The kinematic differences between accurate and inaccurate squash forehand drives for athletes of different skill levels     

Benjamin K. Williams  Ross H. Sanders  Joong Hyun Ryu  Philip Graham-Smith  Peter J. Sinclair 《Journal of sports sciences》2020,38(10):1115-1123

ABSTRACT

To maintain the accuracy of squash shots under varying conditions, such as the oncoming ball’s velocity and trajectory, players must adjust their technique. Although differences in technique between skilled and less-skilled players have been studied, it is not yet understood how players vary their technique in a functional manner to maintain accuracy under varying conditions. This study compared 3-dimensional joint and racket kinematics and their variability between accurate and inaccurate squash forehand drives of 9 highly skilled and 9 less-skilled male athletes. During inaccurate shots, less-skilled players hit the ball with a more open racket, demonstrating a difference in this task-relevant parameter. No joint kinematic differences were found for accuracy for either group. Coordinated joint rotations at the elbow and wrist both displayed a “zeroing-in” effect, whereby movement variability was reduced from the initiation of propulsive joint rotation to a higher consistency at ball-impact; potentially highlighting the “functionality” of the variability prior to the impact that enabled consistent task-relevant parameters (racket orientation and velocity) under varying conditions. Further, highly skilled players demonstrated greater consistency of task-relevant parameters at impact than less-skilled players. These findings highlight the superior ability of highly skilled players to adjust their technique to achieve consistent task-relevant parameters and a successful shot.  相似文献   

Static and dynamic accuracy of a magnetic-inertial measurement unit used to provide racket swing kinematics     

Benjamin Kane Williams  Ross H. Sanders  Joong Hyun Ryu  Pitre C. Bourdon  Philip Graham-Smith  Peter J. Sinclair 《Sports biomechanics / International Society of Biomechanics in Sports》2019,18(2):202-214

Magnetic-inertial measurement units (MIMUs) are becoming more prevalent in sports biomechanics and may be a viable tool to evaluate kinematic parameters. This study examined the accuracy of a MIMU to estimate orientation angles under static conditions and dynamically from a squash racket during a forehand drive shot. A MIMU was mounted onto a goniometer and moved through 0–90°, with static data collected at 10° increments during 10 repetitions of all three axes. Typical error analyses showed the MIMU to be very reliable (TE ≤ 0.03°). MIMU accuracy was determined via intraclass correlation coefficients (ICC) (r > 0.999, p < 0.001). An ordinary least products regression showed no proportional bias and minimal fixed bias for all axes. Dynamic accuracy was assessed by comparing MIMU and optical motion capture data of squash racket swing kinematics. A MIMU was fixed onto a racket and 10 participants each hit 10 forehand shots. Mean orientation angle error at ball impact was <0.50° and ICC showed very high correlations (r ≥ 0.988, p < 0.001) for all orientations. Swing phase root mean squared errors were ≤2.20°. These results indicate that a MIMU could be used to accurately and reliably estimate selected racket swing kinematics.  相似文献   

Effects of the “Gangnam Style Syndrome” on the South Korean stock market     

Hyun Joung Jin  Jang-Chul Kim 《Journal of Cultural Economics》2018,42(1):139-161

This study attempts to answer two questions. First, can a single cultural event impact the stock prices of a wide range of companies and sectors? Second, was the positive stock market response in the information technology (IT) sector as well as performing arts sector significant? To answer these questions, we examine whether a hit pop single, “Gangnam Style” by Park Jae-Sang in 2012, affected related sectors of the Korean stock market and whether market reactions went beyond the stock price of the singer’s agency to affect those of other firms. We use an event study approach. The results show two notable empirical findings. First, although the findings indicating abnormal returns and cumulative abnormal returns appear mixed, the overall results imply that the unprecedented worldwide hit single by the South Korean singer positively affected the Recreation & Culture and Digital Content sectors. In other words, the market interpreted the event as good news, with shareholders expecting positive effects on the related sectors. Second, a positive stock market response was observed in the IT sector as well.  相似文献   

Classroom Management Strategies for Hyflex Instruction: Setting Students Up for Success in the Hybrid Environment     

Lohmann  Marla J.  Randolph  Kathleen M.  Oh  Ji Hyun 《Early Childhood Education Journal》2021,49(5):807-814

Early Childhood Education Journal - The COVID-19 pandemic changed the way that schools provide instruction to learners and these changes may last for an extended period of time. One current trend...  相似文献   

庄子与伽达默尔:忘己与体道     

贤·霍希曼 《安徽师范大学学报(人文社会科学版)》2002,30(5):514-519

把庄子"忘己以体道"的思想同伽达默尔"一个人只有失去自身才能发现自身"的思想加以比较.伽达默尔发展了海德格尔的一个观点:与一件艺术作品遭遇,就是接受一次"冲击".运用伽达默尔的思想走近庄子,可以得到一种道家诠释学."冲击"的哲学意蕴何在?柏拉图认为哲学始于惊讶,亚里士多德进而认为,哲学始于惊讶,但"并不终止于惊讶的对立面",即惊讶的消失.庄子与伽达默尔把我们带到了哲学思想的开端.我们发现自己处在哲学的源头处:一种惊讶的状态.在惊讶的状态中,我们陷入未知领域之中,失去了置身于熟悉领域之时的确定感.无论是在庄子的认识论,还是在他的伦理学与美学思想中,忘己都是体道的核心.  相似文献   

The Role of Visual Indicators in Dual Sensory Mode Instruction     

Hyun‐Ju Jeung  John Sweller 《教育心理学》1997,17(3):329-345

Advances in our knowledge of the structure of working memory suggest that under some circumstances, effectively more processing capacity is available to learners if instructional materials use multiple information modes (e.g. auditory and visual) instead of equivalent single mode formats. This paper examined this modality effect from a cognitive load perspective in three experiments using geometry instruction. In accordance with cognitive load theory, it was predicted that the additional processing capacity provided in an audio/visual format would only enhance learning if mental resources were not devoted to extensive visual based search in order to coordinate auditory and visual information. Using two different areas of geometry, Experiments 1 and 2 found that if visual search was clearly high, then audio‐visual instruction was only beneficial if visual indicators in the form of electronic flashing were incorporated into the instructional format. Under high search conditions, a standard audio/visual format without the aid of flashing proved no better than visual only instruction. Experiment 3 attempted to clarify earlier results by using instructional materials trivially low in visual search. Data indicated that a standard, audio‐visual format resulted in superior learning to a visual only format. There was no beneficial effect of electronic flashing in Experiment 3, suggesting that visual indicators were not necessary in areas of low visual search. It was concluded that cognitive load as determined by visual search established the effectiveness of visual indicators.  相似文献   

Solving Hitchcock’s transportation problem by a genetic algorithm     

陈海峰  CHO Joong. Rae  LEE Jeong. Tae 《重庆大学学报(英文版)》2004,(2)

IntroductionTheHitchcock’sTransportationProblem(HTP)canbeformulatedasaclassiclinearprogrammingprobleminwhichthesetofconstraintsisofaspecialstructure[1,2].TheHTPisapracticaltransportationprobleminproductiondistributionsector.Alotofpracticaltrans-portationandassignmentproblems,suchastheminimumcostroadnetworktrafficflowproblemwithsolidchargeinlogistics,canbeformulatedinthisway,anditisclearlythattheHTPmaybehasmorethanoneoptimalsolution.Itisveryimportantforadecision-makertoselectafavorableone…  相似文献   

Mixing languages for science learning and participation: an examination of Korean-English bilingual learners in an after-school science-learning programme     

Minjung Ryu 《International Journal of Science Education》2019,41(10):1303-1323

Bilingual and multilingual speakers mix two or more languages for communication, gaining information and sense-making in varieties of contexts. How do bilinguals mix languages and what does the mixing afford for their learning and participation? This study examines these questions, focusing on Korean-English bilingual youths in a community-based after-school science programme in the United States. A close analysis of videorecordings of the programme sessions demonstrates the ways in which bilinguals negotiate their participant positions and negotiate meanings in their study of science topics. The findings reveal that bilinguals utilise their Korean proficiency to craft diverse ways of participation and that linguistic and scientific sense-making co-occur and support each other. Based on these findings, I offer implications as to how science teachers should perceive students’ mixing of multiple languages and how they can support bilinguals’ learning of science content and English. Additionally, I suggest a future research direction that can help teachers to prepare for linguistically diverse science-learning and -teaching contexts.  相似文献   

The Social Adjustment of Three, Young, High-Achieving Korean-English Bilingual Students in Kindergarten     

Jiyoung Ryu 《Early Childhood Education Journal》2004,32(3):165-171

This research article describes the English acquisition of three, young, high-achieving, Korean, bilingual students, their academic development and their social/psychological adjustment in school. All observations and interviews were conducted in the natural classroom setting. The Korean children underwent different school experiences, partially contingent upon their English proficiency, but they generally demonstrated rapid English acquisition and healthy adjustment to school. The study findings suggest that teachers and parents play an important role in supporting their bilingual children's adjustments to new environments while preserving fundamental aspects of their original culture. Recommendations for both mainstream andbilingual teachers are suggested to further an understanding of Korean children, as English language learners and enable these children to become bilingual in Korean and English.  相似文献   

Do Stability of Care and Teacher–Child Interaction Quality Predict Child Outcomes in Early Head Start?     

Ji Young Choi  Diane Horm  Shinyoung Jeon  Dahyung Ryu 《Early education and development》2019,30(3):337-356

Research Findings: This study examined whether children’s outcomes at age 3 were predicted by their experiences in Early Head Start (EHS), focusing on 2 key features of infant and toddler care: (a) stability of care and (b) teacher–child interactions. This study further explored potential interaction effects between stability of care and teacher–child interactions in predicting child outcomes. Three main results were found from secondary analyses of the recently released EHS longitudinal data set the EHS Family and Child Experiences Study (Vogel & Boller, 2009–2012). First, children who had stability of care (no teacher change) were rated as having fewer behavior problems and higher social competence. Second, children were rated as demonstrating better orientation/engagement and emotional regulation when they were in EHS classrooms observed to have higher emotional and behavioral support. Third, teacher–child interactions that are emotionally and behaviorally supportive may mitigate the potential drawbacks of experiencing instability of care on early social-emotional development. Study implications are discussed. Practice or Policy: Both stability and quality teacher–child interactions are important in center-based infant and toddler care, and ensuring quality teacher–child interactions is particularly important for children who experience teacher changes during their infant and toddler years.  相似文献