Wyniki wyszukiwania - Biblioteka Nauki

1

Postural Equilibrium Criteria Concerning Feet Properties for Biped Robots

100%

González de Alba A. , Zielinska T.

Journal of Automation Mobile Robotics and Intelligent Systems

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2012

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tom Vol. 6, No. 1

22-27

EN

This article presents a study on the postural equilibrium conditions for biped robots. Criteria for dynamic walking, such as ZMP and CoP are introduced and their similarities discussed. We also introduce the effects of a compliant foot and take them into consideration during the evaluation of the criteria. A model of a planar biped is used to imitate the movements of a human subject as recorded by the VICON motion capture system. In order to estimate the criteria, body segments accelerations and ground reaction forces are needed. ZMP and CoP are analyzed during both single and double support phases for the model’s motion. A linear shift function is used to transport the load of the biped between the supporting legs during the double support phase. We compare simulated CoP trajectories obtained using a rigid foot and a compliant, deformable spring-damper system located between the ankle joint and the sole of the foot. It is seen that the foot’s deformation smoothes the CoP trajectory and improves the biped’s stability.

2

Hip and Shoulder Kinematics During Initial Sled Acceleration in Luging – A Case Study

80%

Fedotova V. , Pilipiv V.

Human Movement

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2012

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tom 13

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nr 4

344-349

EN

Purpose. The start is treated as one of the most important technical elements in all sliding sports, as it is the only phase when athletes can actively contribute to increasing sled velocity. Nevertheless, start kinematics in luging have seldom been addressed in literature. Therefore, the aim of this study was to analyse hip and shoulder movement of lugers during one of the essential start phases - the pull and push-off from the start handles - to further understanding of the velocity development process at its initial stage. Methods. Three experienced female lugers volunteered to take part in the case study. A number of start attempts were filmed and analysed using a motion tracking method. Results. The study found that an athlete and the sled do not move as a whole rigid system, and a hip movement relative to the sled was found to exist. The study participants used two techniques for achieving high sled velocity: by initially pulling on the start handles with a powerful back extension, and sliding the hips forward on the sled in an attempt to increase forward momentum; a combination of both techniques might provide increased performance. Athletes featured two weaknesses in terms of where horizontal sled velocity was lost - at the end of the initial pull on the handles and during the final moment of the push-off from the handles. The latter was previously believed to be another option at gaining increased sled horizontal velocity. Conclusions. As found in the results, athletes have at least two possibilities of increasing horizontal sled velocity. Hip movement relative to the sled appeared to be important for gains in velocity. Additional studies that analyse larger pulls are necessary for understanding the role of hip and sled relative movement in start technique and its impact on increasing initial velocity.

3

The Effect of Fatigue on the Kinematics of Free Throw Shooting in Basketball

80%

Uygur M. , Goktepe A. , Ak E. , Karabörk H. , Korkusuz F.

Journal of Human Kinetics

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2010

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tom 24

51-56

EN

Fatigue is an indispensible part of a basketball game which may affect an athlete's shooting kinematics. Although kinematic analyses of various sports related movements were extensively done, this study is the first to consider the effects of fatigue on the kinematics of free throw shooting. After measuring the resting heart rate, ten collegiate level, male basketball players (21.8±1.6 y; 192.8±3.6 cm; 84.1±8.5 kg) were asked to perform free throws. Two successful and two unsuccessful free throws were selected. Thereafter, participants were asked to complete the fatigue protocol, which included 30m sprints and 5 vertical jumps at each end, until they reached volitional exhaustion. Additional two successful and two unsuccessful free throws were collected. All shots were recorded by using two digital cameras operating at 60 Hz and placed in a stereoscopic view. The elbow, trunk, knee and ankle joint angles were measured before and after the ball release and at the ball release point. The selected joint angles were compared between successful and unsuccessful free throws, as well as before and after the completion of fatigue protocol. The results demonstrated that fatigue did not effect free throw shooting kinematics (p>0.05) and there was no significant joint angle difference between successful and unsuccessful shots (p>0.05). This study suggested that high level athletes are able to cope with the possible detrimental effects of fatigue while performing coordinated movements such as free throw shooting.

4

Szybkie kamery wideo jako narzędzie pomiarów dynamicznych

80%

Tarnowski J.

Czasopismo Techniczne. Mechanika

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2004

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tom R. 101, z. 5-M

371--377

PL

W pracy omówiono aktualne tendencje rozwoju techniki szybkich kamer. Przedstawiono i przeanalizowano wyniki testów porównawczych pomiarów dynamicznych wykonanych za pomocą szybkiej kamery i innymi powszechnie stosowanymi technikami.

EN

In the paper the present trends of development of high speed cameras and their application in dynamic measurements were presented. Some tests of dynamic measurements made by high speed camera and classical methods were described, and their results compared and analysed.

5

Mode based hierarchical optical flow estimation

80%

Otero J. , Otero A. , Sanchez L.

Machine Graphics and Vision

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2001

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tom Vol. 10, No. 4

489-501

EN

In this paper, a robust estimation of the optical flow field that preserves the boundaries of the movement is shown. Arising from the techniques based on the Optical Flow Constraint (OFC), an estimation that takes several measures around a given pixel, discarding the erroneous ones, has been developed. This in done through performing a bidimensional clustering is conducted in the velocity space and not in the (slope, intercept) parameter space of the OFCs. Finally, a hierarchical implementation that has a lesser error when large displacements are present in the image is shown.

6

The Kinematics of Trunk and Upper Extremities in One-Handed and Two-Handed Backhand Stroke

80%

Stępień A. , Bober T. , Zawadzki J.

Journal of Human Kinetics

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2011

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tom 30

37-47

EN

The aim of this study was to present kinematics of trunk and upper extremities in tennis players who perform one-handed and two-handed backhand strokes. The study aimed to address the question of whether one of those techniques has some important advantage over the other. If so, what makes it superior?The study included 10 tennis coaches with average coaching experience of 9 years. The coaches were asked to hit 15 one-handed and two-handed backhands. The tests were carried out in a laboratory. A sponge ball was used in order to protect the measurement equipment. Video motion analysis was carried out using BTS SMART system; images were recorded with 6 cameras with a rate of 120 frames per second. The analysis of both backhand strokes focused on the second phase of the stroke (acceleration).The use of an eight-element model of human body for description of upper body motion in both techniques revealed kinematic differences in how both backhands are performed. The two-handed backhand was performed in closed kinetic chain with 8 degrees of freedom, whereas the one-handed backhand involved an open kinetic chain with 7 degrees of freedom. Higher rigidity of upper extremities which are connected with trunk in the two-handed backhand, contributes to an elevated trunk effect in this stroke. This is confirmed by higher component velocities for racket handle, which result from trunk rotation in the two-handed backhand and a negative separation angle in the two-handed backhand at the moment of contact of the racket with the ball.The study does not provide a clear-cut answer to the question of advantages of one technique over the other; however, it reveals dissimilar patterns of driving the racket in both techniques, which suggests the need for extending the analysis of techniques of both backhands with additional kinematics of tennis racket in consideration of measurements of ball velocities.

7

An analysis of the barbell motion depending on its weight in disabled powerlifting

80%

Seidel W. , Zurowska A.

Baltic Journal of Health and Physical Activity

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2014

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tom 6

|

nr 3

193-198

EN

Background: The aim of the study was to assess the symmetry of flexion and extension movements in upper limbs in disabled powerlifters during bench press with different barbell loads. Material/Methods: 29 disabled athletes from the National Powerlifting Team were examined. Mean age was between 23.9 ± 6.1. Mean sport experience was 5.4 ± 3.6 years. Results: Both flexion and extension movement were performed symmetrically, which was indicated by an insignificant (p < 0.05) difference in the movement onset in the left and the right upper limb. Conclusions: Time differences in the movement onset and the achievement of maximal angular velocity were statistically insignificant in all trials (loads from 40% to 95% 1RM). During extension with loads over 60% 1RM differences in time of achieving maximal angular velocity were statistically significant or close.

8

Experimental Investigations of the Effects of Low - Frequency Training on Vibration of Selected Backbone Sections

80%

Tarnowski J. , Książek M. , Damijan Z.

Molecular and Quantum Acoustics

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2006

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tom Vol. 27

285-294

EN

The study presents the experimental data of values of selected human vertebra sections in the course of day-by-day training sections. The control group included 28 women volunteers subjected to low - frequency vibration exposure. Experiments were conducted using a high speed camera and computer image processing techniques.

9

Kinematic and Kinetic Analysis of Two Gymnastics Acrobatic Series to Performing the Backward Stretched Somersault

80%

Mkaouer B. , Jemni M. , Amara S. , Chaabène H. , Tabka Z.

Journal of Human Kinetics

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2013

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tom 37

|

nr 1

17-26

EN

Back swing connections during gymnastics acrobatic series considerably influence technical performance and difficulties, particularly in the back somersault. The aim of this study was to compare the take-off’s kinetic and kinematic variables between two acrobatic series leading to perform the backward stretched somersault (also called salto): round-off, flic-flac to stretched salto versus round-off, tempo-salto to stretched salto. Five high level male gymnasts (age 23.17 ± 1.61 yrs; body height 1.65 ± 0.05 m; body mass 56.80 ± 7.66 kg) took part in this investigation. A force plate synchronized with a two dimensional movement analysis system was used to collect kinetic and kinematic data. Statistical analysis via the non-parametric Wilcoxon Rank-sum test showed significant differences between the take-offs’ variables. The backswing connections were different in the take-off angle, linear momentum, vertical velocity and horizontal and vertical displacements. In conclusion, considering that the higher elevation of the centre of mass in the flight phase would allow best performance and lower the risk of falls, particularly when combined to a great angular momentum, this study demonstrated that the optimal connection series was round-off, flic-flac to stretched salto which enabled the best height in the somersault. Analysis of the results suggests that both connections facilitate the performance of single and double (or triple) backward somersaults with or without rotations around the longitudinal axis. Gymnasts could perform these later while gaining height if they chose the round-off, flic-flac technique or gaining some backward displacement if they choose the round-off, salto tempo.

10

Ellipsoid Fourier Descriptor : hierarchical shape representation and deformable model

70%

Dufrenois F.

Machine Graphics and Vision

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2000

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tom Vol. 9, No. 1/2

103-113

EN

This paper describes a new model-based segmentation and motion analysis technic combining Euler-Lagrange formalism and shape representation by Fourier decomposition. First, we propose to extend the concept of the 2D Fourier representation for closed curves to a new 3D hierarchical descriptor for closed surfaces. To study the shape deformation during motion, we establish also, the dynamic equations of motion of the Fourier parameters. Finally, some results on 2D data traking, 3D reconstructions and 3D data fitting are presented.

11

Experimental study on ball motions in thrust ball bearings

70%

Fuji T. , Takenouchi K. , Ariyoshi S. , Kawakita K.

Applied Mechanics and Engineering

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1999

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tom Vol. 4, no spec.

311-316

EN

An experimental apparatus and measuring system has been developed for the measurement of actual ball motions in thrust ball bearings. In the apparatus, a representative point on the ball, a magnetic pole of a magnetized ball, is traced by Hall elements arranged on the orthogonal three axes. With the apparatus, an experimental investigation of ball motions in the thrust ball bearing #51308 was carried out under various axial load conditions. Experimental results were plotted in space and projected onto a plane, illustrating a clear view of ball motions. Ball behavior in operation under various load conditions were compared each other and discussed from the viewpoint of stability of ball rotation. It was inferred that the ball rotary axis was not constant at low axial loads below 149N and it was almost constantly pointing radially at axial loads over 149N. The results demonstrated complicated ball motions under low loads, offering fundamental knowledge on the minimum axial load required for the ball without generating slip and slide.

12

Match performance in Polish amputee soccer Extra Ligue – a pilot study

70%

Nowak A. M.

Advances in Rehabilitation

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2020

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tom 34

|

nr 2

16-25

EN

Introduction The purpose of this pilot study was to determine match performance in AS considering playing positions, two halves, and playing time. Material and methods Twelve amputee soccer players were monitored for two days during the tournament of Polish Extra Ligue. The match performance data and heart rate (HR) response were collected from 4 matches (lasted 2x20 min) by Polar Team Pro. Gathered data included HR parameters, time in HRmax zones, speed, covered distance, and speed zones. Differences between two halves, 6-10 min vs. above 10 min playing time, and playing positions were assessed. Results There were not statistically differences between two halves in HR response, percentage of time in HRmax zones, speed, distance, and percentage of time in speed zones (except III HRmax zone). Significantly higher heart rate reserve and HRmax values, and total cover distance were observed in the longer playing time. Goalkeepers had significantly lower results than other players. Midfielders and defenders were similar in terms of HR response and percentage of time spent in HRmax zones. Strikers spent significantly more percentage of time in high-intensity running zone than other players. Conclusions These results brought a new knowledge to amputee soccer coaches and players about significant differences in match load relating to playing position as well as playing time. This knowledge can be beneficial in planning amputee soccer training as well as preparing special physical fitness tests corresponding to real effort during a game.

13

Effect of Three Technical Arms Swings on The Elevation of the Center of Mass During a Standing Back Somersault

70%

Mkaouer B. , Jemni M. , Amara S. , Chaabène H. , Padulo J. , Tabka Z.

Journal of Human Kinetics

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2014

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tom 40

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nr 1

37-48

EN

Arms swing during standing back somersaults relates to three different “gymnastics schools”, each is considered “optimal” by its adepts. In the three cases, technical performance, elevation and safety differ. Therefore, the aim of this study was to compare the mechanical variables of three different arms swing techniques in the performance of a standing back tucked somersault. Five high-level male gymnasts (age: 23.17±1.61 yrs; body height: 1.65±0.05 m; body mass: 56.80±7.66 kg) randomly performed standing somersaults under three conditions, each following a different arms’ swing technical angle (270°, 180° and 90°). A force plate synchronized with a three dimensional movement analysis system was used to collect kinetic and kinematic data. Significant differences were observed between somersaults’ performance. The back somersault performed with 270° arms swing showed the best vertical displacement (up to 13.73%), while the back somersaults performed with 180° arms swing showed a decrease in power (up to 22.20%). The back somersault with 90° arms swing showed the highest force (up to 19.46%). Considering that the higher elevation of the centre of mass during the flight phase would allow best performance and lower the risk of falls, this study demonstrated that optimal arms’ swing technique prior to back tucked somersault was 270°.

14

THE EFFECT OF DYNAMIC BALANCE EXERCISES ON CERTAIN KINEMATIC VARIABLES AND JUMP SHOOT ACCURACY AMONG FEMALE BASKETBALL PLAYERS

70%

Alhawary R.

Journal of Physical Education & Health - Social Perspective

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2019

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tom 8

|

nr 14

41-48

EN

The aim of the research is to identify the impact of dynamic balance exercises on certain Kinematic Variables and Jump Shoot Accuracy among Female Basketball Players. Researchers used the experimental method for one group with pre - post Tests. The research sample was intentionally selected for Female Basketball Players under the age of 16 at the Beni Suef club registered in the Egyptian Basketball Federation for the 2019 sports season and totalling ten (10) players who were filmed during the Jump Shoot after dribbling to recognize certain Kinematic Variables that affect shooting accuracy. Researchers conducted tests of front and lateral balance using a (MFT) device, Hexagon Test, Vertical jump from motion and skill tests to measure the accuracy and speed of the shoot. The implementation of the training program was conducted for eight weeks - five units per week; the time of each unit was 120 minutes, including 40 min. devoted to balance exercises. The main findings showed improvement in the results of balance tests using the (MFT)device, Hexagon, vertical jump from motion, and improvement in the motion path of the centre of gravity for the horizontal and vertical paths. It also showed benefits for the horizontal displacement transfer of Momentum to vertical motion energy which enabled the player to reach the highest point, and improvement of shooting angles which is considered the main factor in giving the ball the right trajectory in order to enter the ring to improve the ratio of the jump shoot. Researchers recommended the necessity of using dynamic balance exercises within Female training programs.

15

New possibilities for motion analysis in Hungary

70%

Kocsis L. , Kiss R. M.

Acta of Bioengineering and Biomechanics

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2004

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tom Vol. 6, nr 2

55-64

EN

Nowadays the clinical motion analysis is a usual method. More and more laboratories offer their possibilities and use their investigations for supporting doctors in their decisions. During the last two years a new and modern on-line motion analysis system was established at the Department of Applied Mechanics that allows analysis of the upper limb, gait, run, other cyclic movements and the spine.

16

The Test-Retest Reliability of Anatomical Co-Ordinate Axes Definition for the Quantification of Lower Extremity Kinematics During Running

70%

Sinclair J. , Taylor P. J. , Greenhalgh A. , Edmundson C. J. , Brooks D. , Hobbs S. J.

Journal of Human Kinetics

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2012

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tom 35

|

nr 1

15-25

EN

Three-dimensional (3-D) kinematic analyses are used widely in both sport and clinical examinations. However, this procedure depends on reliable palpation of anatomical landmarks and mal-positioning of markers between sessions may result in improperly defined segment co-ordinate system axes which will produce in-consistent joint rotations. This had led some to question the efficacy of this technique. The aim of the current investigation was to assess the reliability of the anatomical frame definition when quantifying 3-D kinematics of the lower extremities during running. Ten participants completed five successful running trials at 4.0 m·s-1 ± 5%. 3-D angular joint kinematics parameters from the hip, knee and ankle were collected using an eight camera motion analysis system. Two static calibration trials were captured. The first (test) was conducted prior to the running trials following which anatomical landmarks were removed. The second was obtained following completion of the running trials where anatomical landmarks were re-positioned (retest). Paired samples t-tests were used to compare 3-D kinematic parameters quantified using the two static trials, and intraclass correlations were employed to examine the similarities between the sagittal, coronal and transverse plane waveforms. The results indicate that no significant (p>0.05) differences were found between test and retest 3-D kinematic parameters and strong (R2≥0.87) correlations were observed between test and retest waveforms. Based on the results obtained from this investigation, it appears that the anatomical co-ordinate axes of the lower extremities can be defined reliably thus confirming the efficacy of studies using this technique.

17

Porównanie przyśpieszeń na poziomie kręgów L5/S1 w różnych pozycjach jazdy na rowerze stacjonarnym

60%

Błażkiewicz M.

Aktualne Problemy Biomechaniki

|

2009

|

tom z. 3

13--16

PL

W ostatniej dekadzie można zauważyć coraz większe zainteresowanie akcelerometrią, jako jedną z metod oceny techniki ruchu człowieka. Akcelerometry pozwalają na pomiar przyśpieszenia poszczególnych segmentów oraz całego ciała. Spinning jest jedną z form rekreacji ruchowej, stanowiącej oryginalny program kolarstwa halowego i jest skierowany do ludzi w każdym wieku. Zajęcia polegają na pedałowaniu na stacjonarnym cykloergometrze w takt muzyki, gdzie każdy z uczestników indywidualnie reguluje wartość obciążenia. Problemem jest optymalny dobór obciążenia zewnętrznego i zachowanie odpowiedniej pozycji podczas jazdy. Z tego powodu w niniejszej pracy podjęto próbę wykorzystania pomiaru przyśpieszeń do charakterystyki różnych pozycji jazdy oraz wartości obciążeń działających na człowieka podczas spinningu.

EN

Accelerometry offers a practical and low cost method of objectively monitoring human movements, and has particular applicability to the monitoring of free-living subjects. The main objective of the paper is comparsion of acceleration in four different body position during spinning.

18

Log „NavQuest 600” oraz żyrokompas „KVH 1750” jako system nawigacyjny do wyznaczania współrzędnych pozycji

60%

Naus K.

Autobusy : technika, eksploatacja, systemy transportowe

|

2017

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tom R. 18, nr 12

1159--1162, CD

PL

W artykule opisano badania mające na celu ocenę przydatności systemu nawigacyjnego złożonego z logu „NavQuest 600” oraz żyrokompasu optycznego „KVH 1750” do wyznaczania współrzędnych pozycji w warunkach morskich. W pierwszej części przedstawiono system pomiarowy, metodę badań oraz sposób wykonywania pomiarów w trudnych warunkach hydrometeorologicznych. Część zasadnicza przedstawia analizę dokładności wyznaczania parametrów ruchu i pozycji testowanym systemem nawigacyjnym polegającą na porównywaniu wyników pomiarów wzorcowych – wykonanych kompasem satelitarnym „NovAtel OEM617D-D2S-Z0G-0T0” oraz Inercjalnym Systemem Nawigacyjnym wspomaganym „VN-200” z pomiarami ocenianymi – wykonywanymi logiem „NavQuest 600” oraz żyrokompasem „KVH 1750”. Część końcowa zawiera uogólnione wnioski wyprowadzone na podstawie wyników z przeprowadzonych badań.

EN

This article describes the research that was aimed at evaluating suitability of the navigation system consisting of Doppler Velocity Log "NavQuest 600" and Fiber Optic Gyros "KVH 1750" to determining position coordinates in marine conditions. The first part shows the measurement system, the test method and the way of performing measurements in difficult hydrometeorological conditions. The main part contains analysis of the accuracy of determination of the parameters of motion and position tested by the navigation system performed by comparing the results of the reference measurements - made with the satellite compass "NovAtel OEM617D-D2S-Z0G-0T0" and the Inertial Navigation System assisted "VN-200" with test measurements - performed DVL "NavQuest 600" and FOG "KVH 1750". The final section contains generalized conclusions derived from the results of the studies.

19

Motion analysis for image sequence coding

60%

Marchewka A.

Image Processing & Communications

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2006

|

tom Vol. 11, no 1

101-105

EN

In this article we present with small modification compression standards H.26x new approach to the indexing most important regions in video sequences. This method uses block-based motion vector estimation and random Markov field. In one of section we present a discussion about an influence of block shape on results of segmentation and motion estimation. This work is not completed and many of particular results will be shown later.

20

Rejestracja ruchu żuchwy względem podstawy czaszki

60%

Bukała J. , Małachowski J. , Pietroń K. , Sybilski K. , Szafrańska A.

Aktualne Problemy Biomechaniki

|

2019

|

tom z. 17

11--17

PL

W pracy przedstawiono metodę badawczą pozwalającą na wyznaczenie krzywych opisujących ruch żuchwy względem podstawy czaszki człowieka bazującą na wideo-analizie. Do pomiaru wykorzystuje się markery pasywne odbijające promieniowanie podczerwone, które umieszczane są na nakładkach mocowanych do tkanek twardych osoby badanej.

EN

The study presents a research method for determining movement curves of the human mandible in relation to the base of the skull. The method is based on video analysis of passive markers reflecting IR radiation. Markers are placed on the personalized overlays fastened to the hard tissues of the examined person.