• 한국운동역학회지
• /
• 제12권2호
• /
• pp.109-130
• /
• 2002

따라서 본 연구의 목적은 국가대표 수준급 대학 우수 야구 투수를 대상으로 한 3차원 영상분석을 통한 데이터를 가지고 직구 커브볼에 대한 구간별 운동학적 패턴을 비교 분석하여 자료를 제시하는데 있다. 본 연구는 부산 D대학교 우완 오버핸드 투수 가운데 국가대표 2명과 수준급 대학선수 2명, 총 4명을 대상으로 직구 커브 투구시 구간별로 나타나는 여러 운동학적 변인의 차이를 비교 분석한 결과 다음과 같은 결론을 얻었다. 직구 및 커브볼 투구시 구간별, 국면별 투구시간은 거의 비슷하게 나타냈으며, 직구의 총 소요시간은 1.78${\pm}$0.07초이며 커브 총 소요시간은 1.77${\pm}$0.11초로 나타났다. 직구 및 커브볼 투구시 Z(상 하)방향에 대한 신체 중심의 위치변화는 구간별, 국면별 거의 차이가 나지 않았다. 직구 및 커브볼 투구시 왼쪽 다리의 무릎높이는 각각 $125.38{\pm}11.85cm,\;124.95{\pm}11.63cm$로 큰 차이가 없었다. 신장대비율(%H)로는 직구, 커브 각각 68.42${\pm}$5.53(%H), 68.40${\pm}$5.45(%H)로 나타났다. 직구 및 커브볼 투구시 스트라이드 거리는 각각 140.35${\pm}$4.96cm, 144.83${\pm}$1.69cm로 커브 투구시 더 많은 스트라이드 거리를 보였다. 직구 및 커브볼 투구시 왼쪽 슬관절 ST 구간과 LKU 구간, HBP 구간에서는 별 차이가 없었지만 LFC, MCP, BRP구간에서는 직구보다 커브 투구시 슬관절 각도가 더 굴곡 된 것으로 나타났다. 직구 및 커브볼 투구시 오른팔 견관절 각도는 ST 구간과 LKU구간, HBP 구간에서는 별차이가 없었다. 직구 및 커브볼 투구시 오른팔 주관절 각도는 ST 구간과 LKU구간, HBP 구간에서는 별차이 가 없었다. LFC구간과 MCP구간에서는 직구보다 커브가 다소 많이 굴곡되었고, BRP구간에서 는 직구, 커브 모두 다 근소한 차로 신전 된 것으로 나타났다. 직구 및 커브볼 투구시 오른팔 수관절 각도는 LFC 구간과 MCP 구간에서는 커브가 직구보다 더 신전되었다. 그리고 BRP 구간은 직구가 커브보다 더 신전 된 것으로 나타났다.

• 한국의류학회지
• /
• 제23권3호
• /
• pp.353-360
• /
• 1999

An investigation made of the variations of angle of bias on the top of the sleeve cap curve line and calculated easing contraction ratio by capheights(A ; a,h$\times$5,/6) B: A, H/4 +4cm C:A.H/3 D: A.H/ 4+3cm E:AH/4+2cm, F: A,H/4+1cm, G: A,H/4, H:A,H/6, I:A,H/8) and the efects of easing contraction on the cap curve lines of sleeve A, D, G by easing stitch density with the gathering foot: sewing condition-lockstitch industrial machine stitch density(N1.0 ; 38stitches/3cm N1.5: 26stitches/3cm, N2.0 ; 19stitches/3cm, N2.5 ; 14stitches/ 3cm) The results obtained were as follows; 1) The variations of the angle of bias on the top of the sleeve cap curve line by cap heights can be done according to the angle balance (front; $\alpha$-$\beta$ back ; $\alpha$'- $\beta$') between the angle (front ;$\alpha$, $\beta$, back ; $\alpha$'- $\beta$') of bias of the two base-lines. 2) The higher cap height the more higher the calculated easing contraction ratio. 3) The lower the stitch density the higher easing contraction ratio. 4) The effects of easing contraction was that sleeve G was more than sleeve A, D.

• 한국운동역학회지
• /
• 제28권2호
• /
• pp.93-100
• /
• 2018

Objective: The purpose of this study is to analyze the kinematic characteristics of the national speed skaters in the curve phase of 500-m race. Method: Seven national skaters participated in the study. Race images were acquired using a high - speed camera, and the three-dimensional motion was analyzed. Results: For skaters, whose average velocity in the curve phase is high, the velocity of entry into the straight phase was also fast. The fast skaters showed a larger maximum angle of extension of the knee joints than the relatively slow skaters, and the trunk ROM was smaller. Fast skaters tended to match the timing of the movement of the lower limb with the pelvis, while slow skaters tended to rotate the left pelvis backward. The velocity of the curve phase did not show a clear relationship with stroke time, average trunk angle, and lap time. Conclusion: It is important to skate close to the inner line, keep the trunk ROM below 10 degrees, extend the knee angle to over 160 degrees, and match the movement of the pelvis and lower limb to accelerate in the curve phase. The average velocity of the curves was fast for many athletes, but the competition rankings were low. Therefore, it is possible to improve the performance by optimizing the start technique, the running characteristics of the straight phase, and the physical factors.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 춘계학술대회논문집E
• /
• pp.789-794
• /
• 2001

In this study, a program for the off-design performance prediction of multi-stage axial-compressors is developed based on stage-stacking method. To account for the increased losses at off-design conditions, generalized performance curve is applied. The purpose of this study is to investigate the influence of the choice of generalized performance curve and stator exit angle. For this purpose, we tested various generalized performance curves and stator exit angles. In conclusion, Muir's pressure coefficient curve gives a good prediction results regardless of the efficiency curve for a low-stage compressors. On the other hand, for high-stage compressors, The combination of Muir's pressure coefficient curve and Stone's efficiency curve gives a optimistic results. Stator exit angle has a small effect on overall performance curve.

• 신재생에너지
• /
• 제20권2호
• /
• pp.35-43
• /
• 2024

A pump turbine is a technically matured option for energy production and storage systems. At the off-design operating range, the pump turbine succumbed to flow instabilities, which correlated with the pump turbine geometry. A low specific speed pump turbine was designed and modified according to the impeller blade angle. Reynolds-Average Navier-Stokes is carried out with a shear stress transport turbulence model to evaluate the detailed flow characteristics in the pump turbine. The impeller blade inlet angle (𝛽₁) and outlet angle (𝛽₂) are used to evaluate hydraulic loss in the pump turbine. When 𝛽₁ changed from low to high value, the maximum efficiency is increased by 4.75% in turbine mode. The S-Curve inclination is reduced by 8% and 42% for changes in 𝛽₁ and 𝛽₂ from low to high values, respectively. At α = 21°, the shock loss coefficient (𝜁_s) is reduced by 16% and 19% with increases of 𝛽₁ and 𝛽₂ from low to high values, respectively. When 𝛽₁ and 𝛽₂ values increased from low to high, the impeller friction coefficient (𝜁_f) increased and decreased by 20% and 8%, respectively. Hence, the high 𝛽₂ effectively reduced the loss coefficient and S-Curve inclination.

• 척추신경추나의학회지
• /
• 제5권2호
• /
• pp.33-41
• /
• 2010

Objectives : This study is designed to find out the relationship of scoliotic curve, cervical lordosis, lumbar lordosis and Ferguson's angle. Method : The study was composed of 46 scoliosis patients who had single curvature(Group I) on their lumbar spine(Group I-A) or thoracic spine(Group I-B) and 38 patients who had double curvature(Group II) on their lumbar and thoracic spine. The patients were evaluated with X-ray findings of full spine AP and Lateral views and statistically analyzed. Results : 1. Group II showed a significant increase in scoliotic curve angle as compared with Group I(P<0.05). 2. Scoliotic curve has a negative relationship with cervical lordosis in group II. Conclusion : 1. The patients who has double curvature of spine had higher scoliotic curve angle compared with who has single curvature. 2. The Scoliotic curve and cervical lordosis was statistically concerned on patients who has double curvature of spine.

• Journal of Korean Neurosurgical Society
• /
• 제38권4호
• /
• pp.255-258
• /
• 2005

Objective : Lumbar lordotic curve on L4 to S1 level is important in maintaining spinal sagittal alignment. Although there has been no definite report in lordotic value, loss of lumbar lordotic curve may lead to pathologic change especially in degenerative lumbar disease. This study examines the changes of lumbar lordotic curve after posterior lumbar interbody fusion with wedge shape cage. Methods : We studied 45patients who had undergone posterior lumbar interbody fusion with wedge shape cage and screw fixation due to degenerative lumbar disease. Preoperative and postoperative lateral radiographs were taken and one independent observer measured the change of lordotic curve and height of intervertebral space where cages were placed. Segmental lordotic curve angle was measured by Cobb method. Height of intervertebral space was measured by averaging the sum of anterior, posterior, and midpoint interbody distance. Clinical outcome was assessed on Prolo scale at 1month of postoperative period. Results : Nineteen paired wedge shape cages were placed on L4-5 level and 6 paired same cages were inserted on L5-S1 level. Among them, 18patients showed increased segmental lordotic curve angle. Mean increased segmental lordotic curve angle after placing the wedge shape cages was $1.96^{\circ}$. Mean increased disc height was 3.21mm. No cases showed retropulsion of cage. The clinical success rate on Prolo's scale was 92.0%. Conclusion : Posterior lumbar interbody fusion with wedge shape cage provides increased lordotic curve, increased height of intervertebral space, and satisfactory clinical outcome in a short-term period.

• 한국군사과학기술학회지
• /
• 제13권6호
• /
• pp.998-1005
• /
• 2010

Rifling force has a torsion impulse effect on the gun tube and thus generates undesirable vibration of the gun tube about its bore axis, putting additional stress on the projectile. High rifling force at the muzzle of the gun tube may adversely influence the trajectory of the projectile. And, the service life of rifled gun barrels is known to depend on the rifling force. Rifling force along the path of the projectile in the longitudinal direction of the gun tube can be described with projectile mass, projectile velocity, gas pressure curve and rifling angle. Under the same conditions, the character of the rifling of the gun barrel decisively influences the rifling force curve. To reduce the above mentioned harmful effect, locally distinct maximum of rifling force has to be avoided and maximum rifling force needs to be minimized. The best way to minimize the maximum rifling force is to design a rifling angle function so that the rifling force curve has a near trapezoidal shape. In this paper a new approach to make the optimal rifling force curve is described. The rifling angle determining the rifling force is developed by combined Fourier series and polynomial function to satisfy both the convergence and boundary condition matching problems.

• 대한물리의학회지
• /
• 제11권2호
• /
• pp.13-16
• /
• 2016

PURPOSE: The Fukuda test can be used at home and in school to diagnose scoliosis at an early stage and prevent serious curvature of the spine. This study aimed to use the Fukuda test to detect scoliosis. An additional aim was to invoke the national interest in imbalanced postures and habits, which result in scoliosis, by providing data obtained in periodic assessments. METHODS: The study consisted of 35 idiopathic scoliosis patients (22 in right lumbar spinal region and 13 in the left lumbar spinal region). The distance of displacement and angle of displacement were measured following the Fukuda test. A correlation analysis was then used to examine the distance of displacement and angles of displacement and rotation with regard to the direction of the curve in scoliosis. RESULTS: There was a significant negative correlation (p<0.00) between the direction of the curve in scoliosis and the angle of displacement, but there was no correlation between the cobb's angle and distance of displacement or between the cobb's angle and angle of rotation. CONCLUSION: The Fukuda test did not capture changes in spinal curvature such as the cobb's angle, or subsequent changes in the muscles. Thus, the Fukuda test is not suited to examining the direction or status of the thoracic curve in scoliosis patients. Simple methods to objectively measure scoliosis need to be developed.

• 한국기계가공학회지
• /
• 제10권2호
• /
• pp.110-116
• /
• 2011

The current study investigated the friction property of angle and width effect for micro-scale grooved crosshatch pattern on SKD11 steel surface against bearing steel using pin-on-disk type. The samples fabricated by photolithography process and then these are carry out the electrochemical etching process. We discuss the friction property due to the influence of a hatched-angle and a width of groove on contact surface. We could be explained the lubrication mechanism for a Stribeck curve. So It was found that the friction coefficient depend on an angle of the crosshatch on contact surface. It was thus verified that micro-scale crosshatch grooved pattern could affect the friction reduction. Also, it is play an important a width of groove to be improved the friction property. I was found that friction property has a relationship between a width and an angle for micro-grooved pattern.