• Physical Therapy Rehabilitation Science
• /
• 제4권1호
• /
• pp.22-27
• /
• 2015

Objective: Jump training helps increase the muscle power by improving the muscle strength and reaction time of the muscle in operation. The purpose of this study was to identify the effects of strengthening, stretching exercise and meditation on electromyographic (EMG) onset timing of rectus femoris and gastrocnemius muscle during vertical jump performance. Design: Cross-sectional study. Methods: Ten healthy adults (5 male and 5 female) who were familiar with the vertical jumping task and had no lower extremity injuries or any bone or joint disorders, were recruited for this study. Muscle onset timing was measured by surface EMG. After EMG onset timing were measured during performing three baseline vertical jump trials, strengthening and stretching exercises of the rectus femoris and gastrocnemius, and meditation were performed in random order. EMG onset timing was measured during vertical jump after intervention, respectively. EMG value was averaged for the three trials and analyzed using one-way repeated ANOVA. Results: During vertical jump, EMG onset timing of gastrocnemius was a significant difference after intervention (p<0.05), and then there was significantly faster in strengthening exercise than meditation (p<0.05). Conclusions: These results indicate the potential positive effect of performing strengthening exercise of the gastrocnemius before a jumping event. Future research is required to identify the effects of intervention over a long period.

• 한국운동역학회지
• /
• 제22권3호
• /
• pp.305-314
• /
• 2012

The purpose of this study was to investigate the effects of joint kinetics and coordination on within-individual differences in maximum vertical jump. 10 male subjects aged 20 to 30 performed six trials in maximum vertical jump and with based on jump height the good(GP) and bad(BP) performances for each subject were compared on joint kinetics of lower extremity and coordination parameters such as joint reverse and relative phase. The results showed that maximum moment, power, and work done of hip joint and maximum moment of ankle joint in GP were significantly higher than that in the BP but no significant differences for the knee joint. We could observe a significant difference in joint reverse timing between both conditions. And also the relative phase on ankle-knee and ankle-hip in GP were significantly lower than that in the BP, which means that in GP joint movements were more in-phase synchronized mode. In conclusion, mechanical outputs of hip and ankle joints had an effect on within-individual differences in vertical jump and the inter-joint coordination and coordination including sequence and timing of joint motion also might be high influential factors on the performances within individual.

• Journal of Positioning, Navigation, and Timing
• /
• 제4권1호
• /
• pp.25-31
• /
• 2015

In this paper, we described the timing-offset comparison results between various daily jump compensation methods for GPS carrier phase (CP) measurement data. For the performance comparison, we used about 70 days GPS measurement data obtained from two GPS geodetic receivers which share the reference 1 PPS and RF signals and closely located in each other within a few meters. From the experiment results, the followings were observed. First, daily jumps existed in CP measurements depend on not only the environment but also the receiver which will make a full compensation be very hard or impossible. Second, clock bias can be occurred in the case of using a simple compensation with accumulation of daily jumps but it could be used in a short-period frequency comparison campaign (less than about 7 days) despite of its drawback.

• 한국운동역학회지
• /
• 제32권2호
• /
• pp.43-48
• /
• 2022

Objective: The purpose of this study was to verify the effectiveness among simulating ski jumping trainings by comparing with actual ski jump. Method: Three healthy youth national athletes were recruited for this study (age: 13.70 ± 0.9 yrs, height: 169.30 ± 0.9 cm, jumping caree: 5.3 ± 0.9 yrs). Participants were asked to performed ski jumping with 3 simulating and one actual situation. A 3-dimensional motion analysis with 5 channels of EMG was performed in this study. Muscle activations of Rectus Femoris [RF], Tibialis Anterior [TA], Thoracis [TH], Gluteus maximus [GM], and Gastronemius [GL] were achieved with sampling rate of 2,000 Hz during each jump. Results: In the case of S1 in the actual jumping motion, the deviation of the muscle activity peak did not appear each trial, and the jump timing was consistent. For S2, the timing of the muscles peak activation which can maintain the posture of the upper body and ankles appeared at the beginning. In the case of S3, the part maintaining the ankle posture at the beginning appeared, but it could be expected that it would progress in the vertical direction due to the activation of GL at the time of jumping. Conclusion: The muscle activation peak before the take-off point showed a different pattern for each athlete, and individual differences were large. In addition, it was attempted to confirm the actual jump with simulation jump, and it was found that not only the difference in patterns but also the fluctuations in the timing of each muscle activation peak were large.

• 한국통신학회논문지
• /
• 제19권1호
• /
• pp.47-55
• /
• 1994

이 논문에서는 주파수 편차가 발생하는 채널에서 패킷 직접 대역확산(Direct-Sequence Spread Spectrum) 블록 수신기의 위상 반전 검출(Phase-jump detection) 오류 여부를 확인하는 PJED(Phase Jump Error Detector)의 성능을 고찰한다. 또한 정합 펄스 순간 추출기를 제시한다. 이동통신 채널상에서 발생하는 기존의 방식보다 간단한 구조를 갖는 정함펄스 순간 추출기를 제시한다. 이동통신 채널상에서 발생하는 주파수 편차는 패킷 DS/SS 블록 수신기를 사용함으로써 효율적으로 추정, 보상할 수 있는데 SNR(Signal to Noise Ratio)이 감소할수록 위상 반전 검출의 오류가 발생하며 이러한 위상 반전 검출의 오류를 방지하기 위한 대안으로서, 이 논문에서는 위상의 선형성을 이용하는 PJED를 제안하고 또한 신호 처리 시간을 단축시키고 수신기의 구조를 간단하게 만드는 정함펄스 순간 추출기를 제안한다. 실험 결과, PJED를 패킷 DS/SS 블록 수신기에 적용시킬 경우에는 PJED가 없는 수신기보다 동일한 BER에서 약 2dB정도의 성능개선을 보여준다. 또한 협대역 간섭신호가 존재할 경우도 약 2dB 정도의 성능향상을 나타낸다. 그리고 본 논문에서 제안한 단순한 구조의 정함펄스 순간 추출기를 사용하여도 정확한 정함 펄스 순간을 판단 할 수 있다.

• 대한기계학회논문집A
• /
• 제27권9호
• /
• pp.1589-1596
• /
• 2003

In this paper, we performed the improvement study for the dynamic characteristics enhancement of the motor stator coil vertical winding machine. The dynamic characteristics improvement was done by means of the optimized design and the weight reduction of the flyer configuration, modified design of the servo control system for the flyer and the former actuation, and the development of jump timing digital circuit for the reduction of former jumping error. As the results, the maximum winding speed pattern of the developed machine was attained up to 3000rpm and also reduced the jumping error. In conclusion, domestic design technology for manufacturing the motor coil vertical winding machine was established through this study.

• 오토저널
• /
• 제14권5호
• /
• pp.61-68
• /
• 1992

Knock phenomenon is an abnormal combustion originated from autoignition of unburned gas in the end-gas region during the later stage of combustion process and it accompanys a high pitched metallic noise. Engine Knock is accompanied with a vibration of engine cylinder and when it is severe, it can cause major engine demage. Engine Knock is characterized in terms of knock crank angle, knock pressure, pressure jump and knock intensity. In this study, a 4-cylinder spark ignition engine was used for experiment and eighty consecutive cycles were analyzed statistically. The purpose of this study is to characterize spark ignition engine knock as a function of ignition timing and fuel research octane number. The result of this study can be summerized as follows. Knock occurrence angle approached TDC as ignition timing is advanced. Pressure and knock intensity gradually increased as spark timing is advanced. Mean knock occurence angle gradually approached TDC as fuel research octane number is decreased for identical spark timing. Knock intensity increased linearly as RON is decreased.

• 한국운동역학회지
• /
• 제15권2호
• /
• pp.155-165
• /
• 2005

The purpose of this study was to compare the muscle activities of Double Legged Jump (DLJ) and Single Legged Jump (SLJ) by the normalization of muscle activity. Eight college students without the lower extremity injuries were selected as subjects for collecting EMG data of vastus medialis and gastrocnemius. The entire section of motion was established as eccentric and concentric contractions, and each of the contractions was divided into three sections with equal timing intervals, which becomes a total of 6 phases. The EMG data of each phase was integrated and normalized. The muscle activities of the vastus medialis for both eccentric and concentric contractions were significantly different between DLJ and SLJ(p<.05). The increase in overall muscle activity of SLJ was 33.6%. Approximately, there was an increase of 25.9% in eccentric contraction and 40% in concentric contraction. Moreover, the data of the muscle activity of gastrocnemius was similar to the data of the muscle activity of vastus medialis. In conclusion, this research suggests muscle activity of a certain motion can be normalized for an analysis of another motion.

• 한국운동역학회지
• /
• 제19권1호
• /
• pp.27-36
• /
• 2009

본 연구에서는 수직점프시 몸통운동의 제약이 수직점프의 수행에 미치는 영향을 알아보기 위해 10명의 성인 남성을 대상으로 몸통을 자유롭게 사용한 일반적인 형태와 몸통동작을 제한한 형태의 수직점프를 비교, 분석하였다. 분석 결과 몸통동작을 제한한 경우 비 제약점프에 비해 10% 정도의 수행 손실이 있었는데, 이는 이지 순간의 중심 높이보다는 이 지속도의 차이에 의해 발생하였다. 몸통의 운동은 엉덩관절의 모멘트 파워를 증가시켜 추진의 초기 시점부터 지면반력의 증가에 기여하였는데 이러한 요인이 수행력 증가의 주요한 요인으로 작용하였다. 반면 몸통운동이 제한된 점프에서는 엉덩관절에서의 역학적 출력의 감소를 보상하는 측면에서 무릎관절의 역할이 증가하였으나 충분치 못하였다. 또한 몸통동작의 제한으로 엉덩관절 무릎관절 발목관절의 순차적인 신전패턴과는 상이하게 추진시점 직후 엉덩관절과 무릎관절이 동시에 신전하는 형태의 점프가 이루어져 협응패턴의 변화가 나타났다. 결국 본 연구의 결과 몸통의 적절한 사용은 수직점프의 수행 향상에 효과적으로 기여하는 것으로 나타났다.

• 한국운동역학회지
• /
• 제20권1호
• /
• pp.49-55
• /
• 2010

The purpose of the study was to analyze kinetic factors required to the three-point jump shot of the basketball games through 3-D analysis and ground reaction force(GRF) analysis. Six university male players participated in this study. The results of the study were showed that (1) resultant velocity in the center of mass(COM) was $0.84{\pm}0.27\;m/s$ since a player didn't shot a ball in the highest peak and shot ball at the moment of going up forward and vertical movement. Therefore, it is necessary to find a proper timing to shot a ball; (2) the angular velocity was largely increased in upper arm and fore arm out of the upper-limb segments and the hands had the largest angular velocity since the body is in a fixed situation and angular speed is rapidly increased by the wrist' snap with the rapid movement of upper arm and forearm at the time of release a ball; (3) it is judged that a player can shot a ball at the accurate and high release point when the player collects power vertically to the maximum by keeping GRF to the right and the rear in a proper way and by keeping the body's balance so that a large power may not be dispersed.