• Steel and Composite Structures
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• v.49 no.5
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• pp.487-502
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• 2023

In the realm of nanotechnology, the nonlocal strain gradient theory takes center stage as it scrutinizes the behavior of spinning cantilever nanobeams and nanotubes, pivotal components supporting various mechanical movements in sport structures. The dynamics of these structures have sparked debates within the scientific community, with some contending that nonlocal cantilever models fail to predict dynamic softening, while others propose that they can indeed exhibit stiffness softening characteristics. To address these disparities, this paper investigates the dynamic response of a nonlocal cantilever cylindrical beam under the influence of external discontinuous dynamic loads. The study employs four distinct models: the Euler-Bernoulli beam model, Timoshenko beam model, higher-order beam model, and a novel higher-order tube model. These models account for the effects of functionally graded materials (FGMs) in the radial tube direction, giving rise to nanotubes with varying properties. The Hamilton principle is employed to formulate the governing differential equations and precise boundary conditions. These equations are subsequently solved using the generalized differential quadrature element technique (GDQEM). This research not only advances our understanding of the dynamic behavior of nanotubes but also reveals the intriguing phenomena of both hardening and softening in the nonlocal parameter within cantilever nanostructures. Moreover, the findings hold promise for practical applications, including drug delivery, where the controlled vibrations of nanotubes can enhance the precision and efficiency of medication transport within the human body. By exploring the multifaceted characteristics of nanotubes, this study not only contributes to the design and manufacturing of rotating nanostructures but also offers insights into their potential role in revolutionizing drug delivery systems.

• Korean Journal of Applied Biomechanics
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• v.21 no.5
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• pp.551-560
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• 2011

The purpose of this study was to perform the kinematic analyses of the men's pole vault skills in IAAF World Championships Daegu 2011. Subjects were the 1st through 8th place finishers in the pole vault. The kinematic analyses were divided into four phases: two dimensional run up analysis, and three dimensional analyses for the remaining plant, swing up, and extension phases. Run-up variables consisted of run up distance, number of steps, average step length, the ratio of step length to his height, average velocity at the final 6~11 m, approach position. Three variables were analyzed during plant: pole angle, center of gravity (COG) velocity, and takeoff angle of COG. Swing up phase variables included: pole flexion angle, COG velocity (horizontal, vertical, resultant), COG trajectory and bar approach angle of COG. Compared to the 2009 World Championships in Berlin, the average vault height, run up velocity and approach position increased. However, horizontal velocity during the last two steps of the final approach decreased dramatically compared to speeds from 1990. These results reflect the change in both technique and improved physical fitness in pole vaulters. During extension, the peak height of COG averaged 0.3m higher then COG height when the pole was released. These specific results can help coaches and athletes modify training and improve performance.

• Journal of the Korea Safety Management & Science
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• v.15 no.4
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• pp.153-160
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• 2013

The purpose of this study was to compare biomechanical factors on badminton shoes between anti-slip outsole and non anti-slip outsole. Six subjects participated in this experiment. For three-dimensional analysis, eight cameras (Oqus 3series, Qualisys) were used to acquire raw data, and then the parameters were calculated and analyzed with Visual-3D. In conclusion, the patterns of spent time during side step, and maximum velocities of CoGs were consistent without joint angles of lower extremities in spite of small differences. Those of GRFs, and moment of lower extremities were absolutely consistent. This trend of biomechanical factors was that Y shoe (ante-treatment) was much greater and PS shoe (treatment) was greater than Y shoe (treatment). (That was, Y shoe (ante-treatment) > PS shoe (treatment) >Y shoe (treatment)). The findings of this study showed that anti-slip outsole was effective and brought increasing performance and decreasing injuries. It is suggested that further study of these phenomena will help understand many aspects of human locomotion, including work, performance, fatigue and possible injuries.

• Korean Journal of Applied Biomechanics
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• v.23 no.2
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• pp.99-108
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• 2013

The purpose of this study was to analyze the kinematic characteristics of javelin to compare the characteristics between world elite athletes and local male athletes. The subjects selected 9 athletes out of total 13 athletes recorded more than 65 m in the preliminary and main competition participated in the 93rd National Sports Festival held in 2012. Three-Dimensional motion analysis using a system of 4 video cameras(Sony HXR-MC2000) at a sampling frequency of 60 fields/s was performed for this study. The Kwon3D 3.1 was used to obtain the three dimensional coordinates about the top, grip, end of javelin. And the kinematic factors of javelin calculated using Matlab2009a program. The resultant speed of javelin that affects directly to the record of performance showed 26.08 m/s indicated lower speed of about 2-3 m/s than world elite athletes. The release point appeared to have been made at the high of $1.79{\pm}0.07$ m of 99.8% of the height of the athletes. In terms of release angle, it was indicated average $33.0{\pm}3.81^{\circ}$ lower release angle compared to the world elite athletes. The attitude angle(up & down tilt angle, X axis) related to javelin indicated average $38.5{\pm}4.96^{\circ}$, its related attack angle average $5.5{\pm}5.11^{\circ}$, and yaw angle(sideslip, side attack angle) average $15.7{\pm}8.48^{\circ}$.

• Korean Journal of Applied Biomechanics
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• v.23 no.3
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• pp.189-200
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• 2013

The purpose of this study was to compare the kinematic analyses of the women's pole vault skills difference between skilled group (1st to 8th place) and less skilled group (10th to 15th place) who participated in IAAF World Championships Daegu 2011. To achieve this goal, 16 women's pole vault player's kinematic analyses was conducted. Player's best performance was recorded by five normal video cameras operating at 60 Hz. The results of this study through the research procedures above are as follows. First, Skilled group's average step length and the ratio of step length to her height were longer than less skilled's group in run-up phase. Second, Skilled group's horizontal velocity was faster than less Skilled group's results. And pole plant angle was lower than less Skilled group's results in take-off phase. Third, Maximum pole flexion angle did not show difference of between two groups in pole bending phase. However, Skilled group's vertical velocity was higher than less skilled group's results.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.18 no.3
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• pp.84-91
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• 2010

New aircraft category such as Light Sport Aircraft is introduced to prevent Ultralight Vehicle accidents and to promote aviation sports. Therefore, a new rule for airworthiness standard, certification, operation and maintenance of light sport aircraft is being created. The present study deals with LSA concept, development trend of LSA, airworthiness standards and certification policy. In particular, an aircraft type analysis of FAA certified LSA is conducted to establish performance requirements of Light Sport Aircraft designs.

• Korean Journal of Applied Biomechanics
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• v.23 no.3
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• pp.245-252
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• 2013

The purpose of this study was to analyze the effect that various loads have on the lower limb biomechanics. The following variables were measured and analyzed; performance time for each phase, lower limb moments and joint angles, and ground reaction forces. The kinematic and kinetic data was recorded by 2 force platforms and a motion capture system while 12 healthy adults in their twenties stepped down three steps under loads of 0%, 10%, 20% BW. Results are as follows. First, the different loading conditions did not seem to significantly affect the performance times and the joint angles. Second, the largest ground reaction forces were observed at the 1 step at the 10% BW condition. Finally, at the 0% BW loading condition the right hip extension moment was the smallest and the left hip flexion moment was the largest. The results show that there are not any significant changes in the biomechanics of the lower limbs under loading conditions up to 20% BW. Further investigations including more loading conditions with more weights and more additional steps analyzed are needed.

• Journal of the Korea Convergence Society
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• v.11 no.6
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• pp.359-365
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• 2020

The purpose of this study was to collect and analyze information on the major scoring paths, success rate by shooting type, assist, steal, block, and goalkeeper defense rate by shooting type in the 2019 World Women's Handball Championship. Based on the research results, the following conclusions were drawn. First, as a result of the analysis of the scoring route, 1st the Netherlands and 2nd Spain had 6m shots and 7m shots the most. Second, in the success rate analysis results by shooting type, the top 6 teams showed 7m shot, breakthrough shot, and fast shot. Third, according to the result of assist frequency analysis, the fourth place in the competition Norway scored the most assists among the six teams. Fourth, as a result of the steel frequency analysis, Norway scored the most with 5.2 on average among the six teams. Fifth, as a result of analyzing the goalkeeper defense rate by shooting type, it was found that all 6 team's goalkeepers had the highest defense against 9m shooting. Therefore, for an in-depth analysis of the game strategy, it is considered that it is necessary to understand the characteristics of individual player's performance and collect information will be followed by a follow up research in the future.

• Journal of the Korea Convergence Society
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• v.10 no.2
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• pp.301-307
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• 2019

The purpose of this study is to evaluate the lap time of K-1 sprint competition and compare the records of the best group and the other groups. Based on these data we are willing to provide them on pace control strategies for improving their performances. The analysis was conducted on 12 elite kayak players, measuring the lap time by every interval after dividing the entire 1,000-meter race into 10 sections of 100 meters. We divide the group A, B, C and D based on their final time records. Two-factor repeated measures ANOVA, One-way ANOVA, and correlation analysis were performed. There were no significant lap time differences in the section of first 200m and last 200m between A, B and C. But the C's lap time of 200m~600m were significantly later than group A and B. Non-superior athletes need to establish strategies to reduce lap time in the middle section.

• 한국체육학회지인문사회과학편
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• v.55 no.2
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• pp.35-46
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• 2016

This study aims to observe the operation aspect of physical education during before class and further, to search for the utmost improvement direction using IPA (Importance-Performance Analysis). 500 middle & high school students have chosen through a purposeful sampling method, and 430 was used for analysis. The results were as follows. The quadrant I is "the keep up the good work" part. And the quadrant I includes "de-stress", "the pleasure of school life", "improvement in performance", "peer relationship", "help for P.E.", "health promotion", "sport facility surroundings", "rules", "teacher leadership", "passionate coaching", "fair coaching", "improvement in exercise ability", "understanding P.E." The quadrant II is "the concentrate here" part. And the quadrant II includes "develop talent", "excercise time", "safety management for exercise facility", "new sports event", "consider needs and interests", "consider level" "consider gender". The quadrant III is "the low priority" part. And the quadrant III includes "change of personality", "ability to do various sports event", "develope thinking ability". "communication with peer" "an intelligible explanation" In order to improve the quality of before classes, first, "safety connected program" second, "emotional and intellectual development program", third, "divided classes per level and gender", and the last, "professional manpower for developing the quality of class" are needed.