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Yuta Suzuki Michiyoshi Ae Shunsuke Takenaka Norihisa Fujii 《Sports biomechanics / International Society of Biomechanics in Sports》2014,13(2):144-153
The purpose of this study was to investigate differences in the support leg joint moment and moment power between side-step (SS) and cross-step (CS) cutting techniques with a prescribed 90° cutting angle. Ground reaction forces (1,000 Hz) and three-dimensional kinematics (250 Hz) of SS and CS cutting techniques were collected from 20 male college athletes. Normalised peak knee extension moment was larger in the SS technique than in the CS technique (0.40 ± 0.10 in SS; 0.26 ± 0.08 in CS). In the SS technique, the knee extensors ( ? 0.10 ± 0.06 in SS; ? 0.02 ± 0.04 in CS) and ankle plantarflexors ( ? 0.12 ± 0.05 in SS; ? 0.07 ± 0.03 in CS) did significantly more negative work (normalised). The direction change angle (40.5 ± 8.7° in SS; 33.0 ± 6.8° in CS) and the decrease in horizontal velocity of the centre of mass ( ? 0.63 ± 0.23 m/s in SS; ? 0.31 ± 0.23 m/s in CS) were significantly larger in the SS technique. These results suggest that the SS technique is an effective means of changing running direction at the expense of velocity of the centre of mass and that the CS technique is better for minimising the reduction in horizontal velocity of the centre of mass. 相似文献
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Seitaro Kumamoto Kenshiro Nakatake Souichiro Fukuyama Keiichiro Yasuda Yusuke Kitamura Masaaki Iwatsuki Hideo Baba Toshihiro Ihara Yoshitaka Nakanishi Yuta Nakashima 《Biomicrofluidics》2020,14(6)
To study an environmental or biological solution, it is essential to separate its constituents. In this study, a 3D-deformable dynamic microfilter was developed to selectively separate the target substance from a solution. This microfilter is a fine metallic nickel structure fabricated using photolithography and electroplating techniques. It is gold-coated across its entire surface with multiple slits of 10–20 μm in width. Its two-dimensional shape is deformed into a three-dimensional shape when used for fluid separation due to hydrodynamic forces. By adjusting the pressure applied to the microfilter, the size of the gap created by deformation can be changed. To effectively isolate the target substance, the relationship between the solution flow rate and the extent of microfilter deformation was investigated. The filtration experiments demonstrated the microfilter’s ability to isolate the target substance with elastic deformation without undergoing plastic deformation. Additionally, modification of the microfilter surface with nucleic acid aptamers resulted in the selective isolation of the target cell, which further demonstrates the potential application of microfilters in the isolation of specific components of heterogeneous solutions. 相似文献
3.
Takanori Ishii Michiyoshi Ae Yuta Suzuki Yasuto Kobayashi 《Sports biomechanics / International Society of Biomechanics in Sports》2018,17(2):238-250
This study sought to identify biomechanical factors that determine fast and skilful execution of the seoi-nage (shoulder throw) technique by comparing kinematics between elite and college judo athletes. Three-dimensional motion data were captured using a VICON-MX system with 18 cameras operating at 250 Hz as three male elite and seven male college judo athletes performed seoi-nage. No significant difference was found in motion phase time of the turning phase between the two groups, indicating that motion phase time is not necessarily a factor contributing quickness in seoi-nage. The maximum relative velocity of the whole body centre of mass along the anterior–posterior direction was significantly greater in the elite athletes (2.74 ± 0.33 m/s) than in the college athletes (1.62 ± 0.47 m/s) during the turning phase (p = 0.023). The overall angular velocity of the body part lines, particularly the arm line, tended to be greater in the elite athletes (p = 0.068). The results imply that the velocity of the thrower relative to the opponent in the forward drive and turning motion reflects high skill seoi-nage. Coaches should recognise the relative forward velocity as a factor that may contribute to a successful seoi-nage when teaching the judo throw technique. 相似文献
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The main objective of this research was to develop a markerless optical motion capture system that can be used for daily use in swimming training. The butterfly stroke was targeted since it is considered bilaterally symmetric in motion. The system consisted of a segmentation process to obtain the participant’s silhouettes and a matching process to estimate the pose of the participant. A variable thresholding method was used to extract the silhouettes to solve non-uniform illumination in the recorded swimming video. Prior to the matching process, the human body was modeled as a series of nine segments to help the matching process. The model was then mapped so that it aligned with the silhouettes, which were investigated by similarity of intensity value. To minimize the degree of freedom in image matching, the available joint motion in the swimming human simulation model was used as a priori information for kinematics data of the swimming motion. As a result, the rotation angle’s correlation coefficients between the references and result of the matching process were around 0.95 for trunk, thigh, shank, upper arm, forearm, hand and 0.78 for head, hip and foot. The rotation angle and the velocity of the center of mass were put into the swimming human simulation model for a dynamics analysis. The simulation results show that the velocity obtained in the experiment corresponded to the fluid force exerted on the lower and upper limbs. Consequently, the proposed system of obtaining the joint motion of the butterfly stroke is suitable for daily training and coaching. 相似文献
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Hideki Takagi Motomu Nakashima Yohei Sato Kazuo Matsuuchi 《Journal of sports sciences》2016,34(16):1564-1580
This paper reviews unsteady flow conditions in human swimming and identifies the limitations and future potential of the current methods of analysing unsteady flow. The capability of computational fluid dynamics (CFD) has been extended from approaches assuming steady-state conditions to consideration of unsteady/transient conditions associated with the body motion of a swimmer. However, to predict hydrodynamic forces and the swimmer’s potential speeds accurately, more robust and efficient numerical methods are necessary, coupled with validation procedures, requiring detailed experimental data reflecting local flow. Experimental data obtained by particle image velocimetry (PIV) in this area are limited, because at present observations are restricted to a two-dimensional 1.0 m2 area, though this could be improved if the output range of the associated laser sheet increased. Simulations of human swimming are expected to improve competitive swimming, and our review has identified two important advances relating to understanding the flow conditions affecting performance in front crawl swimming: one is a mechanism for generating unsteady fluid forces, and the other is a theory relating to increased speed and efficiency. 相似文献
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Jia Liu Tetsuro Ito Nana Toyokuni Keizo Sato Makoto Nakashima 《Information processing & management》2012
Reading together draws much attention as a societal concern for children not only to yield emotional reaction but also to gradually advance intellectual thinking. We here aim to build a new environment, in which children’s browsing and reading of picture books together with families and/or friends is steadily enhanced, by installing the BrowsReader in the children’s room of a public library or a kindergarten. The original BrowsReader was a system to assist children in finding and reading picture books. The children, by gathering around the BrowsReader, can browse picture books and then choose and read a book by flipping pages on it. After reproducing each printed, digitized or web picture book as a surrogate picture book consisting of the front-cover image followed by the page images, we first introduce two basic notions: (i) an abstracted bookshelf, which presents the front-cover images of the surrogate picture books in the form where all are linearly arranged, with some of the images bundled in places, and (ii) a unified view, which presents each page of any surrogate picture book in a form that seems like a printed picture book’s page. We then specify, based on these notions, the improved version of the BrowsReader which can be installed in each children’s room so that children together with families and/or friends can easily browse a large number of surrogate picture books as if they are browsing in the physical bookshelves of the children’s room, and can read a wide variety of surrogate picture books as if they are reading ordinary printed picture books on a table. The improvement was carried out in a step by step process based on feedback and results from case studies, and its effects were clarified by seeing whether, in a new environment, the children’s activity in browsing/reading together were steadily enhanced when using the BrowsReader. 相似文献
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The occurrence frequencies of the dinucleotides of genes of three thermophilic and three mesophilic species from both archaea
and eubacteria were investigated in this study. The genes encoding water soluble proteins were rich in the dinucleotides of
purine dimers, whereas the genes encoding membrane proteins were rich in pyrimidine dimers. The dinucleotides of purine dimers
are the counterparts of pyrimidine dimers in a double-stranded DNA. The purine/pyrimidine dimers were favored in the thermophiles
but not in the mesophiles, based on comparisons of observed and expected frequencies. This finding is in agreement with our
previous study which showed that purine/pyrimidine dimers are positive factors that increase the thermal stability of DNA.
The dinucleotides AA, AG, and GA are components of the codons of charged residues of Glu, Asp, Lys, and Arg, and the dinucleotides
TT, CT, and TC are components of the codons of hydrophobic residues of Leu, Ile, and Phe. This is consistent with the suitabilities
of the different amino acid residues for water soluble and membrane proteins. Our analysis provides a picture of how thermophilic
species produce water soluble and membrane proteins with distinctive characters: the genes encoding water soluble proteins
use DNA sequences rich in purine dimers, and the genes encoding membrane proteins use DNA sequences rich in pyrimidine dimers
on the opposite strand. 相似文献
8.
Aerodynamic properties of an archery arrow 总被引：1，自引：0，他引：1
Takeshi Miyazaki Keita Mukaiyama Yuta Komori Kyouhei Okawa Satoshi Taguchi Hiroki Sugiura 《Sports Engineering》2013,16(1):43-54
Two support-interference-free measurements of aerodynamic forces exerted on an archery arrow (A/C/E; Easton Technical Products) are described. The first measurement is conducted in a wind tunnel with JAXA’s 60 cm Magnetic Suspension and Balance System, in which an arrow is suspended and balanced by magnetic force against gravity. The maximum wind velocity is 45 m/s, which is less than a typical velocity of an arrow (about 60 m/s) shot by an archer. The boundary layer of the arrow remains laminar in the measured Re number range (4.0 × 103 < Re < 1.5 × 104), and the drag coefficient is about 1.5 for Re > 1.0 × 104. The second measurement is performed by a free flight experiment. Using two high-speed video cameras, we record the trajectory of an archery arrow and analyze its velocity decay rate, from which the drag coefficient is determined. In order to investigate Re number dependence of the drag coefficient in a wider range (9.0 × 103 < Re < 2.4 × 104), we have developed an arrow-shooting system using compressed air as a power source, which launches the A/C/E arrow at an arbitrary velocity up to 75 m/s. We attach two points (piles) of different type (streamlined and bullet) to the arrow-nose. The boundary layer is laminar for both points for Re less than about 1.2 × 104. It becomes turbulent for Re larger than 1.2 × 104 and the drag coefficient increases to about 2.6, when the bullet point is attached. In the same Re range, two values of drag coefficient are found for the streamlined point, of which the lower value is about 1.6 (laminar boundary layer) and the larger value is about 2.6 (turbulent boundary layer), confirming that the point-shape has a crucial influence on the laminar to turbulent transition of the boundary layer. 相似文献
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The cause and effect relationship between the paddling motion and the hull behavior of a kayak in a sprint race has not been sufficiently investigated. The objective of this study was to investigate the effect of the paddling motion on the hull behavior by numerical simulation. A dynamic simulation model of a paddler, paddle and hull in a single kayak, which was previously developed, was used for the simulation. One standard paddling motion and three modified motions were prepared for the simulation. Three modified motions were created based on suggestions by coaches of the Japan Olympic team. These motions were thought to be often seen in paddlers of lower skill level and, therefore, empirically considered to be typically bad motions. From the simulation results, the following findings were obtained: in the simulation of the standard paddling motion, the averaged hull velocity was 5.4 m/s. This was consistent with the actual hull velocity of 5.5 m/s. Typically bad motions which induced undesirable hull fluctuations reduced the propulsive efficiency. 相似文献
10.
This study evaluates whether high levels of executive function predict competition results 18 months later in junior tennis players. Forty junior tennis players (20 girls, 20 boys; 9–15 years old) who regularly participate in prefecture tennis tournaments were recruited. All participants underwent executive function evaluations (the Design Fluency Task) in July 2015 and their prefecture junior rankings in August 2015 and February 2017 were recorded. As a result, after controlling for age and gender, the future ranking (February 2017) was significantly predicted by performance in the Design Fluency Task (β = -.30, p = .02; ΔR2 = .08), whereas the prediction for August 2015 rank as the baseline was not significant (β = -.19, p = .17; ΔR2 = .03). After controlling for age, gender, and ranking in the baseline, the change in ranking was significantly predicted by performance in the Design Fluency Task (β = -.14, p = .02; ΔR2 = .02). This suggests that childhood executive function may play a significant role in success later in life. This study highlights how executive function predicts future success in a specific sport; as such, supporting the development of executive function may contribute to higher competition results. 相似文献
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