WorldWideScience

Sample records for jump countermovement jump

  1. Sex Differences in Countermovement Jump Phase Characteristics

    Directory of Open Access Journals (Sweden)

    John J. McMahon

    2017-01-01

    Full Text Available The countermovement jump (CMJ is commonly used to explore sex differences in neuromuscular function, but previous studies have only reported gross CMJ measures or have partly examined CMJ phase characteristics. The purpose of this study was to explore differences in CMJ phase characteristics between male and female athletes by comparing the force-, power-, velocity-, and displacement-time curves throughout the entire CMJ, in addition to gross measures. Fourteen men and fourteen women performed three CMJs on a force platform from which a range of kinetic and kinematic variables were calculated via forward dynamics. Jump height (JH, reactive strength index modified, relative peak concentric power, and eccentric and concentric displacement, velocity, and relative impulse were all greater for men (g = 0.58–1.79. Relative force-time curves were similar between sexes, but relative power-, velocity-, and displacement-time curves were greater for men at 90%–95% (immediately before and after peak power, 47%–54% (start of eccentric phase and 85%–100% (latter half of concentric phase, and 65%–87% (bottom of countermovement and initial concentric phase of normalized jump time, respectively. The CMJ distinguished between sexes, with men demonstrating greater JH through applying a larger concentric impulse and, thus, achieving greater velocity throughout most of the concentric phase, including take-off.

  2. Choice of jumping strategy in two standard jumps, squat and countermovement jump--effect of training background or inherited preference?

    DEFF Research Database (Denmark)

    Ravn, Susanne; Voigt, M; Simonsen, Erik Bruun

    1999-01-01

    Six male subjects, three professional ballet dancers and three elite volleyball players, performed maximal vertical jumps from 1) a static preparatory position (squat jump), 2) starting with a countermovement (countermovement jump) and 3) a specific jump for ballet and for volleyball, respectively....... The jumps were recorded on highspeed film (500 Hz) combined with registration of ground reaction forces, and net joint moments were calculated by inverse dynamics. The purpose was to investigate the choice of strategy in two standard jumps, squat jump and countermovement jump. The volleyball jump...... was performed with a sequential strategy and the ballet jump was performed with a simultaneous strategy. In the two standard jumps, the choice of strategy was individual and not related to training background. This was additionally confirmed in a test of seven ballet dancers and seven volleyball players....

  3. LOAD THAT MAXIMIZES POWER OUTPUT IN COUNTERMOVEMENT JUMP

    Directory of Open Access Journals (Sweden)

    Pedro Jimenez-Reyes

    2016-02-01

    Full Text Available ABSTRACT Introduction: One of the main problems faced by strength and conditioning coaches is the issue of how to objectively quantify and monitor the actual training load undertaken by athletes in order to maximize performance. It is well known that performance of explosive sports activities is largely determined by mechanical power. Objective: This study analysed the height at which maximal power output is generated and the corresponding load with which is achieved in a group of male-trained track and field athletes in the test of countermovement jump (CMJ with extra loads (CMJEL. Methods: Fifty national level male athletes in sprinting and jumping performed a CMJ test with increasing loads up to a height of 16 cm. The relative load that maximized the mechanical power output (Pmax was determined using a force platform and lineal encoder synchronization and estimating the power by peak power, average power and flight time in CMJ. Results: The load at which the power output no longer existed was at a height of 19.9 ± 2.35, referring to a 99.1 ± 1% of the maximum power output. The load that maximizes power output in all cases has been the load with which an athlete jump a height of approximately 20 cm. Conclusion: These results highlight the importance of considering the height achieved in CMJ with extra load instead of power because maximum power is always attained with the same height. We advise for the preferential use of the height achieved in CMJEL test, since it seems to be a valid indicative of an individual's actual neuromuscular potential providing a valid information for coaches and trainers when assessing the performance status of our athletes and to quantify and monitor training loads, measuring only the height of the jump in the exercise of CMJEL.

  4. Body size and countermovement depth confound relationship between muscle power output and jumping performance

    Science.gov (United States)

    Markovic, Srdjan; Dragan, Mirkov; Nedeljkovic, Aleksandar; Jaric, Slobodan

    2013-01-01

    A number of studies based on maximum vertical jumps have presumed that the maximum jump height reveals the maximum power of lower limb muscles, as well as the tested muscle power output predicts the jumping performance. The objective of the study was to test the hypothesis that both the body size and countermovement depth confound the relationship between the muscle power output and performance of maximum vertical jumps. Sixty young and physically active males were tested on the maximum countermovement (CMJ) and squat jumps (SJ). The jumping performance (Hmax), peak (Ppeak) and the average power output (Pavg) during the concentric phase, countermovement depth (only in CMJ) and body mass as an index of body size were assessed. To assess the power-performance relationship, the correlations between Hmax with both Ppeak and Pavg were calculated without and with controlling for the effects of body mass, as well as for the countermovement depth. The results revealed moderate power-performance relationships (range 0.55jumps. When controlled for body mass, the same values were markedly higher (0.61jumps). When controlled for both the body mass and countermovement depth, CMJ revealed r=0.88 and r=0.77 for Ppeak and Pavg, respectively. Both jumps revealed stronger relationships with Ppeak than with Pavg (p<0.05) when controlled for either body mass or both body mass and countermovement depth. We conclude that both body size (in CMJ and SJ) and countermovement depth (in CMJ) confound the relationship between the muscle power output with the performance of maximum vertical jumps. Regarding routine assessments of muscle power from jumping performance and vice versa, the use of CMJ is recommended, while Ppeak, rather than Pavg, should be the variable of choice. PMID:24280557

  5. Countermovement strategy changes with vertical jump height to accommodate feasible force constraints.

    Science.gov (United States)

    Kim, Seyoung; Park, Sukyung; Choi, Sangkyu

    2014-09-22

    In this study, we developed a curve-fit model of countermovement dynamics and examined whether the characteristics of a countermovement jump can be quantified using the model parameter and its scaling; we expected that the model-based analysis would facilitate an understanding of the basic mechanisms of force reduction and propulsion with a simplified framework of the center of mass (CoM) mechanics. Ten healthy young subjects jumped straight up to five different levels ranging from approximately 10% to 35% of their body heights. The kinematic and kinetic data on the CoM were measured using a force plate system synchronized with motion capture cameras. All subjects generated larger vertical forces compared with their body weights from the countermovement and sufficiently lowered their CoM position to support the work performed by push-off as the vertical elevations became more challenging. The model simulation reasonably reproduced the trajectories of vertical force during the countermovement, and the model parameters were replaced by linear and polynomial regression functions in terms of the vertical jump height. Gradual scaling trends of the individual model parameters were observed as a function of the vertical jump height with different degrees of scaling, depending on the subject. The results imply that the subjects may be aware of the jumping dynamics when subjected to various vertical jump heights and may select their countermovement strategies to effectively accommodate biomechanical constraints, i.e., limited force generation for the standing vertical jump. Copyright © 2014 Elsevier Ltd. All rights reserved.

  6. The Effects of Arms and Countermovement on Vertical Jumping

    Science.gov (United States)

    1989-04-28

    result from potcntiation, during the oertilc stretching phase, of myoelectric activity during the subsequent concentric contraction phase. However...The output signal representing vertical ground reaction force (VGRF) was fed into a Hewlett-Packard (Lexington MA) 310 microcomputer via an Infotek...BOSCO, C., and J.T. VIITASALO. Potentiation of myoelectric activity of human muscles in vertical jumps. Electromyogr clin Neurophysiol 22:549-562, 1982

  7. Low-intensity cycling affects the muscle activation pattern of consequent countermovement jumps.

    Science.gov (United States)

    Marquez, Gonzalo J; Mon, Javier; Acero, Rafael M; Sanchez, Jose A; Fernandez-del-Olmo, Miguel

    2009-08-01

    Players (eg, basketball, soccer, and football) often use a static bicycle during a game to maintain warming. However, the effectiveness of this procedure has not been addressed in the literature. Thus, it remains unknown whether low-intensity cycling movement can affect explosive movement performance. In this study, 10 male subjects performed countermovement jumps before and after a 15-minutes cycling bout at 35% of their maximal power output. Three sessions were tested for 3 different cadences of cycling: freely chosen cadence, 20% lower than freely chosen cadence (FCC-20%), and 20% higher than freely chosen cadence (FCC+20%). Jump height, kinematics, and electromyogram were recorded simultaneously during the countermovement jumps. The results showed a significant decreasing in the height of countermovement jump after cycling at freely chosen cadence and FCC-20% (p = 0.03 and p = 0.04, respectively), but not for FCC+20% cadences. The electromyographic parameters suggest that changes in the countermovement jump after cycling can be attributed to alteration of the pattern of activation and may be modulated by the preceding cycling cadence. Our study indicates that to avoid a possible negative effect of the cycling in the subsequent explosive movements, a cadence 20% higher than the preferred cadence must be used.

  8. The MARS for squat, countermovement, and standing long jump performance analyses: are measures reproducible?

    Science.gov (United States)

    Hébert-Losier, Kim; Beaven, C Martyn

    2014-07-01

    Jump tests are often used to assess the effect of interventions because their outcomes are reported valid indicators of functional performance. In this study, we examined the reproducibility of performance parameters from 3 common jump tests obtained using the commercially available Kistler Measurement, Analysis and Reporting Software (MARS). On 2 separate days, 32 men performed 3 squat jumps (SJs), 3 countermovement jumps (CMJs), and 3 standing long jumps (LJs) on a Kistler force-plate. On both days, the performance measures from the best jump of each series were extracted using the MARS. Changes in the mean scores, intraclass correlation coefficients (ICCs), and coefficients of variations (CVs) were computed to quantify the between-day reproducibility of each parameter. Moreover, the reproducibility quantifiers specific to the 3 separate jumps were compared using nonparametric tests. Overall, an acceptable between-day reproducibility (mean ± SD, ICC, and CV) of SJ (0.88 ± 0.06 and 7.1 ± 3.8%), CMJ (0.84 ± 0.17 and 5.9 ± 4.1%), and LJ (0.80 ± 0.13 and 8.1 ± 4.1%) measures was found using the MARS, except for parameters directly relating to the rate of force development (i.e., time to maximal force) and change in momentum during countermovement (i.e., negative force impulse) where reproducibility was lower. A greater proportion of the performance measures from the standing LJs had low ICCs and/or high CVs values most likely owing to the complex nature of the LJ test. Practitioners and researchers can use most of the jump test parameters from the MARS with confidence to quantify changes in the functional ability of individuals over time, except for those relating to the rate of force development or change in momentum during countermovement phases of jumps.

  9. Acute effects of countermovement jumping and sprinting on shot put performance.

    Science.gov (United States)

    Terzis, Gerasimos; Karampatsos, Giorgos; Kyriazis, Thomas; Kavouras, Stavros A; Georgiadis, Giorgos

    2012-03-01

    The purpose of this study was to investigate the acute effects of countermovement jumping and sprinting on shot put performance in experienced shot putters. Ten shot putters (best performance 13.16-20.36 m) participated in the study. After a standard warm-up including jogging, stretching, and 4-6 submaximal puts, they performed 3 shot put attempts with maximum effort, separated with 1.5-minute interval. Three minutes later, they performed 3 maximal consecutive countermovement jumps (CMJs). Immediately after jumping, they performed 3 shot put attempts with maximum effort, separated with a 1.5-minute interval. One week later, they carried out a similar protocol, at similar external conditions, but they performed a bout of 20-m sprinting instead of the CMJs, to potentiate shot put performance. Muscular strength (1 repetition maximum in squat, snatch, bench press, incline bench press) and body composition (dual x-ray absorptiometry) were measured during the same training period (±10 days from the jumping and sprinting protocols). Shot put performance was significantly increased after the CMJs (15.45 ± 2.36 vs. 15.85 ± 2.41 m, p = 0.0003). Similarly, shot put performance was significantly increased after sprinting (15.34 ± 2.41 vs. 15.90 ± 2.46 m, p = 0.0007). The increase in performance after sprinting was significantly higher compared with the increase after jumping (2.64 ± 1.59 vs. 3.74 ± 1.88%, p = 0.02). In conclusion, the results of this study indicate that a standard warm-up protocol followed by 3 maximal bouts of shot put and either 3 consecutive countermovement jumps or a bout of 20-m sprinting induce an acute increase in shot put performance in experienced shot putters.

  10. Effect of acute fatigue and training adaptation on countermovement jump performance in elite snowboard cross athletes.

    Science.gov (United States)

    Gathercole, Rob J; Stellingwerff, Trent; Sporer, Ben C

    2015-01-01

    Countermovement jump performance was examined in response to acute neuromuscular (NM) fatigue (study I) and chronic training (study II) in elite snowboard cross (SBX) athletes, through both typical (countermovement jump [CMJ]-TYP) and alternative (CMJ-ALT) CMJ variables. Seven (4 men and 3 women) elite (Olympic-level) SBX athletes participated in study I, and 5 of the same athletes (2 men and 3 women) participated in study II. Countermovement jump variables relating to force, velocity, power, and time were measured during both eccentric and concentric jump phases, with CMJ-TYP variables reflecting CMJ output and CMJ-ALT variables reflecting CMJ mechanics. In study I, CMJ performance was assessed before and after a fatiguing lower-body exercise protocol, and in study II, CMJ performance was examined before and after a 19-week structured training block. Meaningful differences in CMJ performance were examined using the magnitude of change (effect sizes [ES]) for group and individual changes. Acute fatigue decreased peak force and eccentric function, while the duration of the jump increased. The structured training block increased peak force and eccentric function, while jump duration markedly decreased. In both study I and study II, the largest ES were associated with CMJ-ALT variables. The CMJ test seems a suitable monitoring tool in elite SBX athletes for the detection of both acute fatigue and training-adaptation. Compared with CMJ output, CMJ mechanics exhibits more marked and divergent changes after both acute NM fatigue and a structured training block. CMJ-ALT variables should therefore be incorporated into CMJ analysis.

  11. Is the effect of a countermovement on jump height due to active state development?

    Science.gov (United States)

    Bobbert, Maarten F; Casius, L J Richard

    2005-03-01

    To investigate whether the difference in jump height between countermovement jumps (CMJ) and squat jumps (SJ) could be explained by a difference in active state during propulsion. Simulations were performed with a model of the human musculoskeletal system comprising four body segments and six muscles. The model's only input was STIM, the stimulation of muscles, which could be switched "off" or "on." After switching "on," STIM increased to its maximum at a fixed rate of change (dSTIM/dt). For various values of dSTIM/dt, stimulation switch times were optimized to produce a maximum height CMJ. From this CMJ, the configuration at the lowest height of the center of gravity (CG) was selected and used as static starting configuration for simulation of SJ. Next, STIM-switch times were optimized to find the maximum height SJ. Simulated CMJ and SJ closely resembled jumps of human subjects. Maximum jump height of the model was greater in CMJ than in SJ, with the difference ranging from 0.4 cm at infinitely high dSTIM/dt to about 2.5 cm at the lowest dSTIM/dt investigated. The greater jump height in CMJ was due to a greater work output of the hip extensor muscles. These muscles could produce more force and work over the first 30% of their shortening range in CMJ, due to the fact that they had a higher active state in CMJ than in SJ. The greater jump height in CMJ than in SJ could be explained by the fact that in CMJ active state developed during the preparatory countermovement, whereas in SJ it inevitably developed during the propulsion phase, so that the muscles could produce more force and work during shortening in CMJ.

  12. Contribution of non-extensor muscles of the leg to maximal-effort countermovement jumping

    OpenAIRE

    Yoshioka Shinsuke; Komura Taku; Nagano Akinori; Fukashiro Senshi

    2005-01-01

    Abstract Background The purpose of this study was to determine the effects of non-extensor muscles of the leg (i.e., muscles whose primary function is not leg extension) on the kinematics and kinetics of human maximal-effort countermovement jumping. Although it is difficult to address this type of question through experimental procedures, the methodology of computer simulation can be a powerful tool. Methods A skeletal model that has nine rigid body segments and twenty degrees of freedom was ...

  13. Acute fatigue effects on ground reaction force of lower limbs during countermovement jumps

    OpenAIRE

    Carlos Gabriel Fábrica; González,Paula V.; Jefferson Fagundes Loss

    2013-01-01

    Parameters associated with the performance of countermovement jumps were identified from vertical ground reaction force recordings during fatigue and resting conditions. Fourteen variables were defined, dividing the vertical ground reaction force into negative and positive external working times and times in which the vertical ground reaction force values were lower and higher than the participant's body weight. We attempted to explain parameter variations by considering the relationship betw...

  14. Acute fatigue effects on ground reaction force of lower limbs during countermovement jumps

    Directory of Open Access Journals (Sweden)

    Carlos Gabriel Fábrica

    2013-12-01

    Full Text Available Parameters associated with the performance of countermovement jumps were identified from vertical ground reaction force recordings during fatigue and resting conditions. Fourteen variables were defined, dividing the vertical ground reaction force into negative and positive external working times and times in which the vertical ground reaction force values were lower and higher than the participant's body weight. We attempted to explain parameter variations by considering the relationship between the set of contractile and elastic components of the lower limbs. We determined that jumping performance is based on impulsion optimization and not on instantaneous ground reaction force value: the time in which the ground reaction force was lower than the body weight, and negative external work time was lower under fatigue. The results suggest that, during fatigue, there is less contribution from elastic energy and from overall active state. However, the participation of contractile elements could partially compensate for the worsening of jumping performance.

  15. Kinetic and Kinematic Analysis for Assessing the Differences in Countermovement Jump Performance in Rugby Players.

    Science.gov (United States)

    Floría, Pablo; Gómez-Landero, Luis A; Suárez-Arrones, Luis; Harrison, Andrew J

    2016-09-01

    Floría, P, Gómez-Landero, LA, Suárez-Arrones, L, and Harrison, AJ. Kinetic and kinematic analysis for assessing the differences in countermovement jump performance in rugby players. J Strength Cond Res 30(9): 2533-2539, 2016-The aim of this study was to ascertain the differences in kinetic and kinematic profiles between better and poorer performers of the vertical jump within a homogeneous group of trained adults. Fifty rugby players were divided into low scoring (LOW) and high scoring (HIGH) groups based on their performance in the vertical jump. The force, velocity, displacement, and rate of force development (RFD)-time curves were analyzed to determine the differences between groups. The analysis of the data showed differences in all the patterns of the ensemble mean curves of the HIGH and LOW groups. During the eccentric phase, the differences in the HIGH group with respect to the LOW group were lower crouch position, higher downward velocity, and higher force and RFD during the braking of the downward movement. During the concentric phase, the HIGH group achieved higher upward velocity, higher force at the end of phase, and a higher position at takeoff. The higher jump performances seem to be related to a more effective stretch-shortening cycle function that is characterized by a deeper and faster countermovement with higher eccentric forces being applied to decelerate the downward movement leading to enhanced force generation during the concentric phase.

  16. Specific warm-up exercise is the best for vertical countermovement jump in young volleyball players

    Directory of Open Access Journals (Sweden)

    Fernando Nazário de Rezende

    Full Text Available Abstract We evaluated the effect of performing various distinct warm-up exercises on vertical countermovement jump (VCMJ performance. Eight volleyball players (age 15.4 ± 0.5 yrs performed five different warm-up activities (in a counterbalanced, randomized crossover study over five days, at 24-h intervals: stretching (4 × 30 s, 30 s between sets, cycloergometer (5 min at 50 W + 5 min at 100 W, resistance exercise (leg press 45°, 3 × 5 repetitions maximum, 3-min pause between sets, specific vertical jumping (4 × 10 VCMJ, 2-min pause between sets, and no warm-up at all (control condition. Beginning 3 min after their warm-up, the players performed 3 attempts (at intervals of 3 min of VCMJ (on a contact carpet, and each player's best jump was considered in the analysis. All warm-up activities presented higher VCMJ performance (p< 0.05 than the control condition, with the exception of stretching. Vertical jumping revealed a large effect size(0.8 than other interventions. We conclude that in practical terms, vertical jumps are the best warm-up exercise (when applied by itself to acutely improve VCMJ performance in volleyball players, but that other exercises can make a complementary contribution.

  17. The 2.5-minute loaded repeated jump test: evaluating anaerobic capacity in alpine ski racers with loaded countermovement jumps.

    Science.gov (United States)

    Patterson, Carson; Raschner, Christian; Platzer, Hans-Peter

    2014-09-01

    The purposes of this study were to test the reproducibility of the 2.5-minute loaded repeated jump test (LRJT) and to test the effectiveness of general preparation period (GPP) training on anaerobic fitness of elite alpine ski racers with the LRJT. Thirteen male volunteers completed 2 LRJTs to examine reliability. Nine male Austrian elite junior racers were tested in June and October 2009. The LRJT consisted of 60 loaded countermovement jumps (LCMJs) with a loaded barbell equivalent to 40% bodyweight. Before the LRJT, the power (P) of a single LCMJ was determined. Power was calculated from ground reaction forces. The mean P was calculated for the complete test and for each 30-second interval. The interclass correlation coefficients (between 0.88 and 0.99) for main variables of the LRJT demonstrated a high reliability. A repeated-measures analysis of variance indicated that anaerobic capacity was significantly higher in October (p ≤ 0.05). The ski racers' single LCMJ P increased from 37.0 ± 1.2 W·kg to 39.0 ± 1.4 W·kg. The mean P of the total test improved from 33.6 ± 1.2 W·kg to 35.8 ± 1.3 W·kg, but relative effect of fatigue did not change. The GPP training improved the athletes' ability to produce and maintain muscular power. The LRJT is a reliable anaerobic test suitable for all alpine ski racing events because the 60 jumps simulate the approximate number of gates in slalom and giant slalom races and the 2.5 minutes is equivalent to the duration of the longest downhill race.

  18. Reliability of squat and countermovement jump tests in children 6 to 8 years of age.

    Science.gov (United States)

    Acero, Rafael Martin; Fernández-del Olmo, Miguel; Sánchez, Jose Andres; Otero, Xose Luis; Aguado, Xavier; Rodríguez, Ferran A

    2011-02-01

    The aim of this study was to determine the reliability of the squat jump test (SJ) and countermovement jump test (CMJ), in fifty-six children (30 girls and 26 boys) with ages ranging from 6 to 8 years. Each subject performed two evaluation sessions (T1, T2) with seven days between tests. The results show that the CMJ test has a high intratrial reproducibility in T1 and T2 measured through intraclass correlation coefficient (ICC ≥ 0.95). The ICC for the SJ test had a high value (0.99) only in T1. The variability for both tests among children under 9 years of age is higher than those reported for adult subjects in other studies. The intersession reliability was questionable with a high methodical error (ME= 9.86-15.1%, for the SJ and CMJ, respectively) and a significant worsening of the results of CMJ in T2 (p < .05).

  19. Effect of unloading and loading on power in simulated countermovement and squat jumps.

    Science.gov (United States)

    Bobbert, Maarten F

    2014-06-01

    In the literature, substantial decreases in power output in jumping have been described for both unloading and loading, and these have been attributed to the intrinsic force-velocity-power relationship of muscle. The purpose of this study was to gain a solid understanding of how and why unloading and loading affect power output during jumping. Vertical jumps were simulated with a model of the musculoskeletal system, consisting of four rigid segments actuated by six muscles. Muscle stimulation over time was optimized to ensure maximal performance in each loading condition. It was found that, in contrast to what is reported in the literature, unloading by an extra vertical force of -60% of body weight caused a small increase in the peak of the rate of change of the effective energy of the center of mass (dEeff/dt). Loading by an extra vertical force of +60% of body weight caused a decrease in peak dEeff/dt, but this decrease was much smaller than that described in the literature. The small variations in peak dEeff/dt among loading conditions in the simulated jumps were only in part due to the intrinsic force-velocity-power relationship of muscle. Why did the effects of unloading and loading in the simulation model deviate from effects reported in subjects? One possible explanation is that subjects tend to make a smaller countermovement when loaded; in the simulation model, making a smaller countermovement caused a major reduction in peak dEeff/dt. A second possible explanation is that subjects cannot quickly optimize their control and therefore produce submaximal power output in unfamiliar loading conditions. The effects of unloading and loading are due only in part to the intrinsic force-velocity-power relationship of muscle.

  20. Contribution of non-extensor muscles of the leg to maximal-effort countermovement jumping

    Directory of Open Access Journals (Sweden)

    Yoshioka Shinsuke

    2005-09-01

    Full Text Available Abstract Background The purpose of this study was to determine the effects of non-extensor muscles of the leg (i.e., muscles whose primary function is not leg extension on the kinematics and kinetics of human maximal-effort countermovement jumping. Although it is difficult to address this type of question through experimental procedures, the methodology of computer simulation can be a powerful tool. Methods A skeletal model that has nine rigid body segments and twenty degrees of freedom was developed. Two sets of muscle models were attached to this skeletal model: all (most of major muscles in the leg ("All Muscles" model and major extensor muscles in the leg (i.e., muscles whose primary function is leg extension; "Extensors Only" model. Neural activation input signal was represented by a series of step functions with a step duration of 0.05 s. Simulations were started from an identical upright standing posture. The optimal pattern of the activation input signal was searched through extensive random-search numerical optimization with a goal of maximizing the height reached by the mass centre of the body after jumping up. Results The simulated kinematics was almost two-dimensional, suggesting the validity of two-dimensional analyses when evaluating net mechanical outputs around the joints using inverse dynamics. A greater jumping height was obtained for the "All Muscles" model (0.386 m than for the "Extensors Only" model (0.301 m. For the "All Muscles" model, flexor muscles developed force in the beginning of the countermovement. For the "All Muscles" model, the sum of the work outputs from non-extensor muscles was 47.0 J, which was 13% of the total amount (359.9 J. The quantitative distribution of the work outputs from individual muscles was markedly different between these two models. Conclusion It was suggested that the contribution of non-extensor muscles in maximal-effort countermovement jumping is substantial. The use of a computer

  1. Intra- and inter-subject variation in lower limb coordination during countermovement jumps in children and adults

    DEFF Research Database (Denmark)

    Raffalt, Peter C; Alkjær, Tine; Simonsen, Erik B

    2016-01-01

    The purpose of the present study was to investigate the coordination pattern and coordination variability (intra-subject and inter-subject) in children and adults during vertical countermovement jumps. Ten children (mean age: 11.5±1.8years) and ten adults (mean age: 26.1±4.9years) participated...... in the experiment. Lower body 3D-kinematics and kinetics from both legs were obtained during 9 vertical jumps of each subject. Coordination pattern and coordination variability of intra-limb and inter-limb coupling were established by modified vector coding and continuous relative phase. The adult group jumped...

  2. Acute Effect of Countermovement Jumping on Throwing Performance in Track and Field Athletes During Competition.

    Science.gov (United States)

    Karampatsos, Giorgos P; Korfiatis, Panagiotis G; Zaras, Nikolaos D; Georgiadis, Giorgos V; Terzis, Gerasimos D

    2017-02-01

    Karampatsos, GP, Korfiatis, PG, Zaras, ND, Georgiadis, GV, and Terzis, GD. Acute effect of countermovement jumping on throwing performance in track and field athletes during competition. J Strength Cond Res 32(1): 359-364, 2017-The purpose of the study was to investigate whether performing 3 consecutive countermovement jumps (CMJs) just before an attempt enhances performance in track and field throwers during competition. Twelve shot putters, 8 hammer throwers, 9 discus throwers, and 3 javelin throwers of both sexes participated in the study. They performed 3 maximal CMJs 85 ± 12 seconds before the second, fourth, and sixth attempt during 3 different official competitions of national level. Maximal strength (1 repetition maximum [1RM]) in squat and bench press was measured 1 week after the competition. Mean throwing performance was significantly higher after the CMJs intervention (2.66 ± 4.3%, range of increase 0.02-18.98%, p = 0.0001). Similarly, maximum throwing performance was significantly higher after the CMJs (2.76 ± 3.29%, range of increase 0.09-13.93%, p = 0.0009). All but 2 athletes increased their best performance after the CMJs. The percentage increase in performance was similar between sexes (male athletes 2.56 ± 3.01%; female athletes 3.06 ± 3.76%, p = 0.677), but it was higher for the "lighter throws" (discus and javelin throw: 4.66 ± 4.11%) compared with the "heavier throws" (shot and hammer throw: 1.62 ± 2.04%, p = 0.008). The percentage increase in performance was not significantly correlated with 1RM squat or bench press, anthropometric characteristics, and personal best performance. These results suggest that performing 3 CMJs approximately 1 minute before an attempt may increase track and field throwing performance during competition.

  3. Unipedal Postural Balance and Countermovement Jumps After a Warm-up and Plyometric Training Session: A Randomized Controlled Trial.

    Science.gov (United States)

    Romero-Franco, Natalia; Jiménez-Reyes, Pedro

    2015-11-01

    The purpose of this study was to analyze the immediate effects of a plyometric training protocol on unipedal postural balance and countermovement jumps. In addition, we analyzed the effects of a warm-up on these parameters. Thirty-two amateur male sprinters (24.9 ± 4.1 years; 72.3 ± 10.7 kg; 1.78 ± 0.05 m; 22.6 ± 3.3 kg·m) were randomly sorted into a control group (n = 16) (they did not perform any physical activity) and a plyometric training group (n = 16) (they performed a 15-minute warm-up and a high-intensity plyometric protocol consisting of 10 sets of 15 vertical jumps). Before and after the warm-up, and immediately after and 5 minutes after the plyometric protocol, all athletes indicated the perceived exertion on calf and quad regions on a scale from 0 (no exertion) to 10 (maximum exertion). They also carried out a maximum countermovement jump and a unipedal postural balance test (athletes would remain as still as possible for 15 seconds in a left leg and right leg support stance). Results showed that, in the plyometric group, length and velocity of center-of-pressure movement in right leg support stance increased compared with baseline (p = 0.001 and p = 0.004, respectively) and to the control group (p = 0.035 and p = 0.029, respectively) immediately after the plyometric protocol. In addition, the countermovement jump height decreased right after the plyometric protocol (p postural balance remained unaltered. As a conclusion, high-intensity plyometric exercises blunt unipedal postural balance and countermovement jump performance. The deterioration lasts at least 5 minutes, which may influence future exercises in the training session. Coaches should plan the training routine according to the immediate effects of plyometry on postural balance and vertical jumps, which play a role in injury prevention and sports performance.

  4. The effect of strength training, recreational soccer and running exercise on stretch-shortening cycle muscle performance during countermovement jumping

    DEFF Research Database (Denmark)

    Jakobsen, Markus Due; Sundstrup, Emil; Randers, Morten Bredsgaard

    2012-01-01

    production, indicating a more explosive-type SSC muscle performance. No effects were detected in CMJ performance after continuous running, high-intensity interval running and recreational soccer, despite an increased muscle fiber CSA and quadriceps muscle activity in SOC. Enhanced neuromuscular activity......The purpose of the present study was to evaluate the effect of contrasting training modalities on mechanical muscle performance and neuromuscular activity during maximal SSC (stretch-shortening cycle) countermovement jumps (CMJ). Bilateral countermovement jumping, surface electromyography (EMG......) and muscle fiber size (CSA) were studied in untrained individuals (n=49, 21-45yrs) pre and post 12weeks of progressive heavy-resistance strength training (ST, n=8), recreational soccer training (SOC, n=15), high-intensity interval running (INT, n=7), continuous running (RUN, n=9) or continuation...

  5. ANALYSIS OF THE VERTICAL GROUND REACTION FORCES AND TEMPORAL FACTORS IN THE LANDING PHASE OF A COUNTERMOVEMENT JUMP

    Directory of Open Access Journals (Sweden)

    Daniel Rojano Ortega

    2010-06-01

    Full Text Available In most common bilateral landings of vertical jumps, there are two peak forces (F1 and F2 in the force-time curve. The combination of these peak forces and the high frequency of jumps during sports produce a large amount of stress in the joints of the lower limbs which can be determinant of injury. The aim of this study was to find possible relationships between the jump height and F1 and F2, between F1 and F2 themselves, and between F1, F2, the time they appear (T1 and T2, respectively and the length of the impact absorption phase (T. Thirty semi-professional football players made five countermovement jumps and the highest jump of each player was analyzed. They were instructed to perform the jumps with maximum effort and to land first with the balls of their feet and then with their heels. All the data were collected using a Kistler Quattro Jump force plate with a sample rate of 500 Hz. Quattro Jump Software, v.1.0.9.0., was used. There was neither significant correlation between T1 and F1 nor between T1 and F2. There was a significant positive correlation between flight height (FH and F1 (r = 0.584, p = 0.01 but no significant correlation between FH and F2. A significant positive correlation between F1 and T2 (r = 0.418, p < 0.05 and a significant negative correlation between F2 and T2 (r = -0.406, p < 0.05 were also found. There is a significant negative correlation between T2 and T (r = -0. 443, p < 0.05. T1 has a little effect in the impact absorption process. F1 increases with increasing T2 but F2 decreases with increasing T2. Besides, increasing T2, with the objective of decreasing F2, makes the whole impact absorption shorter and the jump landing faster.

  6. Effect of squat depth on performance and biomechanical parameters of countermovement vertical jump

    Directory of Open Access Journals (Sweden)

    Rodrigo Ghedini Gheller

    2014-10-01

    Full Text Available The aim of this study was to analyze the effect of different squat depths in the performance and biomechanical parameters at counter movement jump (CMJ. Twenty-two male volleyball or basketball players volunteered to participate in this study and all were currently competing at the college level. The CMJ was performed in three different conditions: 1 with relative knee flexion at the end of counter movement phase smaller than 90° (90°, and; 3 preferred position (PREF. During the CMJ, kinematic, kinetic, and electromyography parameters were assessed. ANOVA for repeated measures with post-hoc Bonferroni´s test was used for variables comparison, with a significance level set at p≤0.05. The higher performance was on PREF and 90°. Average and peak power, as well as absolute and normalized peak forces, were higher in >90° CMJ. The peak velocity of CG and angular velocities of hip and knee were higher in the 90°. Recuts femoris and biceps femoris did not show difference in any jump phases. In conclusion, the knee flexion interferes the performance and the biomechanical variables at the CMJ. The highest jumps were got at a deeper squat, so this technique could be used for athletes in order to optimize the vertical jump performance in the training and competitions.

  7. Ground Reaction Force Differences in the Countermovement Jump in Girls with Different Levels of Performance

    Science.gov (United States)

    Floría, Pablo; Harrison, Andrew J.

    2013-01-01

    Purpose: The aim of this study was to ascertain the biomechanical differences between better and poorer performers of the vertical jump in a homogeneous group of children. Method: Twenty-four girls were divided into low-scoring (LOW; M [subscript age] = 6.3 ± 0.8 years) and high-scoring (HIGH; M [subscript age] = 6.6 ± 0.8 years) groups based on…

  8. Age-Related Variation in Male Youth Athletes' Countermovement Jump After Plyometric Training: A Meta-Analysis of Controlled Trials.

    Science.gov (United States)

    Moran, Jason J; Sandercock, Gavin R H; Ramírez-Campillo, Rodrigo; Meylan, César M P; Collison, Jay A; Parry, Dave A

    2017-02-01

    Moran, J, Sandercock, GRH, Ramírez-Campillo, R, Meylan, CMP, Collison, J, and Parry, DA. Age-related variation in male youth athletes' countermovement jump after plyometric training: A meta-analysis of controlled trials. J Strength Cond Res 31(2): 552-565, 2017-Recent debate on the trainability of youths has focused on the existence of periods of accelerated adaptation to training. Accordingly, the purpose of this meta-analysis was to identify the age- and maturation-related pattern of adaptive responses to plyometric training in youth athletes. Thirty effect sizes were calculated from the data of 21 sources with studies qualifying based on the following criteria: (a) healthy male athletes who were engaged in organized sport; (b) groups of participants with a mean age between 10 and 18 years; and (c) plyometric-training intervention duration between 4 and 16 weeks. Standardized mean differences showed plyometric training to be moderately effective in increasing countermovement jump (CMJ) height (Effect size = 0.73 95% confidence interval: 0.47-0.99) across PRE-, MID-, and POST-peak height velocity groups. Adaptive responses were of greater magnitude between the mean ages of 10 and 12.99 years (PRE) (ES = 0.91 95% confidence interval: 0.47-1.36) and 16 and 18 years (POST) (ES = 1.02 [0.52-1.53]). The magnitude of adaptation to plyometric training between the mean ages of 13 and 15.99 years (MID) was lower (ES = 0.47 [0.16-0.77]), despite greater training exposure. Power performance as measured by CMJ may be mediated by biological maturation. Coaches could manipulate training volume and modality during periods of lowered response to maximize performance.

  9. Influence of muscle-tendon unit structure on rate of force development during the squat, countermovement, and drop jumps.

    Science.gov (United States)

    Earp, Jacob E; Kraemer, William J; Cormie, Prue; Volek, Jeffery S; Maresh, Carl M; Joseph, Michael; Newton, Robert U

    2011-02-01

    Previous research has highlighted the importance of muscle and tendon structure to stretch shortening cycle performance. However, the relationships between muscle and tendon structure to performance are highly dependent on the speed and intensity of the movement. The purpose of this study was to determine if muscle and tendon structure is associated with the rate of force development (RFD) throughout static squat jump (SJ), countermovement jump (CMJ), and drop jump (DJ; 30-cm height). Twenty-five strength- and power-trained men participated in the study. Using ultrasonography, vastus lateralis (VL) and gastrocnemius (GAS) pennation (PEN) and fascicle length (FL), and Achilles tendon (AT) thickness and length were measured. Subjects then performed SJ, CMJ, and DJ, during which RFD was calculated over time 5 distinct time intervals. During CMJs, early RFD could be predicted between 0 and 10 milliseconds by both GAS-FL (r² = 0.213, β = 0.461) and AT-length (r² = 0.191, β = 20.438). Between 10 and 30 milliseconds GAS-FL was a significant predictor of CMJ-RFD (r² = 0.218, β = 0.476). During DJ, initial RFD (0-10 milliseconds) could be significantly predicted by GAS-FL (r² = 0.185, β = 20.434), VL-PEN (r² = 0.189, β = 0.435), and GAS-PEN (r² = 0.188, β = 0.434). These findings suggest that longer ATs may have increased elasticity, which can decrease initial RFD during CMJ; thus, their use in talent identification is not recommended. The GAS fascicle length had an intensity-dependent relationship with RFD, serving to positively predict RFD during early CMJs and an inverse predictor during early DJs. During DDJs, subjects with greater PEN were better able to redirected initial impact forces. Although both strength and plyometric training have been shown to increase FL, only heavy strength training has been shown to increase PEN. Thus, when a high eccentric load or multiple jumps are required, heavy strength training might be used to elicit muscular adaptations

  10. COMPARING THE EFFECTS OF VARIOUS WHOLE-BODY VIBRATION ACCELERATIONS ON COUNTER-MOVEMENT JUMP PERFORMANCE

    Directory of Open Access Journals (Sweden)

    David M. Bazett-Jones

    2008-03-01

    Full Text Available While it seems that whole body vibration (WBV might be an effective modality to enhance physical performance, the proper prescription of WBV for performance enhancement remains unknown. The purpose of this study was to compare the immediate effect of various WBV accelerations on counter movement jump (CMJ height, the duration of any effect, and differences between men and women. Forty-four participants (33 men, 11 women participated in no less than four CMJ familiarization sessions and completed all vibration sessions. Participants performed a pre-test (three maximal CMJs, followed randomly by one of five WBV accelerations; 1g (no-WBV control, 2.16g, 2.80g, 4.87g, and 5.83g. Participants performed three maximal CMJs immediately, five, and 10 minutes following each 45 sec WBV session. The mean of the three performances was used and calculated as a percentage of the pre-vibration mean value. A Repeated Measures Analysis of Variance (ANOVA; acceleration x time x gender model was used to analyze the data. The two-way interactions of acceleration-gender (p = 0.033 and time-gender (p = 0.050 were significant. Women performed significantly better following the 2.80g (p = 0.0064 and 5.83g (p = 0. 0125 WBV sessions compared to the 1g (control session. Men, however, did not experience performance enhancing effects following any of the vibration sessions. While significant differences did not occur between time in either gender, the effects of the 45 sec WBV session in women were transient, lasting approximately five minutes. During the prescription of WBV, gender should be considered given that the results of this study seem to indicate that men and women respond differently to WBV. The results of this study suggest that WBV might be a useful modality as applied during the pre-competition warm-up

  11. and the CMJ jump height

    Directory of Open Access Journals (Sweden)

    Struzik Artur

    2016-04-01

    Full Text Available Study aim: The elastic potential energy accumulated in the musculotendinous units during the countermovement phase of a jump adds up to the energy supplied by the contracting muscles used in the take-off phase. Consequently, the total mechanical energy used during the jump may reach higher values. Stiffness represents a quantitative measure of a body’s elastic properties. Therefore, the aim of this study was to establish the relationship between leg stiffness and the countermovement jump height.

  12. The acute effects of a warm-up including static or dynamic stretching on countermovement jump height, reaction time, and flexibility.

    Science.gov (United States)

    Perrier, Erica T; Pavol, Michael J; Hoffman, Mark A

    2011-07-01

    The purpose of this research was to compare the effects of a warm-up with static vs. dynamic stretching on countermovement jump (CMJ) height, reaction time, and low-back and hamstring flexibility and to determine whether any observed performance deficits would persist throughout a series of CMJs. Twenty-one recreationally active men (24.4 ± 4.5 years) completed 3 data collection sessions. Each session included a 5-minute treadmill jog followed by 1 of the stretch treatments: no stretching (NS), static stretching (SS), or dynamic stretching (DS). After the jog and stretch treatment, the participant performed a sit-and-reach test. Next, the participant completed a series of 10 maximal-effort CMJs, during which he was asked to jump as quickly as possible after seeing a visual stimulus (light). The CMJ height and reaction time were determined from measured ground reaction forces. A treatment × jump repeated-measures analysis of variance for CMJ height revealed a significant main effect of treatment (p = 0.004). The CMJ height was greater for DS (43.0 cm) than for NS (41.4 cm) and SS (41.9 cm) and was not less for SS than for NS. Analysis also revealed a significant main effect of jump (p = 0.005) on CMJ height: Jump height decreased from the early to the late jumps. The analysis of reaction time showed no significant effect of treatment. Treatment had a main effect (p < 0.001) on flexibility, however. Flexibility was greater after both SS and DS compared to after NS, with no difference in flexibility between SS and DS. Athletes in sports requiring lower-extremity power should use DS techniques in warm-up to enhance flexibility while improving performance.

  13. Jumping Dynamics

    DEFF Research Database (Denmark)

    Sannino, Francesco

    2013-01-01

    We propose an alternative paradigm to the conjectured Miransky scaling potentially underlying the physics describing the transition from the conformally broken to the conformally restored phase when tuning certain parameters such as the number of flavors in gauge theories. According to the new...... paradigm the physical scale and henceforth also the massive spectrum of the theory jump at the lower boundary of the conformal window. In particular we propose that a theory can suddenly jump from a Quantum Chromodynamics type spectrum, at the lower boundary of the conformal window, to a conformal one...... without particle interpretation. The jumping scenario, therefore, does not support a near-conformal dynamics of walking type. We will also discuss the impact of jumping dynamics on the construction of models of dynamical electroweak symmetry breaking....

  14. Biomechanical analysis of countermovement jump in people with cerebral palsy Análisis biomecánico del salto vertical con contramovimiento en personas con parálisis cerebral

    OpenAIRE

    K. Gianikellis; Bote, A.; J. M.ª Pulido; Pérez, A.

    2010-01-01

    The main purpose of the study was to evaluate the patterns of the developed ground reaction forces in the two – legged countermovement jumping, performed by persons affected by tetraparesis with ataxia, tetraparesis with athetosis, tetraparesis with spasticity, diplegia with spasticity, right and left hemiplegia and, finally, right and left hemiparesis. After twenty subjects jumped on the surface of a force plate analysis of the ground reaction force &nd...

  15. Long Jump

    CERN Document Server

    Dorobantu, V

    2012-01-01

    When the laws of Physics are taken seriously, the sports can benefit in getting better results, as was the case of the high jump in Flop style, so that the athlete sprints diagonally towards the bar,then curve and leap backwards over it. The jumper, in this case, has the center of mass under the bar, fact which allows improvement of the performance.

  16. Acute Effect of Biomechanical Muscle Stimulation on the Counter-Movement Vertical Jump Power and Velocity in Division I Football Players.

    Science.gov (United States)

    Jacobson, Bert H; Monaghan, Taylor P; Sellers, John H; Conchola, Eric C; Pope, Zach K; Glass, Rob G

    2017-05-01

    Jacobson, BH, Monaghan, TP, Sellers, JH, Conchola, EC, Pope, ZK, and Glass, RG. Acute effect of biomechanical muscle stimulation on the counter-movement vertical jump power and velocity in division I football players. J Strength Cond Res 31(5): 1259-1264, 2017-Research regarding whole body vibration (WBV) largely supports such training augmentation in attempts to increase muscle strength and power. However, localized biomechanical vibration has not received the same attention. The purpose of this study was to assess peak and average power before and after acute vibration of selected lower-body sites in division I athletes. Twenty-one subjects were randomly assigned to 1 of 2 conditions using a cross-over design. Pretest consisted of a counter-movement vertical jump (VJ) followed by either localized vibration (30 Hz) to 4 selected lower-body areas or 4 minutes of moderately low-resistance stationary cycling (70 rpm). Vibration consisted of 1 minute bouts at each lower-leg site for a total of 4 minutes followed by an immediate post-test VJ. Repeated measures analysis of variance yielded no significant differences (p > 0.05) in either peak power or peak velocity. Similarly, no significant differences were found for average power and velocity between conditions. It should be noted that, while not significant, the vibration condition demonstrated an increase in peak power and velocity while the bike condition registered slight decreases. Comparing each of the post-VJ repetitions (1, 2, and 3) the vibration condition experienced significantly greater peak power and velocity from VJ 1 to VJ 3 compared with the bike condition which demonstrated no significant differences among the post-test VJs. These results yielded similar, although not statistically significant outcomes to previous studies using WBV. However, the novelty of selected site biomechanical vibration merits further investigation with respect to frequency, magnitude, and duration of vibration.

  17. A comparison of take-off dynamics during three different spikes, block and counter-movement jump in female volleyball players.

    Science.gov (United States)

    Kabacinski, Jaroslae; Dworak, Lecholslaw B; Murawa, Michal; Ostarello, John; Rzepnicka, Agata; Maczynski, Jacek

    2016-12-01

    The purpose of the study was to compare the take-off dynamics in counter-movement jump (CMJ), volleyball block and spikes. Twelve professional female players, representing the highest volleyball league in Poland, participated in the laboratory tests. A force platform was used to record ground reaction force (GRF) during take-off phase in CMJ test, block from a run-up and spikes: front row attack, slide attack, back row attack. Vertical (v) GRF (peak: Rmax and integral mean: ), impulse of vGRF (J) and mechanical power (peak: Pmax and integral mean: ) were analyzed. Significant differences (P, J, Pmax, and ) were found between CMJ, block from a run-up and three different technique spikes. The highest values were recorded during take-off in the back row attack: peak vGRF (2.93±0.05 BW), integral mean vGRF (1.90±0.08 BW), impulse of vGRF (354±40 Ns), peak power (5320±918 W) and integral mean power (3604±683 W). Peak power (2608±217 W) and integral mean power (1417±94 W) were determined in CMJ test to evaluate the force-velocity capabilities of the players. In terms of GRF and the mechanical power, high level of dynamics in take-off influences positively the jumping height and significantly increases the effectiveness of attacks during spike of the ball over the block of the opponent.

  18. Respuestas agudas al entrenamiento de fuerza con cargas pesadas y al entrenamiento mediante estiramiento sobre el rendimiento en squat jump y countermovement jump. Acute affects of strenght training from heavy loads and static stretching training on squat jump and countermovement jump.

    Directory of Open Access Journals (Sweden)

    Navarro Valdivielso, Fernando José

    2006-07-01

    Full Text Available ResumenEl objetivo de este estudio es examinar los efectos agudos del entrenamiento con cargas pesadas, y del estiramiento estático sobre sujetos no entrenados y determinar si tiene un efecto positivo sobre el rendimiento en SJ y CMJ. 20 sujetos divididos en dos grupos (grupo de fuerza n:10 y grupo de estiramientos n:10. El grupo de fuerza realizó 3 series de 3 repeticiones con la máxima carga que puede soportar en 3RM y 3 min descanso entre serie. En el grupo de estiramientos los sujetos realizaban 3 series de 3 ejercicios de estiramientos correspondientes a flexores de rodilla, extensores de cadera y gemelos manteniendo el estiramiento pasivo durante 15 segundos en cada ejercicio. SJ y CMJ fueron medidos antes y después del ejercicio. La altura de salto se incrementó significativamente en el SJ después de los ejercicios de estiramiento (pAbstractThe purpose of this study were to examine the acute effects of strength training using heavy loads and static stretching for 15 seconds on SJ and CMJ. A population sample of 20 subjects was studied which was divided into two groups (strength training (ST n=10- and static stretching training (SS n=10- ST group performed 3 sets of 3RM load with 3 min rest between all sets. SS group performed 3 stretching exercises, with each exercise held for 15 second repetitions. The stretches included a seated bilateral hamstring stretch; Standing unilateral quadriceps stretch and standing unilateral calf stretch. Vertical jump performance was measured before and after exercise. The height jump in SJ increased significantly after static stretching training (p

  19. Usefulness of the jump-and-reach test in assessment of vertical jump performance.

    Science.gov (United States)

    Menzel, Hans-Joachim; Chagas, Mauro H; Szmuchrowski, Leszek A; Araujo, Silvia R; Campos, Carlos E; Giannetti, Marcus R

    2010-02-01

    The objective was to estimate the reliability and criterion-related validity of the Jump-and-Reach Test for the assessment of squat, countermovement, and drop jump performance of 32 male Brazilian professional volleyball players. Performance of squat, countermovement, and drop jumps with different dropping heights was assessed on the Jump-and-Reach Test and the measurement of flight time, then compared across different jump trials. The very high reliability coefficients of both assessment methods and the lower correlation coefficients between scores on the assessments indicate a very high consistency of each method but only moderate covariation, which means that they measure partly different items. As a consequence, the Jump-and-Reach Test has good ecological validity in situations when reaching height during the flight phase is critical for performance (e.g., basketball and volleyball) but only limited accuracy for the assessment of vertical impulse production with different jump techniques and conditions.

  20. A biomechanical comparison of the vertical jump, power clean, and jump squat.

    Science.gov (United States)

    MacKenzie, Sasho James; Lavers, Robert J; Wallace, Brendan B

    2014-01-01

    The purpose of this study was to compare the kinetics, kinematics, and muscle activation patterns of the countermovement jump, the power clean, and the jump squat with the expectation of gaining a better understanding of the mechanism of transfer from the power clean to the vertical jump. Ground reaction forces, electromyography, and joint angle data were collected from 20 trained participants while they performed the three movements. Relative to the power clean, the kinematics of the jump squat were more similar to those of the countermovement jump. The order in which the ankle, knee, and hip began extending, as well as the subsequent pattern of extension, was different between the power clean and countermovement jump. The electromyography data demonstrated significant differences in the relative timing of peak activations in all muscles, the maximum activation of the rectus femoris and biceps femoris, and in the activation/deactivation patterns of the vastus medialis and rectus femoris. The greatest rate of force development during the upward phase of these exercises was generated during the power clean (17,254 [Formula: see text]), which was significantly greater than both the countermovement jump (3836 [Formula: see text]) and jump squat (3517 [Formula: see text]) conditions (P < .001, [Formula: see text]).

  1. Risk, Jumps, and Diversification

    DEFF Research Database (Denmark)

    Bollerslev, Tim; Law, Tzuo Hann; Tauchen, George

    We test for price discontinuities, or jumps, in a panel of high-frequency intraday returns for forty large-cap stocks and an equiweighted index from these same stocks. Jumps are naturally classified into two types: common and idiosyncratic. Common jumps affect all stocks, albeit to varying degree...

  2. Jumping in Arithmetic

    NARCIS (Netherlands)

    Visser, Albert

    2014-01-01

    In this paper we study a new relation between sentences: the jump relation. The idea of the jump relation is based on an analysis of Feferman's Theorem that the inconsistency of a theory U is interpretable over U. The jump relation is based on a converse of Feferman's Theorem: if a sentence is inter

  3. Contribución segmentaria de los saltos con contramovimiento en vertical y en horizontal. [Segmental contribution on countermovement vertical and horizontal jumps].

    Directory of Open Access Journals (Sweden)

    Marcos Gutiérrez-Dávila

    2014-10-01

    Full Text Available El propósito ha sido realizar un análisis dinámico y cinemático sobre los saltos verticales (SV y horizontales (SH y cuantificar la aportación de los segmentos corporales al desplazamiento del centro de masa (CM durante la fase de propulsión. Han participado 28 deportistas practicantes de modalidades deportivas donde el salto vertical constituye una habilidad básica. Se ha utilizado una plataforma de fuerza, operando a 500 Hz, sincronizada temporalmente a una cámara de vídeo a 210 Hz que registraba el plano sagital de los saltos. Los saltos han sido considerados como un movimiento simétrico que se desarrolla en un plano, compuesto por un modelo mecánico coordinado simplificado de ocho segmentos. En la condición SV, los participantes debían de realizar un salto vertical máximo partiendo de una posición erguida sobre la plataforma de fuerza. En la condición SH, los participantes debían realizar un salto máximo en horizontal desde la misma posición. El tiempo de batida ha sido superior en SH con respecto a SV, (0.898 vs 1.056 s, constatándose una estrategia de rotación-extensión para SH. Los resultados ponen de manifiesto que la fuerza neta ejercida durante el impulso de frenado es mayor para SV debido a la mayor velocidad radial al inicio del impulso de frenado (-1.166 vs -0.992 m/s. Existe una mayor participación de las articulaciones del tobillo y la cadera plasmada en la mayor contribución del tronco en SH durante toda la batida, además de constatarse una mayor contribución de las extremidades superiores al desplazamiento vertical del CM en SV. Abstract The main aim of this research was a dynamics and kinematics analysis of vertical (SV and horizontal (SH jumps and quantify the body segments’ contribution to center of mass, CM, displacement during the propulsion phase. 28 athletes from different sport modalities where the vertical jump is a basic skill have participated. We used a force platform, operating at 500 Hz

  4. Steerable Miniature Jumping Robot

    OpenAIRE

    Kovac, Mirko; Schlegel, Manuel; Zufferey, Jean-Christophe; Floreano, Dario

    2010-01-01

    Jumping is used in nature by many small animals to locomote in cluttered environments or in rough terrain. It offers small systems the benefit of overcoming relatively large obstacles at a low energetic cost. In order to be able to perform repetitive jumps in a given direction, it is important to be able to upright after landing, steer and jump again. In this article, we review and evaluate the uprighting and steering principles of existing jumping robots and present a novel spherical robot w...

  5. Optimal Ski Jump

    Science.gov (United States)

    Rebilas, Krzysztof

    2013-01-01

    Consider a skier who goes down a takeoff ramp, attains a speed "V", and jumps, attempting to land as far as possible down the hill below (Fig. 1). At the moment of takeoff the angle between the skier's velocity and the horizontal is [alpha]. What is the optimal angle [alpha] that makes the jump the longest possible for the fixed magnitude of the…

  6. Jumping Good Fun

    Science.gov (United States)

    Nye, Susan B.

    2010-01-01

    Jumping rope is an activity that can be fun and enjoyable for all students. It requires minimal activity space, can be performed individually or in small groups, and is an inexpensive way to engage students in a lifelong physical activity. Jumping rope is commonly used by coaches and athletes for training purposes to improve aerobic endurance,…

  7. Jumping Good Fun

    Science.gov (United States)

    Nye, Susan B.

    2010-01-01

    Jumping rope is an activity that can be fun and enjoyable for all students. It requires minimal activity space, can be performed individually or in small groups, and is an inexpensive way to engage students in a lifelong physical activity. Jumping rope is commonly used by coaches and athletes for training purposes to improve aerobic endurance,…

  8. Estimation of Jump Tails

    DEFF Research Database (Denmark)

    Bollerslev, Tim; Todorov, Victor

    We propose a new and flexible non-parametric framework for estimating the jump tails of Itô semimartingale processes. The approach is based on a relatively simple-to-implement set of estimating equations associated with the compensator for the jump measure, or its "intensity", that only utilizes ...

  9. Lift-off dynamics in a simple jumping robot

    CERN Document Server

    Aguilar, Jeffrey; Wiesenfeld, Kurt; Goldman, Daniel I

    2012-01-01

    We study vertical jumping in a simple robot comprising an actuated mass-spring arrangement. The actuator frequency and phase are systematically varied to find optimal performance. Optimal jumps occur above and below (but not at) the robot's resonant frequency $f_0$. Two distinct jumping modes emerge: a simple jump which is optimal above $f_0$ is achievable with a squat maneuver, and a peculiar stutter jump which is optimal below $f_0$ is generated with a counter-movement. A simple dynamical model reveals how optimal lift-off results from non-resonant transient dynamics.

  10. Biomechanical analysis of countermovement jump in people with cerebral palsy Análisis biomecánico del salto vertical con contramovimiento en personas con parálisis cerebral

    Directory of Open Access Journals (Sweden)

    K. Gianikellis

    2010-09-01

    Full Text Available

    The main purpose of the study was to evaluate the patterns of the developed ground reaction forces in the two – legged countermovement jumping, performed by persons affected by tetraparesis with ataxia, tetraparesis with athetosis, tetraparesis with spasticity, diplegia with spasticity, right and left hemiplegia and, finally, right and left hemiparesis. After twenty subjects jumped on the surface of a force plate analysis of the ground reaction force – time trend took place. The obtained results confirm the accomplishment of the biomechanical principle of the initial force as in the case of persons not affected by neurological disorders. Finally the calculated ratio between the breaking impulse and the acceleration impulse is very near to optimum values.
    KEY WORDS: cerebral palsy, biomechanics, countermovement jump.

     

    El valor óptimo del impulso de aceleración en el salto vertical con contra -movimiento, es aproximadamente tres veces superior al impulso de “frenaje”. El objetivo de este estudio ha sido investigar el modo de actuación de la cadena biocinemática del tren inferior en el salto vertical con contra -movimiento para personas afectadas por parálisis cerebral, concretamente, tetraparesia con ataxia, tetraparesia con atetosis, tetraparesia con espasticidad, diplegia con espasticidad, hemiplegia izquierda y derecha, y finalmente, hemiparesia izquierda y derecha. Para ello, se han analizado las fuerzas de reacción de veintitrés sujetos que han realizado saltos con contramovimiento sobre una plataforma de fuerzas. El hallazgo de un valor medio de la ratio entre el impulso de “frenaje” y el de aceleración muy próximo al valor teórico para los veintitrés sujetos con diferentes síntomas de parálisis cerebral, confirma el principio de la fuerza inicial mientras que el alto coeficiente de variación de los parámetros utilizados en este estudio confirma la esperada

  11. Biomechanical Analysis of the Jump Shot in Basketball

    Directory of Open Access Journals (Sweden)

    Struzik Artur

    2014-10-01

    Full Text Available Basketball players usually score points during the game using the jump shot. For this reason, the jump shot is considered to be the most important element of technique in basketball and requires a high level of performance. The aim of this study was to compare the biomechanical characteristics of the lower limbs during a jump shot without the ball and a countermovement jump without an arm swing. The differences between variables provide information about the potential that an athlete can utilise during a game when performing a jump shot. The study was conducted among 20 second-league basketball players by means of a Kistler force plate and the BTS SMART system for motion analysis. The variables measured included the take-off time, mean power, peak power, relative mean power, jump height, maximum landing force and calculated impact ratio. Surprisingly, more advantageous variables were found for the jump shot. This finding suggests a very high performance level in the jump shot in the studied group and a maximum utilisation of their motor abilities. Both types of jumps were characterised by high mean and peak power values and average heights. The high forces at landing, which result in considerable impact ratios, may have prompted the studied group to land softly. Use of the countermovement jump without an arm swing is recommended to assess and predict the progression of player’s jumping ability

  12. Quantum Walk with Jumps

    CERN Document Server

    Lavička, H; Kiss, T; Lutz, E; Jex, I

    2011-01-01

    We analyze a special class of 1-D quantum walks (QWs) realized using optical multi-ports. We assume non-perfect multi-ports showing errors in the connectivity, i.e. with a small probability the multi- ports can connect not to their nearest neighbor but to another multi-port at a fixed distance - we call this a jump. We study two cases of QW with jumps where multiple displacements can emerge at one timestep. The first case assumes time-correlated jumps (static disorder). In the second case, we choose the positions of jumps randomly in time (dynamic disorder). The probability distributions of position of the QW walker in both instances differ significantly: dynamic disorder leads to a Gaussian-like distribution, while for static disorder we find two distinct behaviors depending on the parity of jump size. In the case of even-sized jumps, the distribution exhibits a three-peak profile around the position of the initial excitation, whereas the probability distribution in the odd case follows a Laplace-like discre...

  13. Jumping on water

    Science.gov (United States)

    Kim, Ho-Young

    2016-11-01

    Water striders can jump on water as high as they can jump on land. Quick jumps allow them to avoid sudden dangers such as predators' attacks, and therefore understanding how they make such a dramatic motion for survival can shed light on the ultimate level of semi-aquatic motility achievable through evolution. However, the mechanism of their vertical jumping from a water surface has eluded hydrodynamic explanations so far. By observing movements of water strider legs and theoretically analyzing their dynamic interactions with deforming liquid-air interface, we have recently found that different species of jumping striders always tune their leg rotation speed with a force just below that required to break the water surface to reach the maximum take-off velocity. Here, we start with discussing the fundamental theories of dynamics of floating and sinking of small objects. The theories then enable us to analyze forces acting on a water strider while it presses down the water surface to fully exploit the capillary force. We further introduce a 68-milligram at-scale robotic insect capable of jumping on water without splash, strikingly similar to the real strider, by utilizing the water surface just as a trampoline.

  14. Does gymnastics practice improve vertical jump reliability from the age of 8 to 10 years?

    Science.gov (United States)

    Marina, Michel; Torrado, Priscila

    2013-01-01

    The objective of this study was to confirm whether gymnastics practice from a young age can induce greater vertical jump reliability. Fifty young female gymnasts (8.84 ± 0.62 years) and 42 females in the control group (8.58 ± 0.92 years) performed the following jump tests on a contact mat: squat jump, countermovement jump, countermovement jump with arm swing and drop jump from heights of 40 and 60 cm. The two testing sessions had three trials each and were separated by one week. A 2 (groups) × 2 (sessions) × 3 (trials) repeated measures analysis of variance (ANOVA) and a test-retest correlation analysis were used to study the reliability. There was no systematic source of error in either group for non-plyometric jumps such as squat jump, countermovement jump, and countermovement jump with arm swing. A significant group per trial interaction revealed a learning effect in gymnasts' drop jumps from 40 cm height. Additionally, the test-retest correlation analysis and the higher minimum detectable error suggest that the quick drop jump technique was not fully consolidated in either group. At an introductory level of gymnastics and between the ages of 8-10 years, the condition of being a gymnast did not lead to conclusively higher reliability, aside from better overall vertical jump performance.

  15. Spinning hydraulic jump

    Science.gov (United States)

    Abderrahmane, Hamid; Kasimov, Aslan

    2013-11-01

    We report an experimental observation of a new symmetry breaking of circular hydraulic jump into a self-organized structure that consists of a spinning polygonal jump and logarithmic-spiral waves of fluid elevation downstream. The waves are strikingly similar to spiral density waves in galaxies. The fluid flow exhibits counterparts of salient morphological features of galactic flows, in particular the outflow from the center, jets, circum-nuclear rings, gas inflows toward the galactic center, and vortices. The hydrodynamic instability revealed here may have a counterpart that plays a role in the formation and sustainability of spiral arms in galaxies.

  16. The validity and reliability of an iPhone app for measuring vertical jump performance.

    Science.gov (United States)

    Balsalobre-Fernández, Carlos; Glaister, Mark; Lockey, Richard Anthony

    2015-01-01

    The purpose of this investigation was to analyse the concurrent validity and reliability of an iPhone app (called: My Jump) for measuring vertical jump performance. Twenty recreationally active healthy men (age: 22.1 ± 3.6 years) completed five maximal countermovement jumps, which were evaluated using a force platform (time in the air method) and a specially designed iPhone app. My jump was developed to calculate the jump height from flight time using the high-speed video recording facility on the iPhone 5 s. Jump heights of the 100 jumps measured, for both devices, were compared using the intraclass correlation coefficient, Pearson product moment correlation coefficient (r), Cronbach's alpha (α), coefficient of variation and Bland-Altman plots. There was almost perfect agreement between the force platform and My Jump for the countermovement jump height (intraclass correlation coefficient = 0.997, P iPhone 5 s app.

  17. Muscle activation history at different vertical jumps and its influence on vertical velocity

    NARCIS (Netherlands)

    Kopper, Bence; Csende, Zsolt; Safar, Sandor; Hortobagyi, Tibor; Tihanyi, Jozsef

    In the present study we investigated displacement, time, velocity and acceleration history of center of mass (COM) and electrical activity of knee extensors to estimate the dominance of the factors influencing the vertical velocity in squat jumps (SJs), countermovement jumps (CMJs) and drop jumps

  18. Muscle activation history at different vertical jumps and its influence on vertical velocity

    NARCIS (Netherlands)

    Kopper, Bence; Csende, Zsolt; Safar, Sandor; Hortobagyi, Tibor; Tihanyi, Jozsef

    2013-01-01

    In the present study we investigated displacement, time, velocity and acceleration history of center of mass (COM) and electrical activity of knee extensors to estimate the dominance of the factors influencing the vertical velocity in squat jumps (SJs), countermovement jumps (CMJs) and drop jumps (D

  19. Undular Hydraulic Jump

    Directory of Open Access Journals (Sweden)

    Oscar Castro-Orgaz

    2015-04-01

    Full Text Available The transition from subcritical to supercritical flow when the inflow Froude number Fo is close to unity appears in the form of steady state waves called undular hydraulic jump. The characterization of the undular hydraulic jump is complex due to the existence of a non-hydrostatic pressure distribution that invalidates the gradually-varied flow theory, and supercritical shock waves. The objective of this work is to present a mathematical model for the undular hydraulic jump obtained from an approximate integration of the Reynolds equations for turbulent flow assuming that the Reynolds number R is high. Simple analytical solutions are presented to reveal the physics of the theory, and a numerical model is used to integrate the complete equations. The limit of application of the theory is discussed using a wave breaking condition for the inception of a surface roller. The validity of the mathematical predictions is critically assessed using physical data, thereby revealing aspects on which more research is needed

  20. Ridge jump process in Iceland

    OpenAIRE

    Garcia, Sebastian

    2010-01-01

    Eastward ridge jumps bring the volcanic zones of Iceland back to the centre of the hotspot in response to the absolute westward drift of the Mid-Atlantic Ridge. Mantellic pulses triggers these ridge jumps. One of them is occurring in Southern Iceland, whereas the exact conditions of the last ridge jump in Northern Iceland remain controversial. The diachronous evolution of these two parts of Iceland may be related to the asymmetric plume-ridge interaction when comparing Northern and Southern I...

  1. Exploring Lightning Jump Characteristics

    Science.gov (United States)

    Chronis, Themis; Carey, Larry D.; Schultz, Christopher J.; Schultz, Elise; Calhoun, Kristin; Goodman, Steven J.

    2014-01-01

    This study is concerned with the characteristics of storms exhibiting an abrupt temporal increase in the total lightning flash rate (i.e., lightning jump, LJ). An automated storm tracking method is used to identify storm "clusters" and total lightning activity from three different lightning detection systems over Oklahoma, northern Alabama and Washington, D.C. On average and for different employed thresholds, the clusters that encompass at least one LJ (LJ1) last longer, relate to higher Maximum Expected Size of Hail, Vertical Integrated Liquid and lightning flash rates (area-normalized) than the clusters that did not exhibit any LJ (LJ0). The respective mean values for LJ1 (LJ0) clusters are 80 min (35 min), 14 mm (8 mm), 25 kg per square meter (18 kg per square meter) and 0.05 flash per min per square kilometer (0.01 flash per min per square kilometer). Furthermore, the LJ1 clusters are also characterized by slower decaying autocorrelation functions, a result that implies a less "random" behavior in the temporal flash rate evolution. In addition, the temporal occurrence of the last LJ provides an estimate of the time remaining to the storm's dissipation. Depending of the LJ strength (i.e., varying thresholds), these values typically range between 20-60 min, with stronger jumps indicating more time until storm decay. This study's results support the hypothesis that the LJ is a proxy for the storm's kinematic and microphysical state rather than a coincidental value.

  2. More Puddle Jumping

    Science.gov (United States)

    Attari, Babak; Weislogel, Mark; Wollman, Andrew; Chen, Yongkang; Snyder, Trevor

    2016-11-01

    Large droplets and puddles jump spontaneously from sufficiently hydrophobic surfaces during routine drop tower tests. The simple low-cost passive mechanism can in turn be used as an experimental device to investigate dynamic droplet phenomena for drops up to 10,000 times larger than their normal terrestrial counterparts. We provide or confirm quick and qualitative design guides for such 'drop shooters' as employed in drop tower tests including relationships to predict droplet ejection durations and velocities as functions of drop volume, surface texture, surface contour, wettability pattern, drop volume, and fluid properties including contact angle. The latter are determined via profile image comparisons with numerical equilibrium interface computations. Water drop volumes of 0.04 to 400 mL at ejection speeds of -0.007 to 0.12 m/s are demonstrated. An example application of the puddle jump method is made to the classic problem of regime mapping for low-gravity phase change heat transfer for large impinging drops. Many other candidate problems might be identified.

  3. Effect of drop jump technique on the reactive strength index

    Directory of Open Access Journals (Sweden)

    Struzik Artur

    2016-09-01

    Full Text Available The basic drill of plyometric training aimed at improving lower limb power and jump height is a drop jump. This exercise can be performed using different techniques, which substantially affects jump variables. Therefore, the aim of this study was to compare the values of the reactive strength index (RSI for countermovement drop jumps (CDJs and bounce drop jumps (BDJs. The study was carried out in a group of 8 male youth basketball players. The tests were conducted using the AMTI BP600900 force plate to measure ground reaction forces and the Noraxon MyoMotion system to record kinematic data. Each player performed two CDJs and two BDJs from the height of 15, 30, 45 and 60 cm. The RSI was calculated as a ratio of jump height and contact time. Moreover, the RSI was determined for the amortization and take-off phases separately. Significant differences (p < 0.05 between RSI values for CDJs and BDJs were recorded for jumps from 30, 45 and 60 cm. Differences in RSI values for jumps from 15 cm were not significant. Furthermore, CDJ height values were significantly higher (p < 0.05 than the values recorded for BDJs. Times of contact, amortization and take-off during BDJs were significantly shorter (p < 0.05 than the respective values obtained for CDJs. Therefore, the use of the RSI to monitor plyometric training should be based on the drop jump technique that is commonly performed by basketball players.

  4. Hydraulic jumps in a channel

    DEFF Research Database (Denmark)

    Bonn, D.; Andersen, Anders Peter; Bohr, Tomas

    2009-01-01

    We present a study of hydraulic jumps with flow predominantly in one direction, created either by confining the flow to a narrow channel with parallel walls or by providing an inflow in the form of a narrow sheet. In the channel flow, we find a linear height profile upstream of the jump as expected...

  5. Sex Differences in Countermovement Jump Phase Characteristics

    National Research Council Canada - National Science Library

    McMahon, John; Rej, Sophie; Comfort, Paul

    2017-01-01

    .... The purpose of this study was to explore differences in CMJ phase characteristics between male and female athletes by comparing the force-, power-, velocity-, and displacement-time curves throughout...

  6. Electrostatic charging of jumping droplets

    Science.gov (United States)

    Miljkovic, Nenad; Preston, Daniel J.; Enright, Ryan; Wang, Evelyn N.

    2013-09-01

    With the broad interest in and development of superhydrophobic surfaces for self-cleaning, condensation heat transfer enhancement and anti-icing applications, more detailed insights on droplet interactions on these surfaces have emerged. Specifically, when two droplets coalesce, they can spontaneously jump away from a superhydrophobic surface due to the release of excess surface energy. Here we show that jumping droplets gain a net positive charge that causes them to repel each other mid-flight. We used electric fields to quantify the charge on the droplets and identified the mechanism for the charge accumulation, which is associated with the formation of the electric double layer at the droplet-surface interface. The observation of droplet charge accumulation provides insight into jumping droplet physics as well as processes involving charged liquid droplets. Furthermore, this work is a starting point for more advanced approaches for enhancing jumping droplet surface performance by using external electric fields to control droplet jumping.

  7. Jump conditions in transonic equilibria

    Energy Technology Data Exchange (ETDEWEB)

    Guazzotto, L.; Betti, R. [Department of Mechanical Engineering, University of Rochester, Rochester, New York 14627 (United States); Jardin, S. C. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540 (United States)

    2013-04-15

    In the present paper, the numerical calculation of transonic equilibria, first introduced with the FLOW code in Guazzotto et al.[Phys. Plasmas 11, 604 (2004)], is critically reviewed. In particular, the necessity and effect of imposing explicit jump conditions at the transonic discontinuity are investigated. It is found that 'standard' (low-{beta}, large aspect ratio) transonic equilibria satisfy the correct jump condition with very good approximation even if the jump condition is not explicitly imposed. On the other hand, it is also found that high-{beta}, low aspect ratio equilibria require the correct jump condition to be explicitly imposed. Various numerical approaches are described to modify FLOW to include the jump condition. It is proved that the new methods converge to the correct solution even in extreme cases of very large {beta}, while they agree with the results obtained with the old implementation of FLOW in lower-{beta} equilibria.

  8. Could the deep squat jump predict weightlifting performance?

    Science.gov (United States)

    Vizcaya, Francisco J; Viana, Oscar; del Olmo, Miguel Fernandez; Acero, Rafael Martin

    2009-05-01

    This research was carried out with the aim of describing the deep squat jump (DSJ) and comparing it with the squat (SJ) and countermovement (CMJ) jumps, to introduce it as a strength testing tool in the monitoring and control of training in strength and power sports. Forty-eight male subjects (21 weightlifters, 12 triathletes, and 15 physical education students) performed 3 trials of DSJ, SJ, and CMJ with a 1-minute rest among them. For the weightlifters, snatch and clean and jerk results during the Spanish Championship 2004 and the 35th EU Championships 2007 were collected to study the relationship among vertical jumps and weightlifters' performance. A 1-way analysis of variance (ANOVA) showed significant differences between groups in the vertical jumps, with the highest jumps for the weightlifters and the lowest for the triathletes. An ANOVA for repeated measures (type of jump) showed better results for DSJ and CMJ than SJ in all groups. A linear regression analysis was performed to determine the association between weightlifting and vertical jump performances. Correlations among the weightlifting performance and the vertical jumps were also calculated and determined using Pearson r. Results have shown that both CMJ and DSJ are strongly correlated with weightlifting ability. Therefore, both measures can be useful for coaches as a strength testing tool in the monitoring and control of training in weightlifting.

  9. Frequency Jump Detection and Analysis

    Science.gov (United States)

    2008-12-01

    CUMULATIVE SUM JUMP DETECTION The Cumulative Sum ( CUSUM ) is a classic change-point analysis technique that uses the cumulative sum of the...sum and y is the average of the data. The CUSUM slope indicates the value of the data with respect to the overall average. A flat cumulative sum...sudden change in the CUSUM slope indicates a jump in the data. The CUSUM plot for a data set having a single jump will have a V or inverted V shape

  10. Power-Velocity Characteristics and Jumping Abilities in Male Combat Athletes

    Directory of Open Access Journals (Sweden)

    Buśko Krzysztof

    2016-09-01

    Full Text Available Purpose. The aim of the study was to examine differences in power-velocity characteristics, and the maximal power and height of rise of the body’s centre of mass, measured in the counter-movement jump (CMJ and the spike jump (SPJ, between judoists, boxers and taekwondo athletes.

  11. Segmental and Kinetic Contributions in Vertical Jumps Performed with and without an Arm Swing

    Science.gov (United States)

    Feltner, Michael E.; Bishop, Elijah J.; Perez, Cassandra M.

    2004-01-01

    To determine the contributions of the motions of the body segments to the vertical ground reaction force ([F.sub.z]), the joint torques produced by the leg muscles, and the time course of vertical velocity generation during a vertical jump, 15 men were videotaped performing countermovement vertical jumps from a force plate with and without an arm…

  12. Realized Jump Risk and Equity Return in China

    OpenAIRE

    Guojin Chen; Xiaoqun Liu; Peilin Hsieh; Xiangqin Zhao

    2014-01-01

    We utilize the realized jump components to explore a new jump (including nonsystematic jump and systematic jump) risk factor model. After estimating daily realized jumps from high-frequency transaction data of the Chinese A-share stocks, we calculate monthly jump size, monthly jump standard deviation, and monthly jump arrival rate and then use those monthly jump factors to explain the return of the following month. Our empirical results show that the jump tail risk can explain the equity retu...

  13. Rook Jumping Maze Design Considerations

    Science.gov (United States)

    Neller, Todd W.; Fisher, Adrian; Choga, Munyaradzi T.; Lalvani, Samir M.; McCarty, Kyle D.

    We define the Rook Jumping Maze, provide historical perspective, and describe a generation method for such mazes. When applying stochastic local search algorithms to maze design, most creative effort concerns the definition of an objective function that rates maze quality. We define and discuss several maze features to consider in such a function definition. Finally, we share our preferred design choices, make design process observations, and note the applicability of these techniques to variations of the Rook Jumping Maze.

  14. The Effect of Depth Jumps and Weight Training on Leg Strength and Vertical Jump.

    Science.gov (United States)

    Clutch, David; And Others

    1983-01-01

    Two experiments examined the results of depth jumping programs to determine: (1) whether certain depth jumping routines, when combined with weight training, are better than others; and (2) the effect of depth jumping on athletes already in training. Results indicated that depth jumping is effective, but no more so than regular jumping routines.…

  15. The acute effect of vibration applications on jumping performance

    Directory of Open Access Journals (Sweden)

    Suat Yıldız

    2012-12-01

    Full Text Available Recently, vibration has become very popular as a method of exercise and training and drawn attention of researchers. The aim of this study was to analyses the acute affect of vibration applications as a method of exercise and training on jumping performance.In this study experimental group consists of 25 subjects who are studying at Physical Education and Sports Department of Sakarya University (age 22.2±1.7 years, height 179.2±4.8 cm. body weight 71.5±9.0 kg. This study included a vibration at density of 35 Hz (3x30 sec. frequency that result from aerobic exercise that has low density and b just methods of aerobic exercise (without any vibration that has low density. Subjects have taken the tests of countermovement and squat jumping after 2 minutes of each application. All applications and tests have been done in nonconsecutive days in a random scheme. In statistical analysis Wilcoxon has been applied in nonparametric scheme.For counter movement jumping; height of jumping, the difference between before and after the application of vibration related to the point of peak power and average power has been found significiant (respectively, p0.05; p>0.05; p>0.05.As a result, it is concluded that vibration that is applied at the range of 35 Hz frequency could increase the performance of acute countermovement jumping.

  16. Test-retest reliability of jump execution variables using mechanography: A comparison of jump protocols

    Science.gov (United States)

    Mechanography during the vertical jump test allows for evaluation of force-time variables reflecting jump execution, which may enhance screening for functional deficits that reduce physical performance and determining mechanistic causes underlying performance changes. However, utility of jump mechan...

  17. Relationships among jumping performances and sprint parameters during maximum speed phase in sprinters.

    Science.gov (United States)

    Kale, Mehmet; Aşçi, Alper; Bayrak, Coşkun; Açikada, Caner

    2009-11-01

    The purpose of this study was to investigate the relationships among jumping performances and speed parameters during maximum speed phase in sprinters. Twenty-one men sprinters volunteered to participate at the beginning of the preparation training phase. All tests-including 100-m sprint running, squat jump (SJ), countermovement jump (CMJ), drop jump (DJ), 60-second repetitive jump (RJ), standing long jump (SLJ), standing triple jump (STJ), standing quintuple jump (SQJ), and standing 10-stride jump (STENJ)-were done on switching mats. Flight (FT) and contact times (CT) during the vertical jump tests and 10-m split times during 100-m sprint running were measured by a 2-channel precision timing system (PTS) connected to the mats. The trace marking method was used for measuring the stride length (SL) through 60 m in 100-m sprint running. Stride frequency (SF), maximum velocity (Vmax), jump height for all vertical jumps, and lower-body power in DJ and RJ were calculated. Statistical analysis showed that the highest significant correlation was found between Vmax and DJ height (r = 0.69; p sprint running and SJ (r = 0.39; p sprint running than the other vertical and horizontal jump tests at the beginning of the preparation training phase.

  18. Vertical jumping tests in volleyball: reliability, validity, and playing-position specifics.

    Science.gov (United States)

    Sattler, Tine; Sekulic, Damir; Hadzic, Vedran; Uljevic, Ognjen; Dervisevic, Edvin

    2012-06-01

    Vertical jumping is known to be important in volleyball, and jumping performance tests are frequently studied for their reliability and validity. However, most studies concerning jumping in volleyball have dealt with standard rather than sport-specific jumping procedures and tests. The aims of this study, therefore, were (a) to determine the reliability and factorial validity of 2 volleyball-specific jumping tests, the block jump (BJ) test and the attack jump (AJ) test, relative to 2 frequently used and systematically validated jumping tests, the countermovement jump test and the squat jump test and (b) to establish volleyball position-specific differences in the jumping tests and simple anthropometric indices (body height [BH], body weight, and body mass index [BMI]). The BJ was performed from a defensive volleyball position, with the hands positioned in front of the chest. During an AJ, the players used a 2- to 3-step approach and performed a drop jump with an arm swing followed by a quick vertical jump. A total of 95 high-level volleyball players (all men) participated in this study. The reliability of the jumping tests ranged from 0.97 to 0.99 for Cronbach's alpha coefficients, from 0.93 to 0.97 for interitem correlation coefficients and from 2.1 to 2.8 for coefficients of variation. The highest reliability was found for the specific jumping tests. The factor analysis extracted one significant component, and all of the tests were highly intercorrelated. The analysis of variance with post hoc analysis showed significant differences between 5 playing positions in some of the jumping tests. In general, receivers had a greater jumping capacity, followed by libero players. The differences in jumping capacities should be emphasized vis-a-vis differences in the anthropometric measures of players, where middle hitters had higher BH and body weight, followed by opposite hitters and receivers, with no differences in the BMI between positions.

  19. Gravity current jump conditions, revisited

    Science.gov (United States)

    Ungarish, Marius; Hogg, Andrew J.

    2016-11-01

    Consider the flow of a high-Reynolds-number gravity current of density ρc in an ambient fluid of density ρa in a horizontal channel z ∈ [ 0 , H ] , with gravity in - z direction. The motion is often modeled by a two-layer formulation which displays jumps (shocks) in the height of the interface, in particular at the leading front of the dense layer. Various theoretical models have been advanced to predict the dimensionless speed of the jump, Fr = U /√{g' h } ; g' , h are reduced gravity and jump height. We revisit this problem and using the Navier-Stokes equations, integrated over a control volume embedding the jump, derive balances of mass and momentum fluxes. We focus on understanding the closures needed to complete this model and we show the vital need to understand the pressure head losses over the jump, which we show can be related to the vorticity fluxes at the boundaries of the control volume. Our formulation leads to two governing equations for three dimensionless quantities. Closure requires one further assumption, depending on which we demonstrate that previous models for gravity current fronts and internal bores can be recovered. This analysis yield new insights into existing results, and also provides constraints for potential new formulae.

  20. Coalescence-induced nanodroplet jumping

    Science.gov (United States)

    Cha, Hyeongyun; Xu, Chenyu; Sotelo, Jesus; Chun, Jae Min; Yokoyama, Yukihiro; Enright, Ryan; Miljkovic, Nenad

    2016-10-01

    Water vapor condensation on superhydrophobic surfaces has received much attention in recent years due to the ability of such surfaces to shed microscale water droplets via coalescence-induced droplet jumping, resulting in heat transfer, anti-icing, and self-cleaning performance enhancement. Here we report the coalescence-induced removal of water nanodroplets (R ≈500 nm ) from superhydrophobic carbon nanotube (CNT) surfaces. The two-droplet coalescence time is measured for varying droplet Ohnesorge numbers, confirming that coalescence prior to jumping is governed by capillary-inertial dynamics. By varying the conformal hydrophobic coating thickness on the CNT surface, the minimum jumping droplet radius is shown to increase with increasing solid fraction and decreasing apparent advancing contact angle, allowing us to explore both hydrodynamic limitations stemming from viscous dissipation and surface adhesion limitations. We find that, even for the smallest nanostructure length scale (≤100 nm) and lowest surface adhesions, nonideal surface interactions and the evolved droplet morphology play defining roles in limiting the minimum size for jumping on real surfaces. The outcomes of this work demonstrate the ability to passively shed nanometric water droplets, which has the potential to further increase the efficiency of systems that can harness jumping droplets for a wide range of energy and water applications.

  1. How far can Tarzan jump?

    Science.gov (United States)

    Shima, Hiroyuki

    2012-11-01

    The tree-based rope swing is a popular recreational facility, often installed in outdoor areas. Hanging from a rope, users drop from a high platform and then swing at great speed like ‘Tarzan’, finally jumping ahead to land on the ground. The question naturally arises, how far can Tarzan jump using the swing? In this paper, I present an introductory analysis of the mechanics of the Tarzan swing, a large pendulum-like swing with Tarzan himself attached as weight. This enables determination of how much further forward Tarzan can jump using a given swing apparatus. The discussion is based on elementary mechanics and is, therefore, expected to provide rich opportunities for investigations using analytic and numerical methods.

  2. How far can Tarzan jump?

    CERN Document Server

    Shima, Hiroyuki

    2012-01-01

    The tree-based rope swing is a popular recreation facility, often installed in outdoor areas, giving pleasure to thrill-seekers. In the setting, one drops down from a high platform, hanging from a rope, then swings at a great speed like "Tarzan", and finally jumps ahead to land on the ground. The question now arises: How far can Tarzan jump by the swing? In this article, I present an introductory analysis of the Tarzan swing mechanics, a big pendulum-like swing with Tarzan himself attached as weight. The analysis enables determination of how farther forward Tarzan can jump using a given swing apparatus. The discussion is based on elementary mechanics and, therefore, expected to provide rich opportunities for investigations using analytic and numerical methods.

  3. USEFULNESS AND METABOLIC IMPLICATIONS OF A 60-SECOND REPEATED JUMPS TEST AS A PREDICTOR OF ACROBATIC JUMPING PERFORMANCE IN GYMNASTS

    Directory of Open Access Journals (Sweden)

    Ferran Antoni Rodriguez

    2013-01-01

    Full Text Available Gymnastics floor exercises are composed of a set of four to five successive acrobatic jumps usually called a �series�. The aims of the study were: 1 to relate the acrobatic gymnastics performance of these series with a repeated jumps test of similar duration (R60, 2 to study the relation between R60 and physiological parameters (heart rate and blood lactate, and the performance obtained in different kinds of jumps, 3 to confirm whether R60, executed without a damped jumping technique, can be considered an anaerobic lactic power test. Twenty male and twenty-four female gymnasts performed three repeated jumps tests for 5 s (R5, 10 s (R10 and 60 s (R60 and vertical jumps, such as drop jumps (DJ, squat jumps (SJ and countermovement jumps (CMJ. We assessed heart rate (HR and blood lactate during R10 and R60. The average values of the maximal blood lactate concentration (Lmax after R10 (males = 2.5±0.6 mmol.l-1; females = 2.1±0.8 mmol.l-1 confirm that anaerobic glycolysis is not activated to a high level. In R60, the Lmax (males = 7.5±1.7 mmol.l-1; females = 5.9±2.1 mmol.l-1 that was recorded does not validate R60 as an anaerobic lactic power test. We confirmed the relation between the average power obtained in R60 (R60Wm and the acrobatic performance on the floor. The inclusion in the multiple regression equation of the best power in DJ and the best flight-contact ratio (FC in R5 confirms the influence of other non-metabolic components on the variability in R60 performance, at least in gymnasts.

  4. Alzheimer's Deaths Jump 55 Percent: CDC

    Science.gov (United States)

    ... page: https://medlineplus.gov/news/fullstory_165941.html Alzheimer's Deaths Jump 55 Percent: CDC More patients also ... News) -- As more baby boomers age, deaths from Alzheimer's disease have jumped 55 percent, and in a ...

  5. Inherent enumerability of strong jump-traceability

    CERN Document Server

    Diamondstone, David; Turetsky, Daniel

    2011-01-01

    We show that every strongly jump-traceable set obeys every benign cost function. Moreover, we show that every strongly jump-traceable set is computable from a computably enumerable strongly jump-traceable set. This allows us to generalise properties of c.e.\\ strongly jump-traceable sets to all such sets. For example, the strongly jump-traceable sets induce an ideal in the Turing degrees; the strongly jump-traceable sets are precisely those that are computable from all superlow Martin-L\\"{o}f random sets; the strongly jump-traceable sets are precisely those that are a base for $\\text{Demuth}_{\\text{BLR}}$-randomness; and strong jump-traceability is equivalent to strong superlowness.

  6. The "how" and "why" of the ancient Greek long jump with weights: a five-fold symmetric jump in a row?

    Science.gov (United States)

    Lenoir, Matthieu; De Clercq, Dirk; Laporte, Willy

    2005-10-01

    A plausible explanation for the ancient long jump records from Greek antiquity is sought on the basis of pictorial and written sources, and corroborated with practical tests. Ancient sources report that athletes jumped more than 15 m with weights in their hands, which enabled them to jump further than without these weights. It is proposed that the ancient Greek long jump was a continuous succession of five standing broad jumps, in which the landing phase of one jump was also the countermovement for the next jump. Four trained athletes jumped further with (14.64 +/- 0.76 m, range 13.64-15.63 m) than without weights (13.88 +/- 0.70 m, range 12.60-14.75 m; P = 0.001). These results show that this technique is executable, fits with ancient written and pictorial sources, and allows trained modern athletes to jump distances well over 15 m. The extra distance jumped when using weights may be due to changes in the position of the jumper's centre of mass at take-off and at landing, and an increase in take-off velocity stemming from several biomechanical mechanisms.

  7. Effects of kettlebell training on postural coordination and jump performance

    DEFF Research Database (Denmark)

    Jay, Kenneth; Jakobsen, Markus Due; Sundstrup, Emil

    2013-01-01

    ABSTRACT: The aim of this study was to investigate the effectiveness of a worksite intervention using kettlebell training to improve postural reactions to perturbation and jump performance.This single-blind randomized controlled trial involved 40 adults (n=40) from occupations with a high....... The outcome measures were postural reactions to sudden perturbation and maximal countermovement jump height.Compared to the control group, the training group significant decreased stopping time following perturbation (-109ms, 95% CI [-196:-21]). Jump height increased significantly in the training group (1.5cm......, 95% CI [0.5:2.5]), but this was non-significantly different from control.Kettlebell training improves postural reactions to sudden perturbation. Future studies should investigate whether kettlebell training can reduce the risk of low-back injury in occupations with manual material handling or patient...

  8. Model for polygonal hydraulic jumps

    DEFF Research Database (Denmark)

    Martens, Erik Andreas; Watanabe, Shinya; Bohr, Tomas

    2012-01-01

    ) near the free surface in the jump region. The model consists of mass conservation and radial force balance between hydrostatic pressure and viscous stresses on the roller surface. In addition, we consider the azimuthal force balance, primarily between pressure and viscosity, but also including...

  9. Jumping property of Lyapunov values

    Institute of Scientific and Technical Information of China (English)

    毛锐; 王铎

    1996-01-01

    A sufficient condition for fcth Lyapunov value to be zero for planar polynomial vector fields is given, which extends the result of "jumping property’ of Lyapunov values obtained by Wang Duo to more general cases. A concrete example that the origin cannot be weak focus of order 1, 2, 4, 5, 8 is presented.

  10. Effect of various warm-up protocols on jump performance in college football players.

    Science.gov (United States)

    Pagaduan, Jeffrey C; Pojskić, Haris; Užičanin, Edin; Babajić, Fuad

    2012-12-01

    The purpose of this study was to identify the effects of warm-up strategies on countermovement jump performance. Twenty-nine male college football players (age: 19.4 ± 1.1 years; body height: 179.0 ± 5.1 cm; body mass: 73.1 ± 8.0 kg; % body fat: 11.1 ± 2.7) from the Tuzla University underwent a control (no warm-up) and different warm-up conditions: 1. general warm-up; 2. general warm-up with dynamic stretching; 3. general warm-up, dynamic stretching and passive stretching; 4. passive static stretching; 5. passive static stretching and general warm-up; and, 6. passive static stretching, general warm-up and dynamic stretching. Countermovement jump performance was measured after each intervention or control. Results from one way repeated measures ANOVA revealed a significant difference on warm-up strategies at F (4.07, 113.86) = 69.56, p hoc revealed that a general warm-up and a general warm-up with dynamic stretching posted the greatest gains among all interventions. On the other hand, no warm-up and passive static stretching displayed the least results in countermovement jump performance. In conclusion, countermovement jump performance preceded by a general warm-up or a general warm-up with dynamic stretching posted superior gains in countermovement jump performance.

  11. Effects of a Low-Load Gluteal Warm-Up on Explosive Jump Performance

    Directory of Open Access Journals (Sweden)

    Comyns Thomas

    2015-06-01

    Full Text Available The purpose of this study was to investigate the effects of a low-load gluteal warm-up protocol on countermovement and squat jump performance. Research by Crow et al. (2012 found that a low-load gluteal warm-up could be effective in enhancing peak power output during a countermovement jump. Eleven subjects performed countermovement and squat jumps before and after the gluteal warm-up protocol. Both jumps were examined in separate testing sessions and performed 30 seconds, and 2, 4, 6 & 8 minutes post warm-up. Height jumped and peak ground reaction force were the dependent variables examined in both jumps, with 6 additional variables related to fast force production being examined in the squat jump only. All jumps were performed on a force platform (AMTI OR6-5. Repeated measures analysis of variance found a number of significant differences (p ≤ 0.05 between baseline and post warm-up scores. Height jumped decreased significantly in both jumps at all rest intervals excluding 8 minutes. Improvement was seen in 7 of the 8 recorded SJ variables at the 8 minute interval. Five of these improvements were deemed statistically significant, namely time to peak GRF (43.0%, and time to the maximum rate of force development (65.7% significantly decreased, while starting strength (63.4%, change of force in first 100 ms of contraction (49.1% and speed strength (43.6% significantly increased. The results indicate that a gluteal warm-up can enhance force production in squat jumps performed after 8 minutes recovery. Future research in this area should include additional warm-up intervention groups for comparative reasons.

  12. A jump forwards with mathematics and physics

    NARCIS (Netherlands)

    A. Heck; P. Uylings

    2011-01-01

    We jump on human body motions such as bouncing on a jumping stick, hopping, and making kangaroo jumps. Students can record the movements with a digital camera and use their video clips to investigate the motions with suitable video analysis and modelling software. We discuss some mathematical models

  13. Strawberry Shortcake and Other Jumping Rope Ideas.

    Science.gov (United States)

    Adams, Polly K.; Taylor, Michaell K.

    Information, guidelines, and activities for jumping rope are given. A short history of jumping rope explains how it evolved from a spring ritual for men to a play activity involving mostly young girls. Physical and cultural reasons are given as to why jumping rope has been more a sport for girls than for boys. Research studies are noted which show…

  14. Strawberry Shortcake and Other Jumping Rope Ideas.

    Science.gov (United States)

    Adams, Polly K.; Taylor, Michaell K.

    Information, guidelines, and activities for jumping rope are given. A short history of jumping rope explains how it evolved from a spring ritual for men to a play activity involving mostly young girls. Physical and cultural reasons are given as to why jumping rope has been more a sport for girls than for boys. Research studies are noted which show…

  15. Mesopause jumps at Antarctic latitudes

    Science.gov (United States)

    Lübken, Franz-Josef; Höffner, Josef; Becker, Erich; Latteck, Ralph; Murphy, Damian

    2016-04-01

    Recent high resolution temperature measurements by resonance lidar at Davis (69°S) occasionally showed a sudden mesopause altitude increase by ˜5 km and an associated mesopause temperature decrease by ˜10 K. We present further observations which are closely related to this 'mesopause jump', namely the increase of mean height of polar mesospheric summer echoes (PMSE) observed by a VHF radar, very strong westward winds in the upper mesosphere measured by an MF radar, and relatively large eastward winds in the stratosphere taken from reanalysis. We compare to similar observations in the Northern Hemisphere, namely at ALOMAR (69°N) where such mesopause jumps have never been observed. We present a detailed explanation of mesopause jumps. They occur only when stratospheric winds are moderately eastward and mesospheric winds are very large (westward). Under these conditions, gravity waves with comparatively large eastward phase Speeds can pass the stratosphere and propagate to the lower thermosphere because their vertical wavelengths in the mesosphere are rather large which implies reduced dynamical stability. When finally breaking in the lower thermosphere, these waves drive an enhanced residual circulation that causes a cold and high-altitude mesopause. The conditions for a mesopause jump occur only in the Southern Hemisphere (SH) and are associated with the late breakdown of the polar vortex. Mesopause jumps are primarily, but not only, observed prior and close to solstice. We also show that during the onset of PMSE in the SH, stratospheric zonal winds are still eastward (up to 30 m/s), and that the onset is not closely related to the Transition of the stratospheric circulation.

  16. The acute effect of vibration applications on jumping performance

    Directory of Open Access Journals (Sweden)

    Şener Soylu

    2012-12-01

    Full Text Available Recently, vibration has become very popular as a method of exercise and training and drawn attention of researchers. The aim of this study was to analyses the acute affect of vibration applications as a method of exercise and training on jumping performance. In this study experimental group consists of 25 subjects who are studying at Physical Education and Sports Department of Sakarya University (age 22.2±1.7 years, height 179.2±4.8 cm. body weight 71.5±9.0 kg. This study included a vibration at density of 35 Hz (3x30 sec. frequency  that result from  aerobic exercise that has low density and b just  methods of aerobic exercise (without any vibration that has  low density. Subjects have taken the tests of countermovement and squat jumping after 2 minutes of each application. All applications and tests have been done in nonconsecutive days in a random scheme. In statistical analysis Wilcoxon has been applied in nonparametric scheme. For counter movement jumping; height of jumping,  the difference between before and after  the application of vibration related to the point of peak power and average power has been found significiant (respectively, p<0.05; p<0.05; p<0.01. In addition to this, no statistical difference was found for squat vertical jumping before and after the application of vibration related to the point of peak power and average power (respectively, p>0.05; p>0.05; p>0.05. As a result, it is concluded that vibration that is applied at the range of 35 Hz frequency could increase the performance of acute countermovement jumping

  17. Mechanical parameters and flight phase characteristics in aquatic plyometric jumping.

    Science.gov (United States)

    Louder, Talin J; Searle, Cade J; Bressel, Eadric

    2016-09-01

    Plyometric jumping is a commonly prescribed method of training focused on the development of reactive strength and high-velocity concentric power. Literature suggests that aquatic plyometric training may be a low-impact, effective supplement to land-based training. The purpose of the present study was to quantify acute, biomechanical characteristics of the take-off and flight phase for plyometric movements performed in the water. Kinetic force platform data from 12 young, male adults were collected for counter-movement jumps performed on land and in water at two different immersion depths. The specificity of jumps between environmental conditions was assessed using kinetic measures, temporal characteristics, and an assessment of the statistical relationship between take-off velocity and time in the air. Greater peak mechanical power was observed for jumps performed in the water, and was influenced by immersion depth. Additionally, the data suggest that, in the water, the statistical relationship between take-off velocity and time in air is quadratic. Results highlight the potential application of aquatic plyometric training as a cross-training tool for improving mechanical power and suggest that water immersion depth and fluid drag play key roles in the specificity of the take-off phase for jumping movements performed in the water.

  18. Jumps of the eta invariant

    CERN Document Server

    Farber, M S; Farber, Michael S.; Levine, Jerome P.

    1994-01-01

    We study the eta-invariant, defined by Atiyah-Patodi-Singer a real valued invariant of an oriented odd-dimensional Riemannian manifold equipped with a unitary representation of its fundamental group. When the representation varies analytically, the corresponding eta-invariant may have an integral jump, known also as the spectral flow. The main result of the paper establishes a formula for this spectral jump in terms of the signatures of some homological forms, defined naturally by the path of representations. These signatures may also be computed by means of a spectral sequence of Hermitian forms,defined by the deformation data. Our theorem on the spectral jump has a generalization to arbitrary analytic families of self-adjoint elliptic operators. As an application we consider the problem of homotopy invariance of the rho-invariant. We give an intrinsic homotopy theoretic definition of the rho-invariant, up to indeterminacy in the form of a locally constant function on the space of unitary representations. In...

  19. Effect of different knee starting angles on intersegmental coordination and performance in vertical jumps.

    Science.gov (United States)

    Gheller, Rodrigo G; Dal Pupo, Juliano; Ache-Dias, Jonathan; Detanico, Daniele; Padulo, Johnny; dos Santos, Saray G

    2015-08-01

    This study aimed to analyze the effect of different knee starting angles on jump performance, kinetic parameters, and intersegmental coupling coordination during a squat jump (SJ) and a countermovement jump (CMJ). Twenty male volleyball and basketball players volunteered to participate in this study. The CMJ was performed with knee flexion at the end of the countermovement phase smaller than 90° (CMJ(90)), and in a preferred position (CMJ(PREF)), while the SJ was performed from a knee angle of 70° (SJ(70)), 90° (SJ(90)), 110° (SJ(110)), and in a preferred position (SJ(PREF)). The best jump performance was observed in jumps that started from a higher squat depth (CMJ(power was observed in the SJ(110) and CMJ(>90). Analysis of continuous relative phase showed that thigh-trunk coupling was more in-phase in the jumps (CMJ and SJ) performed with a higher squat depth, while the leg-thigh coupling was more in-phase in the CMJ(>90) and SJ(PREF). Jumping from a position with knees more flexed seems to be the best strategy to achieve the best performance. Intersegmental coordination and jump performance (CMJ and SJ) were affected by different knee starting angles.

  20. Effect of Instructions on Selected Jump Squat Variables.

    Science.gov (United States)

    Talpey, Scott W; Young, Warren B; Beseler, Bradley

    2016-09-01

    Talpey, SW, Young, WB, and Beseler, B. Effect of instructions on selected jump squat variables. J Strength Cond Res 30(9): 2508-2513, 2016-The purpose of this study was to compare 2 instructions on the performance of selected variables in a jump squat (JS) exercise. The second purpose was to determine the relationships between JS variables and sprint performance. Eighteen male subjects with resistance training experience performed 2 sets of 4 JS with no extra load with the instructions to concentrate on (a) jumping for maximum height and (b) extending the legs as fast as possible to maximize explosive force. Sprint performance was assessed at 0- to 10-m and 10- to 20-m distances. From the JS jump height, peak power, relative peak power, peak force, peak velocity, and countermovement distance were measured from a force platform and position transducer system. The JS variables under the 2 instructions were compared with paired t-tests, and the relationships between these variables and sprint performance were determined with Pearson's correlations. The jump height instruction produced greater mean jump height and peak velocity (p 0.05). Jump height was the variable that correlated most strongly with 10-m time and 10- to 20-m time under both instructions. The height instruction produced a stronger correlation with 10-m time (r = -0.455), but the fast leg extension JS produced a greater correlation with 10-20 time (r = -0.545). The results indicate that instructions have a meaningful influence on JS variables and therefore need to be taken into consideration when assessing or training athletes.

  1. Price jumps on European stock markets

    Directory of Open Access Journals (Sweden)

    Jan Hanousek

    2014-03-01

    Full Text Available We analyze the dynamics of price jumps and the impact of the European debt crisis using the high-frequency data reported by selected stock exchanges on the European continent during the period January 2008 to June 2012. We employ two methods to identify price jumps: Method 1 minimizes the probability of false jump detection (the Type-II Error-Optimal price jump indicator and Method 2 maximizes the probability of successful jump detection (the Type-I Error-Optimal price jump indicator. We show that individual stock markets exhibited differences in price jump intensity before and during the crisis. We also show that in general the variance of price jump intensity could not be distinguished as different in the pre-crisis period from that during the crisis. Our results indicate that, contrary to common belief, the intensity of price jumps does not uniformly increase during a period of financial distress. However, there do exist differences in price jump dynamics across stock markets and investors have to model emerging and mature markets differently to properly reflect their individual dynamics.

  2. Δ-matroid and jump system

    Directory of Open Access Journals (Sweden)

    Santosh N. Kabadi

    2005-01-01

    Full Text Available The concept of Δ-matroid is a nontrivial, proper generalization of the concept of matroid and has been further generalized to the concept of jump system. In this paper, we show that jump systems are, in some sense, equivalent to Δ-matroids. Using this equivalence and the Δ-matroid theory, we give simple proofs and extensions of many of the results on jump systems.

  3. Time change, jumping measure and Feller measure

    OpenAIRE

    He, Ping

    2007-01-01

    In this paper, we shall investigate some potential theory for time change of Markov processes. Under weak duality, it is proved that the jumping measure and Feller measure are actually independent of time change, and the jumping measure of a time changed process induced by a PCAF supported on $V$ coincides with the sum of the Feller measure on $V$ and the trace of the original jumping measure on $V$.

  4. The aerodynamics of jumping rope

    Science.gov (United States)

    Aristoff, Jeffrey; Stone, Howard

    2011-03-01

    We present the results of a combined theoretical and experimental investigation of the motion of a rotating string that is held at both ends (i.e. a jump rope). In particular, we determine how the surrounding fluid affects the shape of the string at high Reynolds numbers: the string bends toward the axis of rotation, thereby reducing its total drag. We derive a pair of coupled non-linear differential equations that describe the shape, the numerical solution of which compares well with asymptotic approximations and experiments. Implications for successful skipping will be discussed.

  5. Effects of slackline training on postural control, jump performance, and myoelectrical activity in female basketball players

    DEFF Research Database (Denmark)

    Santos, Luis; Fernández-Río, Javier; Fernández-García, Benjamín

    2016-01-01

    The main goal of the study was to assess the effects of slackline training on the postural control system and jump performance of athletes. Twenty-five female basketball players were randomized into 2 groups: control (N 12) and experimental (N 13). The latter experienced a 6-week supervised...... training in both groups. Performance on a countermovement jump test significantly improved only in the experimental group (effect side was 3.21 and 1.36 [flight time and jump height, respectively], which is described as a large effect). Mechanical power of the legs, as measured through the 30-second...

  6. Influence of Plyometrics on Jump Capabilities in Technical and Aesthetical Sports

    Directory of Open Access Journals (Sweden)

    Mlsnová Gabriela

    2017-05-01

    Full Text Available The aim of the study was to examine the effect of plyometric exercises on explosive strength of lower extremities in girls performing of technical and aesthetical sports. Experiment was carried out on three groups; artistic gymnasts (VG, n = 15; age = 12.4 ± 0.7 years, fitness girls (VF, n = 15; age = 13.8 ± 1.9 years and dancers (VD, n = 15; age = 13.8 ± 2 years. To check, the control group of general population was involved in the study (VK, n = 15; age = 13.9 ± 1.5 years. Following tests on jump ergometer Fitro Jumper were carried out at the beginning and at the end of experimental period: countermovement jump without and with arms swing and 10- second series of repeated vertical jumps. Plyometric program consisted of two plyometric units a week during thirty weeks. The results show that higher improvement in all evaluated tests achieved the group of fitness. In the countermovement jump without arm swing was observed improvement height of the jump 3.4 ± 1.4 cm (p ˂ 0.00001, in the countermovement jump with arm swing 5.7 ± 1.5 cm (p ˂ 0.00001, in difference of height of the jump between countermovement jump with and without arms swing 2.3 ± 1 cm (p ˂ 0.00001, in ten second series of repeated vertical jumps without arms swing in the height of jump 4.2 ± 1.6 cm (p ˂ 0.00001 and in power in active take off phase 8.8 ± 2.2 W.kg-1 (p ˂ 0.00001. Based on finding the study and in coherence with data from literature, we can conclude the effect of plyometric exercises was effective in combination with specific-strength training. Jumping ability is limiting factor of sport performance in technical and aesthetical sports and implementation of plyometric exercises to the training is highly recommend. The high level of jump capabilities can improve the quality and technique of performance complex acrobatic elements and dance leaps thereby increasing overall evaluation of performance in selected sports.

  7. Dynamic jump intensities and risk premiums

    DEFF Research Database (Denmark)

    Christoffersen, Peter; Ornthanalai, Chayawat; Jacobs, Kris

    2012-01-01

    We build a new class of discrete-time models that are relatively easy to estimate using returns and/or options. The distribution of returns is driven by two factors: dynamic volatility and dynamic jump intensity. Each factor has its own risk premium. The models significantly outperform standard...... models without jumps when estimated on S&P500 returns. We find very strong support for time-varying jump intensities. Compared to the risk premium on dynamic volatility, the risk premium on the dynamic jump intensity has a much larger impact on option prices. We confirm these findings using joint...... estimation on returns and large option samples....

  8. Laminar circular hydraulic jumps without separation

    Science.gov (United States)

    Dasgupta, Ratul; Tomar, Gaurav; Govindarajan, Rama

    2009-11-01

    The traditional inviscid criterion for the occurrence of a planar, standing hydraulic jump is to have the Froude number decrease downstream and go through a value of 1 at some location. Here, upstream propagating, small-amplitude, long, non-dispersive gravity waves are trapped, and non-linear steepening is said to result in a near-discontinuous height profile, but it is not clear how. Such a condition on the Froude number is shown in the present axisymmetric Navier-Stokes computations to hold for a circular jump as well. The relevance of non-linear steepening to a circular jump is therefore a question we wish to answer. In circular jumps, moreover, a region of recirculation is usually observed underneath the jump, underlining the importance of viscosity in this process. This led Tani (J. Phys. Soc. Japan, 1949) to hypothesise that boundary-layer separation was the cause of the circular jump. This hypothesis has been debated extensively and the possibility of circular jumps without separation hinted at. In our simulations, we are able to obtain circular hydraulic jumps without any flow separation. This, and the necessity or otherwise of viscosity in jump formation will be discussed.

  9. A Molecular Jump Mechanism of Water Reorientation

    National Research Council Canada - National Science Library

    Damien Laage; James T. Hynes

    2006-01-01

    .... This water reorientation mechanism involves large-amplitude angular jumps, rather than the commonly accepted sequence of small diffusive steps, and therefore calls for reinterpretation of many...

  10. Kinematics and Kinetics of Squats, Drop Jumps and Imitation Jumps of Ski Jumpers.

    Science.gov (United States)

    Pauli, Carole A; Keller, Melanie; Ammann, Fabian; Hübner, Klaus; Lindorfer, Julia; Taylor, William R; Lorenzetti, Silvio

    2016-03-01

    Squats, drop jumps, and imitation jumps are commonly used training exercises in ski jumping to enhance maximum force, explosive force, and sport-specific skills. The purpose of this study was to evaluate the kinetics and kinematics of training exercises in ski jumping and to find objective parameters in training exercises that most correlate with the competition performance of ski jumpers. To this end, barbell squats, drop jumps, and imitation jumps were measured in a laboratory environment for 10 elite ski jumpers. Force and motion data were captured, and the influence of maximum vertical force, force difference, vertical take-off velocity, knee moments, knee joint power, and a knee valgus/varus index was evaluated and correlated with their season jump performance. The results indicate that, especially for the imitation jumps, a good correlation exists between the vertical take-off velocity and the personal jump performance on the hill (R = 0.718). Importantly, however, the more the athletes tended toward a valgus knee alignment during the measured movements, the worse their performance (R = 0.729 imitation jumps; R = 0.685 squats). Although an evaluation of the athletes' lower limb alignment during competitive jumping on the hill is still required, these preliminary data suggest that performance training should additionally concentrate on improving knee alignment to increase ski jumping performance.

  11. Validation of the iPhone app using the force platform to estimate vertical jump height.

    Science.gov (United States)

    Carlos-Vivas, Jorge; Martin-Martinez, Juan P; Hernandez-Mocholi, Miguel A; Perez-Gomez, Jorge

    2016-09-22

    Vertical jump performance has been evaluated with several devices: force platforms, contact mats, Vertec, accelerometers, infrared cameras and high-velocity cameras; however, the force platform is considered the gold standard for measuring vertical jump height. The purpose of this study was to validate the iPhone app, My Jump, that measures vertical jump height by comparing it with other methods that use the force platform to estimate vertical jump height, namely, vertical velocity at take-off and time in the air. A total of 40 sport sciences students (age 21.4 ± 1.9 years) completed five countermovement jumps (CMJs) over a force platform. Thus, 200 CMJ heights were evaluated from the vertical velocity at take-off and the time in the air using the force platform, and from the time in the air with the mobile application My Jump. The height obtained was compared using the intraclass correlation coefficient (ICC). Correlation between APP and force platform using the time in the air was perfect (ICC = 1.000, P vertical velocity at take-off was also very high (ICC = 0.996, P vertical jump performance; however, vertical jump height is slightly overestimated compared with that of the force platform.

  12. Kinematic and kinetic characteristics of vertical jump: comparison between soccer and basketball players

    Directory of Open Access Journals (Sweden)

    Matheus Machado Gomes

    2009-09-01

    Full Text Available The aim of this study was to compare jump height and kinetic and kinematic com-ponents of countermovement vertical jumps between soccer and basketball players performed in two different arm swing conditions: with arm swing (WAS and without arm swing (NAS. Nine basketball players (21.2 ± 2.9 years; 101.64 ± 14.58 kg; 1.95 ± 0.06 m and nine soccer players (18.2 ± 0.7 years; 77.4 ± 7.58 kg; 1.81 ± 0.07 m performed 12 maximal countermo-vement vertical jumps, including 6 WAS jumps and 6 NAS jumps, on a force platform that recorded the ground reaction force (GRF. The vertical component of the GRF was used to estimate jump height and to calculate the kinematic (duration of eccentric phase, duration of concentric phase, and maximal downward displacement of center of mass and kinetic variables (mean power during the eccentric phase, mean power during the concentric, peak power, and peak force. The results showed no differences in jump height or in kinematic or kinetic variables between basketball and soccer players. In addition, the results showed that the participants of the two groups jumped higher in the WAS condition (0.41 m than in the NAS condition (0.36 m because of a higher peak power (WAS=276.8 W/kg0.67 and NAS=241.3 W/kg0.67 and a longer concentric phase duration (WAS=0.20 s/m0.5 and NAS=0.19 s/m0.5 during WAS jump. These results indicate that the basketball and soccer players studied here showed similar performance and the same kinematic and kinetic pattern in maximal vertical jumps and were comparably affected by the use of arm swing.

  13. Electroencephalographic recordings during parachute jump sessions.

    Science.gov (United States)

    Gauthier, P; Jouffray, L; Rodi, M; Gottesmann, C

    1980-04-01

    Electroencephalographic (EEG) recordings of experienced parachutists were done by means of telemetry before, during, and after jumps of up to 3500m. During free-fall and after stabilization, alpha rhythm was recorded from several alpha reactive subjects when they closed their eyes. No pathological EEG recordings were obtained during the different phases of the jump.

  14. Jump Detection in the Danish Stock Market

    DEFF Research Database (Denmark)

    Høg, Esben

    2002-01-01

    It is well known in financial economics that stock market return data are often modelled by a diffusion process with some regular drift function. Occasionally, however, sudden changes or jumps occur in the return data. Wavelet scaling methods are used to detect jumps and cusps in stock market...

  15. Rope Jumping: A Preliminary Developmental Study.

    Science.gov (United States)

    Wickstrom, Ralph L.

    The basic movement pattern used in skilled individual rope jumping performance was determined and used as a model against which to evaluate the rope jumping form used by children at various levels of skills development. The techniques of adults and nursery school children were filmed and analyzed. The specific causes of unsuccessful attempts were…

  16. Separation and pattern formation in hydraulic jumps

    DEFF Research Database (Denmark)

    Bohr, Tomas; Ellegaard, C.; Hansen, A. Espe;

    1998-01-01

    We present theory and experiments on the circular hydraulic jump in the stationary regime. The theory can handle the situation in which the fluid flows over an edge far away from the jump. In the experiments the external height is controlled, and a series of transitions in the flow structure appe...

  17. Internal hydraulic jumps with large upstream shear

    Science.gov (United States)

    Ogden, Kelly; Helfrich, Karl

    2015-11-01

    Internal hydraulic jumps in approximately two-layered flows with large upstream shear are investigated using numerical simulations. The simulations allow continuous density and velocity profiles, and a jump is forced to develop by downstream topography, similar to the experiments conducted by Wilkinson and Wood (1971). High shear jumps are found to exhibit significantly more entrainment than low shear jumps. Furthermore, the downstream structure of the flow has an important effect on the jump properties. Jumps with a slow upper (inactive) layer exhibit a velocity minimum downstream of the jump, resulting in a sub-critical downstream state, while flows with the same upstream vertical shear and a larger barotropic velocity remain super-critical downstream of the jump. A two-layer theory is modified to account for the vertical structure of the downstream density and velocity profiles and entrainment is allowed through a modification of the approach of Holland et al. (2002). The resulting theory can be matched reasonably well with the numerical simulations. However, the results are very sensitive to how the downstream vertical profiles of velocity and density are incorporated into the layered model, highlighting the difficulty of the two layer approximation when the shear is large.

  18. Strong jump traceability and Demuth randomness

    CERN Document Server

    Greenberg, Noam

    2011-01-01

    We solve the covering problem for Demuth randomness, showing that a computably enumerable set is computable from a Demuth random set if and only if it is strongly jump-traceable. We show that on the other hand, the class of sets which form a base for Demuth randomness is a proper subclass of the class of strongly jump-traceable sets.

  19. Stochastic stability properties of jump linear systems

    Science.gov (United States)

    Feng, Xiangbo; Loparo, Kenneth A.; Ji, Yuandong; Chizeck, Howard J.

    1992-01-01

    Jump linear systems are defined as a family of linear systems with randomly jumping parameters (usually governed by a Markov jump process) and are used to model systems subject to failures or changes in structure. The authors study stochastic stability properties in jump linear systems and the relationship among various moment and sample path stability properties. It is shown that all second moment stability properties are equivalent and are sufficient for almost sure sample path stability, and a testable necessary and sufficient condition for second moment stability is derived. The Lyapunov exponent method for the study of almost sure sample stability is discussed, and a theorem which characterizes the Lyapunov exponents of jump linear systems is presented.

  20. A review on the basketball jump shot.

    Science.gov (United States)

    Okazaki, Victor H A; Rodacki, André L F; Satern, Miriam N

    2015-06-01

    The ability to shoot an effective jump shot in the sport of basketball is critical to a player's success. In an attempt to better understand the aspects related to expert performance, researchers have investigated successful free throws and jump shots of various basketball players and identified movement variables that contribute to their success. The purpose of this study was to complete a systematic review of the scientific literature on the basketball free throw and jump shot for the purpose of revealing the critical components of shooting that coaches, teachers, and players should focus on when teaching, learning, practising, and performing a jump shot. The results of this review are presented in three sections: (a) variables that affect ball trajectory, (b) phases of the jump shot, and

  1. Jumping from the Brooklyn Bridge.

    Science.gov (United States)

    Kurtz, R J; Pizzi, W F; Richman, H; Tiefenbrun, J

    1987-07-01

    In an attempt to identify factors contributing to survival of free fall and impact, we evaluated the records of four patients who survived a jump from the Brooklyn Bridge into the East River in New York Harbor between 1977 and 1985. All four patients were male and ranged in age from 22 to 67 years. They had free falls of between 41.0 and 48.8 meters. All of the patients were brought to the hospital within 24 minutes of entering the water. Three of the four had emergency surgical treatment and the fourth patient had only minor injuries. All four patients survived the suicide attempts. The length of the hospital stay ranged from two to 26 days.

  2. Lack of association between postactivation potentiation and subsequent jump performance.

    Science.gov (United States)

    Pearson, Stephen John; Hussain, Syed Robiul

    2014-01-01

    Postactivation potentiation (PAP) is a strategy that has been used to acutely enhance the performance of explosive activities. Although, isometric maximal voluntary contractions (MVCs) have previously been shown to enhance subsequent explosive performance, no information currently exists regarding (1) the optimal variables (intensity/volume) of a MVC that best elicits a PAP response, and (2) the utilisation of evoked isometric twitch contractions in combination with performance measures to directly ascertain the presence of PAP following a MVC, and its relationship to performance. Thus, the purpose of this study was to (1) investigate the influence of isometric contraction duration on the PAP response, and (2) to determine the relationship between PAP, indicated as potentiation of muscle twitch force and subsequent jump performance following different-duration MVCs. Eight males (age: 21 ± 0.99) were assessed using performance measures [countermovement jumps] and evoked twitch contractions, before and 4 minutes after three different conditioning contractions (CCs), (1) a 3-second MVC (MVC3), (2) a 5-second MVC (MVC5) and (3) a 7-second MVC (MVC7). Following all CCs, peak twitch torque of the knee extensor muscles was found to increase (MVC3, + 3.9%; MVC5, + 9.6%; MVC7, + 5.2%), although not significantly (P > 0.05). No significant increases in jump height, jump power, rate of force development or takeoff velocity were observed following any of the CCs (P > 0.05). There was also a lack of association between the changes in PAP (twitch torque) and jump height following all CCs (MVC3, r = 0.25; MVC5, r = 0.28; MVC7, r = -0.47). These data indicate that PAP as assessed via twitch contractions is not associated with performance measures subsequent to single-set isometric CCs of varying durations.

  3. Jumping without using legs: the jump of the click-beetles (Elateridae is morphologically constrained.

    Directory of Open Access Journals (Sweden)

    Gal Ribak

    Full Text Available To return to their feet, inverted click-beetles (Elateridae jump without using their legs. When a beetle is resting on its dorsal side, a hinge mechanism is locked to store elastic energy in the body and releases it abruptly to launch the beetle into the air. While the functional morphology of the jumping mechanism is well known, the level of control that the beetle has over this jumping technique and the mechanical constraints governing the jumps are not entirely clear. Here we show that while body rotations in air are highly variable, the jumps are morphologically constrained to a constant "takeoff" angle (79.9°±1.56°, n = 9 beetles that directs 98% of the jumping force vertically against gravity. A physical-mathematical model of the jumping action, combined with measurements from live beetle, imply that the beetle may control the speed at takeoff but not the jumping angle. In addition, the model shows that very subtle changes in the exact point of contact with the ground can explain the vigorous rotations of the body seen while the beetle is airborne. These findings suggest that the evolution of this unique non-legged jumping mechanism resulted in a jumping technique that is capable of launching the body high into the air but it is too constrained and unstable to allow control of body orientation at landing.

  4. Effects of six warm-up protocols on sprint and jump performance.

    Science.gov (United States)

    Vetter, Rheba E

    2007-08-01

    The purpose of this study was to compare the effects of 6 warm-up protocols, with and without stretches, on 2 different power maneuvers: a 30-m sprint run and a vertical countermovement jump (CJ). The 6 protocols were: (a) walk plus run (WR); (b) WR plus exercises including small jumps (EJ); (c) WR plus dynamic active stretch plus exercises with small jumps (DAEJ); (d) WR plus dynamic active stretch (DA); (e) WR plus static stretch plus exercises with small jumps (SSEJ); and (f) WR plus static stretch (SS). Twenty-six college-age men (n = 14) and women (n = 12) performed each of 6 randomly ordered exercise routines prior to randomly ordered sprint and vertical jump field tests; each routine and subsequent tests were performed on separate days. A 2 x 6 repeated measures analysis of variance revealed a significant overall linear trend (p hoc analysis pairwise comparisons showed the WR protocol produced higher jumps than did SS (p = 0.003 protocols on sprint run performance (p > or = 0.05). No significant interaction occurred between gender and protocol. There were significant differences between men and women on CJ and sprint trials; as expected, in general men ran faster and jumped higher than the women did. The data indicate that a warm-up including static stretching may negatively impact jump performance, but not sprint time.

  5. Realized Jump Risk and Equity Return in China

    Directory of Open Access Journals (Sweden)

    Guojin Chen

    2014-01-01

    Full Text Available We utilize the realized jump components to explore a new jump (including nonsystematic jump and systematic jump risk factor model. After estimating daily realized jumps from high-frequency transaction data of the Chinese A-share stocks, we calculate monthly jump size, monthly jump standard deviation, and monthly jump arrival rate and then use those monthly jump factors to explain the return of the following month. Our empirical results show that the jump tail risk can explain the equity return. For the large capital-size stocks, large cap stock portfolios, and index, one-month lagged jump risk factor significantly explains the asset return variation. Our results remain the same even when we add the size and value factors in the robustness tests.

  6. Bubble visualization in a simulated hydraulic jump

    CERN Document Server

    Witt, Adam; Shen, Lian

    2013-01-01

    This is a fluid dynamics video of two- and three-dimensional computational fluid dynamics simulations carried out at St. Anthony Falls Laboratory. A transient hydraulic jump is simulated using OpenFOAM, an open source numerical solver. A Volume of Fluid numerical method is employed with a realizable k-epsilon turbulence model. The goal of this research is to model the void fraction and bubble size in a transient hydraulic jump. This fluid dynamics video depicts the air entrainment characteristics and bubble behavior within a hydraulic jump of Froude number 4.82.

  7. The trampoline aftereffect: the motor and sensory modulations associated with jumping on an elastic surface.

    Science.gov (United States)

    Márquez, Gonzalo; Aguado, Xavier; Alegre, Luis M; Lago, Angel; Acero, Rafael M; Fernández-del-Olmo, Miguel

    2010-08-01

    After repeated jumps over an elastic surface (e.g. a trampoline), subjects usually report a strange sensation when they jump again overground (e.g. they feel unable to jump because their body feels heavy). However, the motor and sensory effects of exposure to an elastic surface are unknown. In the present study, we examined the motor and perceptual effects of repeated jumps over two different surfaces (stiff and elastic), measuring how this affected maximal countermovement vertical jump (CMJ). Fourteen subjects participated in two counterbalanced sessions, 1 week apart. Each experimental session consisted of a series of maximal CMJs over a force plate before and after 1 min of light jumping on an elastic or stiff surface. We measured actual motor performance (height jump and leg stiffness during CMJ) and how that related to perceptual experience (jump height estimation and subjective sensation). After repeated jumps on an elastic surface, the first CMJ showed a significant increase in leg stiffness (P < or = 0.01), decrease in jump height (P < or = 0.01) increase in perceptual misestimation (P < or = 0.05) and abnormal subjective sensation (P < or = 0.001). These changes were not observed after repeated jumps on a rigid surface. In a complementary experiment, continuous surface transitions show that the effects persist across cycles, and the effects over the leg stiffness and subjective experience are minimized (P < or = 0.05). We propose that these aftereffects could be the consequence of an erroneous internal model resulting from the high vertical forces produced by the elastic surface.

  8. The Crown Bite Jumping Herbst.

    Science.gov (United States)

    Owen, Reuel

    2003-01-01

    The Crown Bite Jumping Herbst Appliance is evaluated and combined with Straight Wire Arch Fixed Orthodontics in treatment of Class II, Division I malocclusions. This article will evaluate a combined orthodontic approach of "straightening teeth" and an orthognathic approach of "moving jaws or making skeletal changes." Orthodontic treatment cannot be accomplished well without establishing a healthy temporomandibular joint. This is defined by Keller as a joint that is "noiseless, painless and has a normal range of motion without deviation and deflection." It is not prudent to separate orthodontic treatment as its own entity without being aware of the changes in the temporomandibular joint before, during and after treatment. In other words, "If you're doing orthodontics you're doing TMJ treatment." One should treat toward a healthy, beautiful face asking, "Will proposed treatment achieve this goal?" Treatment should be able to be carried out in an efficient manner, minimizing treatment time, be comfortable and affordable for the patient, and profitable for the dentist. The finished treatment should meet Andrews' Six Keys of Occlusion, or Loudon's Twelve Commandments. Above all, do no harm to the patient. We think that a specific treatment plan can embrace these tenets. The focus will be to show Class II treatment using a modified Herbst Appliance and fixed straight wire orthodontics.

  9. Volatility jumps and their economic determinants

    DEFF Research Database (Denmark)

    Caporin, Massimiliano; Rossi, Eduardo; Santucci de Magistris, Paolo

    that there is a positive probability of jumps in volatility. A common factor in the volatility jumps is shown to be related to a set of financial covariates (such as variance risk premium, S&P500 volume, credit-default swap, and federal fund rates). The credit-default swap on US banks and variance risk premium have...... predictive power on expected jump moves, thus confirming the common interpretation that sudden and large increases in equity volatility can be anticipated by credit deterioration of the US bank sector as well as changes in the market expectations of future risks. Finally, the model is extended to incorporate...... the credit-default swap and the variance risk premium in the dynamics of the jump size and intensity....

  10. Jump Horse Safety: Reconciling Public Debate and Australian Thoroughbred Jump Racing Data, 2012-2014.

    Science.gov (United States)

    Ruse, Karen; Davison, Aidan; Bridle, Kerry

    2015-10-22

    Thoroughbred jump racing sits in the spotlight of contemporary welfare and ethical debates about horse racing. In Australia, jump racing comprises hurdle and steeplechase races and has ceased in all but two states, Victoria and South Australia. This paper documents the size, geography, composition, and dynamics of Australian jump racing for the 2012, 2013, and 2014 seasons with a focus on debate about risks to horses. We found that the majority of Australian jump racing is regional, based in Victoria, and involves a small group of experienced trainers and jockeys. Australian jump horses are on average 6.4 years of age. The jump career of the majority of horses involves participating in three or less hurdle races and over one season. Almost one quarter of Australian jump horses race only once. There were ten horse fatalities in races over the study period, with an overall fatality rate of 5.1 fatalities per 1000 horses starting in a jump race (0.51%). There was significant disparity between the fatality rate for hurdles, 0.75 fatalities per 1000 starts (0.075%) and steeplechases, 14 fatalities per 1000 starts (1.4%). Safety initiatives introduced by regulators in 2010 appear to have significantly decreased risks to horses in hurdles but have had little or no effect in steeplechases. Our discussion considers these Animals 2015, 5 1073 data in light of public controversy, political debate, and industry regulation related to jump horse safety.

  11. Jump Horse Safety: Reconciling Public Debate and Australian Thoroughbred Jump Racing Data, 2012–2014

    Directory of Open Access Journals (Sweden)

    Karen Ruse

    2015-10-01

    Full Text Available Thoroughbred jump racing sits in the spotlight of contemporary welfare and ethical debates about horse racing. In Australia, jump racing comprises hurdle and steeplechase races and has ceased in all but two states, Victoria and South Australia. This paper documents the size, geography, composition, and dynamics of Australian jump racing for the 2012, 2013, and 2014 seasons with a focus on debate about risks to horses. We found that the majority of Australian jump racing is regional, based in Victoria, and involves a small group of experienced trainers and jockeys. Australian jump horses are on average 6.4 years of age. The jump career of the majority of horses involves participating in three or less hurdle races and over one season. Almost one quarter of Australian jump horses race only once. There were ten horse fatalities in races over the study period, with an overall fatality rate of 5.1 fatalities per 1000 horses starting in a jump race (0.51%. There was significant disparity between the fatality rate for hurdles, 0.75 fatalities per 1000 starts (0.075% and steeplechases, 14 fatalities per 1000 starts (1.4%. Safety initiatives introduced by regulators in 2010 appear to have significantly decreased risks to horses in hurdles but have had little or no effect in steeplechases. Our discussion considers these Animals 2015, 5 1073 data in light of public controversy, political debate, and industry regulation related to jump horse safety.

  12. Portfolio Selection with Jumps under Regime Switching

    Directory of Open Access Journals (Sweden)

    Lin Zhao

    2010-01-01

    Full Text Available We investigate a continuous-time version of the mean-variance portfolio selection model with jumps under regime switching. The portfolio selection is proposed and analyzed for a market consisting of one bank account and multiple stocks. The random regime switching is assumed to be independent of the underlying Brownian motion and jump processes. A Markov chain modulated diffusion formulation is employed to model the problem.

  13. Preschool-aged children's jumps: imitation performances.

    Science.gov (United States)

    Labiadh, Lazhar; Ramanantsoa, Marie-Martine; Golomer, Eveline

    2010-04-01

    Imitative behavior underlaid by perception and action links during children's development in complex locomotor skills has been the object of relatively few studies. In order to explore children's motor coordination modes, 130 children divided into five age groups from 3.5 to 7.5 years were instructed to imitate jumping tasks in spontaneous motor situation and in various imitative contexts by an adult providing verbal orders and gestural demonstrations. Their conformity to the model, stability and variability scores were coded from a video analysis when they performed jumps with obstacles. To evaluate their postural-motor control level, the durations of the preparatory phase and jumping flights were also timed. Results showed that all age groups generated the demonstrator's goal but not necessarily the same coordination modes of jumping. In imitation with temporal proximity, the model helped the youngest age groups to adopt his coordination modes and stabilized only the oldest age groups' performances starting from 5.5 years old, without effect on learning imitation. Differences between the youngest and oldest children in the jump duration suggested that the reproduction of a complex motor activity such as jumping with a one foot take-off would require resolution and adjustment of main postural stability.

  14. Is energy expenditure taken into account in human sub-maximal jumping?--A simulation study.

    Science.gov (United States)

    Vanrenterghem, Jos; Bobbert, Maarten F; Casius, L J Richard; De Clercq, Dirk

    2008-02-01

    This paper presents a simulation study that was conducted to investigate whether the stereotyped motion pattern observed in human sub-maximal jumping can be interpreted from the perspective of energy expenditure. Human sub-maximal vertical countermovement jumps were compared to jumps simulated with a forward dynamic musculo-skeletal model. This model consisted of four interconnected rigid segments, actuated by six Hill-type muscle actuators. The only independent input of the model was the stimulation of muscles as a function of time. This input was optimized using an objective function, in which targeting a specific sub-maximal height value was combined with minimizing the amount of muscle work produced. The characteristic changes in motion pattern observed in humans jumping to different target heights were reproduced by the model. As the target height was lowered, two major changes occurred in the motion pattern. First, the countermovement amplitude was reduced; this helped to save energy because of reduced dissipation and regeneration of energy in the contractile elements. Second, the contribution of rotation of the heavy proximal segments of the lower limbs to the vertical velocity of the centre of gravity at take-off was less; this helped to save energy because of reduced ineffective rotational energies at take-off. The simulations also revealed that, with the observed movement adaptations, muscle work was reduced through improved relative use of the muscle's elastic properties in sub-maximal jumping. According to the results of the simulations, the stereotyped motion pattern observed in sub-maximal jumping is consistent with the idea that in sub-maximal jumping, subjects are trying to achieve the targeted jump height with minimal energy expenditure.

  15. Fast unilateral isometric knee extension torque development and bilateral jump height.

    Science.gov (United States)

    de Ruiter, Cornelis J; Van Leeuwen, Daniel; Heijblom, Arjan; Bobbert, Maarten F; de Haan, Arnold

    2006-10-01

    We hypothesized that the initial rate (first 40 ms) of unilateral knee extensor torque development during a maximally fast isometric contraction would depend on the subjects' ability for fast neural activation and that it would predict bilateral jumping performance. Nine males (21.8 +/- 0.9 yr, means +/- SD) performed unilateral fast isometric knee extensions (120 degrees knee angle) without countermovement on a dynamometer and bilateral squat jumps (SJ) and countermovement jumps (CMJ) starting from 90 and 120 degrees knee angles (full extension = 180 degrees ). The dynamometer contractions started either from full relaxation or from an isometric pre-tension (15% maximal isometric torque, Tmax). Torque time integral for the first 40 ms after torque onset (TTI-40, normalized to Tmax) and averaged normalized rectified knee extensor EMG for 40 ms before fast torque onset (EMG-40) were used to quantify initial torque rise and voluntary muscle activation. TTI-40 without pre-tension (range: 0.02-0.19% Tmax per second) was significantly lower than TTI-40 with pre-tension, and both were significantly (r = 0.81 and 0.80) related to EMG-40. During jumping, similar significant positive relations were found between jump height and knee extensor EMG during the first 100 ms of the rise in ground reaction force. There also were significant positive linear relations between dynamometer TTI-40 and jump height (r = 0.75 (SJ 90), 0.84 (SJ 120), 0.76 (CMJ 90), and 0.86 (CMJ 120)) but not between dynamometer Tmax and jump height (-0.16 < r < 0.02). One-legged TTI-40 to a large extent explained the variation in jump height. The ability to produce a high efferent neural drive before muscle contraction seemed to dominate performance in both the simple single-joint isometric task and the complex multijoint dynamic task.

  16. Performance analysis of jump-gliding locomotion for miniature robotics.

    Science.gov (United States)

    Vidyasagar, A; Zufferey, Jean-Christohphe; Floreano, Dario; Kovač, M

    2015-03-26

    Recent work suggests that jumping locomotion in combination with a gliding phase can be used as an effective mobility principle in robotics. Compared to pure jumping without a gliding phase, the potential benefits of hybrid jump-gliding locomotion includes the ability to extend the distance travelled and reduce the potentially damaging impact forces upon landing. This publication evaluates the performance of jump-gliding locomotion and provides models for the analysis of the relevant dynamics of flight. It also defines a jump-gliding envelope that encompasses the range that can be achieved with jump-gliding robots and that can be used to evaluate the performance and improvement potential of jump-gliding robots. We present first a planar dynamic model and then a simplified closed form model, which allow for quantification of the distance travelled and the impact energy on landing. In order to validate the prediction of these models, we validate the model with experiments using a novel jump-gliding robot, named the 'EPFL jump-glider'. It has a mass of 16.5 g and is able to perform jumps from elevated positions, perform steered gliding flight, land safely and traverse on the ground by repetitive jumping. The experiments indicate that the developed jump-gliding model fits very well with the measured flight data using the EPFL jump-glider, confirming the benefits of jump-gliding locomotion to mobile robotics. The jump-glide envelope considerations indicate that the EPFL jump-glider, when traversing from a 2 m height, reaches 74.3% of optimal jump-gliding distance compared to pure jumping without a gliding phase which only reaches 33.4% of the optimal jump-gliding distance. Methods of further improving flight performance based on the models and inspiration from biological systems are presented providing mechanical design pathways to future jump-gliding robot designs.

  17. Jump Horse Safety: Reconciling Public Debate and Australian Thoroughbred Jump Racing Data, 2012–2014

    Science.gov (United States)

    Ruse, Karen; Davison, Aidan; Bridle, Kerry

    2015-01-01

    Simple Summary This paper documents the dynamics of Australian thoroughbred jump racing in the 2012, 2013, and 2014 seasons with the aim of informing debate about risks to horses and the future of this activity. We conclude that the safety of Australian jump racing has improved in recent years but that steeplechases are considerably riskier for horses than hurdle races. Abstract Thoroughbred jump racing sits in the spotlight of contemporary welfare and ethical debates about horse racing. In Australia, jump racing comprises hurdle and steeplechase races and has ceased in all but two states, Victoria and South Australia. This paper documents the size, geography, composition, and dynamics of Australian jump racing for the 2012, 2013, and 2014 seasons with a focus on debate about risks to horses. We found that the majority of Australian jump racing is regional, based in Victoria, and involves a small group of experienced trainers and jockeys. Australian jump horses are on average 6.4 years of age. The jump career of the majority of horses involves participating in three or less hurdle races and over one season. Almost one quarter of Australian jump horses race only once. There were ten horse fatalities in races over the study period, with an overall fatality rate of 5.1 fatalities per 1000 horses starting in a jump race (0.51%). There was significant disparity between the fatality rate for hurdles, 0.75 fatalities per 1000 starts (0.075%) and steeplechases, 14 fatalities per 1000 starts (1.4%). Safety initiatives introduced by regulators in 2010 appear to have significantly decreased risks to horses in hurdles but have had little or no effect in steeplechases. Our discussion considers these data in light of public controversy, political debate, and industry regulation related to jump horse safety. PMID:26506396

  18. Jumping to conclusions in schizophrenia

    Directory of Open Access Journals (Sweden)

    Evans SL

    2015-07-01

    Full Text Available Simon L Evans,1 Bruno B Averbeck,2 Nicholas Furl31School of Psychology, University of Sussex, Brighton, East Sussex, UK; 2Laboratory of Neuropsychology, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, USA; 3Department of Psychology, Royal Holloway, University of London, Egham, Surrey, UKAbstract: Schizophrenia is a mental disorder associated with a variety of symptoms, including hallucinations, delusions, social withdrawal, and cognitive dysfunction. Impairments on decision-making tasks are routinely reported: evidence points to a particular deficit in learning from and revising behavior following feedback. In addition, patients tend to make hasty decisions when probabilistic judgments are required. This is known as “jumping to conclusions” (JTC and has typically been demonstrated by presenting participants with colored beads drawn from one of two “urns” until they claim to be sure which urn the beads are being drawn from (the proportions of colors vary in each urn. Patients tend to make early decisions on this task, and there is evidence to suggest that a hasty decision-making style might be linked to delusion formation and thus be of clinical relevance. Various accounts have been proposed regarding what underlies this behavior. In this review, we briefly introduce the disorder and the decision-making deficits associated with it. We then explore the evidence for each account of JTC in the context of a wider decision-making deficit and then go on to summarize work exploring JTC in healthy controls using pharmacological manipulations and functional imaging. Finally, we assess whether JTC might have a role in therapy.Keywords: ketamine, decision making, delusions, fMRI, urn task

  19. Optimal coordination of maximal-effort horizontal and vertical jump motions – a computer simulation study

    Directory of Open Access Journals (Sweden)

    Komura Taku

    2007-06-01

    Full Text Available Abstract Background The purpose of this study was to investigate the coordination strategy of maximal-effort horizontal jumping in comparison with vertical jumping, using the methodology of computer simulation. Methods A skeletal model that has nine rigid body segments and twenty degrees of freedom was developed. Thirty-two Hill-type lower limb muscles were attached to the model. The excitation-contraction dynamics of the contractile element, the tissues around the joints to limit the joint range of motion, as well as the foot-ground interaction were implemented. Simulations were initiated from an identical standing posture for both motions. Optimal pattern of the activation input signal was searched through numerical optimization. For the horizontal jumping, the goal was to maximize the horizontal distance traveled by the body's center of mass. For the vertical jumping, the goal was to maximize the height reached by the body's center of mass. Results As a result, it was found that the hip joint was utilized more vigorously in the horizontal jumping than in the vertical jumping. The muscles that have a function of joint flexion such as the m. iliopsoas, m. rectus femoris and m. tibialis anterior were activated to a greater level during the countermovement in the horizontal jumping with an effect of moving the body's center of mass in the forward direction. Muscular work was transferred to the mechanical energy of the body's center of mass more effectively in the horizontal jump, which resulted in a greater energy gain of the body's center of mass throughout the motion. Conclusion These differences in the optimal coordination strategy seem to be caused from the requirement that the body's center of mass needs to be located above the feet in a vertical jumping, whereas this requirement is not so strict in a horizontal jumping.

  20. Segmental and kinetic contributions in vertical jumps performed with and without an arm swing.

    Science.gov (United States)

    Feltner, Michael E; Bishop, Elijah J; Perez, Cassandra M

    2004-09-01

    To determine the contributions of the motions of the body segments to the vertical ground reaction force (Fz), the joint torques produced by the leg muscles, and the time course of vertical velocity generation during a vertical jump, 15 men were videotaped performing countermovement vertical jumps from a force plate with and without an arm swing. Linear kinematic, Fz, and joint torque data were computed and compared using repeated measures analysis of variance. Maximum jump height was significantly larger in the arm swing jumps compared to the no arm swing jumps and was due to both a higher height of the center of mass (CM) at takeoff (54%) and a larger vertical velocity of the CM at takeoff (46%). The net vertical impulse created during the propulsive phase of the arm swing jumps was greater due to a trend of an increased duration (0.021 s) of the propulsive phase and not to larger average values of Fz. In the arm swing jumps, the arm motion resulted in the arms making a larger maximal contribution to Fz during the middle of the propulsive phase and decreased the negative contribution of the trunk-head and thigh to Fz late in the propulsive phase. Last, the arm swing decreased the extensor torques at the hip (13%), knee (10%), and ankle (10%) early in the propulsive phase but augmented these same extensor torques later in the propulsive phase.

  1. The effect of wind on jumping distance in ski jumping--fairness assessed.

    Science.gov (United States)

    Virmavirta, Mikko; Kivekäs, Juha

    2012-09-01

    The special wind compensation system recently adopted by Fédération Internationale de Ski (FIS; International Ski Federation) to consider the effects of changing wind conditions has caused some controversy. Here, the effect of wind on jumping distance in ski jumping was studied by means of computer simulation and compared with the wind compensation factors used by FIS during the World Cup season 2009/2010. The results showed clearly that the effect of increasing head/tail wind on jumping distance is not linear: +17.4 m/-29.1 m, respectively, for a wind speed of 3 m/s. The linear formula used in the trial period of the wind compensation system was found to be appropriate only for a limited range of jumping distances as the gradient of the landing slope slows down the rate of distance change in long jumps.

  2. Filtering and control of stochastic jump hybrid systems

    CERN Document Server

    Yao, Xiuming; Zheng, Wei Xing

    2016-01-01

    This book presents recent research work on stochastic jump hybrid systems. Specifically, the considered stochastic jump hybrid systems include Markovian jump Ito stochastic systems, Markovian jump linear-parameter-varying (LPV) systems, Markovian jump singular systems, Markovian jump two-dimensional (2-D) systems, and Markovian jump repeated scalar nonlinear systems. Some sufficient conditions are first established respectively for the stability and performances of those kinds of stochastic jump hybrid systems in terms of solution of linear matrix inequalities (LMIs). Based on the derived analysis conditions, the filtering and control problems are addressed. The book presents up-to-date research developments and novel methodologies on stochastic jump hybrid systems. The contents can be divided into two parts: the first part is focused on robust filter design problem, while the second part is put the emphasis on robust control problem. These methodologies provide a framework for stability and performance analy...

  3. A locust-inspired miniature jumping robot.

    Science.gov (United States)

    Zaitsev, Valentin; Gvirsman, Omer; Ben Hanan, Uri; Weiss, Avi; Ayali, Amir; Kosa, Gabor

    2015-11-25

    Unmanned ground vehicles are mostly wheeled, tracked, or legged. These locomotion mechanisms have a limited ability to traverse rough terrain and obstacles that are higher than the robot's center of mass. In order to improve the mobility of small robots it is necessary to expand the variety of their motion gaits. Jumping is one of nature's solutions to the challenge of mobility in difficult terrain. The desert locust is the model for the presented bio-inspired design of a jumping mechanism for a small mobile robot. The basic mechanism is similar to that of the semilunar process in the hind legs of the locust, and is based on the cocking of a torsional spring by wrapping a tendon-like wire around the shaft of a miniature motor. In this study we present the jumping mechanism design, and the manufacturing and performance analysis of two demonstrator prototypes. The most advanced jumping robot demonstrator is power autonomous, weighs 23 gr, and is capable of jumping to a height of 3.35 m, covering a distance of 1.37 m.

  4. Mechanical jumping power in young athletes.

    Science.gov (United States)

    Viitasalo, J T; Osterback, L; Alen, M; Rahkila, P; Havas, E

    1987-09-01

    Mechanical jumping power was determined for 286 young male athletes representing six sports events and ranging in calendar and skeletal ages from 8.8 to 17.1 and from 7.8 to 18.1 years, respectively. The subjects performed successive maximal vertical jumps on a contact mat for 30 s. The number of jumps and their cumulative flight time after 15 and 30 s were used for calculations of mechanical power. The jumping performances of the young athletes were found to be reproducible from the age of 10-12 years in respect to the angular displacement of the knee and duration of contact. Absolute mechanical power, as well as power related to body weight, increased with calendar and skeletal ages. Of the anthropometric characteristics, the circumference of the thigh and body weight showed the highest correlation with mechanical power; subjects with the greatest thigh circumference and body weight having the lowest mechanical power. The subjects were divided into 'power' (track and field, gymnastics) and 'endurance' (skiing, orienteering) groups. The former reached higher mechanical power values than the latter. Mechanical power for the second 15-s jumping period was on average 4.7% lower than for the first. The events did not differ from each other in respect of the decrease in power.

  5. Effectiveness of Different Rest Intervals Following Whole-Body Vibration on Vertical Jump Performance between College Athletes and Recreationally Trained Females

    Directory of Open Access Journals (Sweden)

    Nicole C. Dabbs

    2015-09-01

    Full Text Available The purpose of this study was to evaluate the effect of different rest intervals following whole-body vibration on counter-movement vertical jump performance. Sixteen females, eight recreationally trained and eight varsity athletes volunteered to participate in four testing visits separated by 24 h. Visit one acted as a familiarization visit where subjects were introduced to the counter-movement vertical jump and whole-body vibration protocols. Visits 2–4 contained 2 randomized conditions. Whole-body vibration was administered in four bouts of 30 s with 30 s rest between bouts. During whole-body vibration subjects performed a quarter squat every 5 s, simulating a counter-movement vertical jump. Whole-body vibration was followed by three counter-movement vertical jumps with five different rest intervals between the vibration exposure and jumping. For a control condition, subjects performed squats with no whole-body vibration. There was a significant (p < 0.05 main effect for time for vertical jump height, peak power output, and relative ground reaction forces, where a majority of individuals max jump from all whole-body vibration conditions was greater than the control condition. There were significant (p < 0.05 group differences, showing that varsity athletes had a greater vertical jump height and peak power output compared to recreationally trained females. There were no significant (p > 0.05 group differences for relative ground reaction forces. Practitioners and/or strength and conditioning coaches may utilize whole-body vibration to enhance acute counter-movement vertical jump performance after identifying individuals optimal rest time in order to maximize the potentiating effects.

  6. Nonlinear regimes on polygonal hydraulic jumps

    Science.gov (United States)

    Rojas, Nicolas

    2016-11-01

    This work extends previous leading and higher order results on the polygonal hydraulic jump in the framework of inertial lubrication theory. The rotation of steady polygonal jumps is observed in the transition from one wavenumber to the next one, induced by a change in height of an external obstacle near the outer edge. In a previous publication, the study of stationary polygons is considered under the assumption that the reference frame rotates with the polygons when the number of corners change, in order to preserve their orientation. In this research work I provide a Hamiltonian approach and the stability analysis of the nonlinear oscillator that describe the polygonal structures at the jump interface, in addition to a perturbation method that enables to explain, for instance, the diversity of patterns found in experiments. GRASP, Institute of Physics, University of Liege, Belgium.

  7. Aerodynamic Jump for Long Rod Penetrators

    Directory of Open Access Journals (Sweden)

    Mark L. Bundy

    2000-04-01

    Full Text Available Aerodynamic jump for a non-spinning kinetic energy penetrator is neither a discontinuous change in the ,direction of motion at the origin of free night, nor is it the converse, i.e. a cumulativer~direc4on over a domain of infinite extent. Rather aerodynamic jump, for such a projectile, is a localised redirection of the centre of gravity motion, caused ~ the force of lift due to yaw over ther4latively short region from entry into free flight until the yaw reaches its first maximum. The primary objective of this paper is to provide answtfrs to the questions like what is aerodynamic jump, what liauses it, !lnd wh~t aspects df the flight trajectory does it refer to, or account for .

  8. Planarity of 3,4-jump Graphs

    Institute of Scientific and Technical Information of China (English)

    魏二玲; 刘颜佩

    2004-01-01

    For a graph G of size ε≥1 and its edge-induced subgraphs H1 and H2 of size γ(1 < γ < ε), H1 is said to be obtained from H2 by an edge jump if there exist four distinct vertices u, v, ω and x in G such that (u,v)∈E(H2), (ω,x)∈E(G) - E(H2) and H1=H2 - (u, v) + (ω, x). In this article, the γ-jump graphs(r≥3) are discussed. A graph H is said to be an γ-jump graph of G if its vertices correspond to the edge induced graph of size γ in G and two vertices are adjacent if and only if one of the two corresponding subgraphs can be obtained from the other by an edge jump. For k≥2, the k-th iterated γ-jump graph Jrk(G) is defined as Jγ(Jγk-1 (G)), where Jγ1 (G) = Jγ(G). An infinite sequence {Gi} of graphs is planar if every graph Gi is planar. It is shown that there does not exist a graph G for which the sequence {J3k(G)} is planar, where k is any positive integer. Meanwhile, lim gen(J3k(G)) =∞, where gen(G) denotes the genus of a graph G, if the sequence k→∞J3k(G) is defined for every positive integer k. As for the 4-jump graph of a graph G,{J4k(G)} is planar if and only if G = C5. For γ≥5, whether the fix graph of the sequence {Jγk(G))exists is determined.

  9. Spectral Analysis of Diffusions with Jump Boundary

    CERN Document Server

    Kolb, Martin

    2011-01-01

    In this paper we consider one-dimensional diffusions with constant coefficients in a finite interval with jump boundary and a certain deterministic jump distribution. We use coupling methods in order to identify the spectral gap in the case of a large drift and prove that that there is a threshold drift above which the bottom of the spectrum no longer depends on the drift. As a Corollary to our result we are able to answer two questions concerning elliptic eigenvalue problems with non-local boundary conditions formulated previously by Iddo Ben-Ari and Ross Pinsky.

  10. Aerodynamic Jump for Long Rod Penetrators

    OpenAIRE

    Mark L. Bundy

    2000-01-01

    Aerodynamic jump for a non-spinning kinetic energy penetrator is neither a discontinuous change in the ,direction of motion at the origin of free night, nor is it the converse, i.e. a cumulativer~direc4on over a domain of infinite extent. Rather aerodynamic jump, for such a projectile, is a localised redirection of the centre of gravity motion, caused ~ the force of lift due to yaw over ther4latively short region from entry into free flight until the yaw reaches its first maximum. The primary...

  11. The effect of static, ballistic, and proprioceptive neuromuscular facilitation stretching on vertical jump performance.

    Science.gov (United States)

    Bradley, Paul S; Olsen, Peter D; Portas, Matthew D

    2007-02-01

    The purpose of this study was to compare the acute effects of different modes of stretching on vertical jump performance. Eighteen male university students (age, 24.3 +/- 3.2 years; height, 181.5 +/- 11.4 cm; body mass, 78.1 +/- 6.4 kg; mean +/- SD) completed 4 different conditions in a randomized order, on different days, interspersed by a minimum of 72 hours of rest. Each session consisted of a standard 5-minute cycle warm-up, accompanied by one of the subsequent conditions: (a) control, (b) 10-minute static stretching, (c) 10-minute ballistic stretching, or (d) 10-minute proprioceptive neuromuscular facilitation (PNF) stretching. The subjects performed 3 trials of static and countermovement jumps prior to stretching and poststretching at 5, 15, 30, 45, and 60 minutes. Vertical jump height decreased after static and PNF stretching (4.0% and 5.1%, p ballistic stretching (2.7%, p > 0.05). However, jumping performance had fully recovered 15 minutes after all stretching conditions. In conclusion, vertical jump performance is diminished for 15 minutes if performed after static or PNF stretching, whereas ballistic stretching has little effect on jumping performance. Consequently, PNF or static stretching should not be performed immediately prior to an explosive athletic movement.

  12. Recovery Outline: New Mexico Jumping Mouse (Zapus hudsonius luteus)

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The purpose of this recovery outline is to provide an interim strategy to guide the conservation and recovery of the New Mexico meadow jumping mouse (jumping mouse)...

  13. Effects of three different stretching techniques on vertical jumping performance.

    Science.gov (United States)

    Kirmizigil, Berkiye; Ozcaldiran, Bahtiyar; Colakoglu, Muzaffer

    2014-05-01

    The aim of this study was to evaluate 3 different flexibility techniques: (a) ballistic stretching (BS), (b) proprioceptive neuromuscular facilitation stretching (PNF) + BS, and (c) PNF + static stretching (SS) on vertical jump (VJ) performance and to determine the most appropriate stretching method during warm-up period before explosive force disciplines. One hundred voluntary male athletes participated in this study. All subjects performed aerobic warm-up (5-minute jog) followed by BS (5 seconds for each stretching exercise), PNF + BS (PNF performed followed by 5 seconds of BS), and PNF + SS (PNF performed followed by 30 seconds of SS) treatment protocol, respectively in the same day. Each stretching treatment was applied for 4 sets bilaterally. In all stretching treatments, lumbar extensor, gluteus maximus, and hamstring muscles were stretched with a single stretching exercise. After a 2-minute brief rest period, participants performed 3 trials of VJ test followed by one of the treatment protocols. Vertical jump performance was evaluated by countermovement jump (CMJ). Participants were divided into 3 groups according to their flexibility and prejump performances after warm-up. For each individual group and the whole group, after all treatments, differences in CMJ values were obtained (p ≤ 0.05). Ballistic stretching increased the VJ performance in the groups with low and average flexibility, poor prejumping performance, and also in the whole group (p ≤ 0.05). Proprioceptive neuromuscular facilitation stretching + BS affected VJ performance in the group of participants with high flexibility (p ≤ 0.05). Proprioceptive neuromuscular facilitation + SS decreased VJ performance in groups of participants with high flexibility, moderate, and high prejumping performance and in whole group (p ≤ 0.05). Ballistic stretching method increased VJ height, therefore seems to be more suitable than PNF + SS and PNF + BS before events that rely on explosive power as a part

  14. Assessment of musculoskeletal system in women with jumping mechanography

    Directory of Open Access Journals (Sweden)

    Yannis Dionyssiotis

    2009-08-01

    Full Text Available Yannis Dionyssiotis1,2, Antonios Galanos1, Georgios Michas1, Georgios Trovas1, Georgios P Lyritis11Laboratory for Research of the Musculoskeletal System, University of Athens, KAT Hospital, Kifissia, Greece; 2Rehabilitation Department, Rhodes General Hospital, Rhodes, GreeceAbstract: The purpose of this study was to investigate and add reference data about the musculoskeletal system in women. The mechanography system of the Leonardo™ platform (Novotec, Germany was used to measure parameters of movement (velocity, force, power in 176 healthy Greek women aged 20–79 years, separated according to age decade in six groups: group 1 (n = 12, 20–29 years; group 2 (n = 14, 30–39 years; group 3 (n = 33, 40–49 years; group 4 (n = 59, 50–59 years including 21 postmenopausal; group 5 (n = 31, 60–69 years including 12 postmenopausal; and group 6 (n = 27, 70–79 years all postmenopausal. This system measures forces applied to the plate over time, calculates through acceleration the vertical velocity of center of gravity and using force and velocity it calculates power of vertical movements. All women performed a counter-movement jump (brief squat before the jump with freely moving arms. Weight was recorded on the platform before the jump and height was measured with a wall-mounted ruler. Body weight and body mass index were gradually increased; on the contrary height and all movement parameters except force (velocity, power were statistically decreased during aging and after menopause.Keywords: biomechanics, ground reaction force, power, women, menopause

  15. The acute effects of static and ballistic stretching on vertical jump performance in trained women.

    Science.gov (United States)

    Unick, Jessica; Kieffer, H Scott; Cheesman, Wendy; Feeney, Anna

    2005-02-01

    Traditionally stretching has been included as part of a warm-up that precedes athletic participation. However, there is mixed evidence as to whether stretching actually enhances or hinders athletic performance. Therefore, the purpose of this study was to examine the acute effects of static (SS) and ballistic stretching (BS) on vertical jump (VJ) performance and to investigate whether power was altered at 15 and 30 minutes after stretching. Sixteen actively trained women performed a series of vertical jumps (countermovement and drop jumps) after an initial nonstretching (NS) session and after participating in BS and SS sessions that were conducted in a balanced and randomized order. The results indicated that there was no significant difference (p ballistic stretching, elapsed time, or initial flexibility scores. This suggests that stretching prior to competition may not negatively affect the performance of trained women.

  16. Understanding the Physics of Bungee Jumping

    Science.gov (United States)

    Heck, Andre; Uylings, Peter; Kedzierska, Ewa

    2010-01-01

    Changing mass phenomena like the motion of a falling chain, the behaviour of a falling elastic bar or spring, and the motion of a bungee jumper surprise many a physicist. In this article we discuss the first phase of bungee jumping, when the bungee jumper falls, but the bungee rope is still slack. In instructional material this phase is often…

  17. Jumping Rope at Day of Play

    Science.gov (United States)

    2005-01-01

    Sarah Dastugue, 11, leaps in the air as Libby Knox, 9, swings a jump rope. The children were participants in Nickelodeon's Worldwide Day of Play celebration at Stennis Space Center (SSC) on Oct. 1. On the day of the event, children all over the world participate in physical activities as part of the celebration.

  18. Understanding the physics of bungee jumping

    NARCIS (Netherlands)

    Heck, A.; Uylings, P.; Kędzierska, E.

    2010-01-01

    Changing mass phenomena like the motion of a falling chain, the behaviour of a falling elastic bar or spring, and the motion of a bungee jumper surprise many a physicist. In this article we discuss the first phase of bungee jumping, when the bungee jumper falls, but the bungee rope is still slack.

  19. Jumping on the Social Media Bandwagon

    Science.gov (United States)

    Blakeslee, Lori

    2012-01-01

    Should a school district jump on the social media bandwagon? Yes! Social media provide a low-cost way to communicate school district priorities, influence decision makers, and tell its story without filters. Equally important, social media are where constituents are spending a lot of their time. With more than 800 million members, Facebook is an…

  20. Jumping on the Social Media Bandwagon

    Science.gov (United States)

    Blakeslee, Lori

    2012-01-01

    Should a school district jump on the social media bandwagon? Yes! Social media provide a low-cost way to communicate school district priorities, influence decision makers, and tell its story without filters. Equally important, social media are where constituents are spending a lot of their time. With more than 800 million members, Facebook is an…

  1. Jumping-droplet electrostatic energy harvesting

    Science.gov (United States)

    Miljkovic, Nenad; Preston, Daniel J.; Enright, Ryan; Wang, Evelyn N.

    2014-07-01

    Micro- and nanoscale wetting phenomena have been an active area of research due to its potential for improving engineered system performance involving phase change. With the recent advancements in micro/nanofabrication techniques, structured surfaces can now be designed to allow condensing coalesced droplets to spontaneously jump off the surface due to the conversion of excess surface energy into kinetic energy. In addition to being removed at micrometric length scales (˜10 μm), jumping water droplets also attain a positive electrostatic charge (˜10-100 fC) from the hydrophobic coating/condensate interaction. In this work, we take advantage of this droplet charging to demonstrate jumping-droplet electrostatic energy harvesting. The charged droplets jump between superhydrophobic copper oxide and hydrophilic copper surfaces to create an electrostatic potential and generate power during formation of atmospheric dew. We demonstrated power densities of ˜15 pW/cm2, which, in the near term, can be improved to ˜1 μW/cm2. This work demonstrates a surface engineered platform that promises to be low cost and scalable for atmospheric energy harvesting and electric power generation.

  2. DISCONTINUOUS FLOW OF TURBID DENSITY CURRENTS Ⅱ. INTERNAL HYDRAULIC JUMP

    Institute of Scientific and Technical Information of China (English)

    Jiahua FAN

    2005-01-01

    Traveling and stationary internal hydraulic jumps in density currents with positive or negative entrainment coefficients were analyzed based on simple assumptions. An expression of internal hydraulic jumps with entrainment coefficients was derived. Experimental data, published in literature, of stationary internal hydraulic jumps in turbid, thermal and saline density currents including measured values of water entrainment were used to compare with theory. Comparison was also made of traveling internal hydraulic jumps between measured data and theory.

  3. Option Valuation with Observable Volatility and Jump Dynamics

    DEFF Research Database (Denmark)

    Christoffersen, Peter; Feunou, Bruno; Jeon, Yoontae

    Under very general conditions, the total quadratic variation of a jump-diffusion process can be decomposed into diffusive volatility and squared jump variation. We use this result to develop a new option valuation model in which the underlying asset price exhibits volatility and jump intensity dy...

  4. Determination of jumps for functions via derivative Gabor series

    Institute of Scientific and Technical Information of China (English)

    ZHOU Ying-ying; SHI Xian-liang

    2009-01-01

    Recently, Shi Xianliang and Hu Lan published the method of concentration factors for determination of jumps of functions via MCM conjugate wavelets. Usually, it is difficult to calculate the Hilbert transform of general window functions. The aim of this paper is to discuss determination of jumps for functions based on derivative Gabor series. The results will simplify the calculation of jump values.

  5. Comparison of creatine monohydrate and carbohydrate supplementation on repeated jump height performance.

    Science.gov (United States)

    Koenig, Chad A; Benardot, Dan; Cody, Mildred; Thompson, Walter R

    2008-07-01

    Creatine monohydrate (CrMH) supplementation aids the ability to maintain performance during repeated bouts of high-intensity exercise, including jump performance. However, carbohydrate supplementation may also provide similar benefits and is less expensive. This study compared the effects of an energy-free placebo, 2 different caloric concentrations of carbohydrate drinks, and a CrMH supplement on repeated jump heights. Sixty active males (mean age, 22 +/- 3.2 years) performed 2 sets of countermovement static jump height tests (10 jumps over 60 seconds) separated by 5 days to determine the differential effects of the placebo, carbohydrate, and CrMH on jump height sustainability over 10 jumps. Subjects were randomly assigned to groups (15 subjects per group) to receive daily doses (x5 days) of carbohydrate drinks containing 100 or 250 kilocalories (kcal), a 25-g CrMH supplement, or an energy-free placebo. After 5 days, the CrMH group experienced a significant weight gain (+1.52; +/-0.89 kg, p energy-free placebo over the final 3-4 jumps. The 250-kcal carbohydrate-supplemented group experienced a level of benefit (p < 0.01) that was at least equal to that of the CrMH group (p < 0.05), suggesting that the higher dose of carbohydrate was as effective as CrMH in maintaining repeated bouts of high-intensity activity as measured by repeated static jumps. Given the equivalent performance improvement and the absence of weight gain, the carbohydrate supplementation could be considered the preferred option for weight-conscious power athletes involved in activities that require repeated- motion high-intensity activities.

  6. Effect of jumping interval training on neuromuscular and physiological parameters: a randomized controlled study.

    Science.gov (United States)

    Ache-Dias, Jonathan; Dellagrana, Rodolfo A; Teixeira, Anderson S; Dal Pupo, Juliano; Moro, Antônio R P

    2016-01-01

    This study analyzed the effect of 4 weeks of jumping interval training (JIT), included in endurance training, on neuromuscular and physiological parameters. Eighteen recreational runners, randomized in control and experimental groups, performed 40 min of running at 70% of velocity at peak oxygen uptake, for 3 times per week. Additionally, the experimental group performed the JIT twice per week, which consisted of 4 to 6 bouts of continuous vertical jumps (30 s) with 5-min intervals. Three days before and after the training period, the countermovement (CMJ) and continuous jump (CJ30), isokinetic and isometric evaluation of knee extensors/flexors, progressive maximal exercise, and submaximal constant-load exercise were performed. The JIT provoked improvement in neuromuscular performance, indicated by (i) increased jump height (4.7%; effect size (ES) = 0.99) and power output (≈ 3.7%; ES ≈ 0.82) of CMJ and rate of torque development of knee extensors in isometric contraction (29.5%; ES = 1.02); (ii) anaerobic power and capacity, represented by the mean of jump height (7.4%; ES = 0.8), and peak power output (PPO) (5.6%; ES = 0.73) of the first jumps of CJ30 and the mean of jump height (10.2%, ES = 1.04) and PPO (9.5%, ES = 1.1), considering all jumps of CJ30; and (iii) aerobic power and capacity, represented by peak oxygen uptake (9.1%, ES = 1.28), velocity at peak oxygen uptake (2.7%, ES = 1.11), and velocity corresponding to the onset of blood lactate accumulation (9.7%, ES = 1.23). These results suggest that the JIT included in traditional endurance training induces moderate to large effects on neuromuscular and physiological parameters.

  7. Relationships Between Sprint, Jumping and Strength Abilities, and 800 M Performance in Male Athletes of National and International Levels

    Directory of Open Access Journals (Sweden)

    Bachero-Mena Beatriz

    2017-08-01

    Full Text Available This study analysed the relationships between sprinting, jumping and strength abilities, with regard to 800 m running performance. Fourteen athletes of national and international levels in 800 m (personal best: 1:43-1:58 min:ss completed sprint tests (20 m and 200 m, a countermovement jump, jump squat and full squat test as well as an 800 m race. Significant relationships (p < 0.01 were observed between 800 m performance and sprint tests: 20 m (r = 0.72 and 200 m (r = 0.84. Analysing the 200 m run, the magnitude of the relationship between the first to the last 50 m interval times and the 800 m time tended to increase (1st 50 m: r = 0.71; 2nd 50 m: r = 0.72; 3rd 50 m: r = 0.81; 4th 50 m: r = 0.85. Performance in 800 m also correlated significantly (p < 0.01-0.05 with strength variables: the countermovement jump (r = -0.69, jump squat (r = -0.65, and full squat test (r = -0.58. Performance of 800 m in high-level athletes was related to sprint, strength and jumping abilities, with 200 m and the latest 50 m of the 200 m being the variables that most explained the variance of the 800 m performance.

  8. Dynamics of Coalescence-Induced Jumping Water Droplets

    CERN Document Server

    Miljkovic, Nenad; Enright, Ryan; Wang, Evelyn N

    2013-01-01

    This fluid dynamics video shows the different interaction mechanisms of coalescence-induced droplet jumping during condensation on a nanostructured superhydrophobic surface. High speed imaging was used to show jumping behavior on superhydrophobic copper oxide and carbon nanotube surfaces. Videos demonstrating multi-jumping droplets, jumping droplet return to the surface, and droplet-droplet electrostatic repulsions were analyzed. Experiments using external electric fields in conjunction with high speed imaging in a custom built experimental chamber were used to show that all coalescence-induced jumping droplets on superhydrophobic surfaces become positively charged upon leaving the surface, which is detailed in the video.

  9. Effect of early training on the jumping technique of horses.

    Science.gov (United States)

    Santamaría, Susana; Bobbert, Maarten F; Back, Willem; Barneveld, Ab; van Weeren, P Rene

    2005-03-01

    To investigate the effects of early training for jumping by comparing the jumping technique of horses that had received early training with that of horses raised conventionally. 40 Dutch Warmblood horses. The horses were analyzed kinematically during free jumping at 6 months of age. Subsequently, they were allocated into a control group that was raised conventionally and an experimental group that received 30 months of early training starting at 6 months of age. At 4 years of age, after a period of rest in pasture and a short period of training with a rider, both groups were analyzed kinematically during free jumping. Subsequently, both groups started a 1-year intensive training for jumping, and at 5 years of age, they were again analyzed kinematically during free jumping. In addition, the horses competed in a puissance competition to test maximal performance. Whereas there were no differences in jumping technique between experimental and control horses at 6 months of age, at 4 years, the experimental horses jumped in a more effective manner than the control horses; they raised their center of gravity less yet cleared more fences successfully than the control horses. However, at 5 years of age, these differences were not detected. Furthermore, the experimental horses did not perform better than the control horses in the puissance competition. Specific training for jumping of horses at an early age is unnecessary because the effects on jumping technique and jumping capacity are not permanent.

  10. Scaled Jump in Gravity-Reduced Virtual Environments.

    Science.gov (United States)

    Kim, MyoungGon; Cho, Sunglk; Tran, Tanh Quang; Kim, Seong-Pil; Kwon, Ohung; Han, JungHyun

    2017-04-01

    The reduced gravity experienced in lunar or Martian surfaces can be simulated on the earth using a cable-driven system, where the cable lifts a person to reduce his or her weight. This paper presents a novel cable-driven system designed for the purpose. It is integrated with a head-mounted display and a motion capture system. Focusing on jump motion within the system, this paper proposes to scale the jump and reports the experiments made for quantifying the extent to which a jump can be scaled without the discrepancy between physical and virtual jumps being noticed by the user. With the tolerable range of scaling computed from these experiments, an application named retargeted jump is developed, where a user can jump up onto virtual objects while physically jumping in the real-world flat floor. The core techniques presented in this paper can be extended to develop extreme-sport simulators such as parasailing and skydiving.

  11. Mechanical efficiency and force–time curve variation during repetitive jumping in trained and untrained jumpers.

    Science.gov (United States)

    McBride, Jeffrey M; Snyder, James G

    2012-10-01

    Mechanical efficiency (ME), the ratio between work performed and energy expenditure, is a useful criterion in determining the roles of stored elastic energy and chemically deduced energy contributing to concentric performance in stretch-shortening cycle movements. Increased force production during the eccentric phase has been shown to relate to optimal muscle-tendon unit (MTU) length change and thus optimization of usage of stored elastic energy. This phenomenon, as previously reported, is reflected by higher jump heights and ME. The purpose of this investigation was to determine if ME may be different between trained and untrained jumpers and thus be accounted for by variation in force production in the eccentric phase as a reflection of usage of stored elastic energy during various jump types. This investigation involved 9 trained (age 20.7 ± 3.2 years, height 178.6 ± 5.3 cm, body mass 79.0 ± 5.5 kg) and 7 untrained (age 21.43 ± 2.37 years, height 176.17 ± 10.89 cm, body mass 78.8 ± 12.5 kg) male jumpers. Trained subjects were Division I track and field athletes who compete in the horizontal or vertical jumping or running events. Force-time and displacement-time curves were obtained during jumping to determine jump height and to calculate work performed and to observe possible differences in force production in the eccentric phase. Respiratory gases with a metabolic cart were obtained during jumping to calculate energy expenditure. ME was calculated as the ratio between work performed and energy expenditure. The subjects completed four sessions involving 20 repetitions of countermovement jumps (CMJ) and drop jumps from 40 cm (DJ40), 60 cm (DJ60) and 80 cm (DJ80). The trained jumpers jumped significantly higher in the CMJ, DJ40, DJ60 and DJ80 conditions than their untrained counterparts (p ≤ 0.05). ME was significantly higher in the trained in comparison to the untrained jumpers during DJ40. The amount of negative work during all jump types was

  12. Capture of Trojans by Jumping Jupiter

    CERN Document Server

    Nesvorny, David; Morbidelli, Alessandro

    2013-01-01

    Jupiter Trojans are thought to be survivors of a much larger population of planetesimals that existed in the planetary region when planets formed. They can provide important constraints on the mass and properties of the planetesimal disk, and its dispersal during planet migration. Here we tested a possibility that the Trojans were captured during the early dynamical instability among the outer planets (aka the Nice model), when the semimajor axis of Jupiter was changing as a result of scattering encounters with an ice giant. The capture occurs in this model when Jupiter's orbit and its Lagrange points become radially displaced in a scattering event and fall into a region populated by planetesimals (that previously evolved from their natal transplanetary disk to ~5 AU during the instability). Our numerical simulations of the new capture model, hereafter jump capture, satisfactorily reproduce the orbital distribution of the Trojans and their total mass. The jump capture is potentially capable of explaining the ...

  13. Jump-Squat Performance and Its Relationship With Relative Training Intensity in High-Level Athletes.

    Science.gov (United States)

    Jiménez-Reyes, Pedro; Pareja-Blanco, Fernando; Balsalobre-Fernández, Carlos; Cuadrado-Peñafiel, Víctor; Ortega-Becerra, Manuel A; González-Badillo, Juan J

    2015-11-01

    To examine the relationship between the relative load in full squats and the height achieved in jump-squat (JS) exercises and to determine the load that maximizes the power output of high-level athletes. Fifty-one male high-level track-and-field athletes (age 25.2 ± 4.4 y, weight 77. ± 6.2 kg, height 179.9 ± 5.6 cm) who competed in sprinting and jumping events took part in the study. Full-squat 1-repetition-maximum (1-RM) and JS height (JH) with loads from 17 to 97 kg were measured in 2 sessions separated by 48 h. Individual regression analyses showed that JH (R2 = .992 ± .005) and the jump decrease (JD) that each load produced with respect to the unloaded countermovement jump (CMJ) (R2 = .992 ± 0.007) are highly correlated with the full-squat %1-RM, which means that training intensities can be prescribed using JH and JD values. The authors also found that the load that maximizes JS's power output was 0%RM (ie, unloaded CMJ). These results highlight the close relationship between JS performance and relative training intensity in terms of %1-RM. The authors also observed that the load that maximizes power output was 0%1-RM. Monitoring jump height during JS training could help coaches and athletes determine and optimize their training loads.

  14. Does performance of hang power clean differentiate performance of jumping, sprinting, and changing of direction?

    Science.gov (United States)

    Hori, Naruhiro; Newton, Robert U; Andrews, Warren A; Kawamori, Naoki; McGuigan, Michael R; Nosaka, Kazunori

    2008-03-01

    The primary purpose of this study was to investigate whether the athlete who has high performance in hang power clean, a common weightlifting exercise, has high performances in sprinting, jumping, and changing of direction (COD). As the secondary purpose, relationships between hang power clean performance, maximum strength, power and performance of jumping, sprinting, and COD also were investigated. Twenty-nine semiprofessional Australian Rules football players (age, height, and body mass [mean +/- SD]: 21.3 +/- 2.7 years, 1.8 +/- 0.1 m, and 83.6 +/- 8.2 kg) were tested for one repetition maximum (1RM) hang power clean, 1RM front squat, power output during countermovement jump with 40-kg barbell and without external load (CMJ), height of CMJ, 20-m sprint time, and 5-5 COD time. The subjects were divided into top and bottom half groups (n = 14 for each group) based on their 1RM hang power clean score relative to body mass, then measures from all other tests were compared with one-way analyses of variance. In addition, Pearson's product moment correlations between measurements were calculated among all subjects (n = 29). The top half group possessed higher maximum strength (P hang power clean, jumping, sprinting, COD, maximum strength, and power. Therefore, it seems likely there are underlying strength qualities that are common to the hang power clean, jumping, and sprinting.

  15. Comparison of the Capacity of Different Jump and Sprint Field Tests to Detect Neuromuscular Fatigue.

    Science.gov (United States)

    Gathercole, Rob J; Sporer, Ben C; Stellingwerff, Trent; Sleivert, Gord G

    2015-09-01

    Different jump and sprint tests have been used to assess neuromuscular fatigue, but the test with optimal validity remains to be established. The current investigation examined the suitability of vertical jump (countermovement jump [CMJ], squat jump [SJ], drop jump [DJ]) and 20-m sprint (SPRINT) testing for neuromuscular fatigue detection. On 6 separate occasions, 11 male team-sport athletes performed 6 CMJ, SJ, DJ, and 3 SPRINT trials. Repeatability was determined on the first 3 visits, with subsequent 3 visits (0-, 24-, and 72-hour postexercise) following a fatiguing Yo-Yo running protocol. SPRINT performance was most repeatable (mean coefficient of variation ≤2%), whereas DJ testing (4.8%) was significantly less repeatable than CMJ (3.0%) and SJ (3.5%). Each test displayed large decreases at 0-hour (33 of 49 total variables; mean effect size = 1.82), with fewer and smaller decreases at 24-hour postexercise (13 variables; 0.75), and 72-hour postexercise (19 variables; 0.78). SPRINT displayed the largest decreases at 0-hour (3.65) but was subsequently unchanged, whereas SJ performance recovered by 72-hour postexercise. In contrast, CMJ and DJ performance displayed moderate (12 variables; 1.18) and small (6 variables; 0.53) reductions at 72-hour postexercise, respectively. Consequently, the high repeatability and immediate and prolonged fatigue-induced changes indicated CMJ testing as most suitable for neuromuscular fatigue monitoring.

  16. Influence of dorsiflexion shoes on neuromuscular fatigue of the plantar flexors after combined tapping-jumping exercises in volleyball players.

    Science.gov (United States)

    Lapole, Thomas; Ahmaidi, Said; Gaillien, Benjamin; Leprêtre, Pierre-Marie

    2013-07-01

    Dorsiflexion shoes could be useful to increase jumping performance. The aim of the present study was to investigate the impact of wearing shoes inducing moderate dorsiflexion (2°) on neuromuscular fatigue induced by volleyball exercises involving multiple stretch-shortening cycles. Squat jump (SJ) and countermovement jump (CMJ) performance, and plantar flexors isometric voluntary and evoked contractile properties were assessed in 10 unfamiliarized trained volleyball players before and after a 10-minute intensive combined tapping-jumping volleyball exercise performed, in blinded randomized conditions, with neutral (0°) or moderate dorsiflexion (2°). No significant difference was observed on SJ performance in neutral and moderate dorsiflexion conditions. However, CMJ height was initially lower with 2° dorsiflexion compared with 0° (p volleyball exercise also induced a significant decrease in maximal voluntary contraction (p volleyball players.

  17. Quantum jumps of a fluxonium qubit

    Science.gov (United States)

    Vool, U.; Pop, I. M.; Sliwa, K.; Abdo, B.; Brecht, T.; Shankar, S.; Hatridge, M.; Schoelkopf, R. J.; Mirrahimi, M.; Glazman, L.; Devoret, M. H.

    2014-03-01

    The fluxonium qubit has recently been shown to have energy relaxation time (T1) of the order of 1 ms, limited by quasiparticle dissipation. With the addition of a Josephson Parametric Converter (JPC) to the experiment, trajectories corresponding to quantum jumps between the ground and 1st excited state can be measured, thus allowing the observation of the qubit decay in real time instead of that of an ensemble average. Our measurement fidelity with the JPC is in excess of 98% for an acquisition time of 5 us and we can thus continuously monitor the quantum jumps of the qubit in equilibrium with its environment in a time much shorter than its average relaxation time. We observe in our sample a jump statistics that varies from being completely Poissonian with a long (500 us) mean time in the ground state to being highly non-Poissonian with short (100 us) mean time in the ground state. The changes between these regimes occur on time scales of seconds, minutes and even hours. We have studied this effect and its relation to quasiparticle dynamics by injecting quasiparticles with a short intense microwave pulse and by seeding quasiparticle-trapping vortices with magnetic field. Work supported by: IARPA, ARO, and NSF.

  18. POTENTIAL FOR NON-CONTACT ACL INJURY BETWEEN STEP-CLOSE-JUMP AND HOP-JUMP TASKS

    Directory of Open Access Journals (Sweden)

    Li-I Wang

    2010-03-01

    Full Text Available This study aimed to compare the kinematics and kinetics during the landing of hop-jump and step-close-jump movements in order to provide further inferring that the potential risk of ACL injuries. Eleven elite male volleyball players were recruited to perform hop-jump and step-close-jump tasks. Lower extremity kinematics and ground reaction forces during landing in stop-jump tasks were recorded. Lower extremity kinetics was calculated by using an inverse dynamic process. Step-close-jump tasks demonstrated smaller peak proximal tibia anterior shear forces during the landing phase. In step-close-jump tasks, increasing hip joint angular velocity during initial foot-ground contact decreased peak posterior ground reaction force during the landing phase, which theoretically could reduce the risk of ACL injury

  19. An Efficient Interpolation Technique for Jump Proposals in Reversible-Jump Markov Chain Monte Carlo Calculations

    CERN Document Server

    Farr, Will M

    2011-01-01

    Selection among alternative theoretical models given an observed data set is an important challenge in many areas of physics and astronomy. Reversible-jump Markov chain Monte Carlo (RJMCMC) is an extremely powerful technique for performing Bayesian model selection, but it suffers from a fundamental difficulty: it requires jumps between model parameter spaces, but cannot retain a memory of the favored locations in more than one parameter space at a time. Thus, a naive jump between parameter spaces is unlikely to be accepted in the MCMC algorithm and convergence is correspondingly slow. Here we demonstrate an interpolation technique that uses samples from single-model MCMCs to propose inter-model jumps from an approximation to the single-model posterior of the target parameter space. The interpolation technique, based on a kD-tree data structure, is adaptive and efficient in arbitrary dimensions. We show that our technique leads to dramatically improved convergence over naive jumps in an RJMCMC, and compare it ...

  20. An efficient interpolation technique for jump proposals in reversible-jump Markov chain Monte Carlo calculations.

    Science.gov (United States)

    Farr, W M; Mandel, I; Stevens, D

    2015-06-01

    Selection among alternative theoretical models given an observed dataset is an important challenge in many areas of physics and astronomy. Reversible-jump Markov chain Monte Carlo (RJMCMC) is an extremely powerful technique for performing Bayesian model selection, but it suffers from a fundamental difficulty and it requires jumps between model parameter spaces, but cannot efficiently explore both parameter spaces at once. Thus, a naive jump between parameter spaces is unlikely to be accepted in the Markov chain Monte Carlo (MCMC) algorithm and convergence is correspondingly slow. Here, we demonstrate an interpolation technique that uses samples from single-model MCMCs to propose intermodel jumps from an approximation to the single-model posterior of the target parameter space. The interpolation technique, based on a kD-tree data structure, is adaptive and efficient in modest dimensionality. We show that our technique leads to improved convergence over naive jumps in an RJMCMC, and compare it to other proposals in the literature to improve the convergence of RJMCMCs. We also demonstrate the use of the same interpolation technique as a way to construct efficient 'global' proposal distributions for single-model MCMCs without prior knowledge of the structure of the posterior distribution, and discuss improvements that permit the method to be used in higher dimensional spaces efficiently.

  1. Reliability, usefulness, and validity of a repeated sprint and jump ability test.

    Science.gov (United States)

    Buchheit, Martin; Spencer, Matt; Ahmaidi, Said

    2010-03-01

    Two studies involving 122 handball players were conducted to assess the reliability, usefulness, and validity of a repeated shuttle-sprint and jump ability (RSSJA) test. The test consisted of 6x(2x12.5-m) sprints departing on 25 s, with a countermovement jump performed during recovery between sprints. For the reliability and usefulness study, 14 well-trained male handball players performed the RSSJA test 7 d apart. Reliability of the test variables was assessed by the typical error of measurement, expressed as a coefficient of variation (CV). The minimal changes likely to be "real" in sprint time and jump power were also calculated. For the validity study, players of seven teams (national to international levels, women and men) performed the RSSJA test. CV values for best and mean sprint time were 1.0% (90% CL, 0.7 to 1.6) and 1.0% (90% CL, 0.7 to 1.4). CV values for best and mean jump peak power were 1.7% (90% CL, 1.2 to 2.7) and 1.5% (90% CL, 1.1 to 2.5). The percent sprint and jump decrements were less reliable, with CVs of 22.3% (90% CL, 15.7 to 38.3) and 34.8% (90% CL, 24.2 to 61.8). Minimal changes likely to be "real" for mean sprint time and jumping peak power were -2.6% and 4.8%. Qualitative analysis revealed that the majority of between-team differences were rated as "almost certain" (ie, 100% probability that the true differences were meaningful) for mean sprint and jump performances. The RSSJA test is reliable and valid to assess repeated explosive effort sequences in team sports such as handball. Test results are likely to be representative of gender and competition level; thus the test could be used to discriminate across playing standards and monitor fitness levels.

  2. Alterations of Vertical Jump Mechanics after a Half-Marathon Mountain Running Race

    Directory of Open Access Journals (Sweden)

    Elissavet N. Rousanoglou, Konstantinos Noutsos, Achilleas Pappas, Gregory Bogdanis, Georgios Vagenas, Ioannis A. Bayios, Konstantinos D. Boudolos

    2016-06-01

    Full Text Available The fatiguing effect of long-distance running has been examined in the context of a variety of parameters. However, there is scarcity of data regarding its effect on the vertical jump mechanics. The purpose of this study was to investigate the alterations of countermovement jump (CMJ mechanics after a half-marathon mountain race. Twenty-seven runners performed CMJs before the race (Pre, immediately after the race (Post 1 and five minutes after Post 1 (Post 2. Instantaneous and ensemble-average analysis focused on jump height and, the maximum peaks and time-to-maximum peaks of: Displacement, vertical force (Fz, anterior-posterior force (Fx, Velocity and Power, in the eccentric (tECC and concentric (tCON phase of the jump, respectively. Repeated measures ANOVAs were used for statistical analysis (p ≤ 0.05. The jump height decrease was significant in Post 2 (-7.9% but not in Post 1 (-4.1%. Fx and Velocity decreased significantly in both Post 1 (only in tECC and Post 2 (both tECC and tCON. Α timing shift of the Fz peaks (earlier during tECC and later during tCON and altered relative peak times (only in tECC were also observed. Ensemble-average analysis revealed several time intervals of significant post-race alterations and a timing shift in the Fz-Velocity loop. An overall trend of lowered post-race jump output and mechanics was characterised by altered jump timing, restricted anterior-posterior movement and altered force-velocity relations. The specificity of mountain running fatigue to eccentric muscle work, appears to be reflected in the different time order of the post-race reductions, with the eccentric phase reductions preceding those of the concentric one. Thus, those who engage in mountain running should particularly consider downhill training to optimise eccentric muscular action.

  3. The Mechanics and Trajectory Control in Locust Jumping

    Institute of Scientific and Technical Information of China (English)

    Longbao Han; Zhouyi Wang; Aihong Ji; Zhendong Dai

    2013-01-01

    Locusts (Locusta migratoria manilensis) are characterised by their flying ability and abiding jump ability.Research on the jumping mechanics and behavior of locusts plays an important role in elucidating the mechanism of hexapod locomotion.The jump gestures of locusts were observed using high-speed video camera at 250 fps.The reaction forces of the hindlegs were measured using two three-dimensional sensors,in case the two hindlegs attached on separated sensor plates.The jump gestures and reaction forces were used to illustrate the locust jumping mechanism.Results show that the trajectory control is achieved by rapid rolling and yawing movements of the locust body,caused by the forelegs,midlegs and hindlegs in different jumping phases.The final jump trajectory was not determined until hind tarsi left platform.The horizontal co-impulse between two hindlegs might play a key role in jump stability and accuracy.Besides,the angle between two hindlegs affects the control of jump trajectory but has a little effect on the elevation angle of a jump,which is controlled mechanically by the initial position of the hindlegs.This research lays the groundwork for the probable design and development of biomimetic robotics.

  4. STATIC STRETCHING DOES NOT REDUCE VARIABILITY, JUMP AND SPEED PERFORMANCE.

    Science.gov (United States)

    de Oliveira, Fábio Carlos Lucas; Rama, Luís Manuel Pinto Lopes

    2016-04-01

    Stretching is often part of the warm-up routine prior to athletic participation; however, controversial evidence exists on the effects of stretching on countermovement jump (CMJ) and sprint performance. Additionally, analysis of variability between repeated tasks is useful for monitoring players, to analyze factors that could affect the performance, and to guide clinical decisions for training strategies. The purpose of this study was to examine whether static stretching (SS) prior to CMJ and 20-meter (20-m) sprint would affect performance, and to investigate whether SS affects an athlete's ability to perform these tasks consistently. Twenty-two trained healthy athletes (23.2 ± 5.0 years) attended, randomly, two testing sessions, separated by 48 hours. At session one, all participants underwent 10 minutes of dynamic running warm-up followed by the experimental tasks (three CMJ and three 20-m sprint), whereas five minutes of stretching was added after the warm-up routine at session two. All participants performed the same experimental tasks in both sessions. The stretching protocol consisted of five stretching exercises for each lower limb. The paired-samples t-test revealed no significant differences between the stretching protocol condition and no stretching condition for the 20-m sprint (t(21)=.920; p=.368) and CMJ (t(21)=.709; p=.486). There were no significant differences in trial-by-trial variability on 20-m sprint (t(21)=1.934; p=.067) and CMJ scores (t(21)=.793; p=.437) as result of SS. The SS protocol did not modify jumping and running ability in trained healthy athletes. The SS prior to training or competition may not cause detrimental effects to athletic performance. Level III, Nonrandomized controlled trial.

  5. Promoting balance and jumping skills in children with Down syndrome.

    Science.gov (United States)

    Wang, Wai-Yi; Ju, Yun-Huei

    2002-04-01

    The purpose of this study was to investigate the changes in balance and qualitative and quantitative jumping performances by 20 children with Down syndrome (3 to 6 years) on jumping lessons. 30 typical children ages 3 to 6 years were recruited as a comparison group. Before the jumping lesson, a pretest was given subjects for balance and jumping skill measures based on the Motor Proficiency and Motor Skill Inventory, respectively. Subjects with Down syndrome received 3 sessions on jumping per week for 6 weeks but not the typical children. Then, a posttest was administered to all subjects. Analysis of covariance showed the pre- and posttest differences on scores for floor walk, beam walk, and horizontal and vertical jumping by subjects with Down syndrome were significantly greater than those for the typical children.

  6. Theoretical Modeling of Internal Hydraulic Jump in Density Currents

    CERN Document Server

    Firoozabadi, Bahar; Aryanfar, Asghar; Afshin, Hossein

    2013-01-01

    In this paper, we propose an analytical framework for internal hydraulic jumps. Density jumps or internal hydraulic jumps occur when a supper critical flow of water discharges into a stagnant layer of water with slightly different density. The approach used here is control volume method which is also used to analyze ordinary hydraulic jumps. The important difference here is that entrainment is taken into account. Using conservation equations with the aid of some simplifying assumptions we come to an equation that gives jump downstream height as function of jump upstream characteristics and the entrainment. To determine the magnitude of downstream height we use an experimental equation for calculating the entrainment. Finally we verify our framework by comparing the height that we gain from the derived equation with some experimental data.

  7. A-jump in horizontal inverted semicircular open channels

    Directory of Open Access Journals (Sweden)

    I.M.H. Rashwan

    2013-12-01

    Full Text Available The hydraulic jump is a transitional state from supercritical to subcritical flow. The phenomenon of the hydraulic jump has been widely studied because of its frequent occurrence in nature and because of its uses in many practical applications. In the present study the momentum principle is used to derive an equation expressed the hydraulic jump (A-jump occurred in a short horizontal reach of an inverted semicircular open channel. The derived equation indicates that the initial water depth and the tail water depth (conjugate depths are functions of the critical water depth. Various elements of the hydraulic jump are expressed in dimensionless case. The procedure of dimensionless ratios described in the present paper can be used to determine various elements of A-jump in an inverted semicircular channel when either the discharge and the relative initial depth (or tail water depth is known or the discharge and the relative dissipated energy are known.

  8. A Jump-Diffusion Model with Stochastic Volatility and Durations

    DEFF Research Database (Denmark)

    Wei, Wei; Pelletier, Denis

    Market microstructure theories suggest that the durations between transactions carry information about volatility. This paper puts forward a model featuring stochastic volatility, stochastic conditional duration, and jumps to analyze high frequency returns and durations. Durations affect price...... jumps in two ways: as exogenous sampling intervals, and through the interaction with volatility. We adopt a bivariate Ornstein-Ulenbeck process to model intraday volatility and conditional duration. We develop a MCMC algorithm for the inference on irregularly spaced multivariate processes with jumps....... The algorithm provides smoothed estimates of the latent variables such as spot volatility, conditional duration, jump times, and jump sizes. We apply this model to IBM data and find that volatility and conditional duration are interdependent. We also find that jumps play an important role in return variation...

  9. Robust Stabilization for Uncertain Linear Delay Markow Jump System

    Institute of Scientific and Technical Information of China (English)

    钟麦英; 汤兵勇; 黄小原

    2001-01-01

    Markov jump linear systems are defined as a family of linear systems with randomly Markov jumping parameters and are used to model systems subject to failures or changes in structure. The robust stabilization problem of jump linear delay system with umcerratnty was studied. By using of linear matrix inequalities, the existence conditions of robust stabilizing and the state feedback controller designing methods are also presented and proved. Finally, an illustrated example shows the effectiveness of this approach.

  10. Approximation of Jump Diffusions in Finance and Economics

    OpenAIRE

    Nicola Bruti-Liberati; Eckhard Platen

    2006-01-01

    In finance and economics the key dynamics are often specified via stochastic differential equations (SDEs) of jump-diffusion type. The class of jump-diffusion SDEs that admits explicit solutions is rather limited. Consequently, discrete time approximations are required. In this paper we give a survey of strong and weak numerical schemes for SDEs with jumps. Strong schemes provide pathwise approximations and therefore can be employed in scenario analysis, filtering or hedge simulation. Weak sc...

  11. Times and Sizes of Jumps in the Mexican Interest Rate

    OpenAIRE

    José Antonio Núñez Mora; Arturo Lorenzo Valdés

    2008-01-01

    This paper examines the role of jumps in a continuous-time short-term interest rate model for Mexico. A filtering algorithm provides estimates of jumps times and sizes in the time series of Mexican cetes for the 1998-2006 period. The empirical results indicate that the inclusion of jumps in the diffusion model represents a better alternative than not to include them.

  12. Multiobjective Optimization Methodology A Jumping Gene Approach

    CERN Document Server

    Tang, KS

    2012-01-01

    Complex design problems are often governed by a number of performance merits. These markers gauge how good the design is going to be, but can conflict with the performance requirements that must be met. The challenge is reconciling these two requirements. This book introduces a newly developed jumping gene algorithm, designed to address the multi-functional objectives problem and supplies a viably adequate solution in speed. The text presents various multi-objective optimization techniques and provides the technical know-how for obtaining trade-off solutions between solution spread and converg

  13. Planar jumping-drop thermal diodes

    Science.gov (United States)

    Boreyko, Jonathan B.; Zhao, Yuejun; Chen, Chuan-Hua

    2011-12-01

    Phase-change thermal diodes rectify heat transport much more effectively than solid-state ones, but are limited by either the gravitational orientation or one-dimensional configuration. Here, we report a planar phase-change diode scalable to large areas with an orientation-independent diodicity of over 100, in which water/vapor is enclosed by parallel superhydrophobic and superhydrophilic plates. The thermal rectification is enabled by spontaneously jumping dropwise condensate which only occurs when the superhydrophobic surface is colder than the superhydrophilic surface.

  14. Understanding the physics of bungee jumping

    OpenAIRE

    Heck, A; Uylings, P.; Kędzierska, E.

    2010-01-01

    Changing mass phenomena like the motion of a falling chain, the behaviour of a falling elastic bar or spring, and the motion of a bungee jumper surprise many a physicist. In this article we discuss the first phase of bungee jumping, when the bungee jumper falls, but the bungee rope is still slack. In instructional material this phase is often considered a free fall, but when the mass of the bungee rope is taken into account, the bungee jumper reaches acceleration greater than g. This result i...

  15. Quantifying show jumping horse rider expertise using IMUs.

    Science.gov (United States)

    Patterson, M; Doyle, J; Cahill, E; Caulfield, B; McCarthy Persson, U

    2010-01-01

    Horse rider ability has long been measured using horse performance, competition results and visual observation. Scientific methods of measuring rider ability on the flat are emerging such as measuring position angles and harmony of the horse-rider system. To date no research has quantified rider ability in show jumping. Kinematic analysis and motion sensors have been used in sports other than show jumping to measure the quality of motor control patterns in humans. The aim of this study was to quantify rider ability in show jumping using body-mounted IMUs. Preliminary results indicate that there are clear differences in experienced and novice riders during show jumping.

  16. Distance perception in the spiny mouse Acomys cahirinus: vertical jumping.

    Science.gov (United States)

    Goldman, M; Skolnick, A J; Hernandez, T P; Tobach, E

    1992-12-01

    Acomys cahirinus, a precocial muroid, that has shown precise jumping in the natural habitat, did not jump from 25 cm in a laboratory situation. To investigate this further, A. cahirinus were observed jumping from platforms at two different heights, onto different sized checkered substrates and from a visual cliff. Adult animals discriminated between platforms that were 6.4 cm and 25.4 cm above the substrate and between small and large checkered patterns on the floor. Most adult animals and neonates jumped down on the shallow side of the visual cliff. Animals developed individual patterns of jumping over a series of trials, with some jumping often, some rarely, and others jumping only from the low platform. Good distance perception was indicated when they did not jump from heights, and by their making appropriate postural adjustment when they did jump from heights and landed without mishap. Different spacing of trials indicated that height was a more effective stimulus for animals which had all four conditions on the same day, while floor pattern was more effective for animals with each of the four conditions on a separate day.

  17. Long memory behavior of returns after intraday financial jumps

    Science.gov (United States)

    Behfar, Stefan Kambiz

    2016-11-01

    In this paper, characterization of intraday financial jumps and time dynamics of returns after jumps is investigated, and will be analytically and empirically shown that intraday jumps are power-law distributed with the exponent 1 finance, it is important to be able to distinguish between jumps and continuous sample path price movements, and this can be achieved by introducing a statistical test via calculating sums of products of returns over small period of time. In the case of having jump, the null hypothesis for normality test is rejected; this is based on the idea that returns are composed of mixture of normally-distributed and power-law distributed data (∼ 1 /r 1 + μ). Probability of rejection of null hypothesis is a function of μ, which is equal to one for 1 high returns after jumps are the effect; we show that returns caused by jump decay as power-law distribution. To test this idea empirically, we average over the time dynamics of all days; therefore the superposed time dynamics after jump represent a power-law, which indicates that there is a long memory with a power-law distribution of return after jump.

  18. Biomechanics research in ski jumping, 1991-2006.

    Science.gov (United States)

    Schwameder, Hermann

    2008-01-01

    In this paper, I review biomechanics research in ski jumping with a specific focus on publications presented between 1991 and 2006 on performance enhancement, limiting factors of the take-off, specific training and conditioning, aerodynamics, and safety. The first section presents a brief description of ski jumping phases (in-run, take-off, early flight, stable flight, and landing) regarding the biomechanical and functional fundamentals. The most important and frequently used biomechanical methods in ski jumping (kinematics, ground reaction force analyses, muscle activation patterns, aerodynamics) are summarized in the second section. The third section focuses on ski jumping articles and research findings published after the establishment of the V-technique in 1991, as the introduction of this technique has had a major influence on performance enhancement, ski jumping regulations, and the construction of hill profiles. The final section proposes topics for future research in the biomechanics of ski jumping, including: take-off and early flight and the relative roles of vertical velocity and forward somersaulting angular momentum; optimal jumping patterns utilizing the capabilities of individual athletes; development of kinematic and kinetic feedback systems for hill jumps; comparisons of simulated and hill jumps; effect of equipment modifications on performance and safety enhancement.

  19. Competitive Lotka-Volterra Population Dynamics with Jumps

    CERN Document Server

    Bao, Jianhai; Yin, Geroge; Yuan, Chenggui

    2011-01-01

    This paper considers competitive Lotka-Volterra population dynamics with jumps. The contributions of this paper are as follows. (a) We show stochastic differential equation (SDE) with jumps associated with the model has a unique global positive solution; (b) We discuss the uniform boundedness of $p$th moment with $p>0$ and reveal the sample Lyapunov exponents; (c) Using a variation-of-constants formula for a class of SDEs with jumps, we provide explicit solution for 1-dimensional competitive Lotka-Volterra population dynamics with jumps, and investigate the sample Lyapunov exponent for each component and the extinction of our $n$-dimensional model.

  20. pH jump induced α-helix folding.

    Directory of Open Access Journals (Sweden)

    Donten M. L.

    2013-03-01

    Full Text Available pH can be used to impact the folding equilibrium of peptides and proteins. This fact is utilized, similarly to temperature jumps, in pH jump experiments employing laser time-resolved spectroscopy to study the function and structural dynamics of these molecules. Here the application of pH jumps in folding experiments was investigated. Experiments with poly-L-glutamic acid alpha-helix formation shown the critical aspects of pH jump experiments and yielded direct information about the folding kinetics monitored with the amide I IR band.

  1. Development of a Minimally Actuated Jumping-Rolling Robot

    Directory of Open Access Journals (Sweden)

    Thanhtam Ho

    2015-04-01

    Full Text Available This paper presents development of a hybrid mobile robot in order to take advantage of both rolling and jumping locomotion on the ground. According to the unique design of the mechanism, the robot is able to execute both jumping and rolling skilfully by using only one DC motor. Changing the centre of gravity enables rolling of the robot and storage of energy is utilized for jumping. Mechanism design and control logic are validated by computer simulation. Simulation results show that the robot can jump nearly 1.3 times its diameter and roll at the speed of 3.3 times its diameter per second.

  2. Exploiting knowledge of jump-up and jump-down frequencies to determine the parameters of a Duffing oscillator

    Science.gov (United States)

    Ramlan, Roszaidi; Brennan, Michael J.; Kovacic, Ivana; Mace, Brian R.; Burrow, Stephen G.

    2016-08-01

    This work concerns the application of certain non-linear phenomena - jump frequencies in a base-excited Duffing oscillator - to the estimation of the parameters of the system. First, approximate analytical expressions are derived for the relationships between the jump-up and jump-down frequencies, the damping ratio and the cubic stiffness coefficient. Then, experimental results, together with the results of numerical simulations, are presented to show how knowledge of these frequencies can be exploited.

  3. Single-leg lateral, horizontal, and vertical jump assessment: reliability, interrelationships, and ability to predict sprint and change-of-direction performance.

    Science.gov (United States)

    Meylan, Cesar; McMaster, Travis; Cronin, John; Mohammad, Nur Ikhwan; Rogers, Cailyn; Deklerk, Melissa

    2009-07-01

    The purposes of this study were to determine the reliability of unilateral vertical, horizontal, and lateral countermovement jump assessments, the interrelationship between these tests, and their usefulness as predictors of sprint (10 m) and change-of-direction (COD) performance for 80 men and women physical education students. Jump performance was assessed on a contact mat and sprint, and COD performances were assessed using timing lights. With regard to the reliability statistics, the largest coefficient of variation (CV) was observed for the vertical jump (CV = 6.7-7.2%) of both genders, whereas the sprint and COD assessments had smallest variability (CV = 0.8 to 2.8%). All intraclass correlation coefficients (ICC) were greater than 0.85, except for the men's COD assessment with the alternate leg. The shared variance between the single-leg vertical, horizontal, and lateral jumps for men and women was less than 50%, indicating that the jumps are relatively independent of one another and represent different leg strength/power qualities. The ability of the jumps to predict sprint and COD performance was limited (R2 women (R sprint and COD performance in a test battery, the single-leg horizontal countermovement jump would seem the logical choice, given the results of this study. Many of the findings in this study have interesting diagnostic and training implications for the strength and conditioning coach.

  4. Effect of Static and Dynamic Stretching on the Diurnal Variations of Jump Performance in Soccer Players

    Science.gov (United States)

    Chtourou, Hamdi; Aloui, Asma; Hammouda, Omar; Chaouachi, Anis; Chamari, Karim; Souissi, Nizar

    2013-01-01

    Purpose The present study addressed the lack of data on the effect of different types of stretching on diurnal variations in vertical jump height - i.e., squat-jump (SJ) and countermovement-jump (CMJ). We hypothesized that dynamic stretching could affect the diurnal variations of jump height by producing a greater increase in short-term maximal performance in the morning than the evening through increasing core temperature at this time-of-day. Methods Twenty male soccer players (age, 18.6±1.3 yrs; height, 174.6±3.8 cm; body-mass, 71.1±8.6 kg; mean ± SD) completed the SJ and CMJ tests either after static stretching, dynamic stretching or no-stretching protocols at two times of day, 07:00 h and 17:00 h, with a minimum of 48 hours between testing sessions. One minute after warming-up for 5 minutes by light jogging and performing one of the three stretching protocols (i.e., static stretching, dynamic stretching or no-stretching) for 8 minutes, each subject completed the SJ and CMJ tests. Jumping heights were recorded and analyzed using a two-way analysis of variance with repeated measures (3 [stretching]×2 [time-of-day]). Results The SJ and CMJ heights were significantly higher at 17:00 than 07:00 h (pstretching protocol. These daily variations disappeared (i.e., the diurnal gain decreased from 4.2±2.81% (pstretching due to greater increases in SJ and CMJ heights in the morning than the evening (8.4±6.36% vs. 4.4±2.64%, pstretching on the diurnal variations of SJ and CMJ heights was observed. Conclusion Dynamic stretching affects the typical diurnal variations of SJ and CMJ and helps to counteract the lower morning values in vertical jump height. PMID:23940589

  5. Acute effects of static stretching on vertical jump performance in children

    Directory of Open Access Journals (Sweden)

    Ertuğrul Gelen

    2008-05-01

    Full Text Available This research has been made to define the acute effects of static streching on vertical jump performance in children. The research has been applied on 49 healthy male volunteer athletes who have been taking basketball education for 2.1±0.2 years.(age:12.6±0.7 years, height: 157.9±6.9 cm, weight: 49.7±6.7 kg Two different protocols have been made in this research. In the first protocol, 5 minutes aerobic density and 5 x 10 m forward, backward, side general warming up exercice in submaximal level has been applied on each child and in the second protocol, after general warming up, static streching practice has been applied to the same children. After each warming up and streching practice, countermovement jump performance have been measured. Active static streching practice has been applied in a strech sensitivity for 3 times 30 seconds and 15 seconds brakes between repetitions. Descriptive statistical methods and Paired-Samples T test have been applied on statistical analysis of vertical jump data that belong to children. Children jump 28.6 ± 1.1 cm. after a general warming up without any streching practice whereas the children who have made static streching application after warming up jump 27.1 ± 1.3 cm. The1.5 cm. difference (%5.2 has been found significant (t = -10.476; p<0.001. As a result, static streching practice after general warming up effects vertical jump performance negatively.

  6. Acute effects of static stretching on vertical jump performance in children

    Directory of Open Access Journals (Sweden)

    Ertuğrul Gelen

    2008-05-01

    Full Text Available This research has been made to define the acute effects of static streching on vertical jump performance in children. The research has been applied on 49 healthy male volunteer athletes who have been taking basketball education for 2.1±0.2 years.(age:12.6±0.7 years, height: 157.9±6.9 cm, weight: 49.7±6.7 kg Two different protocols have been made in this research. In the first protocol, 5 minutes aerobic density and 5 x 10 m forward, backward, side general warming up exercice in submaximal level has been applied on each child and in the second protocol, after general warming up, static streching practice has been applied to the same children. After each warming up and streching practice, countermovement jump performance have been measured. Active static streching practice has been applied in a strech sensitivity for 3 times 30 seconds and 15 seconds brakes between repetitions. Descriptive statistical methods and Paired-Samples T test have been applied on statistical analysis of vertical jump data that belong to children. Children jump 28.6 ± 1.1 cm. after a general warming up without any streching practice whereas the children who have made static streching application after warming up jump 27.1 ± 1.3 cm. The1.5 cm. difference (%5.2 has been found significant (t = -10.476;  p<0.001. As a result, static streching practice after general warming up effects vertical jump performance negatively.

  7. THE ACUTE EFFECTS OF BACK SQUATS ON VERTICAL JUMP PERFORMANCE IN MEN AND WOMEN

    Directory of Open Access Journals (Sweden)

    Gavin L. Moir

    2010-06-01

    Full Text Available The aim of the present study was to investigate the acute effects of performing back squats on subsequent performance during a series of vertical jumps in men and women. Twelve men and 12 women were tested on three separate occasions, the first of which was used to determine their 1-repetition maximum (1-RM parallel back squat. Following this, subjects performed a potentiation and a control treatment in a counterbalanced order. The potentiation treatment culminated with subjects performing parallel back squats with a load equivalent to 70% 1- RM for three repetitions, following which they performed one countermovement vertical jump (CMJ for maximal height every three minutes for a total of 10 jumps. During the control treatment, subjects performed only the CMJs. Jump height (JH and vertical stiffness (VStiff were calculated for each jump from the vertical force signal recorded from a force platform. There were no significant changes in JH or VStiff following the treatments and no significant differences in the responses between men and women (p > 0.05. Correlations between normalized 1-RM back squat load and the absolute change in JH and VStiff were small to moderate for both men and women, with most correlations being negative. Large variations in response to the back squats were noted in both men and women. The use of resistance exercises performed prior to a series of vertical jumps can result in improvements in performance in certain individuals, although the gains tend to be small and dependent upon the mechanical variable measured. There does not seem to be any differences between men and women in the response to dynamic potentiation protocols

  8. Alterations of Vertical Jump Mechanics after a Half-Marathon Mountain Running Race.

    Science.gov (United States)

    Rousanoglou, Elissavet N; Noutsos, Konstantinos; Pappas, Achilleas; Bogdanis, Gregory; Vagenas, Georgios; Bayios, Ioannis A; Boudolos, Konstantinos D

    2016-06-01

    The fatiguing effect of long-distance running has been examined in the context of a variety of parameters. However, there is scarcity of data regarding its effect on the vertical jump mechanics. The purpose of this study was to investigate the alterations of countermovement jump (CMJ) mechanics after a half-marathon mountain race. Twenty-seven runners performed CMJs before the race (Pre), immediately after the race (Post 1) and five minutes after Post 1 (Post 2). Instantaneous and ensemble-average analysis focused on jump height and, the maximum peaks and time-to-maximum peaks of: Displacement, vertical force (Fz), anterior-posterior force (Fx), Velocity and Power, in the eccentric (tECC) and concentric (tCON) phase of the jump, respectively. Repeated measures ANOVAs were used for statistical analysis (p ≤ 0.05). The jump height decrease was significant in Post 2 (-7.9%) but not in Post 1 (-4.1%). Fx and Velocity decreased significantly in both Post 1 (only in tECC) and Post 2 (both tECC and tCON). Α timing shift of the Fz peaks (earlier during tECC and later during tCON) and altered relative peak times (only in tECC) were also observed. Ensemble-average analysis revealed several time intervals of significant post-race alterations and a timing shift in the Fz-Velocity loop. An overall trend of lowered post-race jump output and mechanics was characterised by altered jump timing, restricted anterior-posterior movement and altered force-velocity relations. The specificity of mountain running fatigue to eccentric muscle work, appears to be reflected in the different time order of the post-race reductions, with the eccentric phase reductions preceding those of the concentric one. Thus, those who engage in mountain running should particularly consider downhill training to optimise eccentric muscular action. Key pointsThe 4.1% reduction of jump height immediately after the race is not statistically significantThe eccentric phase alterations of jump mechanics precede

  9. Jump dynamics due to jump datum of compressible viscous Navier-Stokes flows in a bounded plane domain

    Science.gov (United States)

    Kweon, Jae Ryong

    2016-09-01

    In this paper, when the initial density has a jump across an interior curve in a bounded domain, we show unique existence, piecewise regularity and jump discontinuity dynamics for the density and the velocity vector governed by the Navier-Stokes equations of compressible viscous barotropic flows. A critical difficulty is in controlling the gradient of the pressure across the jump curve. This is resolved by constructing a vector function associated with the pressure jump value on the convecting curve and extending it to the whole domain.

  10. Understanding the physics of bungee jumping

    Science.gov (United States)

    Heck, André; Uylings, Peter; Kędzierska, Ewa

    2010-01-01

    Changing mass phenomena like the motion of a falling chain, the behaviour of a falling elastic bar or spring, and the motion of a bungee jumper surprise many a physicist. In this article we discuss the first phase of bungee jumping, when the bungee jumper falls, but the bungee rope is still slack. In instructional material this phase is often considered a free fall, but when the mass of the bungee rope is taken into account, the bungee jumper reaches acceleration greater than g. This result is contrary to the usual experience with free falling objects and therefore hard to believe for many a person, even an experienced physicist. It is often a starting point for heated discussions about the quality of the experiments and the physics knowledge of the experimentalist, or it may even prompt complaints about the quality of current physics education. But experiments do reveal the truth and students can do them supported by information and communication technology (ICT) tools. We report on a research project done by secondary school students and use their work to discuss how measurements with sensors, video analysis of self-recorded high-speed video clips and computer modelling allow study of the physics of bungee jumping.

  11. Measurement errors when estimating the vertical jump height with flight time using photocell devices: the example of Optojump

    Directory of Open Access Journals (Sweden)

    A Attia

    2016-12-01

    Full Text Available Common methods to estimate vertical jump height (VJH are based on the measurements of flight time (FT or vertical reaction force. This study aimed to assess the measurement errors when estimating the VJH with flight time using photocell devices in comparison with the gold standard jump height measured by a force plate (FP. The second purpose was to determine the intrinsic reliability of the Optojump photoelectric cells in estimating VJH. For this aim, 20 subjects (age: 22.50±1.24 years performed maximal vertical jumps in three modalities in randomized order: the squat jump (SJ, counter-movement jump (CMJ, and CMJ with arm swing (CMJarm. Each trial was simultaneously recorded by the FP and Optojump devices. High intra-class correlation coefficients (ICCs for validity (0.98-0.99 and low limits of agreement (less than 1.4 cm were found; even a systematic difference in jump height was consistently observed between FT and double integration of force methods (-31% to -27%; p 1.2. Intra-session reliability of Optojump was excellent, with ICCs ranging from 0.98 to 0.99, low coefficients of variation (3.98%, and low standard errors of measurement (0.8 cm. It was concluded that there was a high correlation between the two methods to estimate the vertical jump height, but the FT method cannot replace the gold standard, due to the large systematic bias. According to our results, the equations of each of the three jump modalities were presented in order to obtain a better estimation of the jump height.

  12. Vertical jump performance of professional male and female volleyball players: effects of playing position and competition level.

    Science.gov (United States)

    Sattler, Tine; Hadžić, Vedran; Dervišević, Edvin; Markovic, Goran

    2015-06-01

    Vertical jump (VJ) performance is an important element for successful volleyball practice. The aims of the study were (a) to explore the overall VJ performance of elite volleyball players of both sexes, (b) to explore the differences in VJ performance among different competition levels and different playing positions, and (c) to evaluate the sex-related differences in the role of the arm swing and 3-step approach with arm swing on the jump height. We assessed the VJ capacity in 253 volleyball players (113 males and 140 females) from Slovenian first and second Volleyball Division. The height of squat jump (SJ), countermovement jump, block jump, and attack jump was tested using an Optojump system. We observed significant differences (p ≤ 0.05) in VJ height between different levels of play that were most pronounced in the SJ. Position-related differences in VJ performance were observed in male players between receivers and setters (p ≤ 0.05), whereas in females, VJ performance across different playing positions seems equal. Finally, we found that male players significantly better use the arm swing during VJ than females (p ≤ 0.05), whereas the use of eccentric part of the jump and approach before the spike to improve VJ performance seem to be equally mastered activity in both sexes. These results could assist coaches in the development of jumping performance in volleyball players. Furthermore, presented normative data for jump heights of elite male and female volleyball players could be useful in selection and profiling of young volleyball players.

  13. RELIABILITY AND VALIDITY OF AN ACCELEROMETRIC SYSTEM FOR ASSESSING VERTICAL JUMPING PERFORMANCE

    Directory of Open Access Journals (Sweden)

    M.-A. Choukou

    2014-07-01

    Full Text Available The validity of an accelerometric system (Myotest© for assessing vertical jump height, vertical force and power, leg stiffness and reactivity index was examined. 20 healthy males performed 3ד5 hops in place”, 3ד1 squat jump” and 3× “1 countermovement jump” during 2 test-retest sessions. The variables were simultaneously assessed using an accelerometer and a force platform at a frequency of 0.5 and 1 kHz, respectively. Both reliability and validity of the accelerometric system were studied. No significant differences between test and retest data were found (p<0.05, showing a high level of reliability. Besides, moderate to high intraclass correlation coefficients (ICCs (from 0.74 to 0.96 were obtained for all variables whereas weak to moderate ICCs (from 0.29 to 0.79 were obtained for force and power during the countermovement jump. With regards to validity, the difference between the two devices was not significant for 5 hops in place height (1.8 cm, force during squat (-1.4 N · kg-1 and countermovement (0.1 N · kg-1 jumps, leg stiffness (7.8 kN · m-1 and reactivity index (0.4. So, the measurements of these variables with this accelerometer are valid, which is not the case for the other variables. The main causes of non-validity for velocity, power and contact time assessment are temporal biases of the takeoff and touchdown moments detection.

  14. Effects of slackline training on balance, jump performance & muscle activity in young children.

    Science.gov (United States)

    Donath, L; Roth, R; Rueegge, A; Groppa, M; Zahner, L; Faude, O

    2013-12-01

    The study investigated the effects of slackline training (rope balancing) on balance, jump performance and muscle activity in children. Two primary-school classes (intervention, n=21, INT: age: 10.1 (SD 0.4) y, weight: 33.1 (4.5) kg; control, n=13, CON: age: 10.0 (SD 0.4) y, weight: 34.7 (7.4) kg) participated. Training was performed within 6 weeks, 5 times per week for 10 min each day. Balance (static and dynamic stance), countermovement jumps, reverse balancing on beams (3, 4.5 and 6 cm width), slackline standing (single- and double-limb) and electromyographic activity (soleus, gastrocnemius, tibialis anterior) were examined. INT significantly improved single- and double-limb slackline standing (double limb: 5.1 (3.4) s-17.2 (14.4) s; right leg: 8.2 (5.8) s-38.3 (36.0) s; left leg: 10.6 (5.8) s-49.0 (56.3) s; pJump performance remained unchanged (p=0.28, ηp²=0.04). In conclusion, daily slackline training results in large slackline-specific balance improvements. Transfer effects to static and dynamic stance, reverse balancing or jumping performance seemed to be restricted. © Georg Thieme Verlag KG Stuttgart · New York.

  15. EFFECTS OF WHOLE BODY VIBRATION ON STRENGTH AND JUMPING PERFORMANCE IN VOLLEYBALL AND BEACH VOLLEYBALL PLAYERS

    Science.gov (United States)

    Zmijewski, P.; Jimenez-Olmedo, J.M.; Jové-Tossi, M.A.; Martínez-Carbonell, A.; Suárez-Llorca, C.; Andreu-Cabrera, E.

    2014-01-01

    The primary aim of this study was to examine the effects of 6-week strength training with whole body vibration (WBV) on leg strength and jumping performance in volleyball and beach volleyball players. Twenty-three sub-elite male volleyball (VB; n=12) and beach volleyball players (BVB; n=11) aged 21.2±3.0 years were divided into two groups and subjected to 6 weeks of strength training (three one-hour sessions per week): (I) 12 players (6 VB and 6 BVB players) underwent training with WBV (30-40 Hz, 1.7-2.5 mm, 3.0-5.7 g), and (II) 11 players (6 VB and 5 BVB players) underwent traditional strength training. Squat jump (SJ) and countermovement squat jump (CMJ) measurements by the Ergo Tester contact platform and maximum leg press test (1RM) were conducted. Three-factor (2 time x 2 WBV use x 2 discipline) analysis of variance for SJ, CMJ and 1RM revealed a significant time main effect (pvolleyball and beach volleyball players increases leg strength more and leads to greater improvement in jump performance than traditional strength training, but greater improvements can be expected in beach volleyball players than in volleyball players. PMID:25187676

  16. Jumping and Landing Techniques in Elite Women’s Volleyball

    Science.gov (United States)

    Tillman, Mark D.; Hass, Chris J.; Brunt, Denis; Bennett, Gregg R.

    2004-01-01

    Volleyball has become one of the most widely played participant sports in the world. Participation requires expertise in many physical skills and performance is often dependent on an individual’s ability to jump and land. The incidence of injury in volleyball is similar to the rates reported for sports that are considered more physical contact sports. Though the most common source of injury in volleyball is the jump landing sequence, little research exists regarding the prevalence of jumping and landing techniques. The purpose of this study was to quantify the number of jumps performed by female volleyball players in competitive matches and to determine the relative frequency of different jump-landing techniques. Videotape recordings of two matches among four volleyball teams were analyzed for this study. Each activity was categorized by jump type (offensive spike or defensive block) and phase (jump or landing). Phase was subcategorized by foot use patterns (right, left, or both). Each of the players averaged nearly 22 jump-landings per game. Foot use patterns occurred in unequal amounts (p < 0.001) with over 50% of defensive landings occurring on one foot. Coaches, physical educators, and recreation providers may utilize the findings of this inquiry to help prevent injuries in volleyball. Key Points The incidence of injury in volleyball is nearly equivalent to injury rates reported for ice hockey and soccer. Most injuries in volleyball occur during the jump landing sequence, but few data exist regarding jump landing techniques for elite female players. Our data indicate that the vast majority of jumps utilize two feet, but approximately half of landings occur with only one foot. Coaches, physical educators, and recreation providers may utilize the findings of this inquiry to prevent possible injuries in athletes, students, or those who participate in volleyball for recreational purposes. PMID:24497818

  17. Neuromuscular function during drop jumps in young and elderly males.

    Science.gov (United States)

    Piirainen, Jarmo M; Linnamo, Vesa; Sippola, Niina; Avela, Janne

    2012-12-01

    The Hoffman reflex (H-reflex), indicating alpha-motoneuron pool activity, has been shown to be task - and in resting conditions - age dependent. How aging affects H-reflex activity during explosive movements is not clear at present. The purpose of this study was to examine the effects of aging on H-reflexes during drop jumps, and its possible role in drop jump performance. Ten young (26.8 ± 2.7 years) and twenty elderly (64.2 ± 2.7 years) subjects participated in the study. Maximal drop jump performance and soleus H-reflex response (H/M jump) 20 ms after ground contact were measured in a sledge ergometer. Maximal H-reflex, maximal M-wave, Hmax/Mmax-ratio and H-reflex excitability curves were measured during standing rest. Although in young the H-reflex response (Hmax/Mmax) was 6.5% higher during relaxed standing and 19.7% higher during drop jumps (H jump/M jump) than in the elderly group, these differences were not statistically significant. In drop jumps, the elderly subjects had lower jumping height (30.4%, p push-off force (18.0%, p push-off time (31.0% p push-off force (r = 0.833, p push-off time (r = -0.857, p strategies in drop jumps. However, it does not fully explain age related differences in jumping performance, since age related differences in H-reflex activity were non-significant. Copyright © 2012 Elsevier Ltd. All rights reserved.

  18. Effects of loading on maximum vertical jumps: selective effects of weight and inertia

    OpenAIRE

    Leontijevic, Bojan; Pazin, Nemanja; Bozic, Predrag R.; Kukolj, Milos; Ugarkovic, Dusan; Jaric, Slobodan

    2011-01-01

    A novel loading method was applied to explore selective effects of externally added weight (W), weight and inertia (W+I), and inertia (I) on maximum counter-movement jumps (CMJ) performed with arm swing. Externally applied extended rubber bands and/or loaded vest added W, W+I, and I corresponding to 10–40% of subjects' body mass. As expected, an increase in magnitude of all types of load was associated with an increase in ground reaction forces (GRF), as well as with a decrease in both the ju...

  19. Chasing maximal performance: a cautionary tale from the celebrated jumping frogs of Calaveras County.

    Science.gov (United States)

    Astley, H C; Abbott, E M; Azizi, E; Marsh, R L; Roberts, T J

    2013-11-01

    Maximal performance is an essential metric for understanding many aspects of an organism's biology, but it can be difficult to determine because a measured maximum may reflect only a peak level of effort, not a physiological limit. We used a unique opportunity provided by a frog jumping contest to evaluate the validity of existing laboratory estimates of maximum jumping performance in bullfrogs (Rana catesbeiana). We recorded video of 3124 bullfrog jumps over the course of the 4-day contest at the Calaveras County Jumping Frog Jubilee, and determined jump distance from these images and a calibration of the jump arena. Frogs were divided into two groups: 'rental' frogs collected by fair organizers and jumped by the general public, and frogs collected and jumped by experienced, 'professional' teams. A total of 58% of recorded jumps surpassed the maximum jump distance in the literature (1.295 m), and the longest jump was 2.2 m. Compared with rental frogs, professionally jumped frogs jumped farther, and the distribution of jump distances for this group was skewed towards long jumps. Calculated muscular work, historical records and the skewed distribution of jump distances all suggest that the longest jumps represent the true performance limit for this species. Using resampling, we estimated the probability of observing a given jump distance for various sample sizes, showing that large sample sizes are required to detect rare maximal jumps. These results show the importance of sample size, animal motivation and physiological conditions for accurate maximal performance estimates.

  20. Modeling financial contagion using mutually exciting jump processes

    NARCIS (Netherlands)

    Aït-Sahalia, Y.; Cacho-Diaz, J.; Laeven, R.J.A.

    2013-01-01

    We propose a model designed to capture the dynamics of asset returns, with periods of crises that are characterized by contagion. In the model, a jump in one region of the world increases the intensity of jumps both in the same region (self-excitation) as well as in other regions (mutual

  1. Modeling financial contagion using mutually exciting jump processes

    NARCIS (Netherlands)

    Aït-Sahalia, Y.; Cacho-Diaz, J.; Laeven, R.J.A.

    2015-01-01

    We propose a model to capture the dynamics of asset returns, with periods of crises that are characterized by contagion. In the model, a jump in one region of the world increases the intensity of jumps both in the same region (self-excitation) as well as in other regions (cross-excitation),

  2. How Can We Tell if Frogs Jump Further?

    Science.gov (United States)

    Drummond, Gordon B.; Tom, Brian D. M.

    2011-01-01

    How effective is training frogs to jump? This is perhaps the most frequent question in biology that is subjected to statistical analysis: does a treatment make a difference? One can examine whether there is indeed a training effect, by first assuming the opposite. That is, the authors assume that training has no effect on the mean distance jumped.…

  3. Teaching Jump Rope to Children with Visual Impairments

    Science.gov (United States)

    Lieberman, Lauren J.; Schedlin, Haley; Pierce, Tristan

    2009-01-01

    This article presents strategies for jumping rope for children with visual impairments. Giving choices related to the types of rope and the use of mats is important. In addition, using appropriate instructional strategies and modifications will make jumping rope a skill that the children will enjoy and will lead to their involvement in other…

  4. Jump Tails, Extreme Dependencies, and the Distribution of Stock Returns

    DEFF Research Database (Denmark)

    Bollerslev, Tim; Todorov, Viktor

    We provide a new framework for estimating the systematic and idiosyncratic jump tail risks in financial asset prices. The theory underlying our estimates are based on in-fill asymptotic arguments for directly identifying the systematic and idiosyncratic jumps, together with conventional long...

  5. The Triple Jump: Assessing Problem Solving in Psychiatry.

    Science.gov (United States)

    O'Gorman, Ethna C.; Trimble, Peter; Smyth, Joe

    1998-01-01

    Describes an attempt to assess a final-year course in psychiatry using the Triple Jump. In this course, students on placement in psychiatric units perfect psychiatry skills that were acquired during the previous year by direct contact with patients. The Triple Jump is used to assess problem-solving skills in management strategy on cases. (PVD)

  6. Feller Property for a Special Hybrid Jump-Diffusion Model

    Directory of Open Access Journals (Sweden)

    Jinying Tong

    2014-01-01

    Full Text Available We consider the stochastic stability for a hybrid jump-diffusion model, where the switching here is a phase semi-Markovian process. We first transform the process into a corresponding jump-diffusion with Markovian switching by the supplementary variable technique. Then we prove the Feller and strong Feller properties of the model under some assumptions.

  7. A time inhomogeneous Cox-Ingersoll-Ross diffusion with jumps

    CERN Document Server

    Hoepfner, Reinhard

    2009-01-01

    We consider a time inhomogeneous Cox-Ingersoll-Ross diffusion with positive jumps. We exploit a branching property to prove existence of a unique strong solution under a restrictive condition on the jump measure. We give Laplace transforms for the transition probabilities, with an interpretation in terms of limits of mixtures over Gamma laws.

  8. How Can We Tell if Frogs Jump Further?

    Science.gov (United States)

    Drummond, Gordon B.; Tom, Brian D. M.

    2011-01-01

    How effective is training frogs to jump? This is perhaps the most frequent question in biology that is subjected to statistical analysis: does a treatment make a difference? One can examine whether there is indeed a training effect, by first assuming the opposite. That is, the authors assume that training has no effect on the mean distance jumped.…

  9. Tuning Superhydrophobic Nanostructures to Enhance Jumping-Droplet Condensation

    Science.gov (United States)

    Mulroe, Megan; Srijanto, Bernadeta; Collier, Patrick; Boreyko, Jonathan

    2016-11-01

    It was recently discovered that condensation growing on a nanostructured superhydrophobic surface can spontaneously jump off the surface when two or more droplets coalesce together. The minimum droplet size for jumping to occur is of order 10 microns, but it is unclear whether this is the true lower limit of jumping droplets or simply a limitation of current superhydrophobic surfaces. Here, we analyze the dynamics of jumping droplets on six different superhydrophobic surfaces where the topography of the nanopillars was systematically varied. The critical diameter for jumping to occur was observed to be highly dependent upon the height and diameter of the nanopillars; surfaces with very tall and slender nanopillars enabled jumping droplets at a smaller critical size of order 1 micron. An energetic model of the incipient growth of condensate shows that the nanostructure topology affects the rate of increase of a growing droplet's apparent contact angle, with jumping being enabled at very large angles. These findings indicate that the true upper limit to the performance of jumping-droplet condensers has not yet been reached and can be further improved using advanced nanofabrication techniques.

  10. Empirical likelihood inference for diffusion processes with jumps

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    In this paper, we consider the empirical likelihood inference for the jump-diffusion model. We construct the confidence intervals based on the empirical likelihood for the infinitesimal moments in the jump-diffusion models. They are better than the confidence intervals which are based on the asymptotic normality of point estimates.

  11. A Safe and Effective Modification of Thomson's Jumping Ring Experiment

    Science.gov (United States)

    Waschke, Felix; Strunz, Andreas; Meyn, Jan-Peter

    2012-01-01

    The electrical circuit of the jumping ring experiment based on discharging a capacitor is optimized. The setup is scoop proof at 46 V and yet the ring jumps more than 9 m high. The setup is suitable for both lectures and student laboratory work in higher education. (Contains 1 table, 8 figures and 3 footnotes.)

  12. Evaluation of Metabolic Stress between Jumping at Different Cadences on the Digi-Jump Machine.

    Science.gov (United States)

    Lyons, Thomas S; Navalta, James W; Callahan, Zachary J

    The American College of Sports Medicine (ACSM) recommends that healthy adults achieve a minimum of thirty minutes of moderate intensity aerobic exercise five days per week. While cycling, walking, and jogging are commonly observed methods of achieving these recommendations, another option may be repetitive jumping. The purpose of this study was to examine the metabolic responses between repetitive jumping at a cadence of 120 jumps per minute (JPMs) vs. 100 JPMs when utilizing the Digi-Jump machine. Twenty-eight subjects completed two jumping trials, one at 120 JPMs and one at 100 JPMs. Subjects jumped until volitional exhaustion, or for a maximum of fifteen minutes. Oxygen uptake (VO2), heart rate (HR), respiratory exchange ratio (RER), and rating of perceived exertion (RPE) were assessed each minute of each exercise trial. RPE was differentiated, in that subjects reported perceived exertion of their total body, their upper-leg, and their lower leg. Results of this study indicated that there was no significant difference between the two trials for VO2, HR, or total body RPE. Differences were reported between trials for peak and average RER, with the 120 JPM trial eliciting a lower RER for both (peak: 1.08 ± .087 vs. 1.17 ± .1 p=.000; average: .99 ± .076 vs. 1.04 ± .098 p=.002), peak upper leg RPE (120: 15.29 ± 3.89 vs. 100: 16.75 ± 2.52 p=.022), and average lower leg RPE (120: 15.04 ± 2.55 vs. 100: 13.94 ± 2.02 p=.019). Also, there was a significant difference in exercise duration between the trials, with subjects able to exercise longer during the 120 JPM trial (12.4 ± 3.42 mins vs. 9.68 ± 4.31 mins p=.000). These data indicate that while the physiological stress may not be different between the two trials as indicated by VO2 and HR, the 120 JPM trial appears less strenuous as evidenced by RER values and by subjects' ability to exercise longer at that cadence.

  13. The hydraulic jump and ripples in liquid helium

    Energy Technology Data Exchange (ETDEWEB)

    Rolley, E. [Laboratoire de Physique Statistique de l' ENS, associe au CNRS et aux Universites Paris 6 et Paris 7, 24 rue Lhomond, 75005 Paris (France)]. E-mail: rolley@lps.ens.fr; Guthmann, C. [Laboratoire de Physique Statistique de l' ENS, associe au CNRS et aux Universites Paris 6 et Paris 7, 24 rue Lhomond, 75005 Paris (France); Pettersen, M.S. [Washington and Jefferson College, 60 S. Lincoln St., Washington, PA 15301 (United States)

    2007-05-01

    We have studied the characteristics of the circular hydraulic jump using liquid helium. Surprisingly, the radius of the jump does not change at the superfluid transition. We think that the flow is still dissipative below the lambda point because the velocity exceeds the critical one. The jump radius R{sub j} is compared with various models. In our parameter range, we find that the jump can be treated as a shock, and that capillary effects are important. Below the superfluid transition, we observed a standing capillary wave between the impact of the jet and the jump. Assuming that the superfluid flow can be described with an effective viscosity, we calculate the wave vector and thus obtain the value of the liquid thickness, which is in reasonable agreement with predictions. However, the spatial variation of the wave amplitude depends much more strongly on temperature than we calculate.

  14. Effects of isometric scaling on vertical jumping performance.

    Directory of Open Access Journals (Sweden)

    Maarten F Bobbert

    Full Text Available Jump height, defined as vertical displacement in the airborne phase, depends on vertical takeoff velocity. For centuries, researchers have speculated on how jump height is affected by body size and many have adhered to what has come to be known as Borelli's law, which states that jump height does not depend on body size per se. The underlying assumption is that the amount of work produced per kg body mass during the push-off is independent of size. However, if a big body is isometrically downscaled to a small body, the latter requires higher joint angular velocities to achieve a given takeoff velocity and work production will be more impaired by the force-velocity relationship of muscle. In the present study, the effects of pure isometric scaling on vertical jumping performance were investigated using a biologically realistic model of the human musculoskeletal system. The input of the model, muscle stimulation over time, was optimized using jump height as criterion. It was found that when the human model was miniaturized to the size of a mouse lemur, with a mass of about one-thousandth that of a human, jump height dropped from 40 cm to only 6 cm, mainly because of the force-velocity relationship. In reality, mouse lemurs achieve jump heights of about 33 cm. By implication, the unfavourable effects of the small body size of mouse lemurs on jumping performance must be counteracted by favourable effects of morphological and physiological adaptations. The same holds true for other small jumping animals. The simulations for the first time expose and explain the sheer magnitude of the isolated effects of isometric downscaling on jumping performance, to be counteracted by morphological and physiological adaptations.

  15. Effects of isometric scaling on vertical jumping performance.

    Science.gov (United States)

    Bobbert, Maarten F

    2013-01-01

    Jump height, defined as vertical displacement in the airborne phase, depends on vertical takeoff velocity. For centuries, researchers have speculated on how jump height is affected by body size and many have adhered to what has come to be known as Borelli's law, which states that jump height does not depend on body size per se. The underlying assumption is that the amount of work produced per kg body mass during the push-off is independent of size. However, if a big body is isometrically downscaled to a small body, the latter requires higher joint angular velocities to achieve a given takeoff velocity and work production will be more impaired by the force-velocity relationship of muscle. In the present study, the effects of pure isometric scaling on vertical jumping performance were investigated using a biologically realistic model of the human musculoskeletal system. The input of the model, muscle stimulation over time, was optimized using jump height as criterion. It was found that when the human model was miniaturized to the size of a mouse lemur, with a mass of about one-thousandth that of a human, jump height dropped from 40 cm to only 6 cm, mainly because of the force-velocity relationship. In reality, mouse lemurs achieve jump heights of about 33 cm. By implication, the unfavourable effects of the small body size of mouse lemurs on jumping performance must be counteracted by favourable effects of morphological and physiological adaptations. The same holds true for other small jumping animals. The simulations for the first time expose and explain the sheer magnitude of the isolated effects of isometric downscaling on jumping performance, to be counteracted by morphological and physiological adaptations.

  16. Dynamics and stability of directional jumps in the desert locust

    Science.gov (United States)

    Gvirsman, Omer

    2016-01-01

    Locusts are known for their ability to jump large distances to avoid predation. The jump also serves to launch the adult locust into the air in order to initiate flight. Various aspects of this important behavior have been studied extensively, from muscle physiology and biomechanics, to the energy storage systems involved in powering the jump, and more. Less well understood are the mechanisms participating in control of the jump trajectory. Here we utilise video monitoring and careful analysis of experimental directional jumps by adult desert locusts, together with dynamic computer simulation, in order to understand how the locusts control the direction and elevation of the jump, the residual angular velocities resulting from the jump and the timing of flapping-flight initiation. Our study confirms and expands early findings regarding the instrumental role of the initial body position and orientation. Both real-jump video analysis and simulations based on our expanded dynamical model demonstrate that the initial body coordinates of position (relative to the hind-legs ground-contact points) are dominant in predicting the jumps’ azimuth and elevation angles. We also report a strong linear correlation between the jumps’ pitch-angular-velocity and flight initiation timing, such that head downwards rotations lead to earlier wing opening. In addition to offering important insights into the bio-mechanical principles of locust jumping and flight initiation, the findings from this study will be used in designing future prototypes of a bio-inspired miniature jumping robot that will be employed in animal behaviour studies and environmental monitoring applications. PMID:27703846

  17. Dynamics and stability of directional jumps in the desert locust

    Directory of Open Access Journals (Sweden)

    Omer Gvirsman

    2016-09-01

    Full Text Available Locusts are known for their ability to jump large distances to avoid predation. The jump also serves to launch the adult locust into the air in order to initiate flight. Various aspects of this important behavior have been studied extensively, from muscle physiology and biomechanics, to the energy storage systems involved in powering the jump, and more. Less well understood are the mechanisms participating in control of the jump trajectory. Here we utilise video monitoring and careful analysis of experimental directional jumps by adult desert locusts, together with dynamic computer simulation, in order to understand how the locusts control the direction and elevation of the jump, the residual angular velocities resulting from the jump and the timing of flapping-flight initiation. Our study confirms and expands early findings regarding the instrumental role of the initial body position and orientation. Both real-jump video analysis and simulations based on our expanded dynamical model demonstrate that the initial body coordinates of position (relative to the hind-legs ground-contact points are dominant in predicting the jumps’ azimuth and elevation angles. We also report a strong linear correlation between the jumps’ pitch-angular-velocity and flight initiation timing, such that head downwards rotations lead to earlier wing opening. In addition to offering important insights into the bio-mechanical principles of locust jumping and flight initiation, the findings from this study will be used in designing future prototypes of a bio-inspired miniature jumping robot that will be employed in animal behaviour studies and environmental monitoring applications.

  18. Jumping Jupiter can explain Mercury's orbit

    CERN Document Server

    Roig, Fernando; DeSouza, Sandro Ricardo

    2016-01-01

    The orbit of Mercury has large values of eccentricity and inclination that cannot be easily explained if this planet formed on a circular and coplanar orbit. Here, we study the evolution of Mercury's orbit during the instability related to the migration of the giant planets in the framework of the jumping Jupiter model. We found that some instability models are able to produce the correct values of Mercury's eccentricity and inclination, provided that relativistic effects are included in the precession of Mercury's perihelion. The orbital excitation is driven by the fast change of the normal oscillation modes of the system corresponding to the perihelion precession of Jupiter (for the eccentricity), and the nodal regression of Uranus (for the inclination).

  19. The Voter Model and Jump Diffusion

    CERN Document Server

    Majmudar, Jimit; Baumgaertner, Bert O; Tyson, Rebecca C

    2015-01-01

    Opinions, and subsequently opinion dynamics, depend not just on interactions among individuals, but also on external influences such as the mass media. The dependence on local interactions, however, has received considerably more attention. In this paper, we use the classical voter model as a basis, and extend it to include external influences. We show that this new model can be understood using the theory of jump diffusion processes. We derive results pertaining to fixation probability and expected consensus time of the process, and find that the contribution of an external influence significantly dwarfs the contribution of the node-to-node interactions in terms of driving the social network to eventual consensus. This result suggests the potential importance of ``macro-level'' phenomena such as the media influence as compared to the ``micro-level'' local interactions, in modelling opinion dynamics.

  20. CAPTURE OF TROJANS BY JUMPING JUPITER

    Energy Technology Data Exchange (ETDEWEB)

    Nesvorny, David [Department of Space Studies, Southwest Research Institute, 1050 Walnut St., Suite 300, Boulder, CO 80302 (United States); Vokrouhlicky, David [Institute of Astronomy, Charles University, V Holesovickach 2, 180 00 Prague 8 (Czech Republic); Morbidelli, Alessandro [Departement Cassiopee, University of Nice, CNRS, Observatoire de la Cote d' Azur, Nice, F-06304 (France)

    2013-05-01

    Jupiter Trojans are thought to be survivors of a much larger population of planetesimals that existed in the planetary region when planets formed. They can provide important constraints on the mass and properties of the planetesimal disk, and its dispersal during planet migration. Here, we tested a possibility that the Trojans were captured during the early dynamical instability among the outer planets (aka the Nice model), when the semimajor axis of Jupiter was changing as a result of scattering encounters with an ice giant. The capture occurs in this model when Jupiter's orbit and its Lagrange points become radially displaced in a scattering event and fall into a region populated by planetesimals (that previously evolved from their natal transplanetary disk to {approx}5 AU during the instability). Our numerical simulations of the new capture model, hereafter jump capture, satisfactorily reproduce the orbital distribution of the Trojans and their total mass. The jump capture is potentially capable of explaining the observed asymmetry in the number of leading and trailing Trojans. We find that the capture probability is (6-8) Multiplication-Sign 10{sup -7} for each particle in the original transplanetary disk, implying that the disk contained (3-4) Multiplication-Sign 10{sup 7} planetesimals with absolute magnitude H < 9 (corresponding to diameter D = 80 km for a 7% albedo). The disk mass inferred from this work, M{sub disk} {approx} 14-28 M{sub Earth}, is consistent with the mass deduced from recent dynamical simulations of the planetary instability.

  1. Bone Mineralization in Rhythmic Gymnasts Entering Puberty: Associations with Jumping Performance and Body Composition Variables

    Science.gov (United States)

    Võsoberg, Kristel; Tillmann, Vallo; Tamm, Anna-Liisa; Maasalu, Katre; Jürimäe, Jaak

    2017-01-01

    This study examined bone mineral density (BMD) accrual in prepubertal rhythmic gymnasts entering puberty and their age-matched untrained control girls, and associations with baseline jumping performance and body composition over the 3-year period. Whole body (WB) and femoral neck (FN) BMD, WB fat mass (FM) and fat free mass (FFM), countermovement jump (CMJ) and rebound jumps for 15 s (RJ15s) were assessed in 25 rhythmic gymnasts and 25 untrained controls at baseline and after 3-year period. The changes over this period were calculated (Δ scores). Pubertal maturation over the 3-year period was slower in rhythmic gymnasts compared to untrained controls, while no difference in bone age development was seen. WB BMD increased similarly in both groups, while the increase in FN BMD was higher in rhythmic gymnasts compared with untrained controls. In rhythmic gymnasts, baseline FFM was the most significant predictor of ΔWB BMD explaining 19.2% of the variability, while baseline RJ15s was the most significant predictor of ΔFN BMD explaining 18.5% of the variability. In untrained controls, baseline FM explained 51.8 and 18.9% of the variability in ΔWB BMD and ΔFN BMD, respectively. In conclusion, mechanical loading of high-intensity athletic activity had beneficial effect on BMD accrual in rhythmic gymnasts and may have counterbalanced such negative factors on bone development as slower pubertal maturation and lower body FM. Baseline FFM and repeated jumps test performance were related to BMD accrual in rhythmic gymnasts, while baseline FM was related to BMD accrual in untrained controls. Key points Sudy examined bone mineralization in prepubertal rhythmic gymnasts entering puberty and their age-matched untrained control girls, and associations with baseline jumping performance and body composition. Jumping performance and fat free mass values predicted bone mineral accrual in rhythmic gymnasts. Fat mass predicted bone mineral accrual in untrained control girls

  2. Peak power in the hexagonal barbell jump squat and its relationship to jump performance and acceleration in elite rugby union players.

    Science.gov (United States)

    Turner, Thomas S; Tobin, Daniel P; Delahunt, Eamonn

    2015-05-01

    Recent research suggests that jump squats with a loaded hexagonal barbell are superior for peak power production to comparable loads in a traditional barbell loaded jump squat. The aim of this study was to investigate the relationship between relative peak power output during performance of the hexagonal barbell jump squat (HBJS), countermovement jump (CMJ) height, and linear acceleration speed in rugby union players. Seventeen professional rugby union players performed 10- and 20-m sprints, followed by a set of 3 unloaded CMJs and a set of 3 HBJS at a previously determined optimal load corresponding with peak power output. The relationship between HBJS relative peak power output, 10- and 20-m sprint time, and CMJ height was investigated using correlation analysis. The contribution of HBJS relative peak power output and CMJ height to 10- and 20-m sprint time was investigated using standard multiple regression. Strong, significant, inverse correlations were observed between HBJS relative peak power output, 10-m sprint time (r = -0.70, p < 0.01), and 20-m sprint time (r = -0.75, p < 0.01). A strong, significant, positive correlation was observed between HBJS relative peak power output and CMJ height (r = 0.80, p < 0.01). Together, HBJS relative peak power output and CMJ height explained 46% of the variance in 10-m sprint time while explaining 59% of the variance in 20-m sprint time. The findings of the current study demonstrate a significant relationship between relative peak power in the HBJS and athletic performance as quantified by CMJ height and 10- and 20-m sprint time.

  3. Hydraulic jumps within pyroclastic density currents and their sedimentary record

    Science.gov (United States)

    Douillet, G.; Mueller, S.; Kueppers, U.; Dingwell, D. B.

    2013-12-01

    This contribution presents a complete and comprehensive formulation of the hydraulic jump phenomenon and reviews sedimentary structures that may be associated with them. Beginning from the general fluid phenomenon, we then focus on examples from pyroclastic density currents in order to infer dynamic parameters on the parent flows. A hydraulic jump is a fluid dynamics phenomenon that corresponds to the sudden increase of the thickness of a flow accompanied by a decrease of its velocity and/or density. A hydraulic jump is the expression of the transition of the flow from two different flow regimes: supercritical to subcritical. This entrains a change in the energy balance between kinetic energy and gravity potential energy. Recently, the terms of 'pneumatic jumps' have been used for similar phenomenon driven within a gas phase, and granular jumps for dense granular flows. It is thought that such strong changes in the flow conditions may leave characteristic structures in the sedimentary record. Indeed, the main variables influencing the sedimentation rate are the flow velocity, particle concentration and turbulence level, all of them strongly affected by a hydraulic jump. Structures deposited by hydraulic/pneumatic jumps have been called cyclic steps and chute and pool structures. Chute and pools represent the record of a single supercritical to subcritical transition, whereas cyclic steps are produced by stable trains of hydraulic jumps and subsequent re-accelerations. Pyroclastic density currents (PDCs) are gas and pyroclasts flows. As such, they can be subjected to granular and pneumatic jumps and their deposit have often been interpreted as containing records of jumps. Steep sided truncations covered by lensoidal layers have been interpreted as the record of internal jumps within density stratified flows. Fines-depleted breccias at breaks in slope are thought to result from the enhanced turbulence at a jump of the entire flow. Sudden increases in thickness of

  4. Jumping Abilities and Power-Velocity Relationship in Judo Athletes: Comparative Analysis Among Age Categories

    Directory of Open Access Journals (Sweden)

    Buśko Krzysztof

    2015-06-01

    Full Text Available Purpose. The aim of the study was to examine age differences in the maximal power and height of rise of the body mass centre measured in spike jump (SPJ and counter-movement jump (CMJ, and power-velocity relationship of lower extremities between cadet and U23 age class judo athletes. Methods. Seven cadets (age 16.6 ± 0.7 years and eight U23 age class (21.3 ± 1.4 years Polish judoists took part in the study. The maximal power and height of jump were measured at SPJ and CMJ jumps. Power- velocity relations (P-v were determined from 5 maximal cycle ergometer exercise bouts at increasing external loads equal to 2.5, 5.0, 7.5, 10.0 and 12.5% of body weight (BW. Results. Cadet judoists had a significantly smaller maximal power output (11.56 ± 1.21 W ・ kg-1 than U23 athletes (12.69 ± 0.67 W ・ kg-1. The optimal velocity was similar in both group (119.3 ± 16.0 rpm and 119.6 ± 15.5 rpm, respectively. Significant age differences were founded between the cadet and U23 athletes for power output at external load equal 12.5% BW. Cadet judoists generated insignificantly lower maximal power in CMJ and SPJ than U23 judo athletes with except of the absolute maximal power in SPJ. The age difference was observed in height of CMJ. Conclusions. Based on the characteristics of F-v curve we can see in which direction follow the effects of training. Application of CMJ and SPJ in jumping test allows to assess changes in neuromuscular coordination. The use of the both methods give better information to optimal training control.

  5. A caffeinated energy drink improves jump performance in adolescent basketball players.

    Science.gov (United States)

    Abian-Vicen, Javier; Puente, Carlos; Salinero, Juan José; González-Millán, Cristina; Areces, Francisco; Muñoz, Gloria; Muñoz-Guerra, Jesús; Del Coso, Juan

    2014-05-01

    This study aimed at investigating the effects of a commercially available energy drink on shooting precision, jump performance and endurance capacity in young basketball players. Sixteen young basketball players (first division of a junior national league; 14.9 ± 0.8 years; 73.4 ± 12.4 kg; 182.3 ± 6.5 cm) volunteered to participate in the research. They ingested either (a) an energy drink that contained 3 mg of caffeine per kg of body weight or (b) a placebo energy drink with the same appearance and taste. After 60 min for caffeine absorption, they performed free throw shooting and three-point shooting tests. After that, participants performed a maximal countermovement jump (CMJ), a repeated maximal jumps test for 15 s (RJ-15), and the Yo-Yo intermittent recovery test level 1 (Yo-Yo IR1). Urine samples were obtained before and 30 min after testing. In comparison to the placebo, the ingestion of the caffeinated energy drink did not affect precision during the free throws (Caffeine = 70.7 ± 11.8 % vs placebo = 70.3 ± 11.0 %; P = 0.45), the three-point shooting test (39.9 ± 11.8 vs 38.1 ± 12.8 %; P = 0.33) or the distance covered in the Yo-Yo IR1 (2,000 ± 706 vs 1,925 ± 702 m; P = 0.19). However, the energy drink significantly increased jump height during the CMJ (38.3 ± 4.4 vs 37.5 ± 4.4 cm; P energy drink (3 mg/kg body weight) increased jump performance although it did not affect basketball shooting precision.

  6. A COMPARISON OF PAIRS FIGURE SKATERS IN REPEATED JUMPS

    Directory of Open Access Journals (Sweden)

    William A. Sands

    2012-03-01

    Full Text Available Trends in pairs figure skating have shown that increasingly difficult jumps have become an essential aspect of high-level performance, especially in the latter part of a competitive program. We compared a repeated jump power index in a 60 s repeated jump test to determine the relationship of repeated jump test to competitive rank and to measure 2D hip, knee, and ankle angles and angular velocities at 0, 20, 40, and 60 s. Eighteen National Team Pairs Figure Skaters performed a 60 s repeated jump test on a large switch-mat with timing of flight and ground durations and digital video recording. Each 60-s period was divided into 6, 10-s intervals, with power indexes (W/kg calculated for each 10-s interval. Power index by 10-s interval repeated measures ANOVAs (RMANOVA showed that males exceeded females at all intervals, and the highest power index interval was during 10 to 20 s for both sexes. RMANOVAs of angles and angular velocities showed main effects for time only. Power index and jumping techniques among figure skaters showed rapid and steady declines over the test duration. Power index can predict approximately 50% of competitive rank variance, and sex differences in jumping technique were rare

  7. Effects of Foam Rolling on Vertical Jump Performance

    Directory of Open Access Journals (Sweden)

    Andrew Jones

    2015-07-01

    Full Text Available Background: Foam rolling is a popular activity utilized by strength and conditioning coaches as it is believed to increase muscle length and break up fibrous adhesions located in connective tissue. However, there is little research investigating the effects of foam rolling on athletic performance. Objective: The purpose of this study was to investigate the effects of lower body foam rolling on vertical jump performance. Methods: Twenty males (age 24.05 ± 2.02 years; height 177.43 ± 6.31 cm; mass 81.41 ± 8.76 kg volunteered to participate. Subjects completed three days of testing, separated by at least twenty-four hours. Day one consisted of baseline vertical jumps on a force plate, followed by familiarization with foam rolling and control protocols. Subjects returned on days two and three and performed 30-second bouts of lower body foam rolling or mimicked foam rolling movements on a skateboard followed by vertical jumps on a force plate. The highest jump from each day was used for statistical analyses. Results: Repeated measures ANOVAs revealed no significant differences in Jump height, impulse, relative ground reaction force, or take-off velocity between conditions. Conclusion: 30-second bouts of lower body foam rolling do not improve vertical jump performance. Keywords: Dynamic Warm-Up, Foam Rolling, Vertical Jump

  8. Condensed droplet jumping: Capillary to inertial energy transfer

    Science.gov (United States)

    Enright, Ryan; Miljkovic, Nenad; Morris, Michael; Wang, Evelyn

    2013-03-01

    When condensed droplets coalesce on a superhydrophobic nanostructured surface, the resulting droplet can jump from the surface due to the release of excess surface energy. This behavior has been shown to follow a simple inertial-capillary scaling. However, questions remain regarding the nature of the energy conversion process linking the excess surface energy of the system before coalescence and the kinetic energy of the jumping droplet. Furthermore, the primary energy dissipation mechanisms limiting this jumping behavior remain relatively unexplored. In this work, we present new experimental data from a two-camera setup capturing the trajectory of jumping droplets on nanostructured surfaces with a characteristic surface roughness length scale on the order of 10 nm. Coupled with a model developed to capture the main details of the bridging flow during coalescence, our findings suggest that: 1. the excess surface energy available for jumping is a fraction of that suggested by simple scaling due to incomplete energy transfer, 2. internal viscous dissipation is not a limiting factor on the jumping process at droplet sizes on the order of 10 μm and 3. jumping performance is strongly affected by forces associated with the external flow and fields around the droplet. This work suggests bounds on the heat transfer performance of superhydrophobic condensation surfaces.

  9. Aerial jumping in the Trinidadian guppy (Poecilia reticulata).

    Science.gov (United States)

    Soares, Daphne; Bierman, Hilary S

    2013-01-01

    Many fishes are able to jump out of the water and launch themselves into the air. Such behavior has been connected with prey capture, migration and predator avoidance. We found that jumping behavior of the guppy Poecilia reticulata is not associated with any of the above. The fish jump spontaneously, without being triggered by overt sensory cues, is not migratory and does not attempt to capture aerial food items. Here, we use high speed video imaging to analyze the kinematics of the jumping behavior P. reticulata. Fish jump from a still position by slowly backing up while using its pectoral fins, followed by strong body trusts which lead to launching into the air several body lengths. The liftoff phase of the jump is fast and fish will continue with whole body thrusts and tail beats, even when out of the water. This behavior occurs when fish are in a group or in isolation. Geography has had substantial effects on guppy evolution, with waterfalls reducing gene flow and constraining dispersal. We suggest that jumping has evolved in guppies as a behavioral phenotype for dispersal.

  10. Aerial jumping in the Trinidadian guppy (Poecilia reticulata.

    Directory of Open Access Journals (Sweden)

    Daphne Soares

    Full Text Available Many fishes are able to jump out of the water and launch themselves into the air. Such behavior has been connected with prey capture, migration and predator avoidance. We found that jumping behavior of the guppy Poecilia reticulata is not associated with any of the above. The fish jump spontaneously, without being triggered by overt sensory cues, is not migratory and does not attempt to capture aerial food items. Here, we use high speed video imaging to analyze the kinematics of the jumping behavior P. reticulata. Fish jump from a still position by slowly backing up while using its pectoral fins, followed by strong body trusts which lead to launching into the air several body lengths. The liftoff phase of the jump is fast and fish will continue with whole body thrusts and tail beats, even when out of the water. This behavior occurs when fish are in a group or in isolation. Geography has had substantial effects on guppy evolution, with waterfalls reducing gene flow and constraining dispersal. We suggest that jumping has evolved in guppies as a behavioral phenotype for dispersal.

  11. Optimizing the Distribution of Leg Muscles for Vertical Jumping.

    Science.gov (United States)

    Wong, Jeremy D; Bobbert, Maarten F; van Soest, Arthur J; Gribble, Paul L; Kistemaker, Dinant A

    2016-01-01

    A goal of biomechanics and motor control is to understand the design of the human musculoskeletal system. Here we investigated human functional morphology by making predictions about the muscle volume distribution that is optimal for a specific motor task. We examined a well-studied and relatively simple human movement, vertical jumping. We investigated how high a human could jump if muscle volume were optimized for jumping, and determined how the optimal parameters improve performance. We used a four-link inverted pendulum model of human vertical jumping actuated by Hill-type muscles, that well-approximates skilled human performance. We optimized muscle volume by allowing the cross-sectional area and muscle fiber optimum length to be changed for each muscle, while maintaining constant total muscle volume. We observed, perhaps surprisingly, that the reference model, based on human anthropometric data, is relatively good for vertical jumping; it achieves 90% of the jump height predicted by a model with muscles designed specifically for jumping. Alteration of cross-sectional areas-which determine the maximum force deliverable by the muscles-constitutes the majority of improvement to jump height. The optimal distribution results in large vastus, gastrocnemius and hamstrings muscles that deliver more work, while producing a kinematic pattern essentially identical to the reference model. Work output is increased by removing muscle from rectus femoris, which cannot do work on the skeleton given its moment arm at the hip and the joint excursions during push-off. The gluteus composes a disproportionate amount of muscle volume and jump height is improved by moving it to other muscles. This approach represents a way to test hypotheses about optimal human functional morphology. Future studies may extend this approach to address other morphological questions in ethological tasks such as locomotion, and feature other sets of parameters such as properties of the skeletal

  12. Optimizing the Distribution of Leg Muscles for Vertical Jumping.

    Directory of Open Access Journals (Sweden)

    Jeremy D Wong

    Full Text Available A goal of biomechanics and motor control is to understand the design of the human musculoskeletal system. Here we investigated human functional morphology by making predictions about the muscle volume distribution that is optimal for a specific motor task. We examined a well-studied and relatively simple human movement, vertical jumping. We investigated how high a human could jump if muscle volume were optimized for jumping, and determined how the optimal parameters improve performance. We used a four-link inverted pendulum model of human vertical jumping actuated by Hill-type muscles, that well-approximates skilled human performance. We optimized muscle volume by allowing the cross-sectional area and muscle fiber optimum length to be changed for each muscle, while maintaining constant total muscle volume. We observed, perhaps surprisingly, that the reference model, based on human anthropometric data, is relatively good for vertical jumping; it achieves 90% of the jump height predicted by a model with muscles designed specifically for jumping. Alteration of cross-sectional areas-which determine the maximum force deliverable by the muscles-constitutes the majority of improvement to jump height. The optimal distribution results in large vastus, gastrocnemius and hamstrings muscles that deliver more work, while producing a kinematic pattern essentially identical to the reference model. Work output is increased by removing muscle from rectus femoris, which cannot do work on the skeleton given its moment arm at the hip and the joint excursions during push-off. The gluteus composes a disproportionate amount of muscle volume and jump height is improved by moving it to other muscles. This approach represents a way to test hypotheses about optimal human functional morphology. Future studies may extend this approach to address other morphological questions in ethological tasks such as locomotion, and feature other sets of parameters such as properties of

  13. Jumping numbers and ordered tree structures on the dual graph

    CERN Document Server

    Hyry, Eero

    2010-01-01

    Let R be a two-dimensional regular local ring having an algebraically closed residue field and let a be a complete ideal of finite colength in R. In this article we investigate the jumping numbers of a by means of the dual graph of the minimal log resolution of the pair (X,a). Our main result is a combinatorial criterium for a positive rational number to be a jumping number. In particular, we associate to each jumping number certain ordered tree structures on the dual graph.

  14. Nonstandard analysis and jump conditions for converging shock waves

    Science.gov (United States)

    Baty, Roy S.; Farassat, F.; Tucker, Don H.

    2008-06-01

    Nonstandard analysis is an area of modern mathematics that studies abstract number systems containing both infinitesimal and infinite numbers. This article applies nonstandard analysis to derive jump conditions for one-dimensional, converging shock waves in a compressible, inviscid, perfect gas. It is assumed that the shock thickness occurs on an infinitesimal interval and the jump functions in the thermodynamic and fluid dynamic parameters occur smoothly across this interval. Predistributions of the Heaviside function and the Dirac delta measure are introduced to model the flow parameters across a shock wave. The equations of motion expressed in nonconservative form are then applied to derive unambiguous relationships between the jump functions for the flow parameters.

  15. [Autogenic training in psychophysiological preparation for parachute jumps].

    Science.gov (United States)

    Reshetnikov, M M

    1978-01-01

    The efficiency of specific psychophysiological preparation--autogenic training--to parachute jumps was measured in two groups of cadets (test subjects and controls). Hetero- and autogenic training was carried out according to a scheme specially developed for this type of activity. The study of questionnaires and physiological data demonstrated that the specific psychophysiological preparation by means of autogenic training for a certain type of activity helped to develop active self-control over one's own state and emotions, alleviated tension, arrested adverse neurotic manifestations (sleep disturbances, depression, anxiety), contributed to the feeling of confidence in the successful completion of the jump and promoted positive tuning towards subsequent jumps.

  16. Stochastic mutualism model with Lévy jumps

    Science.gov (United States)

    Liu, Qun; Jiang, Daqing; Shi, Ningzhong; Hayat, Tasawar; Alsaedi, Ahmed

    2017-02-01

    In this paper, we consider a stochastic mutualism model with Lévy jumps. First of all, we show that the positive solution of the system is stochastically ultimate bounded. Then under a simple assumption, we establish sufficient and necessary conditions for the stochastic permanence and extinction of the system. The results show an important property of the Lévy jumps: they are unfavorable for the permanence of the species. Moreover, when there are no Lévy jumps, we show that there is a unique ergodic stationary distribution of the corresponding system under certain conditions. Some numerical simulations are introduced to validate the theoretical results.

  17. RESEARCH ON JUMPING SEQUENCE PLANNING ISSUES OF HOPPING ROBOTS

    Institute of Scientific and Technical Information of China (English)

    LIUZhuang-zhi; ZHUJian-ying

    2004-01-01

    The wheeled or crawled robots often suffer from big obstacles or ditches, so a hopping robot needs to fit the tough landform in the field environments. In order to jump over obstacles rapidly, a jumping sequence must be generated based on the landform information from sensors or user input. The planning method for planar mobile robots is compared with that of hopping robots. Several factors can change the planning result. Adjusting these coefficients, a heuristic searching algorithm for the jumping sequence is developed on a simplified landform. Calculational result indicates that the algorithm can achieve safety and efficient control sequences for a desired goal.

  18. Jump-Down Performance Alterations after Space Flight

    Science.gov (United States)

    Reschke, M. F.; Kofman, I. S.; Cerisano, J. M.; Fisher, E. A.; Peters, B. T.; Miller, C. A.; Harm, D. L.; Bloomberg, J. J.

    2011-01-01

    INTRODUCTION: Successful jump performance requires functional coordination of visual, vestibular, and somatosensory systems, which are affected by prolonged exposure to microgravity. Astronauts returning from space flight exhibit impaired ability to coordinate effective landing strategies when jumping from a platform to the ground. This study compares jump strategies used by astronauts before and after flight, changes to those strategies within a test session, and recoveries in jump-down performance parameters across several postflight test sessions. These data were obtained as part of an ongoing interdisciplinary study (Functional Task Test, FTT) designed to evaluate both astronaut postflight functional performance and related physiological changes. METHODS: Seven astronauts from short-duration (Shuttle) and three from long-duration (International Space Station) flights performed 3 two-footed jumps from a platform 30 cm high onto a force plate that measured the ground reaction forces and center-of-pressure displacement from the landings. Neuromuscular activation data were collected from the medial gastrocnemius and anterior tibialis of both legs using surface electromyography electrodes. Two load cells in the platform measured the load exerted by each foot during the takeoff phase of the jump. Data were collected in 2 preflight sessions, on landing day (Shuttle only), and 1, 6, and 30 days after flight. RESULTS: Postural settling time was significantly increased on the first postflight test session and many of the astronauts tested were unable to maintain balance on their first jump landing but recovered by the third jump, showing a learning progression in which performance improvements could be attributed to adjustments in takeoff or landing strategy. Jump strategy changes were evident in reduced air time (time between takeoff and landing) and also in increased asymmetry in foot latencies on takeoff. CONCLUSIONS: The test results revealed significant decrements

  19. Detection of weak frequency jumps for GNSS onboard clocks.

    Science.gov (United States)

    Huang, Xinming; Gong, Hang; Ou, Gang

    2014-05-01

    In this paper, a weak frequency jump detection method is developed for onboard clocks in global navigation satellite systems (GNSS). A Kalman filter is employed to facilitate the onboard real-time processing of atomic clock measurements, whose N-step prediction residuals are used to construct the weak frequency jump detector. Numerical simulations show that the method can successfully detect weak frequency jumps. The detection method proposed in this paper is helpful for autonomous integrity monitoring of GNSS satellite clocks, and can also be applied to other frequency anomalies with an appropriately modified detector.

  20. Jump diffusion models and the evolution of financial prices

    Science.gov (United States)

    Figueiredo, Annibal; de Castro, Marcio T.; da Silva, Sergio; Gleria, Iram

    2011-08-01

    We analyze a stochastic model to describe the evolution of financial prices. We consider the stochastic term as a sum of the Wiener noise and a jump process. We point to the effects of the jumps on the return time evolution, a central concern of the econophysics literature. The presence of jumps suggests that the process can be described by an infinitely divisible characteristic function belonging to the De Finetti class. We then extend the De Finetti functions to a generalized nonlinear model and show the model to be capable of explaining return behavior.

  1. Influence of stretching on warm up in jump and speed

    OpenAIRE

    Gálvez Ruiz, Pablo; Tapia Flores, A; Jurado Lavanant, A

    2013-01-01

    El objetivo del estudio es determinar si la realización de estiramientos pasivos, incluidos como parte del calentamiento, influyen en el rendimiento de la fuerza explosiva, en este caso en varios tests de salto vertical: Squat Jump (SJ), Countermouvement Jump (CMJ) y Reactive Jump (RJ); y también en un test de velocidad de 30 metros (mts.) con salida lanzada de 5 mts. Para ello, 9 jugadores del Málaga Club de Fútbol de categoría juvenil (18,22 ± 0,441 años) realizaron 2 protocolos de...

  2. Asymptotic Distribution of the Jump Change-Point Estimator

    Institute of Scientific and Technical Information of China (English)

    Changchun TAN; Huifang NIU; Baiqi MIAO

    2012-01-01

    The asymptotic distribution of the change-point estimator in a jump changepoint model is considered.For the jump change-point model Xi =a + θI{[nTo] < i ≤n} + εi,where εi (i =1,…,n) are independent identically distributed random variables with Eεi=0 and Var(εi) < oo,with the help of the slip window method,the asymptotic distribution of the jump change-point estimator (T) is studied under the condition of the local alternative hypothesis.

  3. Quantum jumps induced by matter-wave fluctuations

    CERN Document Server

    Torres, J M; Zippilli, S; Morigi, G

    2010-01-01

    We theoretically study the occurrence of quantum jumps in the resonance fluorescence of a trapped atom. Here, the atom is laser cooled in a configuration of level such that the occurrence of a quantum jump is associated to a change of the vibrational center-of-mass motion by one phonon. The statistics of the occurrence of the dark fluorescence period is studied as a function of the physical parameters and the corresponding features in the spectrum of resonance fluorescence are identified. We discuss the information which can be extracted on the atomic motion from the observation of a quantum jump in the considered setup.

  4. Rate Theory for Correlated Processes: Double Jumps in Adatom Diffusion

    DEFF Research Database (Denmark)

    Jacobsen, J.; Jacobsen, Karsten Wedel; Sethna, J.

    1997-01-01

    We study the rate of activated motion over multiple barriers, in particular the correlated double jump of an adatom diffusing on a missing-row reconstructed platinum (110) surface. We develop a transition path theory, showing that the activation energy is given by the minimum-energy trajectory...... which succeeds in the double jump. We explicitly calculate this trajectory within an effective-medium molecular dynamics simulation. A cusp in the acceptance region leads to a root T prefactor for the activated rate of double jumps. Theory and numerical results agree....

  5. Aeromechanics of the Spider Cricket Jump: How to Jump 60+ Times Your Body Length and Still Land on Your Feet

    Science.gov (United States)

    Palmer, Emily; Deshler, Nicolas; Gorman, David; Neves, Catarina; Mittal, Rajat

    2015-11-01

    Flapping, gliding, running, crawling and swimming have all been studied extensively in the past and have served as a source of inspiration for engineering designs. In the current project, we explore a mode of locomotion that straddles ground and air: jumping. The subject of our study is among the most proficient of long-jumpers in Nature: the spider cricket of the family Rhaphidophoridae, which can jump more than 60 times its body length. Despite jumping this immense distance, these crickets usually land on their feet, indicating an ability to control their posture during ``flight.'' We employ high-speed videogrammetry, to examine the jumps and to track the crickets' posture and appendage orientation throughout their jumps. Simple aerodynamic models are developed to predict the aerodynamic forces and moment on the crickets during `flight`. The analysis shows that these wingless insects employ carefully controlled and coordinated positioning of the limbs during flight so as to increase jump distance and to stabilize body posture during flight. The principles distilled from this study could serve as an inspiration for small jumping robots that can traverse complex terrains.

  6. EFFECTS OF MAXIMAL SQUAT EXERCISE TESTING ON VERTICAL JUMP PERFORMANCE IN AMERICAN COLLEGE FOOTBALL PLAYERS

    Directory of Open Access Journals (Sweden)

    Jay R. Hoffman

    2007-03-01

    on the first day of pre-season training camp. All athletes provided their informed consent as part of their sport requirements consistent with the college's Institutional Review Board's policies for use of human subjects in research. They were familiar with all testing protocols and had performed these assessments for the previous 2 - 6 years. All athletes reported to the athletic training facility for strength and vertical jump testing and performed a 5-min warm-up (pedaling at 60 rpm at 300 kg·m·min-1 interspersed with five all-out sprints during the last 5-s of each minute on a cycle ergometer prior to testing. Following the warm-up the athletes performed two countermovement vertical jumps. The higher of the two trials was recorded. The athletes then performed a 1-RM strength test for the barbell back squat exercise. Following a 5-minute rest interval, each athlete performed an additional countermovement vertical jump trial. The 1-RM squat test was performed using methods previously described by Hoffman, 2006. Each athlete performed a warm-up set using a resistance that was approximately 40-60% of his perceived maximum, and then performed three-to- four subsequent trials to determine the 1-RM. A 3 - 5 minute rest period was provided between each trial. The squat exercise required the athlete to place an Olympic bar across the trapezius muscle at a self-selected location. The athlete then descended to the parallel position which was attained when the greater trochanter of the femur reached the same level as the knee. The athlete then ascended until full knee extension. Trials not meeting the range of motion criteria were discarded.The counter-movement vertical jump height was measured using a VertecTM (Sports Imports, Columbus, OH. Prior to testing, each athlete's standing vertical reach height was determined. Vertical jump height was calculated by subtracting the standing reach height from the jump height. Power outputs were calculated based upon the formula of

  7. [Effects of Reactive Jump Training in Handball Players Regarding Jump Height and Power Development in the Triceps Surae Muscle].

    Science.gov (United States)

    Rensing, N; Westermann, A; Möller, D; von Piekartz, H

    2015-12-01

    Studies have shown changes in the technical and physical demands in modern handball. The game has increased considerably in speed, power and dynamics. Jump training has, therefore, become ever more important in the training of the athletes. These developments contribute to the fact that handball is now one of the most injury-prone types of sport, with the lower extremities being most frequently affected. Reactive jump training is not only used in training by now, but also increasingly in injury prevention. The aim of this study was to investigate the effectiveness of reactive jump training with handball players. 21 regional league handball players were randomly divided into an intervention group (n = 12) and a control group (n = 9). The intervention group completed a six-week reactive jump training programme while the control group went through a non-specific training programme. Jump height (squat and counter movement jump), isokinetic and isometric maximum power as well as muscle activity served as measuring parameters. A comparison of the intervention and control groups revealed that the reactive jump training led to significant improvements in jump height. The isometric and isokinetic maximum power measurements and the electromyographic activities of the triceps surae muscle demonstrated an improvement in the values within the intervention group. However, this improvement was not significant compared with the control group. Likewise both jumps correlated with the muscle activity of the soleus muscle as shown by electromyography. A moderate correlation was noticed between the isokinetic maximum power measurement and the electromyographic activity of the soleus and gastrocnemius medialis muscles. Furthermore, the correlations of the isometric and isokinetic maximum power meas-urements resulted in a strong correlation coefficient. This study revealed a significant increase in jump height after reactive jump training. There was no significant difference in

  8. The ingestion of a caffeinated energy drink improves jump performance and activity patterns in elite badminton players.

    Science.gov (United States)

    Abian, Pablo; Del Coso, Juan; Salinero, Juan José; Gallo-Salazar, Cesar; Areces, Francisco; Ruiz-Vicente, Diana; Lara, Beatriz; Soriano, Lidon; Muñoz, Victor; Abian-Vicen, Javier

    2015-01-01

    The aim of this study was to investigate the effectiveness of a caffeine-containing energy drink to enhance physical and match performance in elite badminton players. Sixteen male and elite badminton players (25.4 ± 7.3 year; 71.8 ± 7.9 kg) participated in a double-blind, placebo-controlled and randomised experiment. On two different sessions, badminton players ingested 3 mg of caffeine per kg of body mass in the form of an energy drink or the same drink without caffeine (placebo). After 60 min, participants performed the following tests: handgrip maximal force production, smash jump without and with shuttlecock, squat jump, countermovement jump and the agility T-test. Later, a 45-min simulated badminton match was played. Players' number of impacts and heart rate was measured during the match. The ingestion of the caffeinated energy drink increased squat jump height (34.5 ± 4.7 vs. 36.4 ± 4.3 cm; P energy drink may be an effective nutritional aid to increase jump performance and activity patterns during game in elite badminton players.

  9. Testability Synthesis for Jumping Carry Adders

    Directory of Open Access Journals (Sweden)

    Chien-In Henry Chen

    2002-01-01

    Full Text Available Synthesis for testability ensures that the synthesized circuit is testable by exploring the fundamental relationship between don't care and redundancy. With the exploration of the relationship, redundancy removal can be applied to improve the testability, reduce the area and improve the speed of a synthesized circuit. The test generation problems have been adequately solved, therefore an innovative testability synthesis strategy is necessary for achieving the maximum fault coverage and area reduction for maximum speed. This paper presents a testability synthesis methodology applicable to a top–down design method based on the identification and removal of redundant faults. Emphasis has been placed on the testability synthesis of a high-speed binary jumping carry adder. A synthesized 32-bit testable adder implemented by a 1.2 μm CMOS technology performs addition in 4.09 ns. Comparing with the original synthesized circuit, redundancy removal yields a 100% testable design with a 15% improvement in speed and a 25% reduction in area.

  10. Vortex jump behavior in coupled nanomagnetic heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, S.; Phatak, C., E-mail: cd@anl.gov [Materials Science Division, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, Illinois 60439 (United States); Petford-Long, A. K. [Materials Science Division, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, Illinois 60439 (United States); Department of Materials Science and Engineering, Northwestern University, 2220 Campus Drive, Evanston, Illinois 60208 (United States); Heinonen, O. [Materials Science Division, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, Illinois 60439 (United States); Department of Physics and Astronomy, Northwestern University, 2145 Sheridan Rd, Evanston, Illinois 60208-3112 (United States)

    2014-11-24

    The spin configuration and magnetic behavior in patterned nanostructures can be controlled by manipulating the interplay between the competing energy terms. This in turn requires fundamental knowledge of the magnetic interactions at the local nanometer scale. Here, we report on the spin structure and magnetization behavior of patterned discs containing exchange coupled ferromagnetic layers with additional exchange bias to an antiferromagnetic layer. The magnetization reversal was explored by direct local visualization of the domain behavior using in-situ Lorentz transmission electron microscopy, from which quantitative magnetic induction maps were reconstructed. The roles of the main competing energy terms were elucidated and the reversal mechanism was identified as a coupled phenomenon of incoherent rotation in the exchange-biased layer and localized vortex nucleation and discontinuous propagation in the free layer, including an anomalous jump in the trajectory. The observations were supported by micromagnetic simulations and modeled phase shift simulations. The work presented here provides fundamental insights into opportunities for macroscopic control of the energy landscape of magnetic heterostructures for functional applications.

  11. Ethics in radiology: wait lists queue jumping.

    Science.gov (United States)

    Cunningham, Natalie; Reid, Lynette; MacSwain, Sarah; Clarke, James R

    2013-08-01

    Education in ethics is a requirement for all Royal College residency training programs as laid out in the General Standards of Accreditation for residency programs in Canada. The ethical challenges that face radiologists in clinical practice are often different from those that face other physicians, because the nature of the physician-patient interaction is unlike that of many other specialties. Ethics education for radiologists and radiology residents will benefit from the development of teaching materials and resources that focus on the issues that are specific to the specialty. This article is intended to serve as an educational resource for radiology training programs to facilitate teaching ethics to residents and also as a continuing medical education resource for practicing radiologists. In an environment of limited health care resources, radiologists are frequently asked to expedite imaging studies for patients and, in some respects, act as gatekeepers for specialty care. The issues of wait lists, queue jumping, and balancing the needs of individuals and society are explored from the perspective of a radiologist.

  12. A jumping shape memory alloy under heat.

    Science.gov (United States)

    Yang, Shuiyuan; Omori, Toshihiro; Wang, Cuiping; Liu, Yong; Nagasako, Makoto; Ruan, Jingjing; Kainuma, Ryosuke; Ishida, Kiyohito; Liu, Xingjun

    2016-02-16

    Shape memory alloys are typical temperature-sensitive metallic functional materials due to superelasticity and shape recovery characteristics. The conventional shape memory effect involves the formation and deformation of thermally induced martensite and its reverse transformation. The shape recovery process usually takes place over a temperature range, showing relatively low temperature-sensitivity. Here we report novel Cu-Al-Fe-Mn shape memory alloys. Their stress-strain and shape recovery behaviors are clearly different from the conventional shape memory alloys. In this study, although the Cu-12.2Al-4.3Fe-6.6Mn and Cu-12.9Al-3.8Fe-5.6Mn alloys possess predominantly L2(1) parent before deformation, the 2H martensite stress-induced from L2(1) parent could be retained after unloading. Furthermore, their shape recovery response is extremely temperature-sensitive, in which a giant residual strain of about 9% recovers instantly and completely during heating. At the same time, the phenomenon of the jumping of the sample occurs. It is originated from the instantaneous completion of the reverse transformation of the stabilized 2H martensite. This novel Cu-Al-Fe-Mn shape memory alloys have great potentials as new temperature-sensitive functional materials.

  13. Triple jump examinations for dental student assessment.

    Science.gov (United States)

    Navazesh, Mahvash; Rich, Sandra K; Chopiuk, Nasrin Bahari; Keim, Robert G

    2013-10-01

    The triple jump examination (TJE) attempts to assess a higher level of learning with demand for analysis, critical thinking, and resolution of problems presented by written scenarios based on patient care situations. The purpose of this study was to examine the internal consistency, scale reliability, and interrater reliability of the TJE used at the Ostrow School of Dentistry, University of Southern California. On the sample of 2,227 examinations administered by seventy-seven raters across a three-year time period, the Cronbach's coefficient alpha for internal consistency of the overall TJE was found to be good (a=0.869). The internal consistency of the three subscales was found to be acceptable (a=0.731), good (a=0.820), and good (a=0.820). Average and single measures intraclass correlation coefficients (ICC) for scale reliability were significant at p<0.001, indicating strong interrater reliability. There were no statistically significant differences (p≤0.05) in the mean scores assigned on the TJE between rater groups defined by rater experience level with the TJE. A very high level of agreement among rater pairs was also observed. Across the entire three-year study period, with over 19,152 ratings, the seventy-seven raters were in general agreement 99.5 percent of the time and in exact agreement 77.2 percent of the time.

  14. Tissue flossing on ankle range of motion, jump and sprint performance: A follow-up study.

    Science.gov (United States)

    Driller, Matthew; Mackay, Kelsi; Mills, Blair; Tavares, Francisco

    2017-08-24

    Previous results from our laboratory suggest that band flossing results in increased ankle range of motion (ROM) and jump performance 5-min following application. However, the time-course of such benefits is yet to be examined. Parallel group design. University laboratory. 69 recreational athletes (32 male/37 female). Participants performed a weight-bearing lunge test (WBLT), a counter-movement jump (CMJ) and a 15 m sprint test (SPRINT) pre and up to 45-min post application of a floss band to both ankles (FLOSS) or without flossing of the ankle joints (CON). There was a significant intervention × time interaction in favour of FLOSS when compared to CON for the WBLT (p  0.05) benefits were seen for FLOSS when compared to CON for CMJ force (mean ± 90%CI: 89 ± 101 N) and 15 m SPRINT times (-0.06 ± 0.04 s) at 45-min post. There is a trend towards a benefit for the use of floss bands applied to the ankle joint to improve ROM, jump and sprint performance in recreational athletes for up to 45-min following their application. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Effects of loading on maximum vertical jumps: Selective effects of weight and inertia.

    Science.gov (United States)

    Leontijevic, Bojan; Pazin, Nemanja; Bozic, Predrag R; Kukolj, Milos; Ugarkovic, Dusan; Jaric, Slobodan

    2012-04-01

    A novel loading method was applied to explore selective effects of externally added weight (W), weight and inertia (W+I), and inertia (I) on maximum counter-movement jumps (CMJ) performed with arm swing. Externally applied extended rubber bands and/or loaded vest added W, W+I, and I corresponding to 10-40% of subjects' body mass. As expected, an increase in magnitude of all types of load was associated with an increase in ground reaction forces (GRF), as well as with a decrease in both the jumping performance and power output. However, of more importance could be that discernible differences among the effects of W, W+I, and I were recorded despite a relatively narrow loading range. In particular, an increase in W was associated with the minimal changes in movement kinematic pattern and smallest reduction of jumping performance, while also allowing for the highest power output. Conversely, W+I was associated with the highest ground reaction forces. Finally, the lowest maxima of GRF and power were associated with I. Although further research is apparently needed, the obtained finding could be of potential importance not only for understanding fundamental properties of the neuromuscular system, but also for optimization of loading in standard athletic training and rehabilitation procedures.

  16. SOLUTION TO BSDE WITH NONHOMOGENEOUS JUMPS UNDER LOCALLY LIPSCHITZIAN CONDITION

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    In this paper, we investigate the existence and uniqueness of the solution to a quasilinear backward stochastic differential equation with Poisson jumps. By introducing a series of approximate equations, we can show that BSDE has a unique adapted solution.

  17. Spontaneous Jumping of Coalescing Drops on a Superhydrophobic Surface

    Science.gov (United States)

    Boreyko, Jonathan; Chen, Chuan-Hua

    2009-11-01

    When micrometric drops coalesce in-plane on a superhydrophobic surface, a surprising out-of-plane jumping motion was observed. Such jumping motion triggered by drop coalescence was reproduced on a Leidenfrost surface. High-speed imaging revealed that this jumping motion results from the elastic interaction of the bridged drops with the superhydrophobic/Leidenfrost surface. Experiments on both the superhydrophobic and Leidenfrost surfaces compare favorably to a simple scaling model relating the kinetic energy of the merged drop to the surface energy released upon coalescence. The spontaneous jumping motion on water repellent surfaces enables the autonomous removal of water condensate independently of gravity; this process is highly desirable for sustained dropwise condensation.

  18. Spontaneous Jumping of Coalescing Drops on a Superhydrophobic Surface

    CERN Document Server

    Boreyko, Jonathan

    2009-01-01

    When micrometric drops coalesce in-plane on a superhydrophobic surface, a surprising out-of-plane jumping motion was observed. Such jumping motion triggered by drop coalescence was reproduced on a Leidenfrost surface. High-speed imaging revealed that this jumping motion results from the elastic interaction of the bridged drops with the superhydrophobic/Leidenfrost surface. Experiments on both the superhydrophobic and Leidenfrost surfaces compare favorably to a simple scaling model relating the kinetic energy of the merged drop to the surface energy released upon coalescence. The spontaneous jumping motion on water repellent surfaces enables the autonomous removal of water condensate independently of gravity; this process is highly desirable for sustained dropwise condensation.

  19. Jump Testing and the Speed of Market Adjustment

    DEFF Research Database (Denmark)

    Rasmussen, Torben B.

    Asymptotic properties of jump tests rely on the property that any jump occurs within a single time interval no matter what the observation frequency is. Market microstructure effects in relation to news-induced revaluation of the underlying variable is likely to make this an unrealistic assumption...... for high-frequency transaction data. To capture these microstructure effects, this paper suggests a model in which market prices adjust gradually to jumps in the underlying effcient price. A case study illustrates the empirical relevance of the model, and the performance of different jump tests...... is investigated here and in a simulation study. Evidence indicates that tests based on the largest of scaled price increments perform better than tests comparing measures of variability. Resolving the matter by testing at lower frequencies turns out to be less straightforward....

  20. Stick-jump mode in surface droplet dissolution

    CERN Document Server

    Dietrich, Erik; Zhang, Xuehua; Zandvliet, Harold J W; Lohse, Detlef

    2016-01-01

    The analogy between evaporating surface droplets in air to dissolving long-chain alcohol droplets in water is worked out. We show that next to the three known modi for surface droplet evaporation or dissolution (constant contact angle mode, constant contact radius mode, and stick-slide mode), a fourth mode exists for small droplets on supposedly smooth substrates, namely the stick-jump mode: intermittent contact line pinning causes the droplet to switch between sticking and jumping during the dissolution. We present experimental data and compare them to theory to predict the dissolution time in this stick-jump mode. We also explain why these jumps were easily observed for microscale droplets but not for larger droplets.

  1. METRIC TESTS CHARACTERISTIC FOR ESTIMATING JUMPING FOR VOLLEYBALL PLAYERS

    Directory of Open Access Journals (Sweden)

    Toplica Stojanović

    2008-08-01

    Full Text Available With goal to establish metric tests characteristics for estimating jumping for volleyball players, it was organized a pilot research on pattern of 23 volleyball players from cadet team and 23 students from high-school. For needs of this research four tests are valid for estimation, jump in block with left and right leg and jump in spike with left and right leg. Each test has been taken three times, so that we could with test-re test method determine their reliability, and with factor analysis their validity. Data were processed by multivariate analysis (item analysis, factor analysis from statistical package „Statistica 6.0 for windows“. On the results of research and discussion we can say that the tests had high coefficient of reliability, as well as factor validity, and these tests can be used to estimate jumping for volleyball players.

  2. Bird Flu Strain May Have Jumped from Cat to Human

    Science.gov (United States)

    ... page: https://medlineplus.gov/news/fullstory_162717.html Bird Flu Strain May Have Jumped From Cat to ... would be the first known transmission of this bird flu strain from cat to human, officials said. ...

  3. Spontaneous azimuthal breakout and instability at the circular hydraulic jump

    CERN Document Server

    Ray, Arnab K; Basu, Abhik; Bhattacharjee, Jayanta K

    2015-01-01

    We consider a shallow, two-dimensional flow of a liquid in which the radial and the azimuthal dynamics are coupled to each other. The steady and radial background flow of this system creates an axially symmetric circular hydraulic jump. On this background we apply time-dependent perturbations of the matter flow rate and the azimuthal flow velocity, with the latter strongly localized at the hydraulic jump. The perturbed variables depend spatially on both the radial and azimuthal coordinates. Linearization of the perturbations gives a coupled system of wave equations. The characteristic equations extracted from these wave equations show that under a marginally stable condition a spontaneous breaking of axial symmetry occurs at the position of the hydraulic jump. Departure from the marginal stability shows further that a linear instability develops in the azimuthal direction, resulting in an azimuthal transport of liquid at the hydraulic jump. The time for the growth of azimuthal instability is scaled by viscosi...

  4. The fluid dynamics of swimming by jumping in copepods

    DEFF Research Database (Denmark)

    Jiang, Houshuo; Kiørboe, Thomas

    2011-01-01

    Copepods swim either continuously by vibrating their feeding appendages or erratically by repeatedly beating their swimming legs resulting in a series of small jumps. The two swimming modes generate different hydrodynamic disturbances and therefore expose the swimmers differently to rheotactic...... limited and temporally ephemeral owing to jump-impulsiveness and viscous decay. In contrast, continuous steady swimming generates two well-extended long-lasting momentum jets both in front of and behind the swimmer, as suggested by the well-known steady stresslet model. Based on the observed jump-swimming...... kinematics of a small copepod Oithona davisae, we further showed that jump-swimming produces a hydrodynamic disturbance with much smaller spatial extension and shorter temporal duration than that produced by a same-size copepod cruising steadily at the same average translating velocity. Hence, small copepods...

  5. The fluid dynamics of swimming by jumping in copepods

    DEFF Research Database (Denmark)

    Jiang, Houshuo; Kiørboe, Thomas

    2011-01-01

    Copepods swim either continuously by vibrating their feeding appendages or erratically by repeatedly beating their swimming legs resulting in a series of small jumps. The two swimming modes generate different hydrodynamic disturbances and therefore expose the swimmers differently to rheotactic...... limited and temporally ephemeral owing to jump-impulsiveness and viscous decay. In contrast, continuous steady swimming generates two well-extended long-lasting momentum jets both in front of and behind the swimmer, as suggested by the well-known steady stresslet model. Based on the observed jump-swimming...... kinematics of a small copepod Oithona davisae, we further showed that jump-swimming produces a hydrodynamic disturbance with much smaller spatial extension and shorter temporal duration than that produced by a same-size copepod cruising steadily at the same average translating velocity. Hence, small copepods...

  6. Jump diffusion models and the evolution of financial prices

    Energy Technology Data Exchange (ETDEWEB)

    Figueiredo, Annibal; Castro, Marcio T. de [Institute of Physics, University of Brasilia (Brazil); Silva, Sergio da [Department of Economics, Federal University of Santa Catarina (Brazil); Gleria, Iram, E-mail: iram@pq.cnpq.br [Institute of Physics, Federal University of Alagoas (Brazil)

    2011-08-08

    We analyze a stochastic model to describe the evolution of financial prices. We consider the stochastic term as a sum of the Wiener noise and a jump process. We point to the effects of the jumps on the return time evolution, a central concern of the econophysics literature. The presence of jumps suggests that the process can be described by an infinitely divisible characteristic function belonging to the De Finetti class. We then extend the De Finetti functions to a generalized nonlinear model and show the model to be capable of explaining return behavior. -- Highlights: → We analyze a stochastic model to describe the evolution of financial prices. → The stochastic term is considered as a sum of the Wiener noise and a jump process. → The process can be described by an infinitely divisible characteristic function belonging to the De Finetti class. → We extend the De Finetti functions to a generalized nonlinear model.

  7. Detection of Dew-Point by substantial Raman Band Frequency Jumps (A new Method)

    DEFF Research Database (Denmark)

    Hansen, Susanne Brunsgaard; Berg, Rolf W.; Stenby, Erling Halfdan

    Detection of Dew-Point by substantial Raman Band Frequency Jumps (A new Method). See poster at http://www.kemi.dtu.dk/~ajo/rolf/jumps.pdf......Detection of Dew-Point by substantial Raman Band Frequency Jumps (A new Method). See poster at http://www.kemi.dtu.dk/~ajo/rolf/jumps.pdf...

  8. Fundamental Studies of Jumping-Drop Thermal Diodes

    Science.gov (United States)

    2016-02-29

    Reverse mode with liquid trapped by the colder superhydrophilic surface. ............... 2 Figure 2. Fabrication of the jumping-drop thermal diode...mode, Figure 1b), liquid water is trapped by it and no phase-change heat transfer takes place; heat mainly escapes through ineffective conduction...self- propelled jumping drops returning the working fluid from the colder superhydrophobic surface; (b) Reverse mode with liquid trapped by the colder

  9. ANALYSIS OF INCOMPLETE STOCK MARKET WITH JUMP-DIFFUSION UNCERTAINTY

    Institute of Scientific and Technical Information of China (English)

    Xiuli Chao; Indrajit Bardhan

    2002-01-01

    This paper studies incomplete stock market that includes discontinuous priceprocesses. The discontinuity is modeled by very general point processes admitting onlystochastic intensities. Prices are driven by jump-diffusion uncertainty and have randombut predictable jumps. The space of risk-neutral measures that are associated with themarket is identified and related to fictitious completions. The construction of replicatingportfolios is discussed, and convex duality methods are used to prove existence of optimalconsumption and investment policies for a problem of utility maximization.

  10. Nonlinear H∞ filtering for interconnected Markovian jump systems

    Institute of Scientific and Technical Information of China (English)

    Zhang Xiaomei; Zheng Yufan

    2006-01-01

    The problem of nonlinear H∞ filtering for interconnected Markovian jump systems is discussed. The aim of this note is the design of a nonlinear Markovian jump filter such that the resulting error system is exponentially meansquare stable and ensures a prescribed H∞ performance. A sufficient condition for the solvability of this problem is given in terms of linear matrix inequalities(LMIs). A simulation example is presented to demonstrate the effectiveness of the proposed design approach.

  11. Psycho-physiological response in an automatic parachute jump

    OpenAIRE

    Clemente Suárez, Vicente Javier; Robles Pérez, José Juan; Fernández Lucas, Jesús

    2016-01-01

    Parachute jump is an extreme activity that elicits an intense stress response that affects jumpers' body systems being able to put them at risk. The present research analysed modifications in blood oxygen saturation (BOS), heart rate (HR), cortisol, glucose, lactate, creatine kinase (CK), muscles strength, cortical arousal, autonomic modulation, pistol magazine reload time (PMRT) and state anxiety before and after an automatic open parachute jump in 38 male Spanish soldiers (25.6 ± 5.9 years)...

  12. Gravity-free hydraulic jumps and metal femtocups

    OpenAIRE

    Govindarajan, Rama; Mathur, Manikandan; DasGupta, Ratul; Selvi, N. R.; John, Neena Susan; Kulkarni, G. U.

    2006-01-01

    Hydraulic jumps created by gravity are seen every day in the kitchen sink. We show that at small scales a circular hydraulic jump can be created in the absence of gravity, by surface tension. The theory is motivated by our experimental finding of a height discontinuity in spreading submicron molten metal droplets created by pulsed-laser ablation. By careful control of initial conditions, we show that this leads to solid femtolitre cups of gold, silver, copper, niobium and tin.

  13. Smoothed Particle Hydrodynamic of Hydraulic Jumps in Spillways

    OpenAIRE

    Jonsson, Patrick

    2015-01-01

    This thesis focus on the complex natural phenomena of hydraulic jumps using the numerical method Smoothed Particle Hydrodynamics (SPH). A hydraulic jump is highly turbulent and associated with turbulent energy dissipation, air entrainment, surface waves and spray and strong dissipative processes. It can be found not only in natural streams and in engineered open channels, but also in your kitchen sink at home. The dissipative features are utilized in hydropower spillways and stilling basins t...

  14. Gravity-free hydraulic jumps and metal femtoliter cups.

    Science.gov (United States)

    Mathur, Manikandan; DasGupta, Ratul; Selvi, N R; John, Neena Susan; Kulkarni, G U; Govindarajan, Rama

    2007-04-20

    Hydraulic jumps created by gravity are seen everyday in the kitchen sink. We show that at small scales a circular hydraulic jump can be created in the absence of gravity by surface tension. The theory is motivated by our experimental finding of a height discontinuity in spreading submicron molten metal droplets created by pulsed-laser ablation. By careful control of initial conditions, this leads to solid femtoliter cups of gold, silver, copper, niobium, and tin.

  15. On the Spectral Gap of Brownian Motion with Jump Boundary

    CERN Document Server

    Kolb, Martin

    2011-01-01

    In this paper we consider the Brownian motion with jump boundary and present a new proof of a recent result of Li, Leung and Rakesh concerning the exact convergence rate in the one-dimensional case. Our methods are different and mainly probabilistic relying on coupling methods adapted to the special situation under investigation. Moreover, we answer a question raised by Ben-Ari and Pinsky concerning the dependence of the spectral gap on the jump distribution in a multi-dimensional setting.

  16. Forecasting Exchange Rate Volatility in the Presence of Jumps

    DEFF Research Database (Denmark)

    Busch, Thomas; Christensen, Bent Jesper; Nielsen, Morten Ørregaard

    of exchange rate futures options, allowingcalculation of option implied volatility. We find that implied volatility is an informationallyefficient but biased forecast of future realized exchange rate volatility. Furthermore,we show that log-normality is an even better distributional approximation...... for impliedvolatility than for realized volatility in this market. Finally, we show that the jump componentof future realized exchange rate volatility is to some extent predictable, and thatoption implied volatility is the dominant forecast of the future jump component....

  17. A drop jumps to weightlessness: a lecture demo

    Science.gov (United States)

    Mayer, V. V.; Varaksina, E. I.; Saranin, V. A.

    2017-04-01

    The paper discusses the lecture demonstration of the phenomenon in which a drop lying on a solid unwettable substrate jumps when making the transition to weightlessness. An elementary theory of the phenomenon is given. A jump speed estimate is obtained for small and large drops. The natural vibrational frequency of a flying drop is determined. A full-scale model of Einstein’s elevator is described. Experimental and theoretical results are found to agree satisfactorily.

  18. Importance sampling for jump processes and applications to finance

    OpenAIRE

    Badouraly Kassim, Laetitia; Lelong, Jérôme; Loumrhari, Imane

    2013-01-01

    International audience; Adaptive importance sampling techniques are widely known for the Gaussian setting of Brownian driven diffusions. In this work, we want to extend them to jump processes. Our approach relies on a change of the jump intensity combined with the standard exponential tilting for the Brownian motion. The free parameters of our framework are optimized using sample average approximation techniques. We illustrate the efficiency of our method on the valuation of financial derivat...

  19. Temperature Jump Pyrolysis Studies of RP 2 Fuel

    Science.gov (United States)

    2017-01-09

    Briefing Charts 3. DATES COVERED (From - To) 15 December 2016 – 11 January 2017 4. TITLE AND SUBTITLE Temperature Jump Pyrolysis Studies of RP-2 Fuel...Rev. 8- 98) Prescribed by ANSI Std. 239.18 1 TEMPERATURE JUMP PYROLYSIS STUDIES OF RP-2 FUEL Owen Pryor1, Steven D. Chambreau2, Ghanshyam L...Mixture Distribution A: Approved for public release; distribution unlimited. PA Clearance 17026 4 RP-2 Pyrolysis /Combustion Chemistries? • Recent

  20. Dynamic Jump Intensities and Risk Premiums in Crude Oil Futures and Options Markets

    DEFF Research Database (Denmark)

    Christoffersen, Peter; Jacobs, Kris; Li, Bingxin

    2016-01-01

    and dynamic jump intensities in these markets. Allowing for jumps is crucial for modeling crude oil futures and futures options, and we find evidence in favor of time-varying jump intensities. During crisis periods, jumps occur more frequently. The properties of the jump processes implied by the option data......Options on crude oil futures are the most actively traded commodity options. We develop a class of computationally efficient discrete-time jump models that allow for closed-form option valuation, and we use crude oil futures and options data to investigate the economic importance of jumps...

  1. Electric-Field-Enhanced Jumping-Droplet Condensation

    Science.gov (United States)

    Miljkovic, Nenad; Preston, Daniel; Enright, Ryan; Limia, Alexander; Wang, Evelyn

    2013-11-01

    When condensed droplets coalesce on a superhydrophobic surface, the resulting droplet can jump due to the conversion of surface energy into kinetic energy. This frequent out-of-plane droplet jumping has the potential to enhance condensation heat and mass transfer. In this work, we demonstrated that these jumping droplets accumulate positive charge that can be used to further increase condensation heat transfer via electric fields. We studied droplet jumping dynamics on silanized nanostructured copper oxide surfaces. By characterizing the droplet trajectories under various applied external electric fields (0 - 50 V/cm), we show that condensation on superhydrophobic surfaces results in a buildup of negative surface charge (OH-) due to dissociated water ion adsorption on the superhydrophobic coating. Consequently, the opposite charge (H3O +) accumulates on the coalesced jumping droplet. Using this knowledge, we demonstrate electric-field-enhanced jumping droplet condensation whereby an external electric field opposes the droplet vapor flow entrainment towards the condensing surface to increase the droplet removal rate and overall surface heat transfer by 100% when compared to state-of-the-art dropwise condensing surfaces. This work not only shows significant condensation heat transfer enhancement through the passive charging of condensed droplets, but promises a low cost approach to increase efficiency for applications such as atmospheric water harvesting and dehumidification.

  2. Kinematic structure at the early flight position in ski jumping.

    Science.gov (United States)

    Vodičar, Janez; Coh, Milan; Jošt, Bojan

    2012-12-01

    The purpose of our research was to establish the variability of correlation between the length of the jumps and selected multi-item kinematic variables (n=9) in the early flight phase technique of ski jumping. This study was conducted on a sample of elite Slovenian ski jumpers (N=29) who participated in the experiment on a jumping hill in Hinterzarten, Germany (HS95m) on the 20(th) of August, 2008. The highest and most significant correlations (p=0.01) with the length of the ski jump were found in the multi-item variable height of flying, which was also expressed with the highest level of stability of the explained total variance (TV) on the first factor (TV=69.13%). The most important characteristic of the aerodynamic aspect of early flight was the variable angle between the body chord and the horizontal axis with significantly high correlations (pski and left leg (TV=50.13%), had an explained common variance on the first factor greater than 50% of total variance. The results indicated that some kinematic parameters of ski jumping early flight technique were more important for success considering the length of the jump.

  3. Kinetic asymmetries between forward and drop jump landing tasks

    Directory of Open Access Journals (Sweden)

    Morgana Alves de Britto

    2015-11-01

    Full Text Available Landing asymmetry is a risk factor for knee anterior cruciate ligament injury. The aim of this study was to identify kinetic asymmetries in healthy recreational athletes performing different jump-landing techniques. Twelve recreational athletes engaged in regular training underwent kinetic evaluation using two 3D force plates and were analyzed for: (a three-dimensional peak forces, (b time to peak vertical force, and (c initial phase asymmetries. All data were collected during performance of unilateral and bilateral trials of forward and drop jump tasks. Forward jump-landing tasks elicited greater kinetic asymmetry than drop-landing tasks. Regardless of jump-landing technique, the preferred leg experienced higher forces than the non-preferred leg. The initial landing phase showed more kinetic asymmetries than the later phase when peak vertical forces occur. It was concluded that when screening athletes for kinetic asymmetries that may predispose them to injury, forward jump-landing tasks and the early landing phase might show more kinetic asymmetries than drop jump-landing tasks and the late landing phase, respectively.

  4. The $k$-Tuple Jumping Champions among Consecutive Primes

    CERN Document Server

    Xiaosheng, Wu

    2011-01-01

    For any real $x$ and any integer $k\\ge1$, we say that a set $\\mathcal{D}_{k}$ of $k$ distinct integers is a $k$-tuple jumping champion if it is the most common differences that occurs among $k+1$ consecutive primes less than or equal to $x$. For $k=1$, it's known as the jumping champion introduced by J. H. Conway. In 1999 A. Odlyzko, M. Rubinstein, and M. Wolf announced the Jumping Champion Conjecture that the jumping champions greater than 1 are 4 and the primorials 2, 6, 30, 210, 2310,.... They also made a weaker and possibly more accessible conjecture that any fixed prime $p$ divides all sufficiently large jumping champions. These two conjectures were proved by Goldston and Ledoan under the assumption of appropriate forms of the Hardy-Littlewood conjecture recently. In the present paper we consider the situation for any $k\\ge2$ and prove that any fixed prime $p$ divides every element of all sufficiently large $k$-tuple jumping champions under the assumption that the Hardy-Littlewood prime $k+1$-tuple conje...

  5. Can jumping capacity of adult show jumping horses be predicted on the basis of submaximal free jumps at foal age? A longitudinal study.

    Science.gov (United States)

    Bobbert, Maarten F; Santamaría, Susana; van Weeren, P René; Back, Wim; Barneveld, Albert

    2005-09-01

    The purpose of this study was to quantify performance characteristics of good jumping horses, and to determine whether these were already detectable at foal age. Kinematic data were collected of horses performing free jumps over a 0.60 m high fence at six months of age and of these same horses jumping with a rider over a 1.15 m high fence at five years of age. At five years of age the horses were divided into three groups on the basis of a puissance competition: a group of seven best jumpers that made no errors and in the end cleared a 1.50 m high fence, a group of nine worst jumpers that were unable to clear a 1.40 m high fence, and an intermediate group of 13 horses. Longitudinal kinematic data was available for all seven best jumpers and for six of the nine worst jumpers. Average values of variables for the best jumpers were compared with those of the worst jumpers for the jumps over 1.15 m. In the group of best jumpers, the forelimbs were shorter at forelimb clearance due to increased elbow flexion, and the hind limbs were further retroflexed at hind limb clearance. The same superior technique in clearing fences with the limbs was also found in this group at six months of age. Nevertheless, for individual horses it turned out to be too far-fetched to predict adult jumping capacity on the basis of kinematic variables collected during submaximal jumps at foal age.

  6. Structural-Parameter-Based Jumping-Height-and-Distance Adjustment and Obstacle Sensing of a Bio-Inspired Jumping Robot

    Directory of Open Access Journals (Sweden)

    Jun Zhang

    2015-06-01

    Full Text Available Jumping-height-and-distance (JHD active adjustment capability is important for jumping robots to overcome different sizes of obstacle. This paper proposes a new structural parameter-based JHD active adjustment approach for our previous jumping robot. First, the JHD adjustments, modifying the lengths of different legs of the robot, are modelled and simulated. Then, three mechanisms for leg-length adjustment are proposed and compared, and the screw-and-nut mechanism is selected. And for adjusting of different structural parameters using this mechanism, the one with the best JHD adjusting performance and the lowest mechanical complexity is adopted. Thirdly, an obstacle-distance-and-height (ODH detection method using only one infrared sensor is designed. Finally, the performances of the proposed methods are tested. Experimental results show that the jumping-height-and distance adjustable ranges are 0.11 m and 0.96 m, respectively, which validates the effectiveness of the proposed JHD adjustment method.

  7. A comparison of pairs figure skaters in repeated jumps.

    Science.gov (United States)

    Sands, William A; Kimmel, Wendy L; McNeal, Jeni R; Murray, Steven Ross; Stone, Michael H

    2012-01-01

    Trends in pairs figure skating have shown that increasingly difficult jumps have become an essential aspect of high-level performance, especially in the latter part of a competitive program. We compared a repeated jump power index in a 60 s repeated jump test to determine the relationship of repeated jump test to competitive rank and to measure 2D hip, knee, and ankle angles and angular velocities at 0, 20, 40, and 60 s. Eighteen National Team Pairs Figure Skaters performed a 60 s repeated jump test on a large switch-mat with timing of flight and ground durations and digital video recording. Each 60-s period was divided into 6, 10-s intervals, with power indexes (W/kg) calculated for each 10-s interval. Power index by 10-s interval repeated measures ANOVAs (RMANOVA) showed that males exceeded females at all intervals, and the highest power index interval was during 10 to 20 s for both sexes. RMANOVAs of angles and angular velocities showed main effects for time only. Power index and jumping techniques among figure skaters showed rapid and steady declines over the test duration. Power index can predict approximately 50% of competitive rank variance, and sex differences in jumping technique were rare. Key pointsThe repeated jumps test can account for about 50% of the variance in pairs ranks.Changes in technique are largely due to fatigue, but the athletes were able to maintain a maximum flexion knee angle very close to the desired 90 degrees. Changes in angular velocity and jump heights occurred as expected, again probably due to fatigue.As expected from metabolic information, the athletes' power indexes peak around 20s and decline thereafter. Coaches should be aware of this time as a boundary beyond which fatigue becomes more manifest, and use careful choreographic choices to provide rest periods that are disguised as less demanding skating elements to afford recovery.The repeated jumps test may be a helpful off-ice test of power-endurance for figure skaters.

  8. Four weeks of optimal load ballistic resistance training at the end of season attenuates declining jump performance of women volleyball players.

    Science.gov (United States)

    Newton, Robert U; Rogers, Ryan A; Volek, Jeff S; Häkkinen, Keijo; Kraemer, William J

    2006-11-01

    Anecdotal and research evidence is that vertical jump performance declines over the competitive volleyball season. The purpose of this study was to evaluate whether a short period of ballistic resistance training would attenuate this loss. Fourteen collegiate women volleyball players were trained for 11 weeks with periodized traditional and ballistic resistance training. There was a 5.4% decrease (p ballistic training period (midseason to end of season), but values were not different from start to end of season. These changes in overall jump performance were reflective of changes in underlying neuromuscular performance variables: in particular, power output and peak velocity during loaded jump squats, countermovement jumps, and drop jumps. During the first 7 weeks of traditional heavy resistance training, it appears that the neuromuscular system is depressed, perhaps by the combination of training, game play, and skills practice precluding adequate recovery. Introduction of a novel training stimulus in the form of ballistic jump squats and reduction of heavy resistance training of the leg extensors stimulated a rebound in performance, in some cases to exceed the athlete's ability at the start of the season. Periodization of in-season training programs similar to that used in this study may provide volleyball players with good vertical jump performance for the crucial end-of-season games.

  9. High-Intensity Jump Training Is Tolerated during 60 Days of Bed Rest and Is Very Effective in Preserving Leg Power and Lean Body Mass: An Overview of the Cologne RSL Study

    Science.gov (United States)

    Kümmel, Jakob; Mulder, Edwin; Gollhofer, Albert; Frings-Meuthen, Petra; Gruber, Markus

    2017-01-01

    Purpose Space agencies are looking for effective and efficient countermeasures for the degrading effects of weightlessness on the human body. The aim of this study was to assess the effects of a novel jump exercise countermeasure during bed rest on vitals, body mass, body composition, and jump performance. Methods 23 male participants (29±6 years, 181±6 cm, 77±7 kg) were confined to a bed rest facility for 90 days: a 15-day ambulatory measurement phase, a 60-day six-degree head-down-tilt bed rest phase (HDT), and a 15-day ambulatory recovery phase. Participants were randomly allocated to the jump training group (JUMP, n = 12) or the control group (CTRL, n = 11). A typical training session consisted of 4x10 countermovement jumps and 2x10 hops in a sledge jump system. The training group had to complete 5–6 sessions per week. Results Peak force for the reactive hops (3.6±0.4 kN) as well as jump height (35±4 cm) and peak power (3.1±0.2 kW) for the countermovement jumps could be maintained over the 60 days of HDT. Lean body mass decreased in CTRL but not in JUMP (-1.6±1.9 kg and 0±1.0 kg, respectively, interaction effect p = 0.03). Resting heart rate during recovery was significantly increased for CTRL but not for JUMP (interaction effect p<0.001). Conclusion Participants tolerated the near-daily high-intensity jump training and maintained high peak forces and high power output during 60 days of bed rest. The countermeasure was effective in preserving lean body mass and partly preventing cardiac deconditioning with only several minutes of training per day. PMID:28081223

  10. Scaling and jumping: gravity loses grip on small jumpers.

    Science.gov (United States)

    Scholz, Melanie N; Bobbert, Maarten F; Knoek van Soest, A J

    2006-06-21

    There are several ways to quantify jumping performance, a common definition being the height gained by the body's centre of mass (CM) in the airborne phase. Under this definition, jump height is determined by take-off velocity. According to the existing literature on jumping and scaling, take-off velocity, and hence jumping performance is independent of size because the energy that differently sized geometrically scaled jumpers can generate with their muscles is proportional to their mass. In this article it is shown, based on a simple energy balance, that it is incorrect to presume that jump height does not depend on size. Contrary to common belief, size as such has does have an effect on take-off velocity, putting small jumpers at a mechanical advantage, as is shown analytically. To quantify the effect of size on take-off velocity, a generic jumper model was scaled geometrically and evaluated numerically. While a 70-kg jumper took off at 2.65 m/s and raised its CM by 0.36 m after take-off, a perfectly geometrically similar jumper of 0.7 g reached a take-off velocity of 3.46 m/s and raised its CM by 0.61 m. The reason for the better performance of small jumpers is their higher efficacy in transforming the energy generated by the actuators into energy due to vertical velocity of the CM. Considering the ecological and evolutionary relevance of different definitions of jump height, size-dependent efficacy might explain why habitual jumping is especially prominent among small animals such as insects.

  11. Isokinetic knee extension and vertical jumping: are they related?

    Science.gov (United States)

    Iossifidou, Anna; Baltzopoulos, Vasilios; Giakas, Giannis

    2005-10-01

    The aim of this study was to examine joint power generation during a concentric knee extension isokinetic test and a squat vertical jump. The isokinetic test joint power was calculated using four different methods. Five participants performed concentric knee extensions at 0.52, 1.57, 3.14 and 5.23 rad x s(-1) on a Lido isokinetic dynamometer. The squat vertical jump was performed on a Kistler force plate. Kinematic data from both tests were collected and analysed using an ELITE optoelectronic system. An inverse dynamics model was applied to measure knee joint moment in the vertical jump. Knee angular position data from the kinematic analysis in the isokinetic test were used to derive the actual knee angular velocity and acceleration, which, in turn, was used to correct the dynamometer moment for inertial effects. Power was measured as the product of angular velocity and moment at the knee joint in both tests. Significant differences (P knee joint power in the two tests (squat vertical jump: 2255 +/- 434 W; isokinetic knee extension: 771 +/- 81 W). Correlation analysis revealed that there is no relationship between the peak knee joint power during the vertical jump and the slow velocity isokinetic tests. Higher isokinetic velocity tests show better relationships with the vertical jump but only if the correct method for joint power calculation is used in the isokinetic test. These findings suggest that there are important differences in muscle activation and knee joint power development that must be taken into consideration when isokinetic tests are used to predict jumping performance.

  12. Effect of static and dynamic stretching on the diurnal variations of jump performance in soccer players.

    Directory of Open Access Journals (Sweden)

    Hamdi Chtourou

    Full Text Available PURPOSE: The present study addressed the lack of data on the effect of different types of stretching on diurnal variations in vertical jump height - i.e., squat-jump (SJ and countermovement-jump (CMJ. We hypothesized that dynamic stretching could affect the diurnal variations of jump height by producing a greater increase in short-term maximal performance in the morning than the evening through increasing core temperature at this time-of-day. METHODS: Twenty male soccer players (age, 18.6±1.3 yrs; height, 174.6±3.8 cm; body-mass, 71.1±8.6 kg; mean ± SD completed the SJ and CMJ tests either after static stretching, dynamic stretching or no-stretching protocols at two times of day, 07:00 h and 17:00 h, with a minimum of 48 hours between testing sessions. One minute after warming-up for 5 minutes by light jogging and performing one of the three stretching protocols (i.e., static stretching, dynamic stretching or no-stretching for 8 minutes, each subject completed the SJ and CMJ tests. Jumping heights were recorded and analyzed using a two-way analysis of variance with repeated measures (3 [stretching]×2 [time-of-day]. RESULTS: The SJ and CMJ heights were significantly higher at 17:00 than 07:00 h (p<0.01 after the no-stretching protocol. These daily variations disappeared (i.e., the diurnal gain decreased from 4.2±2.81% (p<0.01 to 1.81±4.39% (not-significant for SJ and from 3.99±3.43% (p<0.01 to 1.51±3.83% (not-significant for CMJ after dynamic stretching due to greater increases in SJ and CMJ heights in the morning than the evening (8.4±6.36% vs. 4.4±2.64%, p<0.05 for SJ and 10.61±5.49% vs. 6.03±3.14%, p<0.05 for CMJ. However, no significant effect of static stretching on the diurnal variations of SJ and CMJ heights was observed. CONCLUSION: Dynamic stretching affects the typical diurnal variations of SJ and CMJ and helps to counteract the lower morning values in vertical jump height.

  13. Does whole-body cryotherapy improve vertical jump recovery following a high-intensity exercise bout?

    Directory of Open Access Journals (Sweden)

    Vieira A

    2015-02-01

    Full Text Available Amilton Vieira,1 Martim Bottaro,1 Joao B Ferreira-Junior,1,4 Carlos Vieira,1 Vitor A Cleto,1 Eduardo L Cadore,2 Herbert G Simões,3 Jake Do Carmo,1 Lee E Brown5 1College of Physical Education, University of Brasília, Brasília, 2College of Physical Education, Federal University of Rio Grande do Sul (UFRGS, Porto Alegre, 3College of Physical Education, Catholic University of Brasília, Brasília, 4Federal Institute of Triângulo Mineiro, Paracatu, Brazil; 5Department of Kinesiology, California State University, Fullerton, CA, USA Abstract: Whole-body cryotherapy (WBC has been used as a recovery strategy following different sports activities. Thus, the aim of the study reported here was to examine the effect of WBC on vertical jump recovery following a high-intensity exercise (HIE bout. Twelve trained men (mean ± standard deviation age = 23.9±5.9 years were randomly exposed to two different conditions separated by 7 days: 1 WBC (3 minutes of WBC at −110°C immediately after the HIE and 2 control (CON; no WBC after the HIE. The HIE consisted of six sets of ten repetitions of knee extensions at 60° · s−1 concentric and 180° · s−1 eccentric on an isokinetic dynamometer. The vertical jump test was used to evaluate the influence of HIE on lower extremity muscular performance. The vertical jump was performed on a force platform before HIE (T1 and 30 minutes after (T2 the WBC and CON conditions. As a result of HIE, jump height, muscle power, and maximal velocity (Vmax had significant decreases between T1 and T2, however no significance was found between the WBC and CON conditions. The results indicate that one session of WBC had no effect on vertical jump following an HIE compared with a CON condition. WBC may not improve muscle-function (dependent on stretch-shortening cycle recovery in very short periods (ie, 30 minutes following HIE. Keywords: functional performance, muscular recovery, countermovement jump

  14. Jump point detection for real estate investment success

    Science.gov (United States)

    Hui, Eddie C. M.; Yu, Carisa K. W.; Ip, Wai-Cheung

    2010-03-01

    In the literature, studies on real estate market were mainly concentrating on the relation between property price and some key factors. The trend of the real estate market is a major concern. It is believed that changes in trend are signified by some jump points in the property price series. Identifying such jump points reveals important findings that enable policy-makers to look forward. However, not all jump points are observable from the plot of the series. This paper looks into the trend and introduces a new approach to the framework for real estate investment success. The main purpose of this paper is to detect jump points in the time series of some housing price indices and stock price index in Hong Kong by applying the wavelet analysis. The detected jump points reflect to some significant political issues and economic collapse. Moreover, the relations among properties of different classes and between stocks and properties are examined. It can be shown from the empirical result that a lead-lag effect happened between the prices of large-size property and those of small/medium-size property. However, there is no apparent relation or consistent lead in terms of change point measure between property price and stock price. This may be due to the fact that globalization effect has more impact on the stock price than the property price.

  15. Unilateral jump behavior in young professional female ballet dancers.

    Science.gov (United States)

    Golomer, E; Féry, Y A

    2001-09-01

    In the field of dance, lateral body actions should be differently influenced by training. Classes should develop symmetrical jump behavior by the alternate working of the two body sides. In contrast, asymmetrical training effect linked to hemispheric laterality should be also expected. Indeed, for aesthetic reasons, the preferred led has to give the jump direction while the other leg has to carry out the impulsion during take-off. In addition, and for functional reasons, the preferred leg also has to ensure a soft landing and to avoid imbalance upon landing. To address the question, we studied ten professional right-footed female ballet dancers in a unilateral experimental task: the maximal vertical jump (MVJ). The MVJ height was compared for each leg in ten trials. In addition, the side of the leg usually involved in a choreographic bilateral task was determined. All these right-footed dancers selected their left leg as the impulsion leg for the choreographic jump so as to reserve the right leg for the expression of the artistic gesture linked to emotional laterality. However, ANOVA did not show differences between the right and left legs in MVJ. In these young ballerinas, jump actions of the two body sides seem to develop symmetrically by class training effects.

  16. Volatility Forecasting: Downside Risk, Jumps and Leverage Effect

    Directory of Open Access Journals (Sweden)

    Francesco Audrino

    2016-02-01

    Full Text Available We provide empirical evidence of volatility forecasting in relation to asymmetries present in the dynamics of both return and volatility processes. Using recently-developed methodologies to detect jumps from high frequency price data, we estimate the size of positive and negative jumps and propose a methodology to estimate the size of jumps in the quadratic variation. The leverage effect is separated into continuous and discontinuous effects, and past volatility is separated into “good” and “bad”, as well as into continuous and discontinuous risks. Using a long history of the S & P500 price index, we find that the continuous leverage effect lasts about one week, while the discontinuous leverage effect disappears after one day. “Good” and “bad” continuous risks both characterize the volatility persistence, while “bad” jump risk is much more informative than “good” jump risk in forecasting future volatility. The volatility forecasting model proposed is able to capture many empirical stylized facts while still remaining parsimonious in terms of the number of parameters to be estimated.

  17. CONNECTION OF FUNCTIONAL ABILITIES WITH JUMPING AND THROWING ATHLETIC DISCIPLINES

    Directory of Open Access Journals (Sweden)

    Igor Stanojević

    2014-06-01

    Full Text Available The aim of this study was to determine the connection between functional abilities with results of jumping and throwing athletic disciplines with athletes. The sample was taken from a population of elementary school students from Prokuplje region, 13 and 14 old, included in regular physical education classes. The sample consisted of 200 male athletes involved in the training process in sports clubs at least three times a week in addition to physical education classes. For assessment of functional abilities six functional tests were used: resting heart rate, Cooper test, heart rate in the first minute after Cooper test, heart rate in the second minute after Cooper test, systolic arterial blood pressure, diastolic arterial blood pressure. For assessment of jumping and throwing athletic disciplines four tests were used: long jump, high jump, shot put and javelin. Data analysis was performed with canonical correlation and regression analysis. The results showed a statistically significant correlation between functional abilities with all of tests in jumping and throwing athletic disciplines.

  18. Biological Jumping Mechanism Analysis and Modeling for Frog Robot

    Institute of Scientific and Technical Information of China (English)

    Meng Wang; Xi-zhe Zang; Ji-zhuang Fan; Jie Zhao

    2008-01-01

    This paper presents a mechanical model of jumping robot based on the biological mechanism analysis of frog. By biological observation and kinematic analysis the frog jump is divided into take-off phase, aerial phase and landing phase. We find the similar trajectories of hindlimb joints during jump, the important effect of foot during take-off and the role of forelimb in supporting the body. Based on the observation, the frog jump is simplified and a mechanical model is put forward. The robot leg is represented by a 4-bar spring/linkage mechanism model, which has three Degrees of Freedom (DOF) at hip joint and one DOF (passive) at tarsometatarsal joint on the foot. The shoulder and elbow joints each has one DOF for the balancing function of arm.The ground reaction force of the model is analyzed and compared with that of frog during take-off. The results show that the model has the same advantages of low likelihood of premature lift-off and high efficiency as the frog. Analysis results and the model can be employed to develop and control a robot capable of mimicking the jumping behavior of flog.

  19. Physiological arousal and perception of bodily state during parachute jumping.

    Science.gov (United States)

    Schedlowski, M; Tewes, U

    1992-01-01

    Heart rate and respiration rate were recorded with a portable data recording system before and during a parachute jump in 36 male sport parachutists with differing degrees of experience. The recordings were analyzed at 12 psychologically relevant points in time along with the subjective ratings of physical arousal. Novice parachutists showed a higher degree of self-rated arousal during jumps. However, the two groups displayed nearly parallel curves for heart and respiration rates, differing significantly from each other only in the level of their respective heart rates. Furthermore, experienced jumpers seem to be better informed about their state of physiological arousal during the jump than are novice jumpers. These results do not confirm the proposed anxiety inhibition process, postulated by Epstein (1967).

  20. Condensation and jumping relay of droplets on lotus leaf

    Science.gov (United States)

    Lv, Cunjing; Hao, Pengfei; Yao, Zhaohui; Song, Yu; Zhang, Xiwen; He, Feng

    2013-07-01

    Dynamic behavior of micro water droplet condensed on a lotus leaf with two-tier roughness is studied. Under laboratory environment, the contact angle of the micro droplet on single micro papilla increases smoothly from 80° to 160° during the growth of condensed water. The best-known "self-cleaning" phenomenon will be lost. A striking observation is the out-of-plane jumping relay of condensed droplets triggered by falling droplets, as well as its sustained speed obtained in continuous jumping relays. The underlying mechanism can be used to enhance the automatic removal of dropwise condensation without the help from any external force. The surface tension energy dissipation is the main reason controlling the critical size of jumping droplet and its onset velocity of rebounding.

  1. Dynamical Jumps in a Shape Memory Alloy Oscillator

    Directory of Open Access Journals (Sweden)

    H. S. Oliveira

    2014-01-01

    Full Text Available The dynamical response of systems with shape memory alloy (SMA elements presents a rich behavior due to their intrinsic nonlinear characteristic. SMA’s nonlinear response is associated with both adaptive dissipation related to hysteretic behavior and huge changes in properties caused by phase transformations. These characteristics are attracting much technological interest in several scientific and engineering fields, varying from medical to aerospace applications. An important characteristic associated with dynamical response of SMA system is the jump phenomenon. Dynamical jumps result in abrupt changes in system behavior and its analysis is essential for a proper design of SMA systems. This paper discusses the nonlinear dynamics of a one degree of freedom SMA oscillator presenting pseudoelastic behavior and dynamical jumps. Numerical simulations show different aspects of this kind of behavior, illustrating its importance for a proper understanding of nonlinear dynamics of SMA systems.

  2. Aerodynamic Jump: A Short Range View for Long Rod Projectiles

    Directory of Open Access Journals (Sweden)

    Mark Bundy

    2001-01-01

    Full Text Available It is shown that aerodynamic jump for a nonspinning kinetic energy penetrator is not – as conventional definitions may infer – a discontinuous change in the direction of motion at the origin of free flight, nor is it the converse, a cumulative redirection over a domain of infinite extent. Rather, with the aid of an alternative kinematical definition, it is shown that aerodynamic jump for such a projectile is a localized redirection of the center-of-gravity motion, caused by the force of lift due to yaw over the relatively short region from entry into free flight until the yaw reaches its first maximum. A rigorous proof of this statement is provided, but the primary objective of this paper is to provide answers to the questions: what is aerodynamic jump, what does it mean, and what aspects of the flight trajectory does it refer to, or account for.

  3. Multiple Tune Jumps to Overcome Horizontal Depolarizing Resonances

    Science.gov (United States)

    Huang, H.; Ahrens, L. A.; Bai, M.; Brown, K. A.; Dutheil, Y.; Gardner, C.; Glenn, J. W.; Lin, F.; Mackay, W. W.; Meot, F.; Poblaguev, A.; Ranjbar, V.; Roser, T.; Schoefer, V.; Tepikian, S.; Tsoupas, N.; Yip, K.; Zelenski, A.; Zeno, K.

    2016-02-01

    Imperfection and vertical intrinsic depolarizing resonances have been overcome by the two partial Siberian snakes in the Alternative Gradient Synchrotron(AGS). The relatively weak but numerous horizontal resonances are the main source of polarization loss in the AGS. A pair of horizontal tune jump quads have been used to overcome these weak resonances. The locations of the two quads have to be chosen such that the disturbance to the beam optics is minimum. The emittance growth has to be mitigated for this method to work. In addition, this technique needs very accurate jump timing. Using two partial Siberian snakes, with vertical tune inside the spin tune gap and 80% polarization at AGS injection, polarized proton beam had reached 1.5 × 1011 proton per bunch with 65% polarization. With the tune jump timing optimized and emittance preserved, more than 70% polarization with 2 × 1011 protons per bunch has been achieved.

  4. Condensation and jumping relay of droplets on lotus leaf

    CERN Document Server

    Lv, Cunjing; Yao, Zhaohui; Song, Yu; Zhang, Xiwen; He, Feng

    2013-01-01

    Dynamic behavior of micro water droplet condensed on a lotus leaf with two-tier roughness is studied. Under laboratory environment, the contact angle of the micro droplet on single micro papilla increases smoothly from 80 deg to 160 deg during the growth of condensed water. The best-known "self-clean" phenomenon, will be lost. A striking observation is the out-of-plane jumping relay of condensed droplets triggered by falling droplets, as well as its sustained speed obtained in continuous jumping relays, enhance the automatic removal of dropwise condensation without the help from any external force. The surface tension energy dissipation is the main reason controlling the critical size of jumping droplet and its onset velocity of rebounding.

  5. Vertical Jump Biomechanics Altered With Virtual Overhead Goal.

    Science.gov (United States)

    Ford, Kevin R; Nguyen, Anh-Dung; Hegedus, Eric J; Taylor, Jeffrey B

    2017-04-01

    Virtual environments with real-time feedback can simulate extrinsic goals that mimic real life conditions. The purpose was to compare jump performance and biomechanics with a physical overhead goal (POG) and with a virtual overhead goal (VOG). Fourteen female subjects participated (age: 18.8 ± 1.1 years, height: 163.2 ± 8.1 cm, weight 63.0 ± 7.9 kg). Sagittal plane trunk, hip, and knee biomechanics were calculated during the landing and take-off phases of drop vertical jump with different goal conditions. Repeated-measures ANOVAs determined differences between goal conditions. Vertical jump height displacement was not different during VOG compared with POG. Greater hip extensor moment (P biomechanical testing, screening, and training conditions.

  6. Coalescence-induced jumping of droplet: Inertia and viscosity effects

    Science.gov (United States)

    Farokhirad, Samaneh; Morris, Jeffrey F.; Lee, Taehun

    2015-10-01

    The problem of coalescence-induced self-propelled jumping of droplet is studied using three-dimensional numerical simulation. The focus is on the effect of inertia and in particular the effect of air density on the behavior of the merged droplet during jumping. A lattice Boltzmann method is used for two identical, static micro-droplets coalescing on a homogeneous substrate with contact angle ranging from 0∘ to 180∘. The results reveal that the effect of air density is significant on detachment of the merged droplet from the substrate at the later stage of the jumping process; the larger the air density, the larger the jumping height of the droplet. Analysis of streamlines and vorticity contours is performed for density ratios ranging from 60 to 800. These show a generation of vortical structures inside and around the droplet. The intensity of these structures gets weaker after droplet departure as the air inertia is decreased. The results are also presented in terms of phase diagrams of the merged droplet jumping for different Ohnesorge numbers (Oh) and surface wettabilities for both small and large density ratios. The critical value of contact angle where the merged droplet jumps away from the substrate is independent of density ratio and has a value around 150∘. However, the critical value of Oh depends on both density ratio and wettability of the surface for contact angles greater than 150∘. In this range of contact angle, the diagrams show two distinct dynamical regimes for different density ratios, namely, inertial and viscous regimes.

  7. AirJump: Using Interfaces to Instantly Perform Simultaneous Extractions.

    Science.gov (United States)

    Berry, Scott M; Pezzi, Hannah M; LaVanway, Alex J; Guckenberger, David J; Anderson, Meghan A; Beebe, David J

    2016-06-22

    Analyte isolation is an important process that spans a range of biomedical disciplines, including diagnostics, research, and forensics. While downstream analytical techniques have advanced in terms of both capability and throughput, analyte isolation technology has lagged behind, increasingly becoming the bottleneck in these processes. Thus, there exists a need for simple, fast, and easy to integrate analyte separation protocols to alleviate this bottleneck. Recently, a new class of technologies has emerged that leverages the movement of paramagnetic particle (PMP)-bound analytes through phase barriers to achieve a high efficiency separation in a single or a few steps. Specifically, the passage of a PMP/analyte aggregate through a phase interface (aqueous/air in this case) acts to efficiently "exclude" unbound (contaminant) material from PMP-bound analytes with higher efficiency than traditional washing-based solid-phase extraction (SPE) protocols (i.e., bind, wash several times, elute). Here, we describe for the first time a new type of "exclusion-based" sample preparation, which we term "AirJump". Upon realizing that much of the contaminant carryover stems from interactions with the sample vessel surface (e.g., pipetting residue, wetting), we aim to eliminate the influence of that factor. Thus, AirJump isolates PMP-bound analyte by "jumping" analyte directly out of a free liquid/air interface. Through careful characterization, we have demonstrated the validity of AirJump isolation through comparison to traditional washing-based isolations. Additionally, we have confirmed the suitability of AirJump in three important independent biological isolations, including protein immunoprecipitation, viral RNA isolation, and cell culture gene expression analysis. Taken together, these data sets demonstrate that AirJump performs efficiently, with high analyte yield, high purity, no cross contamination, rapid time-to-isolation, and excellent reproducibility.

  8. Sponsored parachute jumps--can they cause prolonged pain?

    OpenAIRE

    Straiton, N; Sterland, J

    1986-01-01

    A survey of parachute injuries sustained in 1984 at a local parachute club was made using hospital notes and a questionnaire. The overall injury rate was 0.2%. The injury rate in first time jumpers was 1.1%. The injuries often resulted in a prolonged hospital stay, time off work and residual pain and disability. Injury rates may be reduced by more prolonged and intensive training preceding the first jumps. Those people not interested in parachuting as a regular sport and who jump once only in...

  9. Sponsored parachute jumps--can they cause prolonged pain?

    Science.gov (United States)

    Straiton, N; Sterland, J

    1986-06-01

    A survey of parachute injuries sustained in 1984 at a local parachute club was made using hospital notes and a questionnaire. The overall injury rate was 0.2%. The injury rate in first time jumpers was 1.1%. The injuries often resulted in a prolonged hospital stay, time off work and residual pain and disability. Injury rates may be reduced by more prolonged and intensive training preceding the first jumps. Those people not interested in parachuting as a regular sport and who jump once only in order to raise money for charity are at risk of serious injury and perhaps should consider less dangerous alternatives.

  10. ASCAN Helms simulates parachute jump during VAFB training exercises

    Science.gov (United States)

    1990-01-01

    1990 Group 13 Astronaut Candidate (ASCAN) Susan J. Helms simulates a parachute jump during ground egress and parasail training exercises at Vance Air Force Base (VAFB), Enid, Oklahoma. With her arms folded against her chest, Helms jumps from a brick platform onto the ground. In line behind her are Charles J. Precourt followed by Leroy Chiao. The training is designed to prepare the ASCANs for proper survival measures to take in the event of an emergency aboard the T-38 jet trainer aircraft they will frequently use once they become full-fledged astronauts. ASCANs completed the VAFB training courses from 07-29-90 through 07-31-90.

  11. Hydrodynamics and energetics of jumping copepod nauplii and copepodids

    DEFF Research Database (Denmark)

    Wadhwa, Navish; Andersen, Anders Peter; Kiørboe, Thomas

    2014-01-01

    , we measured the swimming kinematics and fluid flow around jumping Acartia tonsa at different stages of its life cycle, using particle image velocimetry and particle tracking velocimetry. We found that the flow structures around nauplii and copepodids are topologically different, with one and two...... vortex rings, respectively. Our measurements suggest that copepodids cover a larger distance compared to their body size in each jump and are also hydrodynamically quieter, as the flow disturbance they create attenuates faster with distance. Also, copepodids are energetically more efficient than nauplii...

  12. Aerodynamic Jump: A Short Range View for Long Rod Projectiles

    OpenAIRE

    Mark Bundy

    2001-01-01

    It is shown that aerodynamic jump for a nonspinning kinetic energy penetrator is not – as conventional definitions may infer – a discontinuous change in the direction of motion at the origin of free flight, nor is it the converse, a cumulative redirection over a domain of infinite extent. Rather, with the aid of an alternative kinematical definition, it is shown that aerodynamic jump for such a projectile is a localized redirection of the center-of-gravity motion, caused by the force of lift ...

  13. Jumps into democracy: The transition in the Polity Index

    DEFF Research Database (Denmark)

    Paldam, Martin; Gundlach, Erich

    The Democratic Transition is the process of regime change from authoritarian at the traditional level of development to democratic at the modern level. This process is analyzed on 7,565 pairs of income and political regime data. Regimes are normally in local status quo equilibrium, so they have s......-run changes are due to triggering events that cause regime jumps. Triggering events are almost random, while most jumps are in the direction of the tension. This mechanism integrates the short and the long run to give the transition....

  14. Tunneling of the blocked wave in a circular hydraulic jump

    Science.gov (United States)

    Bhattacharjee, Jayanta K.

    2017-02-01

    The formation of a circular hydraulic jump in a thin liquid layer involves the creation of a horizon where the incoming wave (surface ripples) is blocked by the fast flowing fluid. That there is a jump at the horizon is due to the viscosity of the fluid which is not relevant for the horizon formation. By using a tunneling formalism developed for the study of the Hawking radiation from black holes, we explicitly show that there will be an exponentially small tunneling of the blocked wave across the horizons as anticipated in studies of "analog gravity".

  15. Pricing Participating Products under a Generalized Jump-Diffusion Model

    Directory of Open Access Journals (Sweden)

    Tak Kuen Siu

    2008-01-01

    Full Text Available We propose a model for valuing participating life insurance products under a generalized jump-diffusion model with a Markov-switching compensator. It also nests a number of important and popular models in finance, including the classes of jump-diffusion models and Markovian regime-switching models. The Esscher transform is employed to determine an equivalent martingale measure. Simulation experiments are conducted to illustrate the practical implementation of the model and to highlight some features that can be obtained from our model.

  16. Actionable Information, Repeatability, Quantum Jumps, and the Wavepacket Collapse

    CERN Document Server

    Zurek, Wojciech H

    2013-01-01

    Unknown quantum state cannot be discovered as the measured system is re-prepared -- it jumps into an eigenstate of the measured observable. This impossibility to find out a quantum state and other symptoms of the wavepacket collapse follow (as was recently demonstrated for pure states of measured systems) from unitarity (that doesn't, however, allow for a literal collapse) and from the repeatability of measurements. Here we extend this result to mixtures and decohering systems. This accounts for quantum jumps in a macroscopic and open (but ultimately quantum) apparatus.

  17. Suicides by jumping from a height in Hong Kong: a review of coroner court files.

    Science.gov (United States)

    Wong, Paul W C; Caine, Eric D; Lee, Carmen K M; Beautrais, Annette; Yip, Paul S F

    2014-02-01

    Jumping from a height is the most common method for suicide in Hong Kong and other urban cities, but it remains understudied locally and internationally. We used Coroner records in exploring the ecological factors associated with these deaths and the personal characteristics of persons who jumped to their death (hereafter, "jumping suicides"). We compared suicides by jumping with all other suicides and examined the suicides that occurred at ten different jumping sites. The Coroner's files of all suicides in Hong Kong from 2002 to 2007 included 6,125 documented deaths. 2,964 (48.4%) involved jumping during the study period. Eighty-three percent (83%) of suicide jumps occurred in residential buildings, and of these, 61% occurred from the decedent's own home. Jumping suicides differed from non-jumping suicides in terms of their socio-demographic characteristics (e.g., for male: 60.8 vs. 67.3% of jumping suicide and non-jumping suicides, p suicides, p suicides (p suicide prevention. Installation of physical barriers, one of the mean restriction strategies, at common places for suicide has strong evidence to avert suicides without substitution effects. There seems to be challenges to implement physical barriers to prevent residential jumping suicides. Simply applying physical barriers to preclude jumping in Hong Kong appears to be difficult given its ubiquitous "high-rise" residential dwellings. Hence, we also need to develop alternative strategies aimed at preventing people from becoming suicidal.

  18. Species status assessment report New Mexico meadow jumping mouse (Zapus hudsonius luteus)

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The New Mexico meadow jumping mouse (Zapus hudsonius luteus) (jumping mouse) lives in dense riparian herbaceous vegetation along streams from southern Colorado to...

  19. Application of biological feedback for estimation of anaerobic performance in jumping test

    Directory of Open Access Journals (Sweden)

    Kovalenko S.O.

    2014-10-01

    Full Text Available Purpose : - To determine the effect of biofeedback to determine the level of anaerobic performance of healthy young men. Material: The characteristics of physical performance in 60-seconds jumping test without and with visual and audible biofeedback (BFB are determined at 23 healthy young men. Results : Significant individual peculiarities are found in performance features of 60-seconds jumping test both without and with BFB. The groups of performance indexes are maximum jumping height; jumping frequency and achieved performance level; correlation of jumping phases and achieved capacity of a separate jump; jumping dynamics during the test. The positive effect mostly on performance in BFB regime is found in the group of persons with low level of physical performance. Conclusion : The application of BFB in 60-seconds jumping test is proved to increase the objective character of measuring anaerobic performance.

  20. Aerobic Requirements for and Heart Rate Responses to Variations in Rope Jumping Techniques.

    Science.gov (United States)

    Solis, Ken; And Others

    1988-01-01

    Highly skilled ropejumpers can maintain their exercise intensity by varying their jumping technique. Research on heart rate responses and aerobic requirements of different jumping techniques is discussed. Methodology and data are reported. (Author/JL)

  1. Acute effect of whole-body vibration on high velocity squat and jump performance

    Directory of Open Access Journals (Sweden)

    Carlos Ugrinowitsch

    2010-09-01

    Full Text Available The objective of this study was to assess the acute effect of whole-body vibration (WBV on power production of the lower limbs during squat exercise and on vertical jump height. The performance of 30 strength-trained subjects was assessed during high velocity squat exercise (HVS and countermovement vertical jump (CMJ before and after being submitted to four different vibration protocols in a counterbalanced random manner. The HVS and CMJ assessments were performed 3 min before and 6, 9 and 12 min after the WBV interventions, and 6 min before and 9 and 15 min after the interventions, respectively. The different WBV protocols did not change relative peak or average power production during HVS and CMJ. However, time exerted a main effect, with a decrease in CMJ height at 3 min (-2% and 15 min (-3.1% after treatment. These results suggest that the WBV protocols employed in this study do not induce acute improvement in performance. However, this finding does not rule out the application of WBV as a useful strategy for training or warm-up routines.

  2. Lean mass asymmetry influences force and power asymmetry during jumping in collegiate athletes.

    Science.gov (United States)

    Bell, David R; Sanfilippo, Jennifer L; Binkley, Neil; Heiderscheit, Bryan C

    2014-04-01

    The purpose of this investigation was to (a) examine how asymmetry in lower extremity lean mass influenced force and power asymmetry during jumping, (b) determine how power and force asymmetry affected jump height, and (c) report normative values in collegiate athletes. Force and power were assessed from each limb using bilateral force plates during a countermovement jump in 167 division 1 athletes (mass = 85.7 ± 20.3 kg, age = 20.0 ± 1.2 years; 103 men and 64 women). Lean mass of the pelvis, thigh, and shank was assessed using dual-energy x-ray absorptiometry. Percent asymmetry was calculated for lean mass at each region (pelvis, thigh, and shank) as well as force and power. Forward stepwise regressions were performed to determine the influence of lean mass asymmetry on force and power asymmetry. Thigh and shank lean mass asymmetry explained 20% of the variance in force asymmetry (R = 0.20, p lean mass asymmetry of the pelvis, thigh, and shank explained 25% of the variance in power asymmetry (R = 0.25, p 0.05) and greater than 10% asymmetry in power tended to decrease the performance (effect size >1.0). Ninety-five percent of this population (2.5th to 97.5th percentile) displayed force asymmetry between -11.8 and 16.8% and a power asymmetry between -9.9 and 11.5%. A small percentage (lean mass asymmetry in the lower extremity is at least partially responsible for asymmetries in force and power. However, a large percentage remains unexplained by lean mass asymmetry.

  3. Anthropometric profile, vertical jump, and throwing velocity in elite female handball players by playing positions.

    Science.gov (United States)

    Vila, Helena; Manchado, Carmen; Rodriguez, Nuria; Abraldes, José Arturo; Alcaraz, Pedro Emilio; Ferragut, Carmen

    2012-08-01

    Women's handball is a sport, which has seen an accelerated development over the last decade. Although anthropometric and physical characteristics have been studied for male sports teams, in women's handball, studies are scarce. The aim of this study was twofold: first, to describe the anthropometric characteristics, throwing velocity, hand grip, and muscular power of the lower limbs in female handball players and second, to identify the possible differences in these parameters in terms of individual playing positions (center, back, wing, pivot, and goalkeeper). A total of 130 elite female Spanish handball players participated in the study (age 25.74 ± 4.84 years; playing experience 14.92 ± 4.88 years). Anthropometric assessment was performed for all the subjects following the International Society for the Advancement of Kinanthropometry protocols. Furthermore, all the subjects performed a vertical jump test (squat jump and countermovement jump). Hand grip and throwing velocity in several situations were also assessed. A 1-way analysis of variance and a Tukey post hoc test were used to study the differences among individual playing positions. Wings were less heavy, shorter, and showed a smaller arm span than did goalkeepers, backs and pivots (p ≤ 0.001). Additionally, pivots were heavier than centers. Backs and pivots exhibited higher muscular mass than did wings. Total players' somatotype was mesomorphy endomorphy (3.89-4.28-2.29). Centers showed higher throwing velocity levels than did wings in 9-m throws from just behind the line, with a goalkeeper. Backs exhibited higher hand-grip values than did wings. Statistical differences have been established between wings and other specific playing positions, especially with pivot and backs. Coaches can use this information to select players for the different specific positions.

  4. Mechanically induced ankle inversion during human walking and jumping.

    NARCIS (Netherlands)

    Nieuwenhuijzen, P.H.J.A.; Grüneberg, C.; Duysens, J.E.J.

    2002-01-01

    A new method to study sudden ankle inversions during human walking and jumping is presented. Ankle inversions of 25 degrees were elicited using a box containing a trap door. During the gait task, subjects walked at a speed of 4 km/h. At a pre-programmed delay after left heel strike, an electromagnet

  5. Structural estimation of jump-diffusion processes in macroeconomics

    DEFF Research Database (Denmark)

    Posch, Olaf

    2009-01-01

    This paper shows how to solve and estimate a continuous-time dynamic stochastic general equilibrium (DSGE) model with jumps. It also shows that a continuous-time formulation can make it simpler (relative to its discrete-time version) to compute and estimate the deep parameters using the likelihoo...

  6. Jump Conditions for Maxwell Equations and Their Consequences

    Science.gov (United States)

    2013-01-28

    critical issues in computational modeling of electromagnetic systems containing sliding contacts, such as railguns , is the relationship between...an armature is propelled by electromagnetic force. Two stationary conductors (rails) are connected to a capacitor bank. An armature, typically a solid...experimental results. 15. SUBJECT TERMS Maxwell equation, computational electromagnetics , jump condition 16. SECURITY CLASSIFICATION OF: 17

  7. Environmentally transmitted parasites: Host-jumping in a heterogeneous environment.

    Science.gov (United States)

    Caraco, Thomas; Cizauskas, Carrie A; Wang, Ing-Nang

    2016-05-21

    Groups of chronically infected reservoir-hosts contaminate resource patches by shedding a parasite׳s free-living stage. Novel-host groups visit the same patches, where they are exposed to infection. We treat arrival at patches, levels of parasite deposition, and infection of the novel host as stochastic processes, and derive the expected time elapsing until a host-jump (initial infection of a novel host) occurs. At stationarity, mean parasite densities are independent of reservoir-host group size. But within-patch parasite-density variances increase with reservoir group size. The probability of infecting a novel host declines with parasite-density variance; consequently larger reservoir groups extend the mean waiting time for host-jumping. Larger novel-host groups increase the probability of a host-jump during any single patch visit, but also reduce the total number of visits per unit time. Interaction of these effects implies that the waiting time for the first infection increases with the novel-host group size. If the reservoir-host uses resource patches in any non-uniform manner, reduced spatial overlap between host species increases the waiting time for host-jumping.

  8. Delayed Frost Growth on Jumping-Drop Superhydrophobic Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Boreyko, Jonathan B [ORNL; Collier, Pat [ORNL

    2013-01-01

    Self-propelled jumping drops are continuously removed from a condensing superhydrophobic surface to enable a micrometric steady-state drop size. Here, we report that subcooled condensate on a chilled superhydrophobic surface are able to repeatedly jump off the surface before heterogeneous ice nucleation occurs. Frost still forms on the superhydrophobic surface due to ice nucleation at neighboring edge defects, which eventually spreads over the entire surface via an inter-drop frost wave. The growth of this inter-drop frost front is shown to be up to three times slower on the superhydrophobic surface compared to a control hydrophobic surface, due to the jumping-drop effect dynamically minimizing the average drop size and surface coverage of the condensate. A simple scaling model is developed to relate the success and speed of inter-drop ice bridging to the drop size distribution. While other reports of condensation frosting on superhydrophobic surfaces have focused exclusively on liquid-solid ice nucleation for isolated drops, these findings reveal that the growth of frost is an inter-drop phenomenon that is strongly coupled to the wettability and drop size distribution of the surface. A jumping-drop superhydrophobic condenser was found to be superior to a conventional dropwise condenser in two respects: preventing heterogeneous ice nucleation by continuously removing subcooled condensate, and delaying frost growth by minimizing the success of interdrop ice bridge formation.

  9. Delayed frost growth on jumping-drop superhydrophobic surfaces.

    Science.gov (United States)

    Boreyko, Jonathan B; Collier, C Patrick

    2013-02-26

    Self-propelled jumping drops are continuously removed from a condensing superhydrophobic surface to enable a micrometric steady-state drop size. Here, we report that subcooled condensate on a chilled superhydrophobic surface are able to repeatedly jump off the surface before heterogeneous ice nucleation occurs. Frost still forms on the superhydrophobic surface due to ice nucleation at neighboring edge defects, which eventually spreads over the entire surface via an interdrop frost wave. The growth of this interdrop frost front is shown to be up to 3 times slower on the superhydrophobic surface compared to a control hydrophobic surface, due to the jumping-drop effect dynamically minimizing the average drop size and surface coverage of the condensate. A simple scaling model is developed to relate the success and speed of interdrop ice bridging to the drop size distribution. While other reports of condensation frosting on superhydrophobic surfaces have focused exclusively on liquid-solid ice nucleation for isolated drops, these findings reveal that the growth of frost is an interdrop phenomenon that is strongly coupled to the wettability and drop size distribution of the surface. A jumping-drop superhydrophobic condenser minimized frost formation relative to a conventional dropwise condenser in two respects: preventing heterogeneous ice nucleation by continuously removing subcooled condensate, and delaying frost growth by limiting the success of interdrop ice bridge formation.

  10. Jump Patterns: Percussive Dance and the Path to Math

    Science.gov (United States)

    Rosenfeld, Malke

    2011-01-01

    In this article, the author describes an innovative collaboration with an elementary school math teacher that leads to original student choreography and engaging mathematical thinking. Using a tool the author created called Jump Patterns, students at Fox Hill Elementary School in Indianapolis, Indiana, engage in a robust, creative, choreographic…

  11. A logarithmic interpretation of Edixhoven's jumps for Jacobians

    DEFF Research Database (Denmark)

    Eriksson, Dennis; Halle, Lars Halvard; Nicaise, Johannes

    2015-01-01

    Let A be an abelian variety over a discretely valued field. Edixhoven has defined a filtration on the special fiber of the N\\'eron model of A that measures the behaviour of the N\\'eron model under tame base change. We interpret the jumps in this filtration in terms of lattices of logarithmic...

  12. The Hydraulic Jump: Finding Complexity in Turbulent Water

    Science.gov (United States)

    Vondracek, Mark

    2013-01-01

    Students who do not progress to more advanced science disciplines in college generally do not realize that seemingly simple physical systems are--when studied in detail--more complex than one might imagine. This article presents one such phenomenon--the hydraulic jump--as a way to help students see the complexity behind the seemingly simple, and…

  13. Anticipating the Species Jump: Surveillance for Emerging Viral Threats

    Science.gov (United States)

    2010-12-01

    broken skin or injection). Tropism is the affinity that a given virus has for particular host cell receptors, cells or tissues. Fusion/Entry...be a descendant of a cat virus ( feline panleukopenia virus, FPV) that jumped from cats to dogs within five years prior to its emergence. Since that

  14. The Viability Property of Controlled Jump Diffusion Processes

    Institute of Scientific and Technical Information of China (English)

    Shi Ge PENG; Xue Hong ZHU

    2008-01-01

    In this paper,we first give a comparison theorem of viscosity solution to some nonlinear second order integrodifferential equation.And then using the comparison theorem,we obtain a necessary and sufficient condition for the viability property of some controlled jump diffusion processes which can keep the solution within a constraint K.

  15. Jumping across the gap - a series of atrial extrastimuli.

    Science.gov (United States)

    Swamy, Mahadeva; Katyal, Deepak; Raja J, Kaushal

    2015-01-01

    The "gap phenomenon" is an interesting phenomenon in electrophysiology arising from the differences in refractory periods at two or more levels of the atrioventricular (AV) conduction system. We present a patient with dual AV nodal physiology in whom the AH jump mediates the gap phenomenon. We also briefly discuss the other mechanisms of gap phenomenon that have been described in this setting.

  16. Hydraulic Jump and Energy Dissipation with Sluice Gate

    Directory of Open Access Journals (Sweden)

    Youngkyu Kim

    2015-09-01

    Full Text Available Movable weirs have been developed to address the weaknesses of conventional fixed weirs. However, the structures for riverbed protection downstream of movable weirs are designed using the criteria of fixed weirs in most cases, and these applications cause problems, such as scour and deformation of structures, due to misunderstanding the difference between different types of structures. In this study, a hydraulic experiment was conducted to examine weir type-specific hydraulic phenomena, compare hydraulic jumps and downstream flow characteristics according to different weir types, and analyze hydraulic characteristics, such as changes in water levels, velocities and energy. Additionally, to control the flow generated by a sluice gate, energy dissipators were examined herein for their effectiveness in relation to different installation locations and heights. As a result, it was found that although sluice gates generated hydraulic jumps similar to those of fixed weirs, their downstream supercritical flow increased to eventually elongate the overall hydraulic jumps. In energy dissipator installation, installation heights were found to be sensitive to energy dissipation. The most effective energy dissipator height was 10% of the downstream free surface water depth in this experiment. Based on these findings, it seems desirable to use energy dissipators to reduce energy, as such dissipators were found to be effective in reducing hydraulic jumps and protecting the riverbed under sluice gates.

  17. Mechanically induced ankle inversion during human walking and jumping.

    NARCIS (Netherlands)

    Nieuwenhuijzen, P.H.J.A.; Grüneberg, C.; Duysens, J.E.J.

    2002-01-01

    A new method to study sudden ankle inversions during human walking and jumping is presented. Ankle inversions of 25 degrees were elicited using a box containing a trap door. During the gait task, subjects walked at a speed of 4 km/h. At a pre-programmed delay after left heel strike, an electromagnet

  18. Fact or friction: jumps at ultra high frequency

    NARCIS (Netherlands)

    K. Christensen; R. Oomen; M. Podolskij

    2011-01-01

    In this paper, we demonstrate that jumps in financial asset prices are not nearly as common as generally thought, and that they account for only a very small proportion of total return variation. We base our investigation on an extensive set of ultra high-frequency equity and foreign exchange rate d

  19. Mechanical output in jumps of marmosets (Callithrix jacchus).

    Science.gov (United States)

    Bobbert, Maarten F; Plas, Rogier L C; Weide, Guido; Clairbois, H E Bert; Hofman, Sam O; Jaspers, Richard T; Philippens, Ingrid H C H M

    2014-02-15

    In this study we determined the mechanical output of common marmosets (Callithrix jacchus) during jumping. Vertical ground reaction forces were measured in 18 animals while they jumped from an instrumented crossbar to a crossbar located 70 cm higher. From the vertical force time histories, we calculated the rate of change of mechanical energy of the centre of mass (dE/dt). The mean value of dE/dt during the push-off amounted to 51.8±6.2 W kg(-1) body mass, and the peak value to 116.4±17.6 W kg(-1) body mass. We used these values in combination with masses of leg muscles, determined in two specimens, to estimate mean and peak values of dE/dt of 430 and 970 W kg(-1) muscle, respectively. These values are higher than values reported in the literature for jumps of humans and bonobos, but smaller than those of jumps of bushbabies. Surprisingly, the mean value of dE/dt of 430 W kg(-1) muscle was close to the maximal power output of 516 W kg(-1) muscle reported in the literature for isokinetic contractions of rat medial gastrocnemius, one of the fastest mammalian muscles. Further study of the force-velocity relationship of muscle tissue of small primates is indicated.

  20. Propulsion efficiency and imposed flow fields of a copepod jump

    DEFF Research Database (Denmark)

    Jiang, H.; Kiørboe, Thomas

    2011-01-01

    velocity vectors pointing towards the copepod; such a flow field may inform the predator of the whereabouts of the escaping copepod prey. High Froude propulsion efficiency (0.94–0.98) was obtained for individual power stroke durations of all simulated jumps. This is unusual for small aquatic organisms...

  1. Firms' Overseas Investment Jumps to US$6.9 Billion

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    @@ Foreign investment by domestic firms, excluding banks,jumped 26% last year to US$6.9 billion, the Ministry of Commerce said on February 10. The government has been encouraging domestic companies to head overseas to secure resources, build brands and win market share, and it also welcomes the effect an outflow of investment has on the yuan.

  2. The Missing Luminous Blue Variables and the Bistability Jump

    NARCIS (Netherlands)

    N. Smith; J.S. Vink; A. de Koter

    2004-01-01

    We discuss an interesting feature of the distribution of luminous blue variables (LBVs) on the H-R diagram, and we propose a connection with the bistability jump seen in the winds of early-type supergiants. There appears to be a deficiency of quiescent LBVs on the S Doradus instability strip at lumi

  3. Asymptotic Behaviour and Extinction of Delay Lotka-Volterra Model with Jump-Diffusion

    OpenAIRE

    Dan Li,; Jing’an Cui; Guohua Song

    2014-01-01

    This paper studies the effect of jump-diffusion random environmental perturbations on the asymptotic behaviour and extinction of Lotka-Volterra population dynamics with delays. The contributions of this paper lie in the following: (a) to consider delay stochastic differential equation with jumps, we introduce a proper initial data space, in which the initial data may be discontinuous function with downward jumps; (b) we show that the delay stochastic differential equation with jumps associate...

  4. Jumping for recognition: Women's ski jumping viewed as a struggle for rights.

    Science.gov (United States)

    Andersen, W; Loland, S

    2017-03-01

    With the campaign for women's participation in international and Olympic ski jumping as a practical case, sport's potential for recognition of individual rights is explored. In line with Honneth's influential ethical theory, recognition of rights refers to a mutual recognition between persons of each other as rational and responsible agents with an equal right to take part in the public formation and development of their community or practice. The argument is that women ski jumpers were entitled to compete as they had actual and/or potential capabilities and skills to contribute in the public formation and development of their sport. Their exclusion was a violation of individual rights. At a more general level, sport is discussed as a sphere for recognition of rights. It is argued that the basic principles of equal opportunity to take part and to perform make sport a particularly clear and potent sphere for such recognition, and also for the identification of rights violations. In sport, rights, or the violation of rights, are demonstrated in concrete and embodied ways. It is concluded that struggles for recognition and individual rights are a continuous process in sport as in most other human institutions and practices.

  5. Time-resolved methods in biophysics. 9. Laser temperature-jump methods for investigating biomolecular dynamics.

    Science.gov (United States)

    Kubelka, Jan

    2009-04-01

    Many important biochemical processes occur on the time-scales of nanoseconds and microseconds. The introduction of the laser temperature-jump (T-jump) to biophysics more than a decade ago opened these previously inaccessible time regimes up to direct experimental observation. Since then, laser T-jump methodology has evolved into one of the most versatile and generally applicable methods for studying fast biomolecular kinetics. This perspective is a review of the principles and applications of the laser T-jump technique in biophysics. A brief overview of the T-jump relaxation kinetics and the historical development of laser T-jump methodology is presented. The physical principles and practical experimental considerations that are important for the design of the laser T-jump experiments are summarized. These include the Raman conversion for generating heating pulses, considerations of size, duration and uniformity of the temperature jump, as well as potential adverse effects due to photo-acoustic waves, cavitation and thermal lensing, and their elimination. The laser T-jump apparatus developed at the NIH Laboratory of Chemical Physics is described in detail along with a brief survey of other laser T-jump designs in use today. Finally, applications of the laser T-jump in biophysics are reviewed, with an emphasis on the broad range of problems where the laser T-jump methodology has provided important new results and insights into the dynamics of the biomolecular processes.

  6. Neuromuscular adaptations to 4 weeks of intensive drop jump training in well-trained athletes

    DEFF Research Database (Denmark)

    Alkjær, Tine; Meyland, Jacob; Raffalt, Peter C

    2013-01-01

    This study examined the effects of 4 weeks of intensive drop jump training in well-trained athletes on jumping performance and underlying changes in biomechanics and neuromuscular adaptations. Nine well-trained athletes at high national competition level within sprinting and jumping disciplines...

  7. Psycho-physiological response in an automatic parachute jump.

    Science.gov (United States)

    Clemente-Suárez, Vicente Javier; Robles-Pérez, José Juan; Fernández-Lucas, Jesús

    2016-10-11

    Parachute jump is an extreme activity that elicits an intense stress response that affects jumpers' body systems being able to put them at risk. The present research analysed modifications in blood oxygen saturation (BOS), heart rate (HR), cortisol, glucose, lactate, creatine kinase (CK), muscles strength, cortical arousal, autonomic modulation, pistol magazine reload time (PMRT) and state anxiety before and after an automatic open parachute jump in 38 male Spanish soldiers (25.6 ± 5.9 years). A MANOVA with samples as a fixed factor and Effect Size (ES) were conducted. MANOVA showed (Wilks lambda = .225; F = 5.980; P = .000) a significantly increase in cortisol (6.2 ± 3.2 vs. 8.2 ± 4.3 nmol/l; P = .025; ES = .47), HR (75.0 ± 14.6 vs. 87.4 ± 17.3 bpm; P = .004; ES = .72), lactate (1.8 ± 1.2 vs. 4.4 ± 2.2 mmol · l(-1); P = .002; ES = 1.18), sympathetic nervous system and leg strength manifestation after the parachute jump. By contrary BOS, PMRT (55.6 ± 27.6 vs. 48.0 ± 16.7 s; P = .021; ES = .46) and somatic anxiety (SA), evaluated by CSAI2R questionnaire, decreased. An automatic parachute jump increased physiological and cortical response and decreased SA of participants. This stress response can affect the jumpers' abilities and allow us to have a better understanding of the organism stress response and to improve training for both military and sport parachute jumps.

  8. The kinematics of swimming and relocation jumps in copepod nauplii.

    Directory of Open Access Journals (Sweden)

    Christian Marc Andersen Borg

    Full Text Available Copepod nauplii move in a world dominated by viscosity. Their swimming-by-jumping propulsion mode, with alternating power and recovery strokes of three pairs of cephalic appendages, is fundamentally different from the way other microplankters move. Protozoans move using cilia or flagella, and copepodites are equipped with highly specialized swimming legs. In some species the nauplius may also propel itself more slowly through the water by beating and rotating the appendages in a different, more complex pattern. We use high-speed video to describe jumping and swimming in nauplii of three species of pelagic copepods: Temora longicornis, Oithona davisae and Acartia tonsa. The kinematics of jumping is similar between the three species. Jumps result in a very erratic translation with no phase of passive coasting and the nauplii move backwards during recovery strokes. This is due to poorly synchronized recovery strokes and a low beat frequency relative to the coasting time scale. For the same reason, the propulsion efficiency of the nauplii is low. Given the universality of the nauplius body plan, it is surprising that they seem to be inefficient when jumping, which is different from the very efficient larger copepodites. A slow-swimming mode is only displayed by T. longicornis. In this mode, beating of the appendages results in the creation of a strong feeding current that is about 10 times faster than the average translation speed of the nauplius. The nauplius is thus essentially hovering when feeding, which results in a higher feeding efficiency than that of a nauplius cruising through the water.

  9. Changes in biomechanical properties during drop jumps of incremental height.

    Science.gov (United States)

    Peng, Hsien-Te

    2011-09-01

    The purpose of this study was to investigate changing biomechanical properties with increasing drop jump height. Sixteen physically active college students participated in this study and performed drop jumps from heights of 20, 30, 40, 50, and 60 cm (DJ20-DJ60). Kinematic and kinetic data were collected using 11 Eagle cameras and 2 force platforms. Data pertaining to the dominant leg for each of 3 trials for each drop height were recorded and analyzed. Statistical comparisons of vertical ground reaction force (vGRF), impulse, moment, power, work, and stiffness were made between different drop jump heights. The peak vGRF of the dominant leg exceeded 3 times the body weight during DJ50 and DJ60; these values were significantly greater than those for DJ20, DJ30, and DJ40 (all p height jumped during DJ60 was significantly less than that during DJ20 and DJ30 (both p = 0.010). Both the landing impulse and total impulse during the contact phase were significantly different between each drop height (all p height. There were no significant differences in the takeoff impulse. Peak and mean power absorption and negative work at the knee and ankle joints during DJ40, DJ50, and DJ60 were significantly greater than those during DJ20 and DJ30 (all p heights >40 cm offered no advantages in terms of mechanical efficiency (SSC power output) and stiffness. Drop jumps from heights in excess of 60 cm are not recommended because of the lack of biomechanical efficiency and the potentially increased risk of injury.

  10. Short-term effects of complex and contrast training in soccer players' vertical jump, sprint, and agility abilities.

    Science.gov (United States)

    Maio Alves, José Manuel Vilaça; Rebelo, António Natal; Abrantes, Catarina; Sampaio, Jaime

    2010-04-01

    The purpose of this study was to analyze the short-term effects of complex and contrast training (CCT) on vertical jump (squat and countermovement jump), sprint (5 and 15 m), and agility (505 Agility Test) abilities in soccer players. Twenty-three young elite Portuguese soccer players (age 17.4 +/- 0.6 years) were divided into 2 experimental groups (G1, n = 9, and G2, n = 8) and 1 control group (G3, n = 6). Groups G1 and G2 have done their regular soccer training along with a 6-week strength training program of CCT, with 1 and 2 training sessions.wk, respectively. G3 has been kept to their regular soccer training program. Each training session from the CCT program was organized in 3 stations in which a general exercise, a multiform exercise, and a specific exercise were performed. The load was increased by 5% from 1 repetition maximum each 2 weeks. Obtained results allowed identifying (a) a reduction in sprint times over 5 and 15 m (9.2 and 6.2% for G1 and 7.0 and 3.1%, for G2; p < 0.05) and () an increase on squat and jump (12.6% for G1 and 9.6% for G2; p < 0.05). The results suggested that the CCT induced the performance increase in 5 and 15 m sprint and in squat jump. Vertical jump and sprint performances after CCT program were not influenced by the number of CCT sessions per week (1 or 2 sessions.wk). From the obtained results, it was suggested that the CCT is an adequate training strategy to develop soccer players' muscle power and speed.

  11. Keeping your eye on the rail: gaze behaviour of horse riders approaching a jump.

    Directory of Open Access Journals (Sweden)

    Carol Hall

    Full Text Available The gaze behaviour of riders during their approach to a jump was investigated using a mobile eye tracking device (ASL Mobile Eye. The timing, frequency and duration of fixations on the jump and the percentage of time when their point of gaze (POG was located elsewhere were assessed. Fixations were identified when the POG remained on the jump for 100 ms or longer. The jumping skill of experienced but non-elite riders (n = 10 was assessed by means of a questionnaire. Their gaze behaviour was recorded as they completed a course of three identical jumps five times. The speed and timing of the approach was calculated. Gaze behaviour throughout the overall approach and during the last five strides before take-off was assessed following frame-by-frame analyses. Differences in relation to both round and jump number were found. Significantly longer was spent fixated on the jump during round 2, both during the overall approach and during the last five strides (p<0.05. Jump 1 was fixated on significantly earlier and more frequently than jump 2 or 3 (p<0.05. Significantly more errors were made with jump 3 than with jump 1 (p = 0.01 but there was no difference in errors made between rounds. Although no significant correlations between gaze behaviour and skill scores were found, the riders who scored higher for jumping skill tended to fixate on the jump earlier (p = 0.07, when the horse was further from the jump (p = 0.09 and their first fixation on the jump was of a longer duration (p = 0.06. Trials with elite riders are now needed to further identify sport-specific visual skills and their relationship with performance. Visual training should be included in preparation for equestrian sports participation, the positive impact of which has been clearly demonstrated in other sports.

  12. Possibility of stretch-shortening cycle movement training using a jump rope.

    Science.gov (United States)

    Miyaguchi, Kazuyoshi; Sugiura, Hiroki; Demura, Shinichi

    2014-03-01

    Although jumping rope has been said to be a typical stretch-shortening cycle movement (SSC) from the dynamic analysis of muscle contraction, there are few research reports that focus on this point. Recently, the function of SSC of the legs with respect to the jumping movement has been evaluated using the rebound jump index (RJ-index). This study aimed to examine the possibility of using rope jumping in SSC training by comparing the RJ-index of the rebound jump (standard value) and the 2 different methods of rope jumping. The subjects included 76 healthy young men. Most subjects were involved in routine sports training 2-3 times per week. They performed the rebound jump (5 consecutive vertical jumps) and both a basic and a double-under jump with the jump rope, according to each participant's individual style (rhythm or timing). The RJ-index was calculated using the ground contact time and the jump height. The reliabilities of the RJ-index in the basic (intraclass correlation coefficient: 0.85) and double-under jump (0.92) were high, and the RJ-index of the latter (1.34 ± 0.24) was significantly higher than that of the former (0.60 ± 0.21). In the case of a group with inferior SSC ability, the RJ-index of the rebound jump only showed a significant correlation with the double-under but not with the basic jump. When using the RJ-index (1.97 ± 0.38) of the rebound jump as a criterion, the double-under-using about 70% of the SSC ability-may be effective for reinforcement of SSC ability.

  13. Development definition of strength and anaerobic abilities in jump tests: classification, methodology of measuring and norms of estimation of standing high jump

    Directory of Open Access Journals (Sweden)

    Leonid Serhiyenko

    2015-10-01

    Full Text Available Purpose: to define the methodology of carrying out the tests: standing high jump and to systematize the general notion about measuring of strength and anaerobic human abilities. Material and Methods: methods of theoretic analysis and generalization, method of search and study of scientific information were used. Results: the standing high jump classification which helps to differentiate jumps according to the way of fulfillment and estimation of the development of motor abilities ware founded. Conclusion: the methodology of doing different kinds of jumps is described

  14. JUMP KINETIC DETERMINANTS OF SPRINT ACCELERATION PERFORMANCE FROM STARTING BLOCKS IN MALE SPRINTERS

    Directory of Open Access Journals (Sweden)

    Peter S. Maulder

    2006-06-01

    Full Text Available The purpose of this research was to identify the jump kinetic determinants of sprint acceleration performance from a block start. Ten male (mean ± SD: age 20 ± 3 years; height 1.82 ± 0.06 m; weight 76.7 ± 7.9 kg; 100 m personal best: 10.87 + 0.36 s {10.37 - 11.42} track sprinters at a national and regional competitive level performed 10 m sprints from a block start. Anthropometric dimensions along with squat jump (SJ, countermovement jump (CMJ, continuous straight legged jump (SLJ, single leg hop for distance, and single leg triple hop for distance measures of power were also tested. Stepwise multiple regression analysis identified CMJ average power (W/kg as a predictor of 10 m sprint performance from a block start (r = 0.79, r2 = 0.63, p<0.01, SEE = 0.04 (s, %SEE = 2.0. Pearson correlation analysis revealed CMJ force and power (r = -0.70 to -0.79; p = 0.011 - 0.035 and SJ power (r = -0.72 to -0.73; p = 0.026 - 0.028 generating capabilities to be strongly related to sprint performance. Further linear regression analysis predicted an increase in CMJ average and peak take-off power of 1 W/kg (3% & 1.5% respectively to both result in a decrease of 0.01 s (0.5% in 10 m sprint performance. Further, an increase in SJ average and peak take-off power of 1 W/kg (3.5% & 1.5% respectively was predicted to result in a 0.01 s (0.5% reduction in 10 m sprint time. The results of this study seem to suggest that the ability to generate power both elastically during a CMJ and concentrically during a SJ to be good indicators of predicting sprint performance over 10 m from a block start

  15. Autonomous Rubidium Clock Weak Frequency Jump Detector for Onboard Navigation Satellite System.

    Science.gov (United States)

    Khare, Akshay; Arora, Rajat; Banik, Alak; Mehta, Sanjay D

    2016-02-01

    Frequency jumps are common in rubidium frequency sources. They affect the estimation of user position in navigational satellite systems. These jumps must be detected and corrected immediately as they have direct impact on the navigation system integrity. A novel weak frequency jump detector is proposed based on a Kalman filter with a multi-interval approach. This detector can be applied for both "sudden" and "slow" frequency transitions. In this detection method, noises of clock data are reduced by Kalman filtering, for accurate estimation of jump size with less latency. Analysis on in-orbit rubidium atomic frequency standard (RAFS) phase telemetry data shows that the detector can be used for fast detection and correction of weak frequency jumps. Furthermore, performance comparison of different existing frequency jump detection techniques with the proposed detector is discussed. A multialgorithm-based strategy is proposed depending on the jump size and latency for onboard navigation satellites having RAFS as the primary frequency source.

  16. Hotspot Cooling with Self-Propelled Jumping Condensate

    Science.gov (United States)

    Qu, Xiaopeng; Boreyko, Jonathan B.; Liu, Fangjie; Chen, Chuan-Hua

    2012-11-01

    Dynamic hotspots are prevalent in electronic systems including microprocessors and power electronics with constantly changing computing tasks or payloads. Here, we report a new adaptive hotspot cooling technique that rapidly responds to moving hotspots in a passive manner independent of external forces. The hotspot cooling is based upon the self-propelled jumping of dropwise condensate, which directly returns the working fluid from a superhydrophobic condenser to an opposing superhydrophilic evaporator. The adaptive thermal management is accomplished by the preferential evaporation of water at the hotspots and the rapid jumping return of the condensate across the very short inter-plate distance. The proof-of-concept for this hotspot cooling technique will be demonstrated by the adaptive response to hotspots at increasing heat fluxes. Corresponding author.

  17. VaR: Exchange Rate Risk and Jump Risk

    Directory of Open Access Journals (Sweden)

    Fen-Ying Chen

    2010-01-01

    Full Text Available Incorporating the Poisson jumps and exchange rate risk, this paper provides an analytical VaR to manage market risk of international portfolios over the subprime mortgage crisis. There are some properties in the model. First, different from past studies in portfolios valued only in one currency, this model considers portfolios not only with jumps but also with exchange rate risk, that is vital for investors in highly integrated global financial markets. Second, in general, the analytical VaR solution is more accurate than historical simulations in terms of backtesting and Christoffersen's independence test (1998 for small portfolios and large portfolios. In other words, the proposed model is reliable not only for a portfolio on specific stocks but also for a large portfolio. Third, the model can be regarded as the extension of that of Kupiec (1999 and Chen and Liao (2009.

  18. Control and filtering for semi-Markovian jump systems

    CERN Document Server

    Li, Fanbiao; Wu, Ligang

    2017-01-01

    This book presents up-to-date research developments and novel methodologies on semi-Markovian jump systems (S-MJS). It presents solutions to a series of problems with new approaches for the control and filtering of S-MJS, including stability analysis, sliding mode control, dynamic output feedback control, robust filter design, and fault detection. A set of newly developed techniques such as piecewise analysis method, positively invariant set approach, event-triggered method, and cone complementary linearization approaches are presented. Control and Filtering for Semi-Markovian Jump Systems is a comprehensive reference for researcher and practitioners working in control engineering, system sciences and applied mathematics, and is also a useful source of information for senior undergraduates and graduates in these areas. The readers will benefit from some new concepts, new models and new methodologies with practical significance in control engineering and signal processing.

  19. Pricing Asian power options under jump-fraction process

    Directory of Open Access Journals (Sweden)

    Bin Peng

    2012-12-01

    Full Text Available A framework for pricing Asian power options is developed when the underlying asset follows a jump-fraction process. The partial differential equation (PDE in the fractional environment with jump is constructed for such option using general Itô's lemma and self-financing dynamic strategy. With the boundary condition, an analytic formula for the option with geometric average starting at any time before maturity is derived by solving the PDE, and the option with arithmetic average is evaluated in Monte Carlo simulation using control variate technique with the help of the above analytic solution. Overwhelming numerical evidence indicates that the technique proposed is computationally efficient and dramatically improves the accuracy of the simulated price. Moreover, this study will pave a novel way to copy with the option contracts based on thinly-traded assets like oil, or currencies or interest rates.

  20. The circular jump as a hydrodynamic white hole

    CERN Document Server

    Jannes, Gil

    2012-01-01

    Surface waves in classical fluids experience a rich array of black/white hole horizon effects. The dispersion relation depends on the characteristics of the fluid as well as on the fluid depth and the wavelength regime. We focus on the shallow-water regime, and discuss the experimental proof that the circular hydraulic jump marks the transition between a supercritical and a subcritical flow regime. This finally confirms a theoretical conjecture formulated by Lord Rayleigh nearly 100 years ago. It also confirms that the circular jump corresponds to the spontaneous formation of a hydrodynamic white hole, with interesting characteristics from the point of view of analogue gravity. We study the dispersive regime, mention some lessons about the trans-Planckian issue and describe possible directions for future work.

  1. The asteroid belt outer region under jumping-Jupiter migration

    Science.gov (United States)

    Gaspar, H. S.; Winter, O. C.; Vieira Neto, E.

    2017-09-01

    The radial configuration of the outer region of the main asteroid belt is quite peculiar, and has much to say about the past evolution of Jupiter. In this work, we investigate the dynamical effects of a jumping-Jupiter-like migration over a more extended primordial asteroid belt. Jupiter's migrations are simulated using a fast jumping-Jupiter synthesizer. Among the results, we highlight non-negligible fractions of primordial objects trapped in 3:2 and 4:3 mean motion resonances (MMRs) with Jupiter. They survived the whole truculent phase of migration and originated populations that are like Hildas and Thules. Fractions ranging from 3 to 6 per cent of the initial distribution remained trapped in 3:2 MMR, and at least 0.05 per cent in 4:3. These results show that the resonance trapping of primordial objects may have originated these resonant populations. This theory is consistent even for Jupiter's truculent evolution.

  2. Characteristics of a hydraulic jump in Bingham fluid

    CERN Document Server

    Shu, Jian-Jun

    2014-01-01

    In this paper, we seek an adequate macroscopic model for a hydraulic jump in Bingham fluid. The formulas for conjugate depths, sequent bottom shear stress and critical depth are established. Since no exact analytical solution in closed form is available for conjugate depths, an approximate formula is developed. This formula can provide good results with an error less than 4%. The analytical results have revealed that the critical depth and the ratio of conjugate depths increase until bottom shear stress exceeds a certain value and then decrease afterwards. The bottom shear stress downstream of the jump is smaller than that upstream. The results are verified by experimental data and observations available in the literature.

  3. A characterization of oil price behavior. Evidence from jump models

    Energy Technology Data Exchange (ETDEWEB)

    Gronwald, Marc [Munich Univ. (Germany). Ifo Institute - Leibniz Institute for Economic Research

    2011-11-15

    This paper is concerned with the statistical behavior of oil prices in two ways. It, firstly, applies a combined jump GARCH in order to characterize the behavior of daily, weekly as well as monthly oil prices. Secondly, it relates its empirical results to implications of Hotelling-type resource extraction models. The empirical analysis shows that oil prices are characterized by GARCH as well as conditional jump behavior and that a considerable portion of the total variance is triggered by sudden extreme price movements. This finding implies that, first, oil price signals are not reliable and, as a consequence, both finding optimal extraction paths and decisions regarding the transmission to alternative technologies are likely to be compromised. Second, this behavior is in stark contrast to the notion of deterministic trends in the price of oil. (orig.)

  4. Forecasting Exchange Rate Volatility in the Presence of Jumps

    DEFF Research Database (Denmark)

    Busch, Thomas; Christensen, Bent Jesper; Nielsen, Morten Ørregaard

    of exchange rate futures options, allowingcalculation of option implied volatility. We find that implied volatility is an informationallyefficient but biased forecast of future realized exchange rate volatility. Furthermore,we show that log-normality is an even better distributional approximation...... for impliedvolatility than for realized volatility in this market. Finally, we show that the jump componentof future realized exchange rate volatility is to some extent predictable, and thatoption implied volatility is the dominant forecast of the future jump component.......We study measures of foreign exchange rate volatility based on high-frequency (5-minute) $/DM exchange rate returns using recent nonparametric statistical techniquesto compute realized return volatility and its separate continuous sample path and jumpcomponents, and measures based on prices...

  5. Frequency jumps in single chip microwave LC oscillators

    Energy Technology Data Exchange (ETDEWEB)

    Gualco, Gabriele; Grisi, Marco; Boero, Giovanni, E-mail: giovanni.boero@epfl.ch [Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne CH-1015 (Switzerland)

    2014-12-15

    We report on the experimental observation of oscillation frequency jumps in microwave LC oscillators fabricated using standard complementary metal-oxide-semiconductor technologies. The LC oscillators, operating at a frequency of about 20 GHz, consist of a single turn planar coil, a metal-oxide-metal capacitor, and two cross-coupled metal-oxide-semiconductor field effect transistors used as negative resistance network. At 300 K as well as at 77 K, the oscillation frequency is a continuous function of the oscillator bias voltage. At 4 K, frequency jumps as large as 30 MHz are experimentally observed. This behavior is tentatively attributed to the emission and capture of single electrons from defects and dopant atoms.

  6. BIOMECHANICAL ANALYSIS OF RUNNING IN THE HIGH JUMP

    Directory of Open Access Journals (Sweden)

    Leite Werlayne

    2013-02-01

    Full Text Available The aim of this paper is to analyze the biomechanics of running at high jump. To this study was realized a bibliographic revision. The running phase is the one which starts when the athlete is set in movement for the jump until the moment that he touches the ground with the takeoff foot in front of the bar, this phase can be divided into two parts: the running in straight line and the running in curve. On the other hand, for better understanding and due to a biomechanical complexity, the running in curve will be divided into three other parts: the three last strides, the two last strides and the last strides. Besides that, we could mention important factors for an efficient approach run: the radius of the curve, the distance and length of the takeoff run.

  7. Option Pricing with Stochastic Volatility and Jump Diffusion Processes

    Directory of Open Access Journals (Sweden)

    Radu Lupu

    2006-05-01

    Full Text Available Option pricing by the use of Black Scholes Merton (BSM model is based on the assumption that asset prices have a lognormal distribution. In spite of the use of these models on a large scale, both by practioners and academics, the assumption of lognormality is rejected by the history of returns. The objective of this article is to present the methods that developed after the Black Scholes Merton environment and deals with the option pricing model adjustment to the empirical properties of asset returns. The main models that appeared after BSM allowed for special changes of the returns that materialized in jump-diffusion and stochastic volatility processes. The article presents the foundations of risk neutral options evaluation and the empirical evidence that fed the amendment of the lognormal assumption in the first part and shows the evaluation procedure under the assumption of stock prices following the jump-diffusion process and the stochastic volatility process.

  8. Option Pricing with Stochastic Volatility and Jump Diffusion Processes

    Directory of Open Access Journals (Sweden)

    Radu Lupu

    2006-03-01

    Full Text Available Option pricing by the use of Black Scholes Merton (BSM model is based on the assumption that asset prices have a lognormal distribution. In spite of the use of these models on a large scale, both by practioners and academics, the assumption of lognormality is rejected by the history of returns. The objective of this article is to present the methods that developed after the Black Scholes Merton environment and deals with the option pricing model adjustment to the empirical properties of asset returns. The main models that appeared after BSM allowed for special changes of the returns that materialized in jump-diffusion and stochastic volatility processes. The article presents the foundations of risk neutral options evaluation and the empirical evidence that fed the amendment of the lognormal assumption in the first part and shows the evaluation procedure under the assumption of stock prices following the jump-diffusion process and the stochastic volatility process.

  9. The effects of a maximal power training cycle on the strength, maximum power, vertical jump height and acceleration of high-level 400-meter hurdlers.

    Science.gov (United States)

    Balsalobre-Fernández, Carlos; Tejero-González, Carlos M; Del Campo-Vecino, Juan; Alonso-Curiel, Dionisio

    2013-03-01

    The aim of this study was to determine the effects of a power training cycle on maximum strength, maximum power, vertical jump height and acceleration in seven high-level 400-meter hurdlers subjected to a specific training program twice a week for 10 weeks. Each training session consisted of five sets of eight jump-squats with the load at which each athlete produced his maximum power. The repetition maximum in the half squat position (RM), maximum power in the jump-squat (W), a squat jump (SJ), countermovement jump (CSJ), and a 30-meter sprint from a standing position were measured before and after the training program using an accelerometer, an infra-red platform and photo-cells. The results indicated the following statistically significant improvements: a 7.9% increase in RM (Z=-2.03, p=0.021, δc=0.39), a 2.3% improvement in SJ (Z=-1.69, p=0.045, δc=0.29), a 1.43% decrease in the 30-meter sprint (Z=-1.70, p=0.044, δc=0.12), and, where maximum power was produced, a change in the RM percentage from 56 to 62% (Z=-1.75, p=0.039, δc=0.54). As such, it can be concluded that strength training with a maximum power load is an effective means of increasing strength and acceleration in high-level hurdlers.

  10. The short-term effect of whole-body vibration training on vertical jump, sprint, and agility performance.

    Science.gov (United States)

    Cochrane, Darryl J; Legg, Stephen J; Hooker, Michael J

    2004-11-01

    Previous studies have suggested that short-term whole-body vibration (WBV) training produces neuromuscular improvement similar to that of power and strength training. However, it is yet to be determined whether short-term WBV exposure produces neurogenic enhancement for power, speed, and agility. The purpose of this study was to investigate the effect short-term WBV training had on vertical jump, sprint, and agility performance in nonelite athletes. Twenty-four sport science students (16 men and 8 women) were randomly assigned to 2 groups: WBV training or control. Each group included 8 men and 4 women. Countermovement jump (CMJ) height, squat jump (SJ) height, sprint speed over 5, 10, and 20 m, and agility (505, up and back) were performed by each participant before and after 9 days of either no training (control) or WBV training. Perceived discomfort of every participant was recorded after daily WBV exposure and nonexposure. There were no significant differences between WBV and control groups for CMJ, SJ, sprints, and agility. Perceived discomfort differed between the first and subsequent days of WBV training (p < 0.05); however, there was no difference between the WBV and control groups. It is concluded that short-term WBV training did not enhance performance in nonelite athletes.

  11. [Continuous electrocardiographic recording during a first parachute jump].

    Science.gov (United States)

    Galante, J; Hernández, A; Colín, L; Camacho, B; Verdejo, J; Férez, S

    1988-01-01

    The behavior of the cardiac rhythm under intense stress was studied with continuous electrocardiographic recording during the first jump with an automatic parachute in 13 members of the Universidad Nacional Autónoma de México sky diving club. There were 12 male (92.3%) and one female (7.68) with an average age of 22.8 years. A complete clinical history, 12 lead electrocardiogram and a treadmill stress test were performed two weeks before jumping. A two-channel Holter recording system was hooked up 30 min. before boarding the airplane and was turned off one hour later. The heart rate values were compared two weeks prior (64.5 beats/min), before (112.8 beats/min), during (170 beats/min) and after the jump (122.8 beats/min). The mean difference between each phase was statistically significant with p less than 0.001 values. The observed cardiac rhythm was sinus tachycardia in each case. In six cases (43.6%) 22 episodes of sudden decrease of the heart rate were seen and there were no major rhythm or conduction disturbances. The urinary catecholamines were similar in nine cases (69.2%) after the jump (x 51.2 micrograms/100 ml) and two weeks later in four control cases (x 10.3 micrograms/100 ml). We concluded there were no significant rhythm disturbances in the presence of an intense but brief stress condition in young healthy people. This study was classified as longitudinally, descriptive, experimental and projective.

  12. LINEAR QUADRATIC NONZERO-SUM DIFFERENTIAL GAMES WITH RANDOM JUMPS

    Institute of Scientific and Technical Information of China (English)

    WU Zhen; YU Zhi-yong

    2005-01-01

    The existence and uniqueness of the solutions for one kind of forwardbackward stochastic differential equations with Brownian motion and Poisson process as the noise source were given under the monotone conditions. Then these results were applied to nonzero-sum differential games with random jumps to get the explicit form of the open-loop Nash equilibrium point by the solution of the forward-backward stochastic differential equations.

  13. Asymptotic Expansions of Transition Densities for Hybrid Jump-Diffusions

    Institute of Scientific and Technical Information of China (English)

    Yuan-jin Liu; G.Yin

    2004-01-01

    A class of hybrid jump diffusions modulated by a Markov chain is considered in this work.The motivation stems from insurance risk models,and emerging applications in production planning and wireless communications.The models are hybrid in that they involve both continuous dynamics and discrete events.Under suitable conditions,asymptotic expansions of the transition densities for the underlying processes are developed.The formal expansions are validated and the error bounds obtained.

  14. The beginning of time observed in quantum jumps

    Energy Technology Data Exchange (ETDEWEB)

    Bohm, Arno [CCQS, Physics Department, University of Texas, Austin, TX (United States); Bryant, Peter W. [IBM Research, Rio de Janeiro (Brazil); Uncu, Haydar [Department of Physics, Adnan Menderes University, Aydin (Turkey); Wickramasekara, Sujeev [Department of Physics, Grinnell College, Grinnell, IA (United States); Schleich, Wolfgang P. [Institut fuer Quantenphysik and Center for Integrated Quantum Science and Technology, Universitaet Ulm (Germany); Hagler Institute for Advanced Study, Texas A and M University, College Station, TX (United States); Texas A and M AgriLife, Institute for Quantum Science and Engineering (IQSE) and Department of Physics and Astronomy, Texas A and M University, College Station, TX (United States)

    2017-06-15

    The phenomenon of quantum jumps observed in a single ion stored in a trap brings to light intimate connections between three different concepts of quantum physics: (i) quantum state trajectories, (ii) Gamow states, and (iii) the arrow of time. In particular, it allows us to identify the starting time of the semigroup time evolution. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  15. The Economics of Bitcoins - Market Characteristics and Price Jumps

    OpenAIRE

    Gronwald, Marc

    2014-01-01

    This paper deals with the economics of Bitcoins in two ways. First, it broadens the discussion on how to capture Bitcoins using economic terms. Center stage in this analysis take the discussion of some unique characteristics of this market as well as the comparison of Bitcoins and gold. Second, the paper empirically analyses Bitcoin prices using an autoregressive jump-intensity GARCH model; a model tested and proven by the empirical finance community. Results suggest that Bitcoin price are pa...

  16. Diversified Portfolios with Jumps in a Benchmark Framework

    OpenAIRE

    Eckhard Platen

    2004-01-01

    This paper considers diversifed portfolios in a sequence of jump diffusion market models. Conditions for the approximation of the growth optimal portfolio (GOP) by diversified portfolios are provided. Under realistic assumptions, it is shown that diversified portfolios approximate the GOP without requiring any major model specifications. This provides a basis for systematic use of diversified stock indices as proxies for the GOP in derivative pricing, risk management and portfolio optimization.

  17. Anticipating Viral Species Jumps: Bioinformatics and Data Needs

    Science.gov (United States)

    2011-06-01

    and colleagues are currently adding SF for dengue, hepatitis C and pox viruses by manually searching the literature; in the future they will begin...2008). Hendra viruses from Australian fruit bats have caused small , isolated fatal disease outbreaks among horses and fatal spillover cases among...species jump to humans. They and others (Pepin et al. 2010) point out that the available sample size is too small to draw conclusions about the

  18. Incomplete Financial Markets and Jumps in Asset Prices

    DEFF Research Database (Denmark)

    Crès, Hervé; Markeprand, Tobias Ejnar; Tvede, Mich

    A dynamic pure-exchange general equilibrium model with uncertainty is studied. Fundamentals are supposed to depend continuously on states of nature. It is shown that: 1. if financial markets are complete, then asset prices vary continuously with states of nature, and; 2. if financial markets...... are incomplete, jumps in asset prices may be unavoidable. Consequently incomplete financial markets may increase volatility in asset prices significantly....

  19. Soap film dynamics and topological jumps under continuous deformation

    Science.gov (United States)

    Moffatt, Keith

    2015-11-01

    Consider the dynamics of a soap-film bounded by a flexible wire (or wires) which can be continuously and slowly deformed. At each instant the soap-film relaxes in quasi-static manner to a minimum-area (i.e. minimum-energy) state compatible with the boundary configuration. This can however pass through a critical configuration at which a topological jump is inevitable. We have studied an interesting example of this behaviour: the jump of a one-sided (Möbius strip) soap-film to a two-sided film as the boundary is unfolded and untwisted from the double cover of a circle. The nature of this jump will be demonstrated and explained. More generally, dynamical systems have a natural tendency to relax through dissipative processes to a minimum-energy state, subject to any relevant constraints. An example is provided by the relaxation of a magnetic field in a perfectly conducting but viscous fluid, subject to the constraint that the magnetic field lines are frozen in the fluid. One may infer the existence of magnetostatic equilibria (and analogous steady Euler flows) of arbitrary field-line topology. In general, discontinuities (current sheets) appear during this relaxation process, and this is where reconnection of field-lines (with associated change of topology) can occur. Just as for the soap film, slow change of boundary conditions can lead to critical conditions in which such topological jumps are inevitable. (Work in collaboration with Ray Goldstein, Adriana Pesci, Renzo Ricca and Gareth Alexander.) This work was supported by Engineering and Physical Sciences Research Council Grant EP/I036060/1.

  20. Shock jump relations for a dusty gas atmosphere

    Science.gov (United States)

    Anand, R. K.

    2014-01-01

    This paper presents simplified forms of jump relations for one dimensional shock waves propagating in a dusty gas. The dusty gas is assumed to be a mixture of a perfect gas and spherically small solid particles, in which solid particles are continuously distributed. The simplified jump relations for the pressure, the temperature, the density, the velocity of the mixture and the speed of sound have been derived in terms of the upstream Mach number. The expressions for the adiabatic compressibility of the mixture and the change-in-entropy across the shock front have also been derived in terms of the upstream Mach number. Further, the handy forms of shock jump relations have been obtained in terms of the initial volume fraction of small solid particles and the ratio of specific heats of the mixture, simultaneously for the two cases viz., (i) when the shock is weak and, (ii) when it is strong. The simplified shock jump relations reduce to the Rankine-Hugoniot conditions for shock waves in an ideal gas when the mass fraction (concentration) of solid particles in the mixture becomes zero. Finally, the effects due to the mass fraction of solid particles in the mixture, and the ratio of the density of solid particles to the initial density of the gas are studied on the pressure, the temperature, the density, the velocity of the mixture, the speed of sound, the adiabatic compressibility of the mixture and the change-in-entropy across the shock front. The results provided a clear picture of whether and how the presence of dust particles affects the flow field behind the shock front. The aim of this paper is to contribute to the understanding of how the shock waves behave in the gas-solid particle two-phase flows.

  1. Forecasting Exchange Rate Volatility in the Presence of Jumps

    OpenAIRE

    Busch, Thomas; Christensen, Bent Jesper; Nielsen, Morten Ørregaard

    2005-01-01

    We study measures of foreign exchange rate volatility based on high-frequency (5-minute) $/DM exchange rate returns using recent nonparametric statistical techniques to compute realized return volatility and its separate continuous sample path and jump components, and measures based on prices of exchange rate futures options, allowing calculation of option implied volatility. We find that implied volatility is an informationally efficient but biased forecast of future realized exchange rate v...

  2. Stabilization of stochastic systems with hidden Markovian jumps

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    This paper considers the adaptive control of discrete-time hybrid stochastic systems with unknown randomly jumping parameters described by a finite-state hidden Markov chain. An intuitive yet longstanding conjecture in this area is that such hybrid systems can be adaptively stabilized whenever the rate of transition of the hidden Markov chain is small enough. This paper provides a rigorous positive answer to this conjecture by establishing the global stability of a gradient-algorithm-based adaptive linear-quadratic control.

  3. Aerodynamics of ski jumping flight and its control: II. Simulations

    Science.gov (United States)

    Lee, Jungil; Lee, Hansol; Kim, Woojin; Choi, Haecheon

    2015-11-01

    In a ski jumping competition, it is essential to analyze the effect of various posture parameters of a ski jumper to achieve a longer flight distance. For this purpose, we conduct a large eddy simulation (LES) of turbulent flow past a model ski jumper which is obtained by 3D scanning a ski jumper's body (Mr. Chil-Ku Kang, member of the Korean national team). The angle of attack of the jump ski is 30° and the Reynolds number based on the length of the jump ski is 540,000. The flow statistics including the drag and lift coefficients in flight are in good agreements with our own experimental data. We investigate the flow characteristics such as the flow separation and three-dimensional vortical structures and their effects on the drag and lift. In addition to LES, we construct a simple geometric model of a ski jumper where each part of the ski jumper is modeled as a canonical bluff body such as the sphere, cylinder and flat plate, to find its optimal posture. The results from this approach will be compared with those by LES and discussed. Supported by NRF program (2014M3C1B1033848, 2014R1A1A1002671).

  4. Kinematic Chains in Ski Jumping In-run Posture.

    Science.gov (United States)

    Janurová, Eva; Janura, Miroslav; Cabell, Lee; Svoboda, Zdeněk; Vařeka, Ivan; Elfmark, Milan

    2013-12-18

    The concept of kinematic chains has been systematically applied to biological systems since the 1950s. The course of a ski jump can be characterized as a change between closed and open kinematic chains. The purpose of this study was to determine a relationship between adjacent segments within the ski jumper's body's kinematic chain during the in-run phase of the ski jump. The in-run positions of 267 elite male ski jumpers who participated in the FIS World Cup events in Innsbruck, Austria, between 1992 and 2001 were analyzed (656 jumps). Two-dimensional (2-D) kinematic data were collected from the bodies of the subjects. Relationships between adjacent segments of the kinematic chain in the ski jumper's body at the in-run position are greater nearer the chain's ground contact. The coefficient of determination between the ankle and knee joint angles is 0.67. Changes in the segments' positions in the kinematic chain of the ski jumper's body are stable during longitudinal assessment. Changes in shank and thigh positions, in the sense of increase or decrease, are the same.

  5. Bubble entrainment, spray and splashing at hydraulic jumps

    Institute of Scientific and Technical Information of China (English)

    CHANSON Hubert

    2006-01-01

    The sudden transition from a high-velocity, supercritical open channel flow into a slow-moving sub-critical flow is a hydraulic jump. Such a flow is characterised by a sudden rise of the free-surface, with some strong energy dissipation and air entrainment, waves and spray. New two-phase flow measurements were performed in the developing flow region using a large-size facility operating at large Reynolds numbers. The experimental results demonstrated the complexity of the flow with a developing mixing layer in which entrained bubbles are advected in a high shear stress flow. The relationship between bubble count rates and void fractions was non-unique in the shear zone, supporting earlier observations of some form of double diffusion process between momentum and air bubbles. In the upper region, the flow consisted primarily of water drops and packets surrounded by air. Visually significant pray and splashing were significant above the jump roller. The present study is the first comprehensive study detailing the two-phase flow properties of both the bubbly and spray regions of hydraulic jumps, a first step towards understanding the interactions between bubble entrainment and droplet ejection processes.

  6. Overcoming horizontal depolarizing resonances with multiple tune jumps

    Science.gov (United States)

    Huang, H.; Ahrens, L. A.; Bai, M.; Brown, K. A.; Dutheil, Y.; Gardner, C.; Glenn, J. W.; Lin, F.; MacKay, W. W.; Meot, F.; Poblaguev, A.; Ranjbar, V.; Roser, T.; Schoefer, V.; Tepikian, S.; Tsoupas, N.; Yip, K.; Zelenski, A.; Zeno, K.

    2014-08-01

    In a medium energy proton synchrotron, strong enough partial Siberian snakes can be used to avoid both imperfection and vertical intrinsic depolarizing resonances. However, partial snakes tilt the stable spin direction away from vertical, which generates depolarizing resonances associated with horizontal tune. The relatively weak but numerous horizontal intrinsic resonances are the main source of the residual polarization losses. A pair of horizontal tune jump quads have been used in the Brookhaven Alternating Gradient Synchrotron to overcome these weak resonances. The locations of the two quads have to be chosen such that the disturbance to the beam optics is minimum. The emittance growth has to be mitigated for this method to work. In addition, this technique needs very accurate jump timing. Using two partial Siberian snakes, with vertical tune inside the spin tune gap and 80% polarization at the Alternating Gradient Synchrotron injection, polarized proton beam had reached 1.5×1011 proton per bunch with 65% polarization. With the tune jump timing optimized and emittance preserved, more than 70% polarization with 2×1011 protons per bunch has been achieved. The polarization transport efficiency is close to 90%.

  7. Jump dynamics with structural breaks for crude oil prices

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Yen-Hsien [Department of Finance, Chung Yuan Christian University (China); Hu, Hsu-Ning [Department of Money, Banking and Finance, TamKang University (China); Chiou, Jer-Shiou [Department of Finance and Banking, Shih Chien University, 70 Ta-Chih Street, Taipei 104 (China)

    2010-03-15

    This study investigates the joint phenomena of permanent and transitory components in conditional variance and jump intensity along with verification of structural breaks for crude oil prices. We adopt a Component-ARJI model with structural break analysis, utilizing daily data on West Texas Intermediate crude oil spot and futures contracts. The analytical results verify the existence of permanent and transitory components in conditional variance, with the permanent component of conditional variance increasing with the occurrence of a sudden major event (such as the Iraqi Invasion of Kuwait, Operation Desert Storm and the war between the US and Iraq), and a relatively greater increase in the transitory component over the same period. Notably, jump intensity fluctuates with an increase in the transitory component of conditional variance in response to abnormal events. It is the transitory component which serves as the primary influential factor for jumps in returns; therefore, speculators are willing to take large risks, particularly with respect to anticipating future price movements, or gambling, in the hopes of rapidly making substantial gains; thus, speculators prefer the temporary volatility component and engage in trade activities. However, investors prefer the permanent volatility component, because they may well be better off relocating their assets into more stable portfolios to outperform the market portfolio over the long run. (author)

  8. JUMP LANDING CHARACTERISTICS IN ELITE SOCCER PLAYERS WITH CEREBRAL PALSY

    Directory of Open Access Journals (Sweden)

    Jesús Cámara

    2013-04-01

    Full Text Available The aim of the present study was to analyse the parameters that characterize the vertical ground reaction force during the landing phase of a jump, and to determine the relationship among these parameters in elite soccer players with cerebral palsy (CP. Thirteen male members of the Spanish national soccer team for people with CP (mean age: 27.1 ± 4.7 years volunteered for the study. Each participant performed three counter movement jumps. The characteristics of the first peak of the vertical ground reaction force during the landing phase of a jump, which corresponds to the forefoot contact with the ground, were similar to the results obtained in previous studies. However, a higher magnitude of rearfoot contact with the ground (F2 was observed in participants with CP than in participants without CP. Furthermore, a significant correlation between F2 magnitude and the elapsed time until its production (T2 was not observed (r = -0.474 for p = 0.102. This result implies that a landing technique based on a delay in the production of F2 might not be effective to reduce its magnitude, contrary to what has been observed in participants without CP. The absence of a significant correlation between these two parameters in the present study, and the high magnitude of F2, suggest that elite soccer players with CP should use footwear with proper cushioning characteristics.

  9. Overcoming horizontal depolarizing resonances with multiple tune jumps

    Directory of Open Access Journals (Sweden)

    H. Huang

    2014-08-01

    Full Text Available In a medium energy proton synchrotron, strong enough partial Siberian snakes can be used to avoid both imperfection and vertical intrinsic depolarizing resonances. However, partial snakes tilt the stable spin direction away from vertical, which generates depolarizing resonances associated with horizontal tune. The relatively weak but numerous horizontal intrinsic resonances are the main source of the residual polarization losses. A pair of horizontal tune jump quads have been used in the Brookhaven Alternating Gradient Synchrotron to overcome these weak resonances. The locations of the two quads have to be chosen such that the disturbance to the beam optics is minimum. The emittance growth has to be mitigated for this method to work. In addition, this technique needs very accurate jump timing. Using two partial Siberian snakes, with vertical tune inside the spin tune gap and 80% polarization at the Alternating Gradient Synchrotron injection, polarized proton beam had reached 1.5×10^{11} proton per bunch with 65% polarization. With the tune jump timing optimized and emittance preserved, more than 70% polarization with 2×10^{11} protons per bunch has been achieved. The polarization transport efficiency is close to 90%.

  10. The kinematics of swimming and relocation jumps in copepod nauplii

    DEFF Research Database (Denmark)

    Borg, Marc Andersen; Bruno, Eleonora; Kiørboe, Thomas

    2012-01-01

    Copepod nauplii move in a world dominated by viscosity. Their swimming-by-jumping propulsion mode, with alternating power and recovery strokes of three pairs of cephalic appendages, is fundamentally different from the way other microplankters move. Protozoans move using cilia or flagella, and cop......Copepod nauplii move in a world dominated by viscosity. Their swimming-by-jumping propulsion mode, with alternating power and recovery strokes of three pairs of cephalic appendages, is fundamentally different from the way other microplankters move. Protozoans move using cilia or flagella......, and copepodites are equipped with highly specialized swimming legs. In some species the nauplius may also propel itself more slowly through the water by beating and rotating the appendages in a different, more complex pattern. We use high-speed video to describe jumping and swimming in nauplii of three species...... larger copepodites. A slow-swimming mode is only displayed by T. longicornis. In this mode, beating of the appendages results in the creation of a strong feeding current that is about 10 times faster than the average translation speed of the nauplius. The nauplius is thus essentially hovering when...

  11. NONINVASIVE DETERMINATION OF KNEE CARTILAGE DEFORMATION DURING JUMPING

    Directory of Open Access Journals (Sweden)

    Djordje Kosanic

    2009-12-01

    Full Text Available The purpose of this investigation was to use a combination of image processing, force measurements and finite element modeling to calculate deformation of the knee cartilage during jumping. Professional athletes performed jumps analyzed using a force plate and high-speed video camera system. Image processing was performed on each frame of video using a color recognition algorithm. A simplified mass-spring-damper model was utilized for determination of global force and moment on the knee. Custom software for fitting the coupling characteristics was created. Simulated results were used as input data for the finite element calculation of cartilage deformation in the athlete's knee. Computer simulation data was compared with the average experimental ground reaction forces. The results show the three-dimensional mechanical deformation distribution inside the cartilage volume. A combination of the image recognition technology, force plate measurements and the finite element cartilage deformation in the knee may be used in the future as an effective noninvasive tool for prediction of injury during jumping

  12. Peak effect and giant flux jumps in hard superconductors: the problem of “islands” jumps on H-T diagram

    Science.gov (United States)

    Chabanenko, V. V.; Rusakov, V. F.; D'yachenko, A. I.; Piechota, S.; Nabialek, A.; Szymczak, H.

    2000-11-01

    Magnetic properties of superconductors with peak effect were investigated both experimentally and theoretically in frames of the critical state model which incorporates the flux jump instability criterion. Theoretical analyses show some “forbidden” band for flux jumps on the magnetic field axis. Features of H-T diagrams of instability of superconductors with peak effect are discussed.

  13. Dynamical approach to displacement jumps in nanoindentation experiments

    Science.gov (United States)

    K, Srikanth; Ananthakrishna, G.

    2017-01-01

    The load-controlled mode is routinely used in nanoindentation experiments. Yet there are no simulations or models that predict the generic features of force-displacement F -z curves, in particular, the existence of several displacement jumps of decreasing magnitude. Here, we show that the recently developed dislocation dynamical model predicts all the generic features when the model is appropriately coupled to an equation defining the load rate. Since jumps in the indentation depth result from the plastic deformation occurring inside the sample, we devise a method for calculating this contribution by setting up a system of coupled nonlinear time evolution equations for the mobile and forest dislocation densities. The equations are then coupled to the force rate equation. We include nucleation, multiplication, and propagation threshold mechanisms for the mobile dislocations apart from other well known dislocation transformation mechanisms between the mobile and forest dislocations. The commonly used Berkovitch indenter is considered. The ability of the approach is illustrated by adopting experimental parameters such as the indentation rate, the geometrical quantities defining the Berkovitch indenter including the nominal tip radius, and other parameters. We identify specific dislocation mechanisms contributing to different regions of the F -z curve as a first step for obtaining a good fit to a given experimental F -z curve. This is done by studying the influence of the parameters on the model F -z curves. In addition, the study demonstrates that the model predicts all the generic features of nanoindentation such as the existence of an initial elastic branch followed by several displacement jumps of decreasing magnitude, and residual plasticity after unloading for a range of model parameter values. Further, an optimized set of parameter values can be easily determined that gives a good fit to the experimental force-displacement curve for Al single crystals of (110

  14. Jumping sans legs: does elastic energy storage by the vertebral column power terrestrial jumps in bony fishes?

    Science.gov (United States)

    Ashley-Ross, Miriam A; Perlman, Benjamin M; Gibb, Alice C; Long, John H

    2014-02-01

    Despite having no obvious anatomical modifications to facilitate movement over land, numerous small fishes from divergent teleost lineages make brief, voluntary terrestrial forays to escape poor aquatic conditions or to pursue terrestrial prey. Once stranded, these fishes produce a coordinated and effective "tail-flip" jumping behavior, wherein lateral flexion of the axial body into a C-shape, followed by contralateral flexion of the body axis, propels the fish into a ballistic flight-path that covers a distance of multiple body lengths. We ask: how do anatomical structures that evolved in one habitat generate effective movement in a novel habitat? Within this context, we hypothesized that the mechanical properties of the axial skeleton play a critical role in producing effective overland movement, and that tail-flip jumping species demonstrate enhanced elastic energy storage through increased body flexural stiffness or increased body curvature, relative to non-jumping species. To test this hypothesis, we derived a model to predict elastic recoil work from the morphology of the vertebral (neural and hemal) spines. From ground reaction force (GRF) measurements and high-speed video, we calculated elastic recoil work, flexural stiffness, and apparent material stiffness of the body for Micropterus salmoides (a non-jumper) and Kryptolebias marmoratus (adept tail-flip jumper). The model predicted no difference between the two species in work stored by the vertebral spines, and GRF data showed that they produce the same magnitude of mass-specific elastic recoil work. Surprisingly, non-jumper M. salmoides has a stiffer body than tail-flip jumper K. marmoratus. Many tail-flip jumping species possess enlarged, fused hypural bones that support the caudal peduncle, which suggests that the localized structures, rather than the entire axial skeleton, may explain differences in terrestrial performance.

  15. Research on one Bio-inspired Jumping Locomotion Robot for Search and Rescue

    Directory of Open Access Journals (Sweden)

    Dunwen Wei

    2014-10-01

    Full Text Available Jumping locomotion is much more effective than other locomotion means in order to tackle the unstructured and complex environment in research and rescue. Here, a bio-inspired jumping robot with a closed-chain mechanism is proposed to achieve the power amplification during taking-off. Through actuating one variable transmission mechanism to change the transmission ratio, the jumping robot reveals biological characteristics in the phase of posture adjustment when adjusting the height and distance of one jump. The kinematics and dynamics of the simplified jumping mechanism model in one jumping cycle sequence are analysed. A compliant contact model considering nonlinear damping is investigated for jumping performance under different terrain characteristics. The numerical simulation algorithm with regard to solving the dynamical equation is described and simulation results are discussed. Finally, one primary prototype and experiment are described. The experimental results show the distance of jumping in the horizontal direction increases with the increasing gear ratio, while the height of jumping decreases in reverse. The jumping robot can enhance the capability to adapt to unknown cluttered environments, such as those encountered in research and rescue, using this strategy.

  16. Salticid predation as one potential driving force of ant mimicry in jumping spiders.

    Science.gov (United States)

    Huang, Jin-Nan; Cheng, Ren-Chung; Li, Daiqin; Tso, I-Min

    2011-05-07

    Many spiders possess myrmecomorphy, and species of the jumping spider genus Myrmarachne exhibit nearly perfect ant mimicry. Most salticids are diurnal predators with unusually high visual acuity that prey on various arthropods, including conspecifics. In this study, we tested whether predation pressure from large jumping spiders is one possible driving force of perfect ant mimicry in jumping spiders. The results showed that small non-ant-mimicking jumping spiders were readily treated as prey by large ones (no matter whether heterospecific or conspecific) and suffered high attack and mortality rates. The size difference between small and large jumping spiders significantly affected the outcomes of predatory interactions between them: the smaller the juvenile jumping spiders, the higher the predation risk from large ones. The attack and mortality rates of ant-mimicking jumping spiders were significantly lower than those of non-ant-mimicking jumping spiders, indicating that a resemblance to ants could provide protection against salticid predation. However, results of multivariate behavioural analyses showed that the responses of large jumping spiders to ants and ant-mimicking salticids differed significantly. Results of this study indicate that predation pressure from large jumping spiders might be one selection force driving the evolution of nearly perfect myrmecomorphy in spiders and other arthropods.

  17. Relationship between jump landing kinematics and peak ACL force during a jump in downhill skiing: a simulation study.

    Science.gov (United States)

    Heinrich, D; van den Bogert, A J; Nachbauer, W

    2014-06-01

    Recent data highlight that competitive skiers face a high risk of injuries especially during off-balance jump landing maneuvers in downhill skiing. The purpose of the present study was to develop a musculo-skeletal modeling and simulation approach to investigate the cause-and-effect relationship between a perturbed landing position, i.e., joint angles and trunk orientation, and the peak force in the anterior cruciate ligament (ACL) during jump landing. A two-dimensional musculo-skeletal model was developed and a baseline simulation was obtained reproducing measurement data of a reference landing movement. Based on the baseline simulation, a series of perturbed landing simulations (n = 1000) was generated. Multiple linear regression was performed to determine a relationship between peak ACL force and the perturbed landing posture. Increased backward lean, hip flexion, knee extension, and ankle dorsiflexion as well as an asymmetric position were related to higher peak ACL forces during jump landing. The orientation of the trunk of the skier was identified as the most important predictor accounting for 60% of the variance of the peak ACL force in the simulations. Teaching of tactical decisions and the inclusion of exercise regimens in ACL injury prevention programs to improve trunk control during landing motions in downhill skiing was concluded. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  18. Surface electromyographic assessment of the effect of static stretching of the gastrocnemius on vertical jump performance.

    Science.gov (United States)

    Wallmann, Harvey W; Mercer, John A; McWhorter, J Wesley

    2005-08-01

    The purpose of this study was to investigate the effects of static stretching of the gastrocnemius muscle on maximal vertical jump performance using electromyographic activity (EMG) of the gastrocnemius musculature to record muscle activation during vertical jump performance. Fourteen healthy adults (8 men and 6 women) aged 18-34 years, who were familiar with the vertical jumping task and had no lower extremity injuries or any bone or joint disorders within the past year, served as participants for this study. After a brief warm-up, participants performed the following sequence: (a) three baseline maximal vertical jump trials, (b) 15 minutes of quiet sitting and three 30-second bilateral static stretches of the gastrocnemius muscles, and (c) 3 maximal vertical jump trials. Jump height data were collected using the Kistler force plate, while muscle activity was recorded during the jumping and stretching trials using a Noraxon telemetry EMG unit. Vertical jump height data as well as EMG values were averaged for the 3 trials and analyzed using paired t-tests for pre- and poststretching (alpha = 0.05). Vertical jump height was 5.6% lower when poststretch heights were compared with prestretch heights (t = -4.930, p static stretching of the gastrocnemius muscles had a negative effect on maximal jumping performance. The practical importance concerns coaches and athletes, who may want to consider the potential adverse effects of performing static stretching of the gastrocnemius muscles only before a jumping event, as jump height may be negatively affected. Future research is required to identify the mechanisms that affect vertical jump performance.

  19. Effects of 12-weeks resistance training on sprint and jump performance in competitive adolescent rugby union players.

    Science.gov (United States)

    Harries, Simon K; Lubans, David R; Buxton, Anthony; MacDougall, Thomas H J; Callister, Robin

    2017-07-17

    Sprint performance is an important characteristic for success in many sports, including rugby union. Resistance training is used to increase muscular fitness (i.e. strength, endurance and power) and may also be effective for improving sprint and jump performances. The aims of this study were to examine the effects of resistance training using two different periodized programs (linear and daily undulating) on sprint and jump performance and explore relationships between performance measures. Sixteen male (16.9 ± 1.0 y) adolescent rugby union players participated in 12 weeks of resistance training. A further 10 male (15.5 ± 1.0 y) participants were recruited as a control group. Assessments of strength (box squat), 10 and 20 m sprint (electronically timed), and jump height (maximal unloaded (body mass only) and loaded (body mass + 10 kg) countermovement jumps) were conducted before and after 12 weeks training. Large to very large increases in 1RM box squat (linear: 33.9%; p < 0.001; ES = 1.64; daily undulating: 44.5%; p < 0.001; ES = 2.33) were observed after training. Small decreases were seen in 10 (linear: -1.6%; p = 0.171; ES = -0.84; daily undulating: -2.5%; p = 0.038; ES = -0.36) and 20 m (linear: -0.5%; p = 0.506; ES = -0.20; daily undulating: -1.7%; p = 0.047; ES = -0.27) sprint times. Small-to-moderate associations between changes in lower body strength and improvements in 10 and 20 m sprint times were found. Resistance training increases lower body strength in adolescent rugby union players and increases in lower body strength may transfer to improved sprinting performance with improvements following daily undulating periodized resistance training slightly superior.

  20. Intermittent But Not Continuous Static Stretching Improves Subsequent Vertical Jump Performance In Flexibility-Trained Athletes.

    Science.gov (United States)

    Bogdanis, Gregory C; Donti, Olyvia; Tsolakis, Charilaos; Smilios, Ilias; Bishop, David J

    2017-02-23

    This study examined changes in countermovement jump (CMJ) height after an intermittent or a continuous static stretching protocol of equal total duration. Sixteen male, elite-level gymnasts performed 90 s of intermittent (3 x 30 s with 30 s rest) or continuous stretching (90 s) of the quadriceps muscle. A single-leg stretching and jumping design was used, with the contra-lateral limb serving as a control. The same individuals performed both conditions with alternate legs in a randomized, counterbalanced order. One leg CMJ height was measured for the stretched and the control leg after warm-up, immediately after stretching, and at regular intervals for 10 min after stretching. Range of motion (ROM) of the hip and knee joints was measured before, after, and 10 min post-stretching. Compared to the control leg, intermittent stretching increased CMJ height by 8.1±2.0%, 4 min into recovery (+2.2±2.0 cm, 95%CI: 1.0-3.4 cm, p=0.001), while continuous stretching decreased CMJ height by 17.5±3.3% immediately after (-2.9±1.7 cm, 95%CI: -2.0 to -3.7 cm, p=0.001) and by 12.0±2.7% one min after stretching (-2.2±2.1 cm, 95%CI: -1.2 to -3.2 cm, p=0.001). The increases in hip (2.9 and 3.6, p=0.001. d=2.4) and knee joint ROM (5.1 and 6.1, p=0.001. d=0.85) after the intermittent and continuous stretching protocols were not different. The opposite effects of intermittent vs. continuous stretching on subsequent CMJ performance suggests that stretching mode is an important variable when examining the acute effects of static stretching on performance in flexibility-trained athletes.

  1. Asymptotic Behaviour and Extinction of Delay Lotka-Volterra Model with Jump-Diffusion

    Directory of Open Access Journals (Sweden)

    Dan Li

    2014-01-01

    Full Text Available This paper studies the effect of jump-diffusion random environmental perturbations on the asymptotic behaviour and extinction of Lotka-Volterra population dynamics with delays. The contributions of this paper lie in the following: (a to consider delay stochastic differential equation with jumps, we introduce a proper initial data space, in which the initial data may be discontinuous function with downward jumps; (b we show that the delay stochastic differential equation with jumps associated with our model has a unique global positive solution and give sufficient conditions that ensure stochastically ultimate boundedness, moment average boundedness in time, and asymptotic polynomial growth of our model; (c the sufficient conditions for the extinction of the system are obtained, which generalized the former results and showed that the sufficiently large random jump magnitudes and intensity (average rate of jump events arrival may lead to extinction of the population.

  2. Telemetric control of heart adaptation during automatic and free-fall parachute jumps.

    Science.gov (United States)

    Deroanne, R; Cession-Fossion, A; Juchmes, J; Servais, J C; Petit, J M

    1975-02-01

    Telmetered heart rate recordings have been ovtaine from 17 parachutists (6 during automatic jumps) 9 Catecholamine (adrenaline and noradrenaline) concentrations have been measured in urine and plasma of six of these subjects. No difference appears between heart rates recorded in the two jumps at egress and at parachute deployment. On the other hand, higher heart rate values are recorded during automatic jumps during descent and at ground impace. The urine catecholamine analysis after jump shows a statistically significant increase in adrenaline and noradrenaline concentration. It is suggested that simulation of the orthosympathetic system is due to two facts; muscular work performed during jumping and the emotional stress which it involves. The importance of these two causes varies with the jump circumstances.

  3. Giant flux jumps through a thin superconducting Nb film in a vortex free region

    Energy Technology Data Exchange (ETDEWEB)

    Tsindlekht, M.I., E-mail: mtsindl@vms.huji.ac.il [The Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 91904 (Israel); Genkin, V.M.; Felner, I.; Zeides, F.; Katz, N. [The Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 91904 (Israel); Gazi, Š.; Chromik, Š. [The Institute of Electrical Engineering SAS, Dúbravská cesta 9, 84104 Bratislava (Slovakia)

    2016-10-15

    Highlights: Giant magnetic flux jumps into thin-walled cylinder were measured using peak up coil method in a swept magnetic field. Magnetic moment jumps were observed in magnetic fields lower and above Hc1. - Abstract: We measure the dynamics of magnetic field penetration into thin-walled superconducting niobium cylinders. It is shown that magnetic field penetrates through the wall of a cylinder in a series of giant jumps with amplitude 1 - 2 mT and duration of less than a microsecond in a wide range of magnetic fields, including the vortex free region. Surprisingly, the jumps take place when the total current in the wall, not the current density, exceeds a critical value. In addition, there are small jumps and/or smooth penetration, but their contribution reaches only ≃ 20 % of the total penetrating flux. The number of jumps decreases with increased temperature. Thermomagnetic instabilities cannot explain the experimental observations.

  4. Phase jump method for efficiency enhancement in free-electron lasers

    Directory of Open Access Journals (Sweden)

    Alan Mak

    2017-06-01

    Full Text Available The efficiency of a free-electron laser can be enhanced by the phase jump method. The method utilizes the phase-shifting chicanes in the drift sections between the undulator segments. By applying appropriate phase jumps, the microbunched electron beam can decelerate and radiate coherently beyond the initial saturation, enabling further energy transfer to the optical beam. This article presents a new physics model for the phase jump method, and supports it with numerical simulations. Based on the electron dynamics in the longitudinal phase space, the model describes the energy extraction mechanism, and addresses the selection criteria for the phase jump magnitude. While the ponderomotive bucket is stationary, energy can be extracted from electrons outside the bucket. With the aid of the new model, a comparison is made between the phase jump method and undulator tapering. The model also explores the potential of the phase jump method to suppress the growth of synchrotron sidebands in the optical spectrum.

  5. Phase jump method for efficiency enhancement in free-electron lasers

    Science.gov (United States)

    Mak, Alan; Curbis, Francesca; Werin, Sverker

    2017-06-01

    The efficiency of a free-electron laser can be enhanced by the phase jump method. The method utilizes the phase-shifting chicanes in the drift sections between the undulator segments. By applying appropriate phase jumps, the microbunched electron beam can decelerate and radiate coherently beyond the initial saturation, enabling further energy transfer to the optical beam. This article presents a new physics model for the phase jump method, and supports it with numerical simulations. Based on the electron dynamics in the longitudinal phase space, the model describes the energy extraction mechanism, and addresses the selection criteria for the phase jump magnitude. While the ponderomotive bucket is stationary, energy can be extracted from electrons outside the bucket. With the aid of the new model, a comparison is made between the phase jump method and undulator tapering. The model also explores the potential of the phase jump method to suppress the growth of synchrotron sidebands in the optical spectrum.

  6. Asymmetrical loading demands associated with vertical jump landings in people with unilateral transtibial amputation

    OpenAIRE

    Marlene Schoeman, PhD; Ceri E. Diss, PhD; Siobhan C. Strike, PhD

    2014-01-01

    Loading symmetry during vertical jump landings between a person with amputation’s intact and prosthetic limbs was assessed to determine the role of each limb in controlling the downward momentum of the center of mass during landing. Six participants with unilateral transtibial amputation (TTA) and ten nondisabled participants completed 10 maximal vertical jumps, of which the highest jump was analyzed. Contralateral symmetry was assessed through the Symmetry Index (SI), while symmetry at the g...

  7. A GENERALIZED EXPLICIT SOLUTION OF THE SEQUENT DEPTH RATIO FOR THE HYDRAULIC JUMP

    Institute of Scientific and Technical Information of China (English)

    NI Han-gen; LIU Ya-kun

    2005-01-01

    By use of the property of the momentum equation describing the hydraulic jump in rectangular channels, a generalized solution of the sequent depth ratio was given. On the basis of the generalized solution the explicit solutions of the sequent depth ratio were obtained for the hydraulic jump in gradual enlargements,the corresponding relative energy losses were also presented, and a method to determine the location of hydraulic jump in gradual enlargements was proposed.

  8. Jump Variation Estimation with Noisy High Frequency Financial Data via Wavelets

    Directory of Open Access Journals (Sweden)

    Xin Zhang

    2016-08-01

    Full Text Available This paper develops a method to improve the estimation of jump variation using high frequency data with the existence of market microstructure noises. Accurate estimation of jump variation is in high demand, as it is an important component of volatility in finance for portfolio allocation, derivative pricing and risk management. The method has a two-step procedure with detection and estimation. In Step 1, we detect the jump locations by performing wavelet transformation on the observed noisy price processes. Since wavelet coefficients are significantly larger at the jump locations than the others, we calibrate the wavelet coefficients through a threshold and declare jump points if the absolute wavelet coefficients exceed the threshold. In Step 2 we estimate the jump variation by averaging noisy price processes at each side of a declared jump point and then taking the difference between the two averages of the jump point. Specifically, for each jump location detected in Step 1, we get two averages from the observed noisy price processes, one before the detected jump location and one after it, and then take their difference to estimate the jump variation. Theoretically, we show that the two-step procedure based on average realized volatility processes can achieve a convergence rate close to O P ( n − 4 / 9 , which is better than the convergence rate O P ( n − 1 / 4 for the procedure based on the original noisy process, where n is the sample size. Numerically, the method based on average realized volatility processes indeed performs better than that based on the price processes. Empirically, we study the distribution of jump variation using Dow Jones Industrial Average stocks and compare the results using the original price process and the average realized volatility processes.

  9. Electromagnetic Transient Response Analysis of DFIG under Cascading Grid Faults Considering Phase Angel Jumps

    DEFF Research Database (Denmark)

    Wang, Yun; Wu, Qiuwei

    2014-01-01

    This paper analysis the electromagnetic transient response characteristics of DFIG under symmetrical and asymmetrical cascading grid fault conditions considering phaseangel jump of grid. On deriving the dynamic equations of the DFIG with considering multiple constraints on balanced and unbalanced...... conditions, phase angel jumps, interval of cascading fault, electromagnetic transient characteristics, the principle of the DFIG response under cascading voltage fault can be extract. The influence of grid angel jump on the transient characteristic of DFIG is analyzed and electromagnetic response...

  10. Adaptive Continuous time Markov Chain Approximation Model to\\ud General Jump-Diffusions

    OpenAIRE

    Cerrato, Mario; Lo, Chia Chun; Skindilias, Konstantinos

    2011-01-01

    We propose a non-equidistant Q rate matrix formula and an adaptive numerical algorithm for a continuous time Markov chain to approximate jump-diffusions with affine or non-affine functional specifications. Our approach also accommodates state-dependent jump intensity and jump distribution, a flexibility that is very hard to achieve with other numerical methods. The Kologorov-Smirnov test shows that the proposed Markov chain transition density converges to the one given by the likelihood expan...

  11. SHORT-TERM JUMP ACTIVITY ON BONE METABOLISM IN FEMALE COLLEGE-AGED NON-ATHLETES

    Directory of Open Access Journals (Sweden)

    Kohei Kishimoto

    2012-03-01

    Full Text Available There have been few studies examining the short-term effect of high-impact activities on bone metabolism measured by bone serum marker concentrations. The purpose of this study was to examine the effect of short-term high-impact jump activity on bone turnover in female college-aged non-athletes. Twenty six healthy females were randomly assigned to a control or jump group. The subjects jumped 5 days per week for 2 weeks. The participants completed 10 jumps per session. A general health questionnaire and a bone-specific physical activity assessment instrument (BPAQ were completed. BPAQ scores were calculated based on the past history of exercise. Blood draws were taken in both groups before and after the two-week experimental period. The vertical ground reaction force (VGRF of all jumps and jump height were measured for each subject daily and the osteogenic index (OI was measured. Concentrations of serum osteocalcin (OC, Bone Specific Alkaline Phosphatase (BAP, C-Terminal Telopeptides of Type I Collagen (CTX and plasma Tartrate-Resistant Acid Phosphatase (TRAP5b were assessed pre and post jump protocol to measure bone formation and resoprtion respectively. A significant interaction (time x group was found in TRAP5b, and BAP values (p < 0.05. There was a significant decrease in CTX and BAP values in the jump group (p < 0.05 after the two week jump protocol. No significant interactions or changes were observed in OC values for either the jump or the control group. Two weeks of jump activity consisting of 10 jumps/day for 5 days/week with a weekly osteogenic index of 52.6 significantly decreased markers of bone resorption (TRAP5b and CTX and bone formation (BAP in young female non- athletes.

  12. Differential effects of 30- vs. 60-second static muscle stretching on vertical jump performance.

    Science.gov (United States)

    Pinto, Matheus D; Wilhelm, Eurico N; Tricoli, Valmor; Pinto, Ronei S; Blazevich, Anthony J

    2014-12-01

    It has been proposed that pre-exercise static stretching may reduce muscle force and power. Recent systematic and meta-analytical reviews have proposed a threshold regarding the effect of short (stretching durations on subsequent performance in a multi-joint task (e.g., jump performance), although its effect on power output remains less clear. Furthermore, no single experimental study has explicitly compared the effect of short (e.g., 30 seconds) and moderate (60 seconds) durations of continuous static stretching on multi-joint performance. Therefore, the aim of the present study was determine the effect of acute short- and moderate-duration continuous stretching interventions on vertical jump performance and power output. Sixteen physically active men (21.0 ± 1.9 years; 1.7 ± 0.1 m; 78.4 ± 12.1 kg) volunteered for the study. After familiarization, subjects attended the laboratory for 3 testing sessions. In the nonstretching (NS) condition, subjects performed a countermovement jump (CMJ) test without a preceding stretching bout. In the other 2 conditions, subjects performed 30-second (30SS; 4 minutes) or 60-second (60SS; 8 minutes) static stretching bouts in calf muscles, hamstrings, gluteus maximus, and quadriceps, respectively, followed by the CMJ test. Results were compared by repeated-measures analysis of variance. In comparison with NS, 60SS resulted in a lower CMJ height (-3.4%, p ≤ 0.05) and average (-2.7%, p ≤ 0.05) and peak power output (-2.0%, p ≤ 0.05), but no difference was observed between 30SS and the other conditions (p > 0.05). These data suggest a dose-dependent effect of stretching on muscular performance, which is in accordance with previous studies. The present results suggest a threshold of continuous static stretching in which muscular power output in a multi-joint task may be impaired immediately following moderate-duration (60 seconds; 8 minutes) static stretching while short-duration (30 seconds; 4 minutes) stretching has a

  13. Motoneuron membrane potentials follow a time inhomogeneous jump diffusion process

    DEFF Research Database (Denmark)

    Jahn, Patrick; Berg, Rune W; Hounsgaard, Jørn

    2011-01-01

    Stochastic leaky integrate-and-fire models are popular due to their simplicity and statistical tractability. They have been widely applied to gain understanding of the underlying mechanisms for spike timing in neurons, and have served as building blocks for more elaborate models. Especially...... models can only be applied over short time windows. However, experimental data show varying time constants, state dependent noise, a graded firing threshold and time-inhomogeneous input. In the present study we build a jump diffusion model that incorporates these features, and introduce a firing...

  14. The physics of articulated toys - a jumping and rotating kangaroo

    CERN Document Server

    Güémez, J

    2014-01-01

    We describe the physics of an articulated toy with an internal source of energy provided by a spiral spring. The toy is a funny low cost kangaroo which jumps and rotates. The study consists of a mechanical and a thermodynamical analysis which makes use of the Newton and center of mass equations, the rotational equations and the first law of thermodynamics. This amazing toy provides a nice demonstrative example how new physics insights can be brought about when links with thermodynamics are established in the study of mechanical systems.

  15. Analysis and design of singular Markovian jump systems

    CERN Document Server

    Wang, Guoliang; Yan, Xinggang

    2014-01-01

    This monograph is an up-to-date presentation of the analysis and design of singular Markovian jump systems (SMJSs) in which the transition rate matrix of the underlying systems is generally uncertain, partially unknown and designed. The problems addressed include stability, stabilization, H∞ control and filtering, observer design, and adaptive control. applications of Markov process are investigated by using Lyapunov theory, linear matrix inequalities (LMIs), S-procedure and the stochastic Barbalat's Lemma, among other techniques.Features of the book include:·???????? study of the stability pr

  16. Stochastic Stability Analysis for Markovian Jump Neutral Nonlinear Systems

    Directory of Open Access Journals (Sweden)

    Bo Wang

    2012-10-01

    Full Text Available In this paper, the stability problem is studied for a class of Markovian jump neutral nonlinear systems with time-varying delay. By Lyapunov-Krasovskii function approach, a novel mean-square exponential stability criterion is derived for the situations that the system's transition rates are completely accessible, partially accessible and non-accessible, respectively. Moreover, the developed stability criterion is extended to the systems with different bounded sector nonlinear constraints. Finally, some numerical examples are provided to illustrate the effectiveness of the proposed methods.

  17. Multifractal Analysis of Infinite Products of Stationary Jump Processes

    Directory of Open Access Journals (Sweden)

    Petteri Mannersalo

    2010-01-01

    Full Text Available There has been a growing interest in constructing stationary measures with known multifractal properties. In an earlier paper, the authors introduced the multifractal products of stochastic processes (MPSP and provided basic properties concerning convergence, nondegeneracy, and scaling of moments. This paper considers a subclass of MPSP which is determined by jump processes with i.i.d. exponentially distributed interjump times. Particularly, the information dimension and a multifractal spectrum of the MPSP are computed. As a side result it is shown that the random partitions imprinted naturally by a family of Poisson point processes are sufficient to determine the spectrum in this case.

  18. Effects of Foam Rolling on Vertical Jump Performance

    OpenAIRE

    Andrew Jones; Brown, Lee E.; Coburn, Jared W.; Guillermo J. Noffal

    2015-01-01

    Background: Foam rolling is a popular activity utilized by strength and conditioning coaches as it is believed to increase muscle length and break up fibrous adhesions located in connective tissue. However, there is little research investigating the effects of foam rolling on athletic performance. Objective: The purpose of this study was to investigate the effects of lower body foam rolling on vertical jump performance. Methods: Twenty males (age 24.05 ± 2.02 years; height 177.43 ± 6.31 cm; m...

  19. Suppressing decoherence of quantum algorithms by jump codes

    CERN Document Server

    Kern, O; Kern, Oliver; Alber, Gernot

    2005-01-01

    The stabilizing properties of one-error correcting jump codes are explored under realistic non-ideal conditions. For this purpose the quantum algorithm of the tent-map is decomposed into a universal set of Hamiltonian quantum gates which ensure perfect correction of spontaneous decay processes under ideal circumstances even if they occur during a gate operation. An entanglement gate is presented which is capable of entangling any two logical qubits of different one-error correcting code spaces. With the help of this gate simultaneous spontaneous decay processes affecting physical qubits of different code spaces can be corrected and decoherence can be suppressed significantly.

  20. Tailored jump operators for purely dissipative quantum magnetism

    Science.gov (United States)

    Weimer, Hendrik

    2017-01-01

    I propose an architecture for the realization of dissipative quantum many-body spin models. The dissipative processes are mediated by interactions with auxiliary particles and lead to a widely tunable class of correlated quantum jump operators. These findings enable the investigation of purely dissipative spin models, where coherent dynamics is entirely absent. I provide a detailed review of a recently introduced variational method to analyze such dissipative quantum many-body systems, and I discuss a specific example in terms of a purely dissipative Heisenberg model, for which I find an additional disordered phase that is not present in the corresponding ground state phase diagram.

  1. Exponential stability for uncertain neutral systems with Markov jumps

    Institute of Scientific and Technical Information of China (English)

    Shuping HE; Fei LIU

    2009-01-01

    This paper deals with the global exponential stability problems for stochastic neutral Markov jump sys-tems(MJSs) with uncertain parameters and multiple time-delays,The delays are respectively considered as constant and time varying cases,and the uncertainties are assumed to be norm bounded.By selecting appropriate Lyapunov-Krasovskii functions,it gives the sufficient condition such that the uncertain neutral MJSs are globally exponentially stochastically stable for all admissible uncertainties.The stability criteria are formulated in the form of linear matrix inequalities(LMIs),which can be easily checked in practice.Finally,two numerical examples are exploited to illustrate the effectiveness of the developed techniques.

  2. Transmittance jump in a thin aluminium layer during laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Bykovsky, N E; Senatsky, Yu V [P N Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Pershin, S M; Samokhin, A A [A M Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

    2016-02-28

    A jump in the transmittance (from ∼0.1% to ∼50% for ∼1 ns) of an optical gate on a Mylar film (a thin aluminium layer on a Lavsan substrate) irradiated by nanosecond (10{sup -7} – 10{sup -8} s) pulses of a neodymium laser with an intensity up to 0.1 GW cm{sup -2} has been recorded. The mechanism of a fast (10{sup -10} – 10{sup -11} s) increase in the transmittance of the aluminium layer upon its overheating (without boiling) to the metal – insulator phase-transition temperature is discussed. (interaction of laser radiation with matter. laser plasma)

  3. Hard-sphere interactions in velocity-jump models

    Science.gov (United States)

    Franz, Benjamin; Taylor-King, Jake P.; Yates, Christian; Erban, Radek

    2016-07-01

    Group-level behavior of particles undergoing a velocity-jump process with hard-sphere interactions is investigated. We derive N -particle transport equations that include the possibility of collisions between particles and apply different approximation techniques to get expressions for the dependence of the collective diffusion coefficient on the number of particles and their diameter. The derived approximations are compared with numerical results obtained from individual-based simulations. The theoretical results compare well with Monte Carlo simulations providing the excluded-volume fraction is small.

  4. Hard-sphere interactions in velocity jump models

    CERN Document Server

    Franz, Benjamin; Yates, Christian; Erban, Radek

    2014-01-01

    Group-level behaviour of particles undergoing a velocity jump process with hard-sphere interactions is investigated. We derive $N$-particle transport equations that include the possibility of collisions between particles and apply different approximation techniques to get expressions for the dependence of the collective diffusion coefficient on the number of particles and their diameter. The derived approximations are compared with numerical results obtained from individual-based simulations. The theoretical results compare well with Monte Carlo simulations providing the excluded volume fraction is small.

  5. Thermodynamics of quantum-jump-conditioned feedback control.

    Science.gov (United States)

    Strasberg, Philipp; Schaller, Gernot; Brandes, Tobias; Esposito, Massimiliano

    2013-12-01

    We consider open quantum systems weakly coupled to thermal reservoirs and subjected to quantum feedback operations triggered with or without delay by monitored quantum jumps. We establish a thermodynamic description of such systems and analyze how the first and second law of thermodynamics are modified by the feedback. We apply our formalism to study the efficiency of a qubit subjected to a quantum feedback control and operating as a heat pump between two reservoirs. We also demonstrate that quantum feedbacks can be used to stabilize coherences in nonequilibrium stationary states which in some cases may even become pure quantum states.

  6. Tailored jump operators for purely dissipative quantum magnetism

    CERN Document Server

    Weimer, Hendrik

    2016-01-01

    I propose an archtitecture for the realization of dissipative quantum many-body spin models. The dissipative processes are mediated by interactions with auxiliary particles and lead to a widely tunable class of correlated quantum jump operators. These findings enable the investigation of purely dissipative spin models, where coherent dynamics is entirely absent. I provide a detailed review of a recently introduced variational method to analyze such dissipative quantum many-body systems, and I discuss a specific example in terms of a purely dissipative Heisenberg model, for which I find an additional disordered phase that is not present in the corresponding ground state phase diagram.

  7. Intertime jump statistics of state-dependent Poisson processes.

    Science.gov (United States)

    Daly, Edoardo; Porporato, Amilcare

    2007-01-01

    A method to obtain the probability distribution of the interarrival times of jump occurrences in systems driven by state-dependent Poisson noise is proposed. Such a method uses the survivor function obtained by a modified version of the master equation associated to the stochastic process under analysis. A model for the timing of human activities shows the capability of state-dependent Poisson noise to generate power-law distributions. The application of the method to a model for neuron dynamics and to a hydrological model accounting for land-atmosphere interaction elucidates the origin of characteristic recurrence intervals and possible persistence in state-dependent Poisson models.

  8. Intertime jump statistics of state-dependent Poisson processes

    Science.gov (United States)

    Daly, Edoardo; Porporato, Amilcare

    2007-01-01

    A method to obtain the probability distribution of the interarrival times of jump occurrences in systems driven by state-dependent Poisson noise is proposed. Such a method uses the survivor function obtained by a modified version of the master equation associated to the stochastic process under analysis. A model for the timing of human activities shows the capability of state-dependent Poisson noise to generate power-law distributions. The application of the method to a model for neuron dynamics and to a hydrological model accounting for land-atmosphere interaction elucidates the origin of characteristic recurrence intervals and possible persistence in state-dependent Poisson models.

  9. Orthogonal Expansions for VIX Options Under Affine Jump Diffusions

    DEFF Research Database (Denmark)

    Barletta, Andrea; Nicolato, Elisa

    2017-01-01

    In this work we derive new closed–form pricing formulas for VIX options in the jump-diffusion SVJJ model proposed by Duffie et al. (2000). Our approach is based on the classic methodology of approximating a density function with an orthogonal expansion of polynomials weighted by a kernel....... Orthogonal expansions based on the Gaussian distribution, such as Edgeworth or Gram–Charlier expansions, have been successfully employed by a number of authors in the context of equity options. However, these expansions are not quite suitable for volatility or variance densities as they inherently assign...

  10. Multiscale integration schemes for jump-diffusion systems

    Energy Technology Data Exchange (ETDEWEB)

    Givon, D.; Kevrekidis, I.G.

    2008-12-09

    We study a two-time-scale system of jump-diffusion stochastic differential equations. We analyze a class of multiscale integration methods for these systems, which, in the spirit of [1], consist of a hybridization between a standard solver for the slow components and short runs for the fast dynamics, which are used to estimate the effect that the fast components have on the slow ones. We obtain explicit bounds for the discrepancy between the results of the multiscale integration method and the slow components of the original system.

  11. A new design of ski-jump-step spillway

    Institute of Scientific and Technical Information of China (English)

    吴建华; 钱尚拓; 马飞

    2016-01-01

    A new kind of ski-jump-step spillway was reported. By means of the effects of the aeration basin, it supplies the sufficient aeration flow from the first step for stepped chutes, especially for large unit discharge. The physical model experiments demonstrated that, this spillway makes a far better hydraulic performance as regards energy dissipation and cavitation damage protection than the current and conventional stepped spillways, and the unit discharge can be enlarged from about 50 m3/s-60 m3/s·m to 118 m3/s·m in order to significantly reduce the width of the spillways.

  12. European option pricing under the Student's t noise with jumps

    Science.gov (United States)

    Wang, Xiao-Tian; Li, Zhe; Zhuang, Le

    2017-03-01

    In this paper we present a new approach to price European options under the Student's t noise with jumps. Through the conditional delta hedging strategy and the minimal mean-square-error hedging, a closed-form solution of the European option value is obtained under the incomplete information case. In particular, we propose a Value-at-Risk-type procedure to estimate the volatility parameter σ such that the pricing error is in accord with the risk preferences of investors. In addition, the numerical results of us show that options are not priced in some cases in an incomplete information market.

  13. The effects of temperature and body mass on jump performance of the locust Locusta migratoria.

    Directory of Open Access Journals (Sweden)

    Edward P Snelling

    Full Text Available Locusts jump by rapidly releasing energy from cuticular springs built into the hind femur that deform when the femur muscle contracts. This study is the first to examine the effect of temperature on jump energy at each life stage of any orthopteran. Ballistics and high-speed cinematography were used to quantify the energy, distance, and take-off angle of the jump at 15, 25, and 35°C in the locust Locusta migratoria. Allometric analysis across the five juvenile stages at 35°C reveals that jump distance (D; m scales with body mass (M; g according to the power equation D = 0.35M (0.17±0.08 (95% CI, jump take-off angle (A; degrees scales as A = 52.5M (0.00±0.06, and jump energy (E; mJ per jump scales as E = 1.91M (1.14±0.09. Temperature has no significant effect on the exponent of these relationships, and only a modest effect on the elevation, with an overall Q10 of 1.08 for jump distance and 1.09 for jump energy. On average, adults jump 87% farther and with 74% more energy than predicted based on juvenile scaling data. The positive allometric scaling of jump distance and jump energy across the juvenile life stages is likely facilitated by the concomitant relative increase in the total length (L f+t; mm of the femur and tibia of the hind leg, L f+t = 34.9M (0.37±0.02. The weak temperature-dependence of jump performance can be traced to the maximum tension of the hind femur muscle and the energy storage capacity of the femur's cuticular springs. The disproportionately greater jump energy and jump distance of adults is associated with relatively longer (12% legs and a relatively larger (11% femur muscle cross-sectional area, which could allow more strain loading into the femur's cuticular springs. Augmented jump performance in volant adult locusts achieves the take-off velocity required to initiate flight.

  14. Adrenocortical responses to repeated parachute jumping and subsequent h-CRH challenge in inexperienced healthy subjects.

    Science.gov (United States)

    Deinzer, R; Kirschbaum, C; Gresele, C; Hellhammer, D H

    1997-04-01

    The present study examined the adrenocortical response to 3 consecutive parachute jumps and a poststress h-CRH challenge. Fifteen participants in a parachute-jumping course took saliva samples for later cortisol analysis every 20 min throughout the day, when they accomplished their very first 3 parachute jumps and throughout a control day. The effects of an h-CRH challenge on salivary cortisol were assessed in the evening of the jumping day and on a control day. Parachute jumping induced 3 distinct highly significant adrenocortical responses. The respective cortisol increases for the first, second, and third jump were 39.4 +/- 26.5 nmol/1, 31.4 +/- 21.4 nmol/l, and 16.5 +/- 11.9 nmol/l. Cortisol responses to the first and second jump did not differ but the response to the third jump was significantly reduced [t(13) = 3.11; p = 0.008]. Two groups of subjects were identified, "decreasers," whose response decreased from one to the other jump, and "increasers," whose response remained unchanged or increased. The magnitude of the preceding cortisol response of decreasers exceeded that of increasers significantly by about 30 nmol. The mean adrenocortical effects of the poststress h-CRH challenge and the time-matched challenge on a control day did not differ although, in 4 subjects, the poststress adrenocortical response to h-CRH was completely suppressed.

  15. Prolactin, thyrotropin, and growth hormone release during stress associated with parachute jumping.

    Science.gov (United States)

    Noel, G L; Dimond, R C; Earll, J M; Frantz, A G

    1976-05-01

    Prolactin, growth hormone, and thyrotropin (TSH) release during the stress of parachute jumping has been evaluated in 14 male subjects. Subjects were studied at several times before and immediately after their first military parachute jump. All three hormones had risen significantly 1 to 14 min after the jump, compared to mean levels measured immediately beforehand. Earlier studies of physical exercise by ourselves and others would suggest that emotional stress played a role in producing changes of this magnitude. We conclude that prolactin, TSH, and growth hormone are released in physiologically significant amounts in association with the stress of parachute jumping.

  16. Discrete Element Method simulations of standing jumps in granular flows down inclines

    Directory of Open Access Journals (Sweden)

    Méjean Ségolène

    2017-01-01

    Full Text Available This paper describes a numerical set-up which uses Discrete Element Method to produce standing jumps in flows of dry granular materials down a slope in two dimensions. The grain-scale force interactions are modeled by a visco-elastic normal force and an elastic tangential force with a Coulomb threshold. We will show how it is possible to reproduce all the shapes of the jumps observed in a previous laboratory study: diffuse versus steep jumps and compressible versus incompressible jumps. Moreover, we will discuss the additional measurements that can be done thanks to discrete element modelling.

  17. Application of a tri-axial accelerometer to estimate jump frequency in volleyball.

    Science.gov (United States)

    Jarning, Jon M; Mok, Kam-Ming; Hansen, Bjørge H; Bahr, Roald

    2015-03-01

    Patellar tendinopathy is prevalent among athletes, and most likely associated with a high jumping load. If methods for estimating jump frequency were available, this could potentially assist in understanding and preventing this condition. The objective of this study was to explore the possibility of using peak vertical acceleration (PVA) or peak resultant acceleration (PRA) measured by an accelerometer to estimate jump frequency. Twelve male elite volleyball players (22.5 ± 1.6 yrs) performed a training protocol consisting of seven typical motion patterns, including jumping and non-jumping movements. Accelerometer data from the trial were obtained using a tri-axial accelerometer. In addition, we collected video data from the trial. Jump-float serving and spike jumping could not be distinguished from non-jumping movements using differences in PVA or PRA. Furthermore, there were substantial inter-participant differences in both the PVA and the PRA within and across movement types (p volleyball. A method for acquiring real-time estimates of jump frequency remains to be verified. However, there are several alternative approaches, and further investigations are needed.

  18. Suicide by jumping from high-rise hotels. Fulton County, Georgia, 1967-1986.

    Science.gov (United States)

    Hanzlick, R; Masterson, K; Walker, B

    1990-12-01

    During a 20-year period from 1967 through 1986, 19 suicidal jumps from high-rise hotels (HRHs) accounted for 24% of all fatal jumping episodes and 1% of all suicides in Fulton County, Georgia, U.S.A. The rate of suicidal jumps from HRHs did not increase during the study period. The number of fatal jumps per hotel-year correlated with the height of the interior hotel atrium. The mean age for all victims was 34 years, and 63% of victims were white males. The majority of victims were local residents who were alone when they jumped and were not registered hotel guests. Registered guests tended to jump from the floor on which their room was located whereas nonregistered individuals tended to jump from the upper-most floors in the hotel. Of 19 HRH jumps, 13 occurred from the inside. Suicide notes were found in 37% of cases. HRH jumps were least common between 6 p.m. and midnight, all decedents were dressed in street clothing, only one was heard to have screamed, and all but one were dead on the scene. Alcohol and drug involvement was minimal. We hope that this information will be useful to those who investigate such deaths and to those who study the behavioral manifestations of suicide.

  19. The effects of temperature and body mass on jump performance of the locust Locusta migratoria.

    Science.gov (United States)

    Snelling, Edward P; Becker, Christie L; Seymour, Roger S

    2013-01-01

    Locusts jump by rapidly releasing energy from cuticular springs built into the hind femur that deform when the femur muscle contracts. This study is the first to examine the effect of temperature on jump energy at each life stage of any orthopteran. Ballistics and high-speed cinematography were used to quantify the energy, distance, and take-off angle of the jump at 15, 25, and 35°C in the locust Locusta migratoria. Allometric analysis across the five juvenile stages at 35°C reveals that jump distance (D; m) scales with body mass (M; g) according to the power equation D = 0.35M (0.17±0.08 (95% CI)), jump take-off angle (A; degrees) scales as A = 52.5M (0.00±0.06), and jump energy (E; mJ per jump) scales as E = 1.91M (1.14±0.09). Temperature has no significant effect on the exponent of these relationships, and only a modest effect on the elevation, with an overall Q10 of 1.08 for jump distance and 1.09 for jump energy. On average, adults jump 87% farther and with 74% more energy than predicted based on juvenile scaling data. The positive allometric scaling of jump distance and jump energy across the juvenile life stages is likely facilitated by the concomitant relative increase in the total length (L f+t; mm) of the femur and tibia of the hind leg, L f+t = 34.9M (0.37±0.02). The weak temperature-dependence of jump performance can be traced to the maximum tension of the hind femur muscle and the energy storage capacity of the femur's cuticular springs. The disproportionately greater jump energy and jump distance of adults is associated with relatively longer (12%) legs and a relatively larger (11%) femur muscle cross-sectional area, which could allow more strain loading into the femur's cuticular springs. Augmented jump performance in volant adult locusts achieves the take-off velocity required to initiate flight.

  20. Towards Stability Analysis of Jump Linear Systems with State-Dependent and Stochastic Switching

    Science.gov (United States)

    Tejada, Arturo; Gonzalez, Oscar R.; Gray, W. Steven

    2004-01-01

    This paper analyzes the stability of hierarchical jump linear systems where the supervisor is driven by a Markovian stochastic process and by the values of the supervised jump linear system s states. The stability framework for this class of systems is developed over infinite and finite time horizons. The framework is then used to derive sufficient stability conditions for a specific class of hybrid jump linear systems with performance supervision. New sufficient stochastic stability conditions for discrete-time jump linear systems are also presented.

  1. No apparent ecological trend to the flight-initiating jump performance of five bat species.

    Science.gov (United States)

    Gardiner, James D; Nudds, Robert L

    2011-07-01

    The jump performance of five insectivorous bat species (Miniopterus schreibersii, Myotis blythii, Myotis capaccinii, Myotis myotis and Rhinolophus blasii) was filmed using a high-speed camera. All study bats jumped using a similar technique, with the wing musculature providing the force. The bats jumped off the wrist joint of their wings, typically with their feet already off the ground. Contrary to expectations, jump performance did not correlate with ecology and was instead strongly determined by body size. In general, the larger bats produced more jump force, left the ground at higher speeds and jumped higher than the smaller bats. The differences in force production disappeared when the data were corrected for body size, with the exception of Myotis capaccinii, which produced significantly less force. Scaling of jump performance with body size measured here was compared against two existing muscle performance scaling models. The model suggesting that muscle contraction velocity is proportional to muscle length was better supported than that based on muscle cross-sectional area. Both models, however, failed to accurately predict the scaling of jump forces, with the slope of the relationship being significantly steeper than predicted, highlighting the need for further investigations of vertebrate muscle performance scaling. The results of this study indicate that a bat's jumping ability is a secondary locomotor ability that uses the strongly selected-for flight apparatus with no apparent ecological trend present, i.e. flight so dominates bat locomotor morphology that other locomotor abilities tend to be derivative.

  2. Stationary distribution and ergodicity of a stochastic food-chain model with Lévy jumps

    Science.gov (United States)

    Yu, Jingyi; Liu, Meng

    2017-09-01

    In this paper, a three-species stochastic food-chain model with Lévy jumps is proposed and analyzed. Sharp sufficient criteria for the existence and uniqueness of an ergodic stationary distribution are established. The effects of Lévy jumps on the existence of the stationary distribution are revealed: in some cases, the Lévy jumps could make the stationary distribution appear, while in some cases, the Lévy jumps could make the stationary distribution disappear. Some numerical simulations are introduced to illustrate the theoretical results.

  3. Optimal dividend policies with transaction costs for a class of jump-diffusion processes

    DEFF Research Database (Denmark)

    Hunting, Martin; Paulsen, Jostein

    2013-01-01

    his paper addresses the problem of finding an optimal dividend policy for a class of jump-diffusion processes. The jump component is a compound Poisson process with negative jumps, and the drift and diffusion components are assumed to satisfy some regularity and growth restrictions. Each dividend...... payment is changed by a fixed and a proportional cost, meaning that if ξ is paid out by the company, the shareholders receive kξ−K, where k and K are positive. The aim is to maximize expected discounted dividends until ruin. It is proved that when the jumps belong to a certain class of light...

  4. MUSCLE STRENGTH AND QUALITATIVE JUMP-LANDING DIFFERENCES IN MALE AND FEMALE MILITARY CADETS: THE JUMP-ACL STUDY

    Directory of Open Access Journals (Sweden)

    Barry P. Boden

    2009-12-01

    Full Text Available Recent studies have focused on gender differences in movement patterns as risk factors for ACL injury. Understanding intrinsic and extrinsic factors which contribute to movement patterns is critical to ACL injury prevention efforts. Isometric lower- extremity muscular strength, anthropometrics, and jump-landing technique were analyzed for 2,753 cadets (1,046 female, 1,707 male from the U.S. Air Force, Military and Naval Academies. Jump- landings were evaluated using the Landing Error Scoring System (LESS, a valid qualitative movement screening tool. We hypothesized that distinct anthropometric factors (Q-angle, navicular drop, bodyweight and muscle strength would predict poor jump-landing technique in males versus females, and that female cadets would have higher scores (more errors on a qualitative movement screen (LESS than males. Mean LESS scores were significantly higher in female (5.34 ± 1.51 versus male (4.65 ± 1.69 cadets (p < 0.001. Qualitative movement scores were analyzed using factor analyses, yielding five factors, or "patterns", contributing to poor landing technique. Females were significantly more likely to have poor technique due to landing with less hip and knee flexion at initial contact (p < 0.001, more knee valgus with wider landing stance (p < 0. 001, and less flexion displacement over the entire landing (p < 0.001. Males were more likely to have poor technique due to landing toe-out (p < 0.001, with heels first, and with an asymmetric foot landing (p < 0.001. Many of the identified factor patterns have been previously proposed to contribute to ACL injury risk. However, univariate and multivariate analyses of muscular strength and anthropometric factors did not strongly predict LESS scores for either gender, suggesting that changing an athlete's alignment, BMI, or muscle strength may not directly improve his or her movement patterns

  5. Quantum jump from singularity to outside of black hole

    Energy Technology Data Exchange (ETDEWEB)

    Dündar, Furkan Semih [Physics and Mathematics Departments, Sakarya University, 54050, Sakarya (Turkey); Hajian, Kamal [School of Physics, Institute for Research in Fundamental Sciences, P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of); Department of Physics, Sharif University of Technology, P.O. Box 11365-8639, Tehran (Iran, Islamic Republic of)

    2016-02-26

    Considering the role of black hole singularity in quantum evolution, a resolution to the firewall paradox is presented. It is emphasized that if an observer has the singularity as a part of his spacetime, then the semi-classical evolution would be non-unitary as viewed by him. Specifically, a free-falling observer inside the black hole would have a Hilbert space with non-unitary evolution; a quantum jump for particles encountering the singularity to outside of the horizon as late Hawking radiations. The non-unitarity in the jump resembles the one in collapse of wave function, but preserves entanglements. Accordingly, we elaborate the first postulate of black hole complementarity: freely falling observers who pass through the event horizon would have non-unitary evolution, while it does not have physically measurable effects for them. Besides, no information would be lost in the singularity. Taking the modified picture into account, the firewall paradox can be resolved, respecting No Drama. A by-product of our modification is that roughly half of the entropy of the black hole is released close to the end of evaporation in the shape of very hot Hawking radiation.

  6. Aerodynamics of ski jumping flight and its control: I. Experiments

    Science.gov (United States)

    Jung, Daehan; Bang, Kyeongtae; Kim, Heesu; Ahn, Eunhye; Choi, Haecheon

    2015-11-01

    In a ski jumping competition, it is essential to analyze the effect of various posture parameters of a ski jumper to achieve a longer flight distance. For this purpose, we construct a model of a ski jumper by using three-dimensional surface data obtained by scanning a ski jumper's body (Mr. Chil-Ku Kang, member of the Korean national team). An experiment on this model is conducted in a wind tunnel. We consider four posture parameters (forward leaning angle, ski opening angle, ski rolling angle, and ski spacing) and measure the drag and lift forces for various flight postures at various angles of attack (α = 0° - 40°) and Reynolds numbers (Re = 5.4 × 105 - 1.6 × 106) based on the length of the jump ski. Then, we derive optimum values of posture parameters for maximum lift-to-drag ratio using a response surface method. We also conduct a full-scale wind tunnel experiment with members of the Korean national team and confirm the results obtained from the experiment on the model. Supported by the NRF program (2014M3C1B1033848).

  7. Robophysical study of jumping dynamics on granular media

    Science.gov (United States)

    Aguilar, Jeffrey; Goldman, Daniel I.

    2016-03-01

    Characterizing forces on deformable objects intruding into sand and soil requires understanding the solid- and fluid-like responses of such substrates and their effect on the state of the object. The most detailed studies of intrusion in dry granular media have revealed that interactions of fixed-shape objects during free impact (for example, cannonballs) and forced slow penetration can be described by hydrostatic- and hydrodynamic-like forces. Here we investigate a new class of granular interactions: rapid intrusions by objects that change shape (self-deform) through passive and active means. Systematic studies of a simple spring-mass robot jumping on dry granular media reveal that jumping performance is explained by an interplay of nonlinear frictional and hydrodynamic drag as well as induced added mass (unaccounted by traditional intrusion models) characterized by a rapidly solidified region of grains accelerated by the foot. A model incorporating these dynamics reveals that added mass degrades the performance of certain self-deformations owing to a shift in optimal timing during push-off. Our systematic robophysical experiment reveals both new soft-matter physics and principles for robotic self-deformation and control, which together provide principles of movement in deformable terrestrial environments.

  8. Correlation between dichromatic colour vision and jumping performance in horses.

    Science.gov (United States)

    Spaas, Julie; Helsen, Werner F; Adriaenssens, Maurits; Broeckx, Sarah; Duchateau, Luc; Spaas, Jan H

    2014-10-01

    There is general agreement that horses have dichromatic colour vision with similar capabilities to human beings with red-green colour deficiencies. However, whether colour perception has an impact on equine jumping performance and how pronounced the colour stimulus might be for a horse is unknown. The present study investigated the relationship between the colour of the fences (blue or green) and the show jumping performance of 20 horses ridden by two riders using an indoor and outdoor set of green and blue fences. In the indoor arena, significantly more touches and faults were made on blue fences in comparison to green fences (median difference of 2.5 bars). When only touched bars were included, a significant median difference of one bar was found. Mares (n = 4) demonstrated more faults and had a significantly greater difference in touches and faults between the two colours than male horses (n = 16). Repeating the same experiment with eight horses in an outdoor grass arena revealed no significant differences between the two colours. In order to draw any definite conclusions, more research concerning the colour perception, influence of contrast with the arena surface and sex of horse is required.

  9. Dynamic control of droplet jumping by tailoring nanoparticle concentrations

    Science.gov (United States)

    Hao, Chonglei; Zhou, Yang; Zhou, Xiaofeng; Che, Lufeng; Chu, Baojin; Wang, Zuankai

    2016-07-01

    The dynamic impact behavior of droplets from solid surfaces has attracted increasing interest, especially propelled by the advances in the bio-inspired interfacial materials. In this work, we investigate the impact and bouncing dynamics of ethylene glycol droplets containing silica nanoparticles on superhydrophobic surfaces (SHS). We find that the rebounding of droplets from SHS is highly dependent on the impact velocity and suspension concentrations. By increasing the impact velocity or suspension concentrations, the probability of droplet bouncing from SHS is greatly reduced. The presence of nanoparticles can significantly increase the viscous energy dissipation inside the liquid droplets, therefore suppressing the jumping from surfaces. Based on the energy dissipation characterization, we also find the critical concentration to determine the manifestation of the viscous effect, above which the liquid suspensions exhibit non-Newtonian fluid properties. Our study provides an efficient approach to dynamically control the liquid jumping behaviors on SHS by tailoring the suspension concentrations. The insights learned from this study can be very useful in many industrial applications.

  10. Prescription-induced jump distributions in multiplicative Poisson processes

    Science.gov (United States)

    Suweis, Samir; Porporato, Amilcare; Rinaldo, Andrea; Maritan, Amos

    2011-06-01

    Generalized Langevin equations (GLE) with multiplicative white Poisson noise pose the usual prescription dilemma leading to different evolution equations (master equations) for the probability distribution. Contrary to the case of multiplicative Gaussian white noise, the Stratonovich prescription does not correspond to the well-known midpoint (or any other intermediate) prescription. By introducing an inertial term in the GLE, we show that the Itô and Stratonovich prescriptions naturally arise depending on two time scales, one induced by the inertial term and the other determined by the jump event. We also show that, when the multiplicative noise is linear in the random variable, one prescription can be made equivalent to the other by a suitable transformation in the jump probability distribution. We apply these results to a recently proposed stochastic model describing the dynamics of primary soil salinization, in which the salt mass balance within the soil root zone requires the analysis of different prescriptions arising from the resulting stochastic differential equation forced by multiplicative white Poisson noise, the features of which are tailored to the characters of the daily precipitation. A method is finally suggested to infer the most appropriate prescription from the data.

  11. Visual perception in the brain of a jumping spider.

    Science.gov (United States)

    Menda, Gil; Shamble, Paul S; Nitzany, Eyal I; Golden, James R; Hoy, Ronald R

    2014-11-03

    Jumping spiders (Salticidae) are renowned for a behavioral repertoire that can seem more vertebrate, or even mammalian, than spider-like in character. This is made possible by a unique visual system that supports their stalking hunting style and elaborate mating rituals in which the bizarrely marked and colored appendages of males highlight their song-and-dance displays. Salticids perform these tasks with information from four pairs of functionally specialized eyes, providing a near 360° field of view and forward-looking spatial resolution surpassing that of all insects and even some mammals, processed by a brain roughly the size of a poppy seed. Salticid behavior, evolution, and ecology are well documented, but attempts to study the neurophysiological basis of their behavior had been thwarted by the pressurized nature of their internal body fluids, making typical physiological techniques infeasible and restricting all previous neural work in salticids to a few recordings from the eyes. We report the first survey of neurophysiological recordings from the brain of a jumping spider, Phidippus audax (Salticidae). The data include single-unit recordings in response to artificial and naturalistic visual stimuli. The salticid visual system is unique in that high-acuity and motion vision are processed by different pairs of eyes. We found nonlinear interactions between the principal and secondary eyes, which can be inferred from the emergence of spatiotemporal receptive fields. Ecologically relevant images, including prey-like objects such as flies, elicited bursts of excitation from single units.

  12. THE INFLUENCE OF MUSICAL CADENCE INTO AQUATIC JUMPING JACKS KINEMATICS

    Directory of Open Access Journals (Sweden)

    Mário J. Costa

    2011-12-01

    Full Text Available The aim of this study was to analyze the relationships between the head-out aquatic exercise "Jumping jacks" kinematics and the musical cadence in healthy and fit subjects. Five young women, with at least one year of experience conducting head- out aquatic programs were videotaped in the frontal plane, with a pair of cameras providing a double projection (above and below the water surface. Subjects performed an incremental protocol of five bouts (120 b·min-1, 135 b·min-1, 150 b·min-1, 165 b·min-1 and 180 b·min-1 with 16 full cycles of the "Jumping jacks" exercise. Data processing and calculation of upper limbs' (i.e. hands, lower limbs' (i.e. feet and center of mass' 2D linear velocity and displacement were computed with the software Ariel Performance Analysis System and applying the 2D-DLT algorithm. Subjects decreased the cycle period during the incremental protocol. Significant and negative relationships with the musical cadence were verified for the center of mass and upper limbs vertical displacement. On the other hand, for the lower limbs lateral velocity, a significant and positive relationship was observed. It is concluded that expert and fit subjects increase the lower limb's velocity to maintain the range of motion, while the upper limb's displacement is reduced to coupe the music cadence.

  13. Differences in vertical jumping and mae-geri kicking velocity between international and national level karateka

    Directory of Open Access Journals (Sweden)

    Carlos Balsalobre-Fernández

    2013-04-01

    Full Text Available Aim: Lower limb explosive strength and mae-geri kicking velocity are fundamental in karate competition; although it is unclear whether these variables could differentiate the high-level athletes. The objective of this research is to analyze the differences in the mae-geri kicking velocity and the counter-movement jump (CMJ between a group of international top level karateka and another group of national-level karateka.Methods: Thirteen international-level karateka and eleven national-level karateka participated in the study. After a standard warm-up, CMJ height (in cm and mae-geri kicking velocity (in m/s was measured using an IR-platform and a high-speed camera, respectively.Results: Proceeding with MANCOVA to analyze the differences between groups controlling the effect of age, the results show that the international-level karateka demonstrated significantly higher levels of CMJ than national-level competitors (+22.1%, F = 9.47, p = 0.006, η2 = 0.311. There were no significant differences between groups in the mae-geri kicking velocity (+5,7%, F=0.80; p=0.38; η2=0.03.Conclusion: Our data shows, first, the importance of CMJ assessment as a tool to detect talent in karate and, second, that to achieve international-level in karate it may be important to increase CMJ levels to values ​​similar to those offered here.

  14. Musculotendinous Stiffness of Triceps Surae, Maximal Rate of Force Development, and Vertical Jump Performance

    Directory of Open Access Journals (Sweden)

    Tarak Driss

    2015-01-01

    Full Text Available The relationships between ankle plantar flexor musculotendinous stiffness (MTS and performance in a countermovement vertical jump (CMJ and maximal rate of torque development (MRTD were studied in 27 active men. MTS was studied by means of quick releases at 20 (S0.2, 40 (S0.4, 60 (S0.6, and 80% (S0.8 of maximal voluntary torque (TMVC. CMJ was not correlated with strength indices but was positively correlated with MRTD/BM, S0.4/BM. The slope α2 and intercept β2 of the torque-stiffness relationships from 40 to 80% TMVC were correlated negatively (α2 and positively (β2 with CMJ. The different stiffness indices were not correlated with MRTD. The prediction of CMJ was improved by the introduction of MRTD in multiple regressions between CMJ and stiffness. CMJ was also negatively correlated with indices of curvature of the torque-stiffness relationship. The subjects were subdivided in 3 groups in function of CMJ (groups H, M, and L for high, medium, and low performers, resp.. There was a downward curvature of the torque-stiffness relationship at high torques in group H or M and the torque-stiffness regression was linear in group L only. These results suggested that torque-stiffness relationships with a plateau at high torques are more frequent in the best jumpers.

  15. Effects of static and dynamic stretching on sprint and jump performance in boys and girls.

    Science.gov (United States)

    Paradisis, Giorgos P; Pappas, Panagiotis T; Theodorou, Apostolos S; Zacharogiannis, Elias G; Skordilis, Emmanouil K; Smirniotou, Athanasia S

    2014-01-01

    The aim of this study was to investigate the acute effects of static (SS) and dynamic stretching (DS) on explosive power, flexibility, and sprinting ability of adolescent boys and girls and to report possible gender interactions. Forty-seven active adolescent boys and girls were randomly tested after SS and DS of 40 seconds on quadriceps, hamstrings, hip extensors, and plantar flexors; no stretching was performed at the control condition. Pretreatment and posttreatment tests examined the effects of stretching on 20-m sprint run (20 m), countermovement jump (CMJ) height, and sit and reach flexibility test. In terms of performance, SS hindered 20 m and CMJ in boys and girls by 2.5 and 6.3%, respectively. Dynamic stretching had no effect on 20 m in boys and girls but impaired CMJ by 2.2%. In terms of flexibility, both SS and DS improved performance with SS being more beneficial (12.1%) compared with DS (6.5%). No gender interaction was found. It can therefore be concluded that SS significantly negates sprinting performance and explosive power in adolescent boys and girls, whereas DS deteriorates explosive power and has no effect on sprinting performance. This diversity of effects denotes that the mode of stretching used in adolescent boys and girls should be task specific.

  16. Musculotendinous stiffness of triceps surae, maximal rate of force development, and vertical jump performance.

    Science.gov (United States)

    Driss, Tarak; Lambertz, Daniel; Rouis, Majdi; Jaafar, Hamdi; Vandewalle, Henry

    2015-01-01

    The relationships between ankle plantar flexor musculotendinous stiffness (MTS) and performance in a countermovement vertical jump (CMJ) and maximal rate of torque development (MRTD) were studied in 27 active men. MTS was studied by means of quick releases at 20 (S0.2), 40 (S0.4), 60 (S0.6), and 80% (S0.8) of maximal voluntary torque (T(MVC)). CMJ was not correlated with strength indices but was positively correlated with MRTD/BM, S 0.4/BM. The slope α 2 and intercept β 2 of the torque-stiffness relationships from 40 to 80% T(MVC) were correlated negatively (α 2) and positively (β 2) with CMJ. The different stiffness indices were not correlated with MRTD. The prediction of CMJ was improved by the introduction of MRTD in multiple regressions between CMJ and stiffness. CMJ was also negatively correlated with indices of curvature of the torque-stiffness relationship. The subjects were subdivided in 3 groups in function of CMJ (groups H, M, and L for high, medium, and low performers, resp.). There was a downward curvature of the torque-stiffness relationship at high torques in group H or M and the torque-stiffness regression was linear in group L only. These results suggested that torque-stiffness relationships with a plateau at high torques are more frequent in the best jumpers.

  17. Keeping your eye on the rail: gaze behaviour of horse riders approaching a jump.

    Science.gov (United States)

    Hall, Carol; Varley, Ian; Kay, Rachel; Crundall, David

    2014-01-01

    The gaze behaviour of riders during their approach to a jump was investigated using a mobile eye tracking device (ASL Mobile Eye). The timing, frequency and duration of fixations on the jump and the percentage of time when their point of gaze (POG) was located elsewhere were assessed. Fixations were identified when the POG remained on the jump for 100 ms or longer. The jumping skill of experienced but non-elite riders (n = 10) was assessed by means of a questionnaire. Their gaze behaviour was recorded as they completed a course of three identical jumps five times. The speed and timing of the approach was calculated. Gaze behaviour throughout the overall approach and during the last five strides before take-off was assessed following frame-by-frame analyses. Differences in relation to both round and jump number were found. Significantly longer was spent fixated on the jump during round 2, both during the overall approach and during the last five strides (priders who scored higher for jumping skill tended to fixate on the jump earlier (p = 0.07), when the horse was further from the jump (p = 0.09) and their first fixation on the jump was of a longer duration (p = 0.06). Trials with elite riders are now needed to further identify sport-specific visual skills and their relationship with performance. Visual training should be included in preparation for equestrian sports participation, the positive impact of which has been clearly demonstrated in other sports.

  18. Immediate effects of different types of stretching exercises on badminton jump smash.

    Science.gov (United States)

    Jang, Hwi S; Kim, Daeho; Park, Jihong

    2017-04-13

    Since different types of stretching exercises may alter athletic performance, we compared the effects of three types of stretching exercises on badminton jump smash. Sixteen male collegiate badminton players performed one of three different stretching exercises in a counterbalanced order on different days. Static stretching had seven typical stretches, while dynamic stretching involved nine dynamic movements, and resistance dynamic stretching was performed with weighted vests and dumbbells. Before and after each stretching exercise, subjects performed 20 trials of jump smashes. Dependent measurements were the jump heights during jump smashes, velocities of jump-smashed shuttlecocks, and drop points of jump-smashed shuttlecocks. To test the effects of each stretching exercise, we performed mixed model ANOVAs and calculated between-time effect sizes (ES). Each stretching exercise improved the jump heights during jump smashes (type main effect: F2,75= 1.19, p=0.31; static stretching: 22.1%, pstretching: 30.1%, pstretching: 17.7%, p=0.03, ES: 0.98) and velocities of jump-smashed shuttlecocks (type main effect: F2,75= 2.18, p=0.12; static stretching: 5.7%, p=0.61, ES: 0.39; dynamic stretching: 3.4%, p=0.94, ES: 0.28; resistance dynamic stretching: 6%, p=0.50, ES: 0.66). However, there were no differences among the stretching exercises for any measurement. The drop point of jump-smashed shuttlecocks did not change (interaction: F2,75= 0.88, p=0.42). All stretching exercises improved badminton jump smash performance, but we could not determine the best protocol. Since badminton requires high-speed movement and explosive force, we suggest performing dynamic stretching or resistance dynamic stretching.

  19. Joint dynamics and intra-subject variability during countermovement jumps in children and adults

    DEFF Research Database (Denmark)

    Raffalt, Peter C; Alkjær, Tine; Simonsen, Erik B

    2016-01-01

    work, hip joint moment and hip and knee joint power. Higher intra-subject variation was observed in horizontal joint reaction force components for the children and higher intra-subject variation in the segment angular inertia components was observed for the adults. The joint dynamics of children during...

  20. Repetitive Hops Induce Postactivation Potentiation in Triceps Surae as well as an Increase in the Jump Height of Subsequent Maximal Drop Jumps

    OpenAIRE

    Julian Bergmann; Andreas Kramer; Markus Gruber

    2013-01-01

    Postactivation potentiation (PAP) has been defined as the increase in twitch torque after a conditioning contraction. The present study aimed to investigate the effectiveness of hops as conditioning contractions to induce PAP and increase performance in subsequent maximal drop jumps. In addition, we wanted to test if and how PAP can contribute to increases in drop jump rebound height. Twelve participants performed 10 maximal two-legged hops as conditioning contractions. Twitch peak torques of...

  1. The acute effects of dynamic and ballistic stretching on vertical jump height, force, and power.

    Science.gov (United States)

    Jaggers, Jason R; Swank, Ann M; Frost, Karen L; Lee, Chong D

    2008-11-01

    Stretching before performance is a common practice among athletes in hopes of increasing performance and reducing the risk of injury. However, cumulative results indicate a negative impact of static stretching and proprioceptive neuromuscular facilitation (PNF) on performance; thus, there is a need for evaluating other stretching strategies for effective warm-up. The purpose of this study was to compare the differences between two sets of ballistic stretching and two sets of a dynamic stretching routine on vertical jump performance. Twenty healthy male and female college students between the ages of 22 and 34 (24.8 +/- 3 years) volunteered to participate in this study. All subjects completed three individual testing sessions on three nonconsecutive days. On each day, the subjects completed one of three treatments (no stretch, ballistic stretch, and dynamic stretch). Intraclass reliability was determined using the data obtained from each subject. A paired samples t-test revealed no significant difference in jump height, force, or power when comparing no stretch with ballistic stretch. A significant difference was found on jump power when comparing no stretch with dynamic stretch, but no significant difference was found for jump height or force. Statistics showed a very high reliability when measuring jump height, force, and power using the Kistler Quattro Jump force plate. It seems that neither dynamic stretching nor ballistic stretching will result in an increase in vertical jump height or force. However, dynamic stretching elicited gains in jump power poststretch.

  2. The Impact of Jumps and Leverage in Forecasting Co-Volatility

    NARCIS (Netherlands)

    M. Asai (Manabu); M.J. McAleer (Michael)

    2015-01-01

    markdownabstract__Abstract__ The paper investigates the impact of jumps in forecasting co-volatility, accommodating leverage effects. We modify the jump-robust two time scale covariance estimator of Boudt and Zhang (2013) such that the estimated matrix is positive definite. Using this approach we

  3. The Impact of Jumps and Leverage in Forecasting Co-Volatility

    NARCIS (Netherlands)

    M. Asai (Manabu); M.J. McAleer (Michael)

    2015-01-01

    markdownabstract__Abstract__ The paper investigates the impact of jumps in forecasting co-volatility, accommodating leverage effects. We modify the jump-robust two time scale covariance estimator of Boudt and Zhang (2013)such that the estimated matrix is positive definite. Using this approach we ca

  4. EFFECTS OF ELECTROSTIMULATION AND PLYOMETRIC TRAINING PROGRAM COMBINATION ON JUMP HEIGHT IN TEENAGE ATHLETES

    Directory of Open Access Journals (Sweden)

    Emilio J. Martínez-López

    2012-12-01

    Full Text Available The purpose of this study was to examine the effects of eight- week (2 days/week training periods of plyometric exercises (PT and neuromuscular electrostimulation (EMS on jump height in young athletes. Squat jump (SJ, counter movement jump (CMJ and drop jump (DJ were performed to assess the effects of the training protocols 98 athletes (100 & 200m and 100m & 110m hurdles voluntarily took part in this study, 51 males (52% and 47 females (48%, 17.91 ± 1.42 years old, and 5.16 ± 2.56 years of training experience. The participants were randomly assigned to four different groups according to the frequency and the timing of the stimulation. Analysis of covariance was used to analyze the effects of every training program on jump height. Our findings suggest that compared to control (Plyometrics (PT only, the combination of 150Hz EMS + PT simultaneously combined in an 8 week (2days/week training program, we could observe significant jump height improvements in the different types of strength: explosive, explosive-elastic, and explosive-elastic-reactive. The combination of PT after < 85 Hz EMS did not show any jump height significant increase in sprinters. In conclusion, an eight week training program (with just two days per week of EMS combined with plyometric exercises has proven useful for the improvement of every kind of vertical jump ability required for sprint and hurdles disciplines in teenage athletes

  5. 60 FR 56561 - Jump Creek Water Quality Planning Project Owyhee County

    Science.gov (United States)

    1995-11-09

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF AGRICULTURE Natural Resources Conservation Service Jump Creek Water Quality Planning Project Owyhee County AGENCY... impact statement is not being prepared for the Jump Creek Water Quality Planning Project, Owyhee...

  6. Measurement of L(III) Subshell Absorption Jump Parameters of Hafnium.

    Science.gov (United States)

    Cengiz, E; Saritas, N; Dogan, M; Koksal, O K; Karabulut, K; Apaydin, G; Tirasoglu, E

    2015-12-01

    The L(III) subshell absorption jump ratio and jump factor of hafnium have been measured using two different ways which are X-ray attenuation method and Energy Dispersive X-ray Fluorescence technique. The results obtained both ways have been compared with theoretical values. They are in good agreement with each other.

  7. Limit theorems for vertex-reinforced jump processes on regular trees

    CERN Document Server

    Collevecchio, Andrea

    2009-01-01

    Consider a vertex-reinforced jump process defined on a regular tree, where each vertex has exactly $b$ children, with $b \\ge 3$. We prove the strong law of large numbers and the central limit theorem for the distance of the process from the root. Notice that it is still unknown if vertex-reinforced jump process is transient on the binary tree.

  8. Critical size ratio for coalescence-induced droplet jumping on superhydrophobic surfaces

    Science.gov (United States)

    Wang, Kai; Li, Ruixin; Liang, Qianqing; Jiang, Rui; Zheng, Yi; Lan, Zhong; Ma, Xuehu

    2017-08-01

    The mechanism of coalescence-induced droplet jumping on superhydrophobic surfaces has been relatively well-established over the years. Most of the related studies are only considering the coalescence process of equal-sized water droplets. However, the coalescence of droplets with different sizes is actually more frequently encountered and the effect of the size ratio on droplet jumping is very crucial to the hydrodynamics of this process. In this work, the effect of the initial droplet size ratio on coalescence-induced jumping of two water droplets is investigated experimentally and numerically. For the previously reported jumping droplet sizes (˜1-100 μm), it is found that the critical droplet size ratio below which the jumping does not occur is about 0.56. The results agree well with the experimental data as the size ratios of observed jumping events collapse into the predicted jumping regime. These findings will gain insights into droplet jumping which has great potential in a number of industrial processes.

  9. Squat Jump Performance during Growth in Both Sexes: Comparison with Cycling Power

    Science.gov (United States)

    Dore, Eric; Bedu, Mario; Van Praagh, Emmanuel

    2008-01-01

    The purpose of this cross-sectional study was to investigate leg muscle power and compare two activities (jumping and cycling) in 383 girls and 407 boys ages 9-19 years. Results in anthropometric characteristics and jumping performance were comparable until midadolescence, and sex differences were observed. Lean leg volume (LLV) was the reason for…

  10. Jump Rope Skills for Fun and Fitness in Grades K-12

    Science.gov (United States)

    Michiels Hernandez, Barbara L.; Gober, Donna; Boatwright, Douglas; Strickland, George

    2009-01-01

    A jump rope is a remarkable piece of exercise equipment. It is inexpensive and easy to store, and it can be used by a wide variety of age groups to improve cardiovascular fitness, increase agility, and tone the body's muscles all at the same time. Consequently, the teaching of jump rope skills is highly suitable for physical education classes in…

  11. Influence of a Horizontal Approach on the Mechanical Output during Drop Jumps

    Science.gov (United States)

    Ruan, Mianfang; Li, Li

    2008-01-01

    This study investigated the influence of a horizontal approach to mechanical output during drop jumps. Participants performed drop jumps from heights of 15, 30, 45, and 60 cm with zero, one, two, and three approach steps. The peak summed power during the push-off phase changed quadratically across heights (6.2 [plus or minus] 0.3, 6.7 [plus or…

  12. Cooperative jump motions of jammed particles in a one-dimensional periodic potential.

    Science.gov (United States)

    Sakaguchi, Hidetsugu

    2009-12-01

    Cooperative jump motions are studied for mutually interacting particles in a one-dimensional periodic potential. The diffusion constant for the cooperative motion in systems including a small number of particles is numerically calculated and it is compared with theoretical estimates. We find that the size distribution of the cooperative jump motions obeys an exponential law in a large system.

  13. Cooperative jump motions of jammed particles in a one-dimensional periodic potential

    OpenAIRE

    Sakaguchi, Hidetsugu

    2009-01-01

    Cooperative jump motions are studied for mutually interacting particles in a one-dimensional periodic potential. The diffusion constant for the cooperative motion in systems including a small number of particles is numerically calculated and it is compared with theoretical estimates. We find that the size distribution of the cooperative jump motions obeys an exponential law in a large system.

  14. Physically based sound synthesis and control of jumping sounds on an elastic trampoline

    DEFF Research Database (Denmark)

    Turchet, Luca; Pugliese, Roberto; Takala, Tapio

    2013-01-01

    This paper describes a system to interactively sonify the foot-floor contacts resulting from jumping on an elastic trampoline. The sonification was achieved by means of a synthesis engine based on physical models reproducing the sounds of jumping on several surface materials. The engine was contr...... on multi-sensory perception involving the auditory and the foot- haptic modalities....

  15. Exertion of forces by children performing a free-style jump

    NARCIS (Netherlands)

    Moes, C.C.M.; Visser, R.J.

    1998-01-01

    This research project focuses on the force characteristics and force/time relationships of loads exerted by jumping children. The current study is an experimental research into children jumping on both hard and soft substrates. The hard substrate is obtained by using a force plate. For the soft subs

  16. Inertia Matching Manipulability and Load Matching Optimization for Humanoid Jumping Robot

    Directory of Open Access Journals (Sweden)

    Zhaohong Xu

    2008-11-01

    Full Text Available Human jumping motion includes stance phase, flight phase and landing impact phase. Jumping robot belongs to a variable constraints system because every phase has different constraint conditions. An unified dynamics equation during stance phase and flight phase is established based on floated-basis space. Inertia matching is used to analyze actuator/gear systems and select the optimum gear ratio based on the transmission performance between the torque produced at the actuator and the torque applied to the load. Load matching is an important index which affects jumping performance and reflects the capability of supporting a weight or mass. It also affects the distributing of the center of gravity (COG. Regarding jumping robot as a redundant manipulator with a load at end-effector, inertia matching can be applied to optimize load matching for jumping robot. Inertia matching manipulability and directional manipulability are easy to analyze and optimize the load matching parameters. A 5th order polynomial function is defined to plan COG trajectory of jumping motion, taking into account the constraint conditions of both velocity and acceleration. Finally, the numerical simulation of vertical jumping and experimental results show inertia matching is in direct proportion to jumping height, and inertia matching manipulability is a valid method to load matching optimization and conceptual design of robot.

  17. Inter-segmental moment analysis characterises the partial correspondence of jumping and jerking

    Science.gov (United States)

    Cleather, Daniel J; Goodwin, Jon E; Bull, Anthony MJ

    2014-01-01

    The aim of this study was to quantify internal joint moments of the lower limb during vertical jumping and the weightlifting jerk in order to improve awareness of the control strategies and correspondence between these activities, and to facilitate understanding of the likely transfer of training effects. Athletic males completed maximal unloaded vertical jumps (n=12) and explosive push jerks at 40 kg (n=9). Kinematic data were collected using optical motion tracking and kinetic data via a force plate, both at 200 Hz. Joint moments were calculated using a previously described biomechanical model of the right lower limb. Peak moment results highlighted that sagittal plane control strategies differed between jumping and jerking (p0.05) possibly indicating a limit to the direct transferability of jerk performance to jumping. Ankle joint moments were poorly related to jump performance (p>0.05). Peak knee and hip moment generating capacity are important to vertical jump performance. The jerk appears to offer an effective strategy to overload joint moment generation in the knee relative to jumping. However, an absence of hip involvement would appear to make it a general, rather than specific, training modality in relation to jumping. PMID:22362089

  18. Roughing It Up: Including Jump Components in the Measurement, Modeling and Forecasting of Return Volatility

    DEFF Research Database (Denmark)

    Bollerslev, Tim; Andersen, Torben G.; Diebold, Francis X.

    A rapidly growing literature has documented important improvements in financial return volatility measurement and forecasting via use of realized variation measures constructed from high-frequency returns coupled with simple modeling procedures. Building on recent theoretical results in Barndorff...... bond yield, we find that jumps are both highly prevalent and distinctly less persistent than the continuous sample path variation process. Moreover, many jumps appear directly associated with specific macroeconomic news announcements. Separating jump from non-jump movements in a simple...... but sophisticated volatility forecasting model, we find that almost all of the predictability in daily, weekly, and monthly return volatilities comes from the non-jump component. Our results thus set the stage for a number of interesting future econometric developments and important financial applications...

  19. Multiple Neuromas Cause Painful "Jumping Stump" in a Transfemoral Amputee: A Case Report.

    Science.gov (United States)

    Buntragulpoontawee, Montana; Pattamapaspong, Nuttaya; Tongprasert, Siam

    2016-09-01

    Painful "jumping stump" is an uncommon but very disturbing complication postamputation. This condition is one of the movement disorder entities resulting from peripheral nerve pathology, often known as "peripherally induced movement disorders." Previously case reports have been written about painful and nonpainful incidence of "jumping stump"; however, only the earliest "jumping stump" article in 1852 suspected that neuromas might influence the involuntary movement. In this study, we describe a 38-year-old man with bilateral transfemoral amputee who suffered from painful "jumping stump" with multiple neuromas confirmed by imaging. He was treated successfully by ultrasound-guided phenol injection into the sciatic neuroma stalks. The pathophysiology of jumping stump and its possible association with neuroma are briefly discussed.

  20. Designing, Building, Measuring and Testing a Constant Equivalent Fall Height Terrain Park Jump

    CERN Document Server

    Petrone, Nicola; McNeil, James A; Hubbard, Mont

    2016-01-01

    Previous work has presented both a theoretical foundation for designing terrain park jumps that control landing impact and computer software to accomplish this task. US ski resorts have been reluctant to adopt this more engineered approach to jump design, in part due to questions of feasibility. The present study demonstrates this feasibility. It describes the design, construction, measurement and experimental testing of such a jump. It improves on previous efforts with more complete instrumentation, a larger range of jump distances, and a new method for combining jumper- and board-mounted accelerometer data to estimate equivalent fall height, a measure of impact severity. It unequivocally demonstrates the efficacy of the engineering design approach, namely that it is possible and practical to design and build free style terrain park jumps with landing surface shapes that control for landing impact as predicted by the theory.