacecraft. A research study was performed that selected an electrically-powered linear actuator that can be used to control the orientation of a large pointed structure. This research surveyed available products, analyzed the capabilities of conventional linear actuators, and designed a first-cut candidate superconducting linear actuator. The study first examined theoretical capabilities of electrical actuators and determined their problems with respect to the application and then determined if any presently available actuators or any modifications to available actuator designs would meet the required performance. The best actuator was then selected based on available design, modified design, or new design for this application. The last task was to proceed with a conceptual design. No commercially-available linear actuator or modification capable of meeting the specifications was found. A conventional moving-coil dc linear actuator would meet the specification, but the back-iron for this actuator would weigh approximately 12,000 lbs. A superconducting field coil, however, eliminates the need for back iron, resulting in an actuator weight of approximately 1000 lbs.

  11. Non-linear cord-rubber composites

    NASA Technical Reports Server (NTRS)

    Clark, S. K.; Dodge, R. N.

    1989-01-01

    A method is presented for calculating the stress-strain relations in a multi-layer composite made up of materials whose individual stress-strain characteristics are non-linear and possibly different. The method is applied to the case of asymmetric tubes in tension, and comparisons with experimentally measured data are given.

  12. Gait characteristics and spatio-temporal variables of climbing in bonobos (Pan paniscus).

    PubMed

    Schoonaert, Kirsten; D'Août, Kristiaan; Samuel, Diana; Talloen, Willem; Nauwelaerts, Sandra; Kivell, Tracy L; Aerts, Peter

    2016-11-01

    Although much is known about the terrestrial locomotion of great apes, their arboreal locomotion has been studied less extensively. This study investigates arboreal locomotion in bonobos (Pan paniscus), focusing on the gait characteristics and spatio-temporal variables associated with locomotion on a pole. These features are compared across different substrate inclinations (0°, 30°, 45°, 60°, and 90°), and horizontal quadrupedal walking is compared between an arboreal and a terrestrial substrate. Our results show greater variation in footfall patterns with increasing incline, resulting in more lateral gait sequences. During climbing on arboreal inclines, smaller steps and strides but higher stride frequencies and duty factors are found compared to horizontal arboreal walking. This may facilitate better balance control and dynamic stability on the arboreal substrate. We found no gradual change in spatio-temporal variables with increasing incline; instead, the results for all inclines were clustered together. Bonobos take larger strides at lower stride frequencies and lower duty factors on a horizontal arboreal substrate than on a flat terrestrial substrate. We suggest that these changes are the result of the better grip of the grasping feet on an arboreal substrate. Speed modulation of the spatio-temporal variables is similar across substrate inclinations and between substrate types, suggesting a comparable underlying motor control. Finally, we contrast these variables of arboreal inclined climbing with those of terrestrial bipedal locomotion, and briefly discuss the results with respect to the origin of habitual bipedalism. Am. J. Primatol. 78:1165-1177, 2016. © 2016 Wiley Periodicals, Inc.

  13. Improved Electrohydraulic Linear Actuators

    NASA Technical Reports Server (NTRS)

    Hamtil, James; Selinsky, T.

    2002-01-01

    A product line of improved electrohydraulic linear actuators has been developed. These actuators are designed especially for use in actuating valves in rocket-engine test facilities. They are also adaptable to similar industrial uses. The advantageous features of the improved electrohydraulic linear actuators are best described with respect to shortcomings of prior electrohydraulic linear actuators that the improved ones are intended to supplant. The shortcomings are the following: They perform unreliably and inconsistently as positioning devices. Their capabilities for end-of-stroke buffering (that is, deceleration to gentle stops at designated stopping positions) range from unsatisfactory to nonexistent, with consequent potential for inducing catastrophic failures. It takes long times to modify standard actuators to meet specifications, and the costs of such modifications are high. In the cases of actuators equipped with fail-safe shutdown systems, the stroking times of these systems cannot be adjusted in the field.

  14. Linear resonance cooler

    NASA Astrophysics Data System (ADS)

    1985-04-01

    The contract requires the incorporation of linear drive technology into a cryocooler design meeting the Specification for the US Army 1/4 Watt Common Module Cooler as closely as possible. The Resonant Cryocooler employs a concept using magnetic forces to linearly move dual opposed pistons in the compressor thus eliminating the use of rotary motors, crankshaft, greases and bearings. While not a requirement of the contract, the expander also employs a linear motor to control displacer stroking. This allows for electronic end stopping to mitigate microphonics problems. In addition, the ability to vary the waveform of the displacer motion and its phasing with respect to the compressor pressure wave form in order to optimize performance offers the potential for extending the operational life of the cooler.

  15. Linear encoding device

    NASA Technical Reports Server (NTRS)

    Leviton, Douglas B. (Inventor)

    1993-01-01

    A Linear Motion Encoding device for measuring the linear motion of a moving object is disclosed in which a light source is mounted on the moving object and a position sensitive detector such as an array photodetector is mounted on a nearby stationary object. The light source emits a light beam directed towards the array photodetector such that a light spot is created on the array. An analog-to-digital converter, connected to the array photodetector is used for reading the position of the spot on the array photodetector. A microprocessor and memory is connected to the analog-to-digital converter to hold and manipulate data provided by the analog-to-digital converter on the position of the spot and to compute the linear displacement of the moving object based upon the data from the analog-to-digital converter.

  16. Multiple Linear Regression

    NASA Astrophysics Data System (ADS)

    Grégoire, G.

    2014-12-01

    This chapter deals with the multiple linear regression. That is we investigate the situation where the mean of a variable depends linearly on a set of covariables. The noise is supposed to be gaussian. We develop the least squared method to get the parameter estimators and estimates of their precisions. This leads to design confidence intervals, prediction intervals, global tests, individual tests and more generally tests of submodels defined by linear constraints. Methods for model's choice and variables selection, measures of the quality of the fit, residuals study, diagnostic methods are presented. Finally identification of departures from the model's assumptions and the way to deal with these problems are addressed. A real data set is used to illustrate the methodology with software R. Note that this chapter is intended to serve as a guide for other regression methods, like logistic regression or AFT models and Cox regression.

  17. Cryogenic submicron linear actuator

    NASA Astrophysics Data System (ADS)

    Serrano, Javier; Moreno Raso, Javier; González de María, David; Argelaguet Vilaseca, Heribert; Lamensans, Mikel; López Justo, David; Sanz Puig, Violeta

    2010-07-01

    The Cryogenic Submicron Linear Actuator (CSA) is a medium range (+/-5 mm) submicron resolution linear actuator suitable to be used at cryogenic temperature (12K). The unit has been developed for fine positioning use. The unit is based on classic motor-gear concept with nut and screw; different materials and lubrications have been tested for the same design configuration to compare performances. Load capability is above 20N. This paper describes main design features, results of different lubrications tested, tested performances, and main lessons learned.

  18. Age- and gender-related changes in the temporal-spatial characteristics of forwards and backwards gaits.

    PubMed

    Laufer, Yocheved

    2003-01-01

    Backward walking is used increasingly as a rehabilitation technique for individuals with neurological and orthopaedic impairments. The purpose of the present study was to examine changes in the temporal-spatial characteristics of gain resulting from walking backwards as opposed to forwards, and to determine age and gender effects on these changes. Thirty young and 40 aged, independently functioning, subjects were asked to walk forwards and backwards across a computer-based walkway system, providing data on gait velocity, stride length, cadence, swing phase and double support phase. Subjects were divided into groups based on age (young and old) and gender, and each subject was tested under two walking conditions (forwards and backwards). Five temporal-spatial gait parameters were evaluated separately as a function of the three independent variables, with the walking condition repeated for each subject. Backwards ambulation is characterized by a slower velocity, shorter stride length and an increased double support phase in both young and older adults. These changes were significantly greater in the older subjects, among whom the swing phase was also decreased. Cadence, however, was not affected by direction of ambulation in either group. The female subjects had a shorter stride length in both movement directions, associated with reduced speed only in backwards ambulation. Older individuals are capable of walking backwards for short distances. However, changes in gait characteristics typical to the reversal of movement direction are accentuated with age. These effects must be considered when planning to use backwards ambulation as a rehabilitation technique for older individuals.

  19. Non-linear current-voltage characteristics of (La 0.5Eu 0.5) 0.7Pb 0.3MnO 3 single crystals: Possible manifestation of the internal heating of chargecarriers

    NASA Astrophysics Data System (ADS)

    Shaykhutdinov, K. A.; Popkov, S. I.; Balaev, D. A.; Semenov, S. V.; Bykov, A. A.; Dubrovskiy, A. A.; Sapronova, N. V.; Volkov, N. V.

    2010-12-01

    Temperature evolution of the current-voltage characteristics (CVCs) of a single-crystal lanthanum manganite (La 0.5Eu 0.5) 0.7Pb 0.3MnO 3 is investigated in a wide (up to 1 А) range of instrumental currents. Effects of a transport current and an applied electric field on the resistance of the material are studied in view of possible implementation of the charge ordering break in dielectric regions occurring due to phase separation in manganites. A negative differential resistance portion observed in the CVCs suggests the presence of a current switching effect. Below the temperature of the metal-dielectric transition in (La 0.5Eu 0.5) 0.7Pb 0.3MnO 3, the hysteresis is observed in the CVC. The detailed analysis of the internal sample heating on the basis of experimental data on thermal conductivity showed, however, that these CVC features can be explained within the concept of non-equilibrium heating of electron gas.

  20. Linear Collider Diagnostics

    SciTech Connect

    Ross, Marc

    2000-05-17

    Each major step toward higher energy particle accelerators relies on new technology. Linear colliders require beams of unprecedented brightness and stability. Instrumentation and control technology is the single most critical tool that enables linear colliders to extend the energy reach. In this paper the authors focus on the most challenging aspects of linear collider instrumentation systems. In the Next Linear Collider (NLC), high brightness multibunch e{sup +}/e{sup {minus}} beams, with I{sub {+-}} = 10{sup 12} particles/pulse and sigma{sub x,y} {approximately} 50 x 5 mu-m, originate in damping rings and are subsequently accelerated to several hundred GeV in 2 X-band 11,424 MHz linacs from which they emerge with typical sigma{sub x,y} {approximately} 7 x 1 mu-m. Following a high power collimation section the e{sup +}/e{sup {minus}} beams are focused to sigma{sub x,y} {approximately} 300 x 5 nm at the interaction point. In this paper they review the beam intensity, position and profile monitors (x,y,z), mechanical vibration sensing and stabilization systems, long baseline RF distribution systems and beam collimation hardware.

  1. Resistors Improve Ramp Linearity

    NASA Technical Reports Server (NTRS)

    Kleinberg, L. L.

    1982-01-01

    Simple modification to bootstrap ramp generator gives more linear output over longer sweep times. New circuit adds just two resistors, one of which is adjustable. Modification cancels nonlinearities due to variations in load on charging capacitor and due to changes in charging current as the voltage across capacitor increases.

  2. On Solving Linear Recurrences

    ERIC Educational Resources Information Center

    Dobbs, David E.

    2013-01-01

    A direct method is given for solving first-order linear recurrences with constant coefficients. The limiting value of that solution is studied as "n to infinity." This classroom note could serve as enrichment material for the typical introductory course on discrete mathematics that follows a calculus course.

  3. Piezoelectric linear actuator

    NASA Technical Reports Server (NTRS)

    Lehrer, S.

    1969-01-01

    Actuator exerts linear force that is controllable and reproducible to microinch tolerance. It is constructed for extremely accurate control of a valve but can also be used as a variable venturi meter, micropositioner, microthruster, and in fluidics and reaction-control systems.

  4. On Solving Linear Recurrences

    ERIC Educational Resources Information Center

    Dobbs, David E.

    2013-01-01

    A direct method is given for solving first-order linear recurrences with constant coefficients. The limiting value of that solution is studied as "n to infinity." This classroom note could serve as enrichment material for the typical introductory course on discrete mathematics that follows a calculus course.

  5. Curiosity Front View, Linearized

    NASA Image and Video Library

    2012-08-06

    This is a version of one of the first images taken by a front Hazard-Avoidance camera on NASA Curiosity rover. It was taken through a fisheye wide-angle lens but has been linearized so that the horizon looks flat rather than curved.

  6. Optical linear discriminant functions

    NASA Technical Reports Server (NTRS)

    Casasent, David; Song, Jian-Zhong

    1989-01-01

    The use of computer generated holograms to implement feature extraction operations has been achieved. The optical realization and use of multiple linear discriminant functions on a high-dimensionality feature space for large class pattern recognition is described and initial experimental results are provided.

  7. Improved Electrohydraulic Linear Actuators

    NASA Technical Reports Server (NTRS)

    Hamtil, James

    2004-01-01

    A product line of improved electrohydraulic linear actuators has been developed. These actuators are designed especially for use in actuating valves in rocket-engine test facilities. They are also adaptable to many industrial uses, such as steam turbines, process control valves, dampers, motion control, etc. The advantageous features of the improved electrohydraulic linear actuators are best described with respect to shortcomings of prior electrohydraulic linear actuators that the improved ones are intended to supplant. The flow of hydraulic fluid to the two ports of the actuator cylinder is controlled by a servo valve that is controlled by a signal from a servo amplifier that, in turn, receives an analog position-command signal (a current having a value between 4 and 20 mA) from a supervisory control system of the facility. As the position command changes, the servo valve shifts, causing a greater flow of hydraulic fluid to one side of the cylinder and thereby causing the actuator piston to move to extend or retract a piston rod from the actuator body. A linear variable differential transformer (LVDT) directly linked to the piston provides a position-feedback signal, which is compared with the position-command signal in the servo amplifier. When the position-feedback and position-command signals match, the servo valve moves to its null position, in which it holds the actuator piston at a steady position.

  8. METRIC GEOMETRY LINEAR MEASURE.

    ERIC Educational Resources Information Center

    FOLEY, JACK L.

    THIS BOOKLET, ONE OF A SERIES, HAS BEEN DEVELOPED FOR THE PROJECT, A PROGRAM FOR MATHEMATICALLY UNDERDEVELOPED PUPILS. A PROJECT TEAM, INCLUDING INSERVICE TEACHERS, IS BEING USED TO WRITE AND DEVELOP THE MATERIALS FOR THIS PROGRAM. THE MATERIALS DEVELOPED IN THIS BOOKLET INCLUDE (1) THE HISTORY AND MEANING OF LINEAR MEASURE, (2) FINDING THE…

  9. Linear motion valve

    NASA Technical Reports Server (NTRS)

    Chandler, J. A. (Inventor)

    1985-01-01

    The linear motion valve is described. The valve spool employs magnetically permeable rings, spaced apart axially, which engage a sealing assembly having magnetically permeable pole pieces in magnetic relationship with a magnet. The gap between the ring and the pole pieces is sealed with a ferrofluid. Depletion of the ferrofluid is minimized.

  10. Competitive inhibition can linearize dose-response and generate a linear rectifier.

    PubMed

    Savir, Yonatan; Tu, Benjamin P; Springer, Michael

    2015-09-23

    Many biological responses require a dynamic range that is larger than standard bi-molecular interactions allow, yet the also ability to remain off at low input. Here we mathematically show that an enzyme reaction system involving a combination of competitive inhibition, conservation of the total level of substrate and inhibitor, and positive feedback can behave like a linear rectifier-that is, a network motif with an input-output relationship that is linearly sensitive to substrate above a threshold but unresponsive below the threshold. We propose that the evolutionarily conserved yeast SAGA histone acetylation complex may possess the proper physiological response characteristics and molecular interactions needed to perform as a linear rectifier, and we suggest potential experiments to test this hypothesis. One implication of this work is that linear responses and linear rectifiers might be easier to evolve or synthetically construct than is currently appreciated.

  11. Competitive inhibition can linearize dose-response and generate a linear rectifier

    PubMed Central

    Savir, Yonatan; Tu, Benjamin P.; Springer, Michael

    2015-01-01

    Summary Many biological responses require a dynamic range that is larger than standard bi-molecular interactions allow, yet the also ability to remain off at low input. Here we mathematically show that an enzyme reaction system involving a combination of competitive inhibition, conservation of the total level of substrate and inhibitor, and positive feedback can behave like a linear rectifier—that is, a network motif with an input-output relationship that is linearly sensitive to substrate above a threshold but unresponsive below the threshold. We propose that the evolutionarily conserved yeast SAGA histone acetylation complex may possess the proper physiological response characteristics and molecular interactions needed to perform as a linear rectifier, and we suggest potential experiments to test this hypothesis. One implication of this work is that linear responses and linear rectifiers might be easier to evolve or synthetically construct than is currently appreciated. PMID:26495436

  12. Linear coding of voice onset time.

    PubMed

    Frye, Richard E; Fisher, Janet McGraw; Coty, Alexis; Zarella, Melissa; Liederman, Jacqueline; Halgren, Eric

    2007-09-01

    Voice onset time (VOT) provides an important auditory cue for recognizing spoken consonant-vowel syllables. Although changes in the neuromagnetic response to consonant-vowel syllables with different VOT have been examined, such experiments have only manipulated VOT with respect to voicing. We utilized the characteristics of a previously developed asymmetric VOT continuum [Liederman, J., Frye, R. E., McGraw Fisher, J., Greenwood, K., & Alexander, R. A temporally dynamic contextual effect that disrupts voice onset time discrimination of rapidly successive stimuli. Psychonomic Bulletin and Review, 12, 380-386, 2005] to determine if changes in the prominent M100 neuromagnetic response were linearly modulated by VOT. Eight right-handed, English-speaking, normally developing participants performed a VOT discrimination task during a whole-head neuromagnetic recording. The M100 was identified in the gradiometers overlying the right and left temporal cortices and single dipoles were fit to each M100 waveform. A repeated measures analysis of variance with post hoc contrast test for linear trend was used to determine whether characteristics of the M100 were linearly modulated by VOT. The morphology of the M100 gradiometer waveform and the peak latency of the dipole waveform were linearly modulated by VOT. This modulation was much greater in the left, as compared to the right, hemisphere. The M100 dipole moved in a linear fashion as VOT increased in both hemispheres, but along different axes in each hemisphere. This study suggests that VOT may linearly modulate characteristics of the M100, predominately in the left hemisphere, and suggests that the VOT of consonant-vowel syllables, instead of, or in addition to, voicing, should be examined in future experiments.

  13. Relativistic linear restoring force

    NASA Astrophysics Data System (ADS)

    Clark, D.; Franklin, J.; Mann, N.

    2012-09-01

    We consider two different forms for a relativistic version of a linear restoring force. The pair comes from taking Hooke’s law to be the force appearing on the right-hand side of the relativistic expressions: dp/dt or dp/dτ. Either formulation recovers Hooke’s law in the non-relativistic limit. In addition to these two forces, we introduce a form of retardation appropriate for the description of a linear (in displacement) force arising from the interaction of a pair of particles with a relativistic field. The procedure is akin to replacing Coulomb’s law in electromagnetism with a retarded form (the first correction in the full relativistic case). This retardation leads to the expected oscillation, but with amplitude growth in both its relativistic and non-relativistic incarnations.

  14. Reciprocating linear motor

    NASA Technical Reports Server (NTRS)

    Goldowsky, Michael P. (Inventor)

    1987-01-01

    A reciprocating linear motor is formed with a pair of ring-shaped permanent magnets having opposite radial polarizations, held axially apart by a nonmagnetic yoke, which serves as an axially displaceable armature assembly. A pair of annularly wound coils having axial lengths which differ from the axial lengths of the permanent magnets are serially coupled together in mutual opposition and positioned with an outer cylindrical core in axial symmetry about the armature assembly. One embodiment includes a second pair of annularly wound coils serially coupled together in mutual opposition and an inner cylindrical core positioned in axial symmetry inside the armature radially opposite to the first pair of coils. Application of a potential difference across a serial connection of the two pairs of coils creates a current flow perpendicular to the magnetic field created by the armature magnets, thereby causing limited linear displacement of the magnets relative to the coils.

  15. Non-linear osmosis

    PubMed Central

    Diamond, Jared M.

    1966-01-01

    1. The relation between osmotic gradient and rate of osmotic water flow has been measured in rabbit gall-bladder by a gravimetric procedure and by a rapid method based on streaming potentials. Streaming potentials were directly proportional to gravimetrically measured water fluxes. 2. As in many other tissues, water flow was found to vary with gradient in a markedly non-linear fashion. There was no consistent relation between the water permeability and either the direction or the rate of water flow. 3. Water flow in response to a given gradient decreased at higher osmolarities. The resistance to water flow increased linearly with osmolarity over the range 186-825 m-osM. 4. The resistance to water flow was the same when the gall-bladder separated any two bathing solutions with the same average osmolarity, regardless of the magnitude of the gradient. In other words, the rate of water flow is given by the expression (Om — Os)/[Ro′ + ½k′ (Om + Os)], where Ro′ and k′ are constants and Om and Os are the bathing solution osmolarities. 5. Of the theories advanced to explain non-linear osmosis in other tissues, flow-induced membrane deformations, unstirred layers, asymmetrical series-membrane effects, and non-osmotic effects of solutes could not explain the results. However, experimental measurements of water permeability as a function of osmolarity permitted quantitative reconstruction of the observed water flow—osmotic gradient curves. Hence non-linear osmosis in rabbit gall-bladder is due to a decrease in water permeability with increasing osmolarity. 6. The results suggest that aqueous channels in the cell membrane behave as osmometers, shrinking in concentrated solutions of impermeant molecules and thereby increasing membrane resistance to water flow. A mathematical formulation of such a membrane structure is offered. PMID:5945254

  16. Relativistic Linear Restoring Force

    ERIC Educational Resources Information Center

    Clark, D.; Franklin, J.; Mann, N.

    2012-01-01

    We consider two different forms for a relativistic version of a linear restoring force. The pair comes from taking Hooke's law to be the force appearing on the right-hand side of the relativistic expressions: d"p"/d"t" or d"p"/d["tau"]. Either formulation recovers Hooke's law in the non-relativistic limit. In addition to these two forces, we…

  17. Linear induction accelerator

    DOEpatents

    Buttram, M.T.; Ginn, J.W.

    1988-06-21

    A linear induction accelerator includes a plurality of adder cavities arranged in a series and provided in a structure which is evacuated so that a vacuum inductance is provided between each adder cavity and the structure. An energy storage system for the adder cavities includes a pulsed current source and a respective plurality of bipolar converting networks connected thereto. The bipolar high-voltage, high-repetition-rate square pulse train sets and resets the cavities. 4 figs.

  18. Combustion powered linear actuator

    DOEpatents

    Fischer, Gary J.

    2007-09-04

    The present invention provides robotic vehicles having wheeled and hopping mobilities that are capable of traversing (e.g. by hopping over) obstacles that are large in size relative to the robot and, are capable of operation in unpredictable terrain over long range. The present invention further provides combustion powered linear actuators, which can include latching mechanisms to facilitate pressurized fueling of the actuators, as can be used to provide wheeled vehicles with a hopping mobility.

  19. Linear abdominal trauma.

    PubMed

    Danto, L A; Wolfman, E F

    1976-03-01

    Three cases of blunt abdominal trauma are presented to exemplify the mechanism of trauma and the problems of diagnosis associated with any linear blow to the abdomen. The mechanisms of visceral injury are reviewed, and special attention is directed to the abdominal wall injury that can be present in these patients. This injury has special implications in directing the operative approach and repair. An unusual aortic occlusion is described which is peculiar to this type of injury.

  20. Electrostatic Linear Actuator

    NASA Technical Reports Server (NTRS)

    Collins, Earl R., Jr.; Curry, Kenneth C.

    1990-01-01

    Electrically charged helices attract or repel each other. Proposed electrostatic linear actuator made with intertwined dual helices, which holds charge-bearing surfaces. Dual-helix configuration provides relatively large unbroken facing charged surfaces (relatively large electrostatic force) within small volume. Inner helix slides axially in outer helix in response to voltages applied to conductors. Spiral form also makes components more rigid. Actuator conceived to have few moving parts and to be operable after long intervals of inactivity.

  1. Digital linear actuator

    SciTech Connect

    Birchard, W.G.

    1988-06-21

    A digital actuator is described comprising: (a) digital actuator cells, each digital actuator cell having an axis of expansion and first and second end surfaces; (b) third connecting means, each for connecting the first end surface of one digital actuator cell to the second end surface of an adjacent actuator cell, the plurality of digital actuator cells being connected in series by respective ones of the third connecting means to form the digital linear actuator.

  2. Relativistic Linear Restoring Force

    ERIC Educational Resources Information Center

    Clark, D.; Franklin, J.; Mann, N.

    2012-01-01

    We consider two different forms for a relativistic version of a linear restoring force. The pair comes from taking Hooke's law to be the force appearing on the right-hand side of the relativistic expressions: d"p"/d"t" or d"p"/d["tau"]. Either formulation recovers Hooke's law in the non-relativistic limit. In addition to these two forces, we…

  3. Spatiotemporal Characteristics of Freezing of Gait in Patients After Hypoxic-Ischemic Brain Injury

    PubMed Central

    Yoon, Seo Yeon; Lee, Sang Chul; Kim, Yong Wook

    2016-01-01

    Abstract The objective of this study was to investigate spatiotemporal characteristics with gait variability in patients with freezing of gait (FOG) after hypoxic-ischemic brain injury (HIBI). Eleven patients showing FOG after HIBI and 15 normal controls were consecutively enrolled. We performed gait analysis using a computerized gait system (VICON MX-T10 Motion Analysis System) and compared spatiotemporal characteristics and gait variability in both groups. Additionally, we performed correlation analysis to identify the gait parameters associated with severity of freezing, which we measured based on unified Parkinson disease Rating Scale subscore. Spatiotemporal characteristic of FOG patients showed increased stance time and double support phase and decreased swing time, single support phase, stride length, step length, and gait velocity compared with normal controls (P < 0.05). Besides baseline spatiotemporal characteristics, step time asymmetry and step length asymmetry were significantly increased in HIBI patients with FOG (P < 0.05). The coefficient of variation, which reflects the variability of each parameter, demonstrated increased cadence, stride time, swing time, single support phase, stride length, step length, and gait velocity variability in HIBI patients with FOG compared with normal controls (P < 0.05). Correlation analysis between FOG severity and spatiotemporal parameters revealed gait velocity, step length, and single support phase to be spatiotemporal parameters related to FOG severity (P < 0.05). Our findings suggest that bilateral gait coordination deterioration plays a considerable role for pathophysiology of FOG in HIBI patients. Additional studies with a larger number of subjects are needed to further investigate the neural mechanism of FOG after HIBI. PMID:27175696

  4. Linear accelerator thalamotomy.

    PubMed

    Frighetto, Leonardo; De Salles, Antonio; Wallace, Robert; Ford, Judith; Selch, Michael; Cabatan-Awang, Cynthia; Solberg, Timothy

    2004-08-01

    The capability of performing functional radiosurgery lesions in the brain using a dedicated linear accelerator (LINAC) have not yet been demonstrated. This study evaluates modern LINAC technology for the creation of a sharp, small and functionally eloquent lesion in the thalamus. Three patients underwent thalamotomy using a dedicated linear accelerator to radiosurgery, 2 females and 1 male, ages were 52, 53, and 73 years. Two patients presented with unilateral poststroke central pain and 1 with unilateral upper extremity pain secondary to metastatic infiltration of the brachial plexus. Maximal doses varied from 150 to 200 Gy, delivered by a 5-mm diameter collimator and 5 to 8 noncoplanar arcs evenly distributed. All patients gained substantial relief of their pain. They were able to reduce their medications and improve their activity levels. The patient with end-stage metastatic disease died of his malignancy 2 weeks after the treatment. One patient presented with recurrence of the pain 4 months after the treatment. No clinical complications were noticed. A dedicated linear accelerator is able to perform a precise and circumscribed lesion in the thalamus for pain control. Moreover, it proved to be safe, because no complications were observed. For patients using chronic anticoagulant therapy or with severe disabilities caused by cardiac, pulmonary or malignant diseases, this technique represents an alternative of treatment to radiofrequency thalamotomy.

  5. LINEAR SOLAR MODELS

    SciTech Connect

    Villante, F. L.; Ricci, B.

    2010-05-01

    We present a new approach to studying the properties of the Sun. We consider small variations of the physical and chemical properties of the Sun with respect to standard solar model predictions and we linearize the structure equations to relate them to the properties of the solar plasma. By assuming that the (variation of) present solar composition can be estimated from the (variation of) nuclear reaction rates and elemental diffusion efficiency in the present Sun, we obtain a linear system of ordinary differential equations which can be used to calculate the response of the Sun to an arbitrary modification of the input parameters (opacity, cross sections, etc.). This new approach is intended to be a complement to the traditional methods for solar model (SM) calculation and allows us to investigate in a more efficient and transparent way the role of parameters and assumptions in SM construction. We verify that these linear solar models recover the predictions of the traditional SMs with a high level of accuracy.

  6. Non-linear behavior of fiber composite laminates

    NASA Technical Reports Server (NTRS)

    Hashin, Z.; Bagchi, D.; Rosen, B. W.

    1974-01-01

    The non-linear behavior of fiber composite laminates which results from lamina non-linear characteristics was examined. The analysis uses a Ramberg-Osgood representation of the lamina transverse and shear stress strain curves in conjunction with deformation theory to describe the resultant laminate non-linear behavior. A laminate having an arbitrary number of oriented layers and subjected to a general state of membrane stress was treated. Parametric results and comparison with experimental data and prior theoretical results are presented.

  7. Split-Stirling-cycle displacer linear-electric drive

    NASA Technical Reports Server (NTRS)

    Ackermann, R. A.; Bhate, S. K.; Byrne, D. V.

    1983-01-01

    The retrofit of a 1/4-W split-Stirling cooler with a linear driven on the displacer was achieved and its performance characterized. The objective of this work was to demonstrate that a small linear motor could be designed to meet the existing envelope specifications of the cooler and that an electric linear drive on the displacer could improve the cooler's reliability and performance. The paper describes the characteristics of this motor and presents cooler test results.

  8. The Stanford Linear Collider

    SciTech Connect

    Seeman, J.T.

    1990-10-01

    The Stanford Linear Collider (SLC) has been in operation for several years with the initial and accelerator physics experiments just completed. A synopsis of these results is included. The second round of experiments is now under preparation to install the new physics detector (SLD) in Fall 1990 and to increase the luminosity significantly by late 1991. Collisions at high intensity and with polarized electrons are planned. Many beam dynamics and technological advances are in progress to meet these goals. 10 refs., 15 figs., 1 tab.

  9. Ultrasonic linear measurement system

    NASA Technical Reports Server (NTRS)

    Marshall, Scot H. (Inventor)

    1991-01-01

    An ultrasonic linear measurement system uses the travel time of surface waves along the perimeter of a three-dimensional curvilinear body to determine the perimeter of the curvilinear body. The system can also be used piece-wise to measure distances along plane surfaces. The system can be used to measure perimeters where use of laser light, optical means or steel tape would be extremely difficult, time consuming or impossible. It can also be used to determine discontinuities in surfaces of known perimeter or dimension.

  10. Lead screw linear actuator

    NASA Technical Reports Server (NTRS)

    Perkins, Gerald S. (Inventor)

    1980-01-01

    A linear actuator which can apply high forces is described, which includes a reciprocating rod having a threaded portion engaged by a nut that is directly coupled to the rotor of an electric motor. The nut is connected to the rotor in a manner that minimizes loading on the rotor, by the use of a coupling that transmits torque to the nut but permits it to shift axially and radially with respect to the rotor. The nut has a threaded hydrostatic bearing for engaging the threaded rod portion, with an oilcarrying groove in the nut being interrupted.

  11. Sparse linear programming subprogram

    SciTech Connect

    Hanson, R.J.; Hiebert, K.L.

    1981-12-01

    This report describes a subprogram, SPLP(), for solving linear programming problems. The package of subprogram units comprising SPLP() is written in Fortran 77. The subprogram SPLP() is intended for problems involving at most a few thousand constraints and variables. The subprograms are written to take advantage of sparsity in the constraint matrix. A very general problem statement is accepted by SPLP(). It allows upper, lower, or no bounds on the variables. Both the primal and dual solutions are returned as output parameters. The package has many optional features. Among them is the ability to save partial results and then use them to continue the computation at a later time.

  12. Reciprocating Linear Electric Motor

    NASA Technical Reports Server (NTRS)

    Goldowsky, M. P.

    1984-01-01

    Features include structural simplicity and good force/displacement characteristics. Reciprocating motor has simple, rugged construction, relatively low reciprocating weight, improved power delivery, and improved force control. Wear reduced by use of magnetic bearings. Intended to provide drivers for long-lived Stirling-cycle cryogenic refrigerators, concept has less exotic applications, such as fuel pumps.

  13. Reciprocating Linear Electric Motor

    NASA Technical Reports Server (NTRS)

    Goldowsky, M. P.

    1984-01-01

    Features include structural simplicity and good force/displacement characteristics. Reciprocating motor has simple, rugged construction, relatively low reciprocating weight, improved power delivery, and improved force control. Wear reduced by use of magnetic bearings. Intended to provide drivers for long-lived Stirling-cycle cryogenic refrigerators, concept has less exotic applications, such as fuel pumps.

  14. Induction linear accelerators

    NASA Astrophysics Data System (ADS)

    Birx, Daniel

    1992-03-01

    Among the family of particle accelerators, the Induction Linear Accelerator is the best suited for the acceleration of high current electron beams. Because the electromagnetic radiation used to accelerate the electron beam is not stored in the cavities but is supplied by transmission lines during the beam pulse it is possible to utilize very low Q (typically<10) structures and very large beam pipes. This combination increases the beam breakup limited maximum currents to of order kiloamperes. The micropulse lengths of these machines are measured in 10's of nanoseconds and duty factors as high as 10-4 have been achieved. Until recently the major problem with these machines has been associated with the pulse power drive. Beam currents of kiloamperes and accelerating potentials of megavolts require peak power drives of gigawatts since no energy is stored in the structure. The marriage of liner accelerator technology and nonlinear magnetic compressors has produced some unique capabilities. It now appears possible to produce electron beams with average currents measured in amperes, peak currents in kiloamperes and gradients exceeding 1 MeV/meter, with power efficiencies approaching 50%. The nonlinear magnetic compression technology has replaced the spark gap drivers used on earlier accelerators with state-of-the-art all-solid-state SCR commutated compression chains. The reliability of these machines is now approaching 1010 shot MTBF. In the following paper we will briefly review the historical development of induction linear accelerators and then discuss the design considerations.

  15. Linearly Forced Isotropic Turbulence

    NASA Technical Reports Server (NTRS)

    Lundgren, T. S.

    2003-01-01

    Stationary isotropic turbulence is often studied numerically by adding a forcing term to the Navier-Stokes equation. This is usually done for the purpose of achieving higher Reynolds number and longer statistics than is possible for isotropic decaying turbulence. It is generally accepted that forcing the Navier-Stokes equation at low wave number does not influence the small scale statistics of the flow provided that there is wide separation between the largest and smallest scales. It will be shown, however, that the spectral width of the forcing has a noticeable effect on inertial range statistics. A case will be made here for using a broader form of forcing in order to compare computed isotropic stationary turbulence with (decaying) grid turbulence. It is shown that using a forcing function which is directly proportional to the velocity has physical meaning and gives results which are closer to both homogeneous and non-homogeneous turbulence. Section 1 presents a four part series of motivations for linear forcing. Section 2 puts linear forcing to a numerical test with a pseudospectral computation.

  16. Sharpness for C1 linearization of planar hyperbolic diffeomorphisms

    NASA Astrophysics Data System (ADS)

    Zhang, Wenmeng; Zhang, Weinian

    2014-12-01

    C1 linearization preserves smooth dynamical behaviors and distinguishes qualitative properties in characteristic directions. Planar hyperbolic diffeomorphisms are the most elementary ones of representatively technical difficulties in the study of C1 linearization. In the Poincaré domain (both eigenvalues inside the unit circle S1) a lower bound α0 was given such that C smoothness with α0<α≤1 admits C1 linearization. Our first purpose of this paper is to prove the sharpness of α0 and give a weaker linearization for α≤α0. In the Siegel domain (one eigenvalue inside S1 but the other outside S1) it is known that C smoothness admits C1 linearization for all α∈(0,1]. The second purpose is to prove that the C1 linearization is actually a C linearization and give sharp estimates for β.

  17. Comet LINEAR Splits Further

    NASA Astrophysics Data System (ADS)

    2001-05-01

    Third Nucleus Observed with the VLT Summary New images from the VLT show that one of the two nuclei of Comet LINEAR (C/2001 A2), now about 100 million km from the Earth, has just split into at least two pieces . The three fragments are now moving through space in nearly parallel orbits while they slowly drift apart. This comet will pass through its perihelion (nearest point to the Sun) on May 25, 2001, at a distance of about 116 million kilometres. It has brightened considerably due to the splitting of its "dirty snowball" nucleus and can now be seen with the unaided eye by observers in the southern hemisphere as a faint object in the southern constellation of Lepus (The Hare). PR Photo 18a/01 : Three nuclei of Comet LINEAR . PR Photo 18b/01 : The break-up of Comet LINEAR (false-colour). Comet LINEAR splits and brightens ESO PR Photo 18a/01 ESO PR Photo 18a/01 [Preview - JPEG: 400 x 438 pix - 55k] [Normal - JPEG: 800 x 875 pix - 136k] ESO PR Photo 18b/01 ESO PR Photo 18b/01 [Preview - JPEG: 367 x 400 pix - 112k] [Normal - JPEG: 734 x 800 pix - 272k] Caption : ESO PR Photo 18a/01 shows the three nuclei of Comet LINEAR (C/2001 A2). It is a reproduction of a 1-min exposure in red light, obtained in the early evening of May 16, 2001, with the 8.2-m VLT YEPUN (UT4) telescope at Paranal. ESO PR Photo 18b/01 shows the same image, but in a false-colour rendering for more clarity. The cometary fragment "B" (right) has split into "B1" and "B2" (separation about 1 arcsec, or 500 km) while fragment "A" (upper left) is considerably fainter. Technical information about these photos is available below. Comet LINEAR was discovered on January 3, 2001, and designated by the International Astronomical Union (IAU) as C/2001 A2 (see IAU Circular 7564 [1]). Six weeks ago, it was suddenly observed to brighten (IAUC 7605 [1]). Amateurs all over the world saw the comparatively faint comet reaching naked-eye magnitude and soon thereafter, observations with professional telescopes indicated

  18. Cognitive tasks during walking affect cerebral blood flow signal features in middle cerebral arteries and their correlation to gait characteristics.

    PubMed

    Gatouillat, Arthur; Bleton, Héloïse; VanSwearingen, Jessie; Perera, Subashan; Thompson, Scott; Smith, Traci; Sejdić, Ervin

    2015-09-26

    Gait is a complex process involving both cognitive and sensory ability and is strongly impacted by the environment. In this paper, we propose to study of the impact of a cognitive task during gait on the cerebral blood flow velocity, the blood flow signal features and the correlation of gait and blood flow features through a dual task methodology. Both cerebral blood flow velocity and gait characteristics of eleven participants with no history of brain or gait conditions were recorded using transcranial Doppler on mid-cerebral artery while on a treadmill. The cognitive task was induced by a backward counting starting from 10,000 with decrement of 7. Central blood flow velocity raw and envelope features were extracted in both time, frequency and time-scale domain; information-theoretic metrics were also extracted and statistical significances were inspected. A similar feature extraction was performed on the stride interval signal. Statistical differences between the cognitive and baseline trials, between the left and right mid-cerebral arteries signals and the impact of the antropometric variables where studied using linear mixed models. No statistical differences were found between the left and right mid-cerebral arteries flows or the baseline and cognitive state gait features, while statistical differences for specific features were measured between cognitive and baseline states. These statistical differences found between the baseline and cognitive states show that cognitive process has an impact on the cerebral activity during walking. The state was found to have an impact on the correlation between the gait and blood flow features.

  19. Meaningful FM transmitter modulation linearity measurements

    NASA Astrophysics Data System (ADS)

    Jeske, H. O.

    The IM products in the demodulator output in this case are due only to the demodulator's transfer characteristics. IM product levels of the test system greater than 60 dB below the simultaneous modulation level of +300 kHz each by 400 and 450 kHz tones are obtained at Sandia Laboratories. The use of two-tone IM tests for the evaluation and specification of FM transmitter modulation linearity is strongly recommended.

  20. Linear polarimetric study of SN 1987A

    NASA Astrophysics Data System (ADS)

    Clocchiatti, A.; Mendez, M.; Benvenuto, O.; Feinstein, C.; Marraco, H.

    Linear polarization measurements of SN 1987A were made with 0.83-m and a 2.15-m telescopes. It is found that the polarization decreases with time (Benvenuto et al., 1987) Because the polarization produced by the interstellar matter is time independent and the wavelength dependence of the observed polarization is far from the interstellar relation (Serkowski et al., 1975) it is suggested that the time dependent characteristic is due to an intrinsic polarization vector.