THE IMPORTANCE OF USING CIRCUIT TRAINING IN THE DEVELOPMENT OF CONDITIONAL AND COORDINATIVE ABILITIES OF MALE U17 HANDBALL PLAYERS

Introduction. The necessity of a proper physical training of athletes and their harmonious development of also implies making them accustomed with the practice of circuit training within handball specific training sessions. This ensures the mastery of a complex set of exercises and its methods of execution. Aims: We started from the premise that the chaining of several handball specific exercises within a training circuit can be beneficial for the development of conditional and coordinative abilities of the male U17 handball players. Methods: The method used was mainly the experimental one, speed testing in different directions was performed, with emphasis on execution, acceleration and force speed, as well as agility and general coordination. Data interpretation was performed by applying the statistical-mathematical method, the method of graphical representations. Results: The results show a statistically significant difference between mean results obtained by the subjects of the two groups in the "Training circuit 1" test for testing speed in different directions, with emphasis on execution, acceleration and force speed, as well as agility and general coordination, the average being 31.98 sec. for the experiment group and 34.48 sec. for the control group. As a result, the average of the experiment group is lower by 2.51 sec. (7.27%). Conclusions: The higher the motor skill indicators, the more the technical-tactical abilities of male U17 handball players will make the difference in achieving maximum efficiency.

Influence of specimen geometry and strain rate on elongation in tensile testing of packaging steel

Packaging steel is characterized by low thickness (0.1 mm – 0.5 mm) and ferritic microstructure resulting from low carbon contents. In combination with continuous annealing processes and temper rolling, this results in only little elongation observed in tensile tests. However, as in real forming processes much higher deformation occurs, it is important to receive true stress-true strain data up to a highest possible level e.g. to characterize material for finite element analysis. Therefore, tensile tests with three different measuring lengths (80 mm, 50 mm, 20 mm) were conducted for the packaging steel TH415. Likewise, the testing speed was reduced to investigate the possibility to receive more elongation under the condition of a constant stress level. The results revealed a significant increase in elongation when using smaller tensile test geometries. As well, the reduction in testing speed leads to much higher elongation while showing only little strain rate influence. While for the 80 mm geometry and standard speed no homogenous forming condition could be reached due to early failure before Lüders strain, this could be improved by using smaller testing specimens and a lower strain rate. Combining the influence of strain rate and geometry a significant increase of more than ten percentage points in elongation was reached.

Investigating the factors influencing the shear behaviour of 0/90∘ non-crimp fabrics to form a reference shear test

Technical textiles have the ability to deform under load by shearing, which distinguishes them from thin sheet materials such as paper. This particular property helps them to deform and take the shape of the complex part that they were intended to create. Draping, flexibility and handling of technical textiles are greatly affected by their shearing behaviour. In this paper, the influence that factors such as stitch (i.e., presence or absence of it), testing speed and the pre-tension force applied have on the shear behaviour of 0/90∘ technical textile is studied to form a reference test. To achieve this, 0/90∘ technical textile samples in two different forms are prepared and subjected to the Trellis picture frame test. It was observed that the presence of stitch greatly affected the critical shear angle and the maximum shear force experienced by the textile. Increase in testing speeds and pre-tension force also increased the shear force experienced by it. However, the critical shear angle decreased with the increase in testing speed, while the value of pre-tension force applied had no effect on the critical shear angle.

OLBVH: octree linear bounding volume hierarchy for volumetric meshes

We present a novel bounding volume hierarchy for GPU-accelerated direct volume rendering (DVR) as well as volumetric mesh slicing and inside-outside intersection testing. Our novel octree-based data structure is laid out linearly in memory using space filling Morton curves. As our new data structure results in tightly fitting bounding volumes, boundary markers can be associated with nodes in the hierarchy. These markers can be used to speed up all three use cases that we examine. In addition, our data structure is memory-efficient, reducing memory consumption by up to 75%. Tree depth and memory consumption can be controlled using a parameterized heuristic during construction. This allows for significantly shorter construction times compared to the state of the art. For GPU-accelerated DVR, we achieve performance gain of 8.4$$\times $$ × –13$$\times $$ × . For 3D printing, we present an efficient conservative slicing method that results in a 3$$\times $$ × –25$$\times $$ × speedup when using our data structure. Furthermore, we improve volumetric mesh intersection testing speed by 5$$\times $$ × –52$$\times $$ × .

Fast Vehicle and Pedestrian Detection Using Improved Mask R-CNN

This study presents a simple and effective Mask R-CNN algorithm for more rapid detection of vehicles and pedestrians. The method is of practical value for anticollision warning systems in intelligent driving. Deep neural networks with more layers have greater capacity but also have to perform more complicated calculations. To overcome this disadvantage, this study adopts a Resnet-86 network as a backbone that differs from the backbone structure of Resnet-101 in the Mask R-CNN algorithm within practical conditions. The results show that the Resnet-86 network can reduce the operation time and greatly improve accuracy. The detected vehicles and pedestrians are also screened out based on the Microsoft COCO dataset. The new dataset is formed by screening and supplementing COCO dataset, which makes the training of the algorithm more efficient. Perhaps, the most important part of our research is that we propose a new algorithm, Side Fusion FPN. The parameters in the algorithm have not increased, the amount of calculation has increased by less than 0.000001, and the mean average precision (mAP) has increased by 2.00 points. The results show that, compared with the algorithm of Mask R-CNN, our algorithm decreased the weight memory size by 9.43%, improved the training speed by 26.98%, improved the testing speed by 7.94%, decreased the value of loss by 0.26, and increased the value of mAP by 17.53 points.

The Behavior of Polymeric Blends (PP + PA6) in Tensile Tests

This paper presents the influence of component concentration for a class of polymeric blends with different concentration of PP (polypropylene) and PA6 (polyamide 6) and a constant concentration of additives: CaCO3, LDPE (low density polyethylene) and a compatibilizer POLYBOND� 3200. Mechanical properties has been investigated for four different test speeds, from 10 mm/min to 1000 mm/min. Young�s modulus performs in a band between 1500...1900 MPa, except for the value for PA6 at the lowest testing speed (v=10 mm/min), that is 1444 MPa. At high concentration of PA6, there were noticed voids in the longitudinal direction of the samples, forming large parallel �empty channels�, as the two polymers are immiscible. Except for values at low testing speed, the average values for tensile stress at break perform in a band of less than 8 MPa. The elongation at break is less than 10% for all materials, except for PA6 at the lowest testing speed, when a higher value was obtained. The lowest values were obtained for the blend with 20% PA6. For blends with 60% and 80% PA6, the difference between values, at the same testing speed, is the smallest. Energy at break has a slightly increase with the concentration of PA6. From the mechanical point of view, among the formulated blends, material D (with 80% PA6) is the most promising as has the highest values for stress and energy at break (11.8 J at v=10 mm/min and 9.6 J at v=1000 mm/min), but values are still less than those for PA6.

Standards for physical fitness of biathletes during the period of sport skills perfectionм

The purpose – perfection of the techniques for controlling speed-strength capabilities and endurance of the rotator cuff muscles of biathletes during the period of sport skills perfection. Research methods and organization. The study involved 204 biathletes aged 15-17. We tested the speed- strength abilities and endurance of rotator cuff muscles with the Skierg Concept2 ski ergometer (USA). Research results. Significant changes in the endurance of rotator cuff muscles of biathletes occur in the age period from 15 to 16 years. The change in speed-strength abilities of female biathletes, in contrast to male biathletes, occurs against the background of an increase in the number of ski pole movements per minute. We processed the obtained data using the method of determining the boundaries of confidence intervals. Based on the data processed, we developed the standards for assessment of the speed-strength abilities and strength endurance of rotator cuff muscles of biathletes during the period of sport skills perfection with the Skierg Concept2 ski ergometer (USA). We tested applicability of the developed standards for speed-strength abilities and strength endurance of rotator cuff muscles in a one-year educational experiment. Conclusion. We proposed a methodology for testing speed-strength abilities and strength endurance of rotator cuff muscles with the Skierg Concept2 ski ergometer (USA) in the framework of our study. The developed stand- ards for assessing speed-strength abilities and strength endurance of rotator cuff muscles of biathletes during the period of sport skills perfection help to identify strong and weak points of fitness and to predict the possibility of achieving certain results by individual parameters.

The effect of sea-water on the tribological properties of polyurethanes

Purpose Ocean exploration is of importance and in great demand throughout the world. This results in a huge challenge in tribology in the marine environment. Moreover, polymeric materials with large molecules or macromolecules play an important role in marine equipment. Design/methodology/approach The tribological performance of sea-water-eroded polyether polyurethane (PU) was systematically studied by using a multi-specimen test machine for different durations from 0 to 60 days. Surface characterization technologies, such as scanning electric microscopy energy dispersive spectroscopy, were used to analyze the PU samples. Findings It can be found that the COF measured against 316 steel increases with the testing load because of the change of contact areas for the original PU samples. The effect of hydrodynamic lubrication and heat resulted in the decline of the COF with the increase in testing speed. The COF of PU sample immersed for 20 days was the lowest compared with other samples. With the immersion time increased to 60 days, the COF increased first and then decreased. The reduced COF of PU resulted in improved anti-wear performance of the PU sample. Originality/value These results enhanced the comprehension of the tribological performances of PU immersed in sea-water.

Reconstruction of head impacts in FIS World Cup alpine skiing

IntroductionPrior to the 2013/2014 season, the International Ski Federation (FIS) increased the helmet testing speed from 5.4 to 6.8 m/s for alpine downhill, super-G and giant slalom. Whether this increased testing speed reflects head impact velocities in real head injury situations on snow is unclear. We therefore investigated the injury mechanisms and gross head impact biomechanics in seven real head injury situations among World Cup (WC) alpine skiers.MethodsWe analysed nine head impacts from seven head injury videos from the FIS Injury Surveillance System, throughout nine WC seasons (2006–2015) in detail. We used commercial video-based motion analysis software to estimate head impact kinematics in two dimensions, including directly preimpact and postimpact, from broadcast video. The sagittal plane angular movement of the head was also measured using angle measurement software.ResultsIn seven of nine head impacts, the estimated normal to slope preimpact velocity was higher than the current FIS helmet rule of 6.8 m/s (mean 8.1 (±SD 0.6) m/s, range 1.9±0.8 to 12.1±0.4 m/s). The nine head impacts had a mean normal to slope velocity change of 9.3±1.0 m/s, range 5.2±1.1 to 13.5±1.3 m/s. There was a large change in sagittal plane angular velocity (mean 43.3±2.9 rad/s (range 21.2±1.5 to 64.2±3.0 rad/s)) during impact.ConclusionThe estimated normal to slope preimpact velocity was higher than the current FIS helmet rule of 6.8 m/s in seven of nine head impacts.