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아마추어 테니스 동호인의 그립형태 변화가 근 활성도에 미치는 영향
송창익(Song, Chang-Ik) 한국체육과학회 2017 한국체육과학회지 Vol.26 No.2
This study recruited four men and four women amateur players of tennis and had them to hold a semi-western grip and a western grip when performing a forehand stroke. Muscle activity analysis of the forehand stroke was used to examine kinematic elements that would change between different grips. First, when men amateur players changed from the semi-western grip to the western grip during performance of the forehand stroke, increase in muscle activity of right brachioradial muscle resulted in decrease in muscle activity of right-side front deltoid, latissimus dorsi muscle, and backbone erector. Second, when women amateur players changed from the semi-western grip to the western grip during performance of the forehand stroke, decrease in muscle activity of right brachioradial muscle resulted in increase in muscle activity of right-side front deltoid, latissimus dorsi muscle, and backbone erector. Third, when women and men amateur players switched from the semi-western grip to the western grip while performing the forehand stroke, there were no statistically significant differences across all major muscles. In short, this study found that changes in wrist joint as per switching of grips affected muscle activity.
송창익(Song, Chang-Ik) 한국체육과학회 2017 한국체육과학회지 Vol.26 No.3
This research aimed to examine the effects of western grip and semi-western grip on muscle coordination change among the members of the Korean tennis national team. Conclusions are as follows. First, there were differences in muscle coordination sequences between western grip and semi-western grip across P1, P2, and P3 periods. For the P1 period, the same muscle manifestation sequence was observed with right-sided latissimus dorsi muscle. For the P2 period, the same muscle manifestation sequence was observed with backbone erector. For the P3 period, however, the same muscle manifestation sequence was not observed. Second, although changing from western grip to semi-western grip for forehand strokes resulted in different muscle manifestation sequences, it did not affect motor actions because of balances among agonistic muscle, antagonist muscle, and synergic muscle when doing a same action. In conclusion, this research shows that it is not easy to obtain deep understanding about muscle coordination and generalize the results. But an important point is that this research provides basic data for clarifying the coordination relationship between agonistic muscle and antagonist muscle. Based on this set of data, it is hoped that future research can examine what happens before and after athletes’ injuries more in depth.
정규화된 결합 공간 분할 다중화 기법의 제한된 피드백 환경에서 성능 분석
송창익(Changick Song) 한국전기전자학회 2021 전기전자학회논문지 Vol.25 No.3
5G통신의 핵심 기술인 거대다중안테나 시스템은 송신단에서 많은 양의 채널정보가 필요하기 때문에 제한된 채널 피드백을 사용하는 주파수 분할 이중 시스템에서 구현이 어려운 문제점이 있었다. 이러한 문제점을 해결하기 위해 장시간 변하지 않는 채널 상관도 정보를 이용하여 단말 그룹 간 간섭을 제거함으로써 채널정보 요구량을 비약적으로 감소시키는 Joint Spatial Division and Multiplexing(JSDM)기법이 제안되었고, 최근에는 그룹 간 잔여 간섭을 허용함으로써 성능을 더욱 향상시키는 정규화된 JSDM기법이 제안된 바 있다. 하지만 기존 JSDM관련 연구들은 주로 그룹 간 간섭제거에 초점을 두고 설계되었기 때문에, 그룹 내 간섭 제거 단계에서 제한적인 피드백을 가정한 보다 실제적인 환경에서 성능분석이 이루어지지 못하였다. 본 논문에서는 JSDM기법과 정규화된 JSDM기법을 제한된 피드백 환경에서 그룹 수와 그룹 내 사용자 수에 따른 성능을 분석하고 시뮬레이션 결과를 통해 정규화된 JSDM기법이 제한된 피드백 환경에서 기존 JSDM대비 더욱 두드러지는 이득을 보임을 입증한다. The massive MIMO system, which is a core technology of 5G communication systems, has a problem that it is difficult to implement in a frequency division duplex system based on limited channel feedback because a large amount of channel information is required at the transmitting end. In order to solve this problem, the Joint Spatial Division and Multiplexing (JSDM) technique that dramatically reduces the channel information requirement by removing interference between the user groups using channel correlation information that does not change for a long time has been proposed. Recently, a regularized JSDM technique has been proposed to further improve performance by allowing residual interference between the user groups. However, such JSDM-related studies were mainly designed to focus on inter-group interference cancellation, and thus performance analysis was not performed in a more realistic environment assuming limited feedback in the intra-group interference cancellation phase. In this paper, we analyze the performance of the JSDM and regularized JSDM techniques according to the number of groups and users in a limited feedback environment, and through the simulation results, demonstrate that the regularized JSDM technique shows a more remarkable advantage compared to the existing JSDM in a limited feedback environments.