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Kinematic Analysis According to the Intentional Curve Ball at Golf Driver Swing (골프 드라이버 스윙 시 의도적인 구질 변화에 따른 운동학적 분석)

  • Hong, Soo-Young;So, Jae-Moo;Kim, Yong-Seok
    • Korean Journal of Applied Biomechanics
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    • v.22 no.3
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    • pp.269-276
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    • 2012
  • The purpose of This study's aim is to examine the difference in the changes of body segment movement, variables for ball quality, and carry at golf driver swing according to the ball quality using comparative analysis. Regarding the impact variables according to the ball quality using the track man and carry, club speed was the fastest at draw shot, ball speed was the fastest at straight shot, and smash factor was the lowest at draw shot. About the vertical launch angle, the fade shot showed the highest launch angle while the max height of the ground and ball was the highest at fade shot. And carry was the longest at draw shot. For the flight time, it was the longest at draw shot. The landing angle was the largest at fade shot. About the club head position change and trajectory, at the overall event point, the fade shot drew a more outer trajectory at the point of the follow through(E6) than the straight or draw shot. Regarding the angular speed of shoulder rotation, at the overall event point, the fade shot showed the greatest angular speed change in the follow through(E6). Also, about the angular speed of pelvic rotation, at the overall event point, the draw shot showed the greatest angular speed change at the point of down swing(E4). Concerning the stance angle change, both straight and fade shots were open as the concept of open stance whereas the draw shot was close as that of close stance. Regarding the previous study, the most important factor of deciding Ball Quality is the club face angle's open and close state at Impact. In short, the Ball Quality and carry were decided by this factor.

A study on the resistance affecting on the engine power in towing fishing gear of a bottom trawl ship (저층 트롤선의 예망 시 기관출력에 영향을 미치는 저항들에 관한 고찰)

  • Woo-Gyeong WANG
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.59 no.4
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    • pp.344-353
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    • 2023
  • In the actual sea, the additional resistance due to external force such as wind, current and wave is accompanied, and the required power is added in response to these resistance. Especially when the ship is sailing at low speed, the effects of wind and current have a great impact on the safe control of the ship. Likewise, it is thought that the effects of wind and current have a great impact on the trawl ship control since the towing speed of a bottom trawl ship is a low speed of 3 to 4 knots. If the reduce of ship speed and the increase of engine power due to the influence of wind and current can be identified, the safe towing power can be calculated based on a given engine output. Thus, the appropriate size of a fishing gear can be determined. In this study, a total of 20 trawl operations were conducted for seasonal maritime research in the same research area according to the operation mode of propeller. Based on navigation data, trawl fishing data, and engine performance data acquired during the towing fishing gear, and data of ship speed, hull resistance, fishing gear resistance, wind force and current force according to an incidence angle were estimated. The overall power for these loads was calculated and compared with the measured engine power, and the effects of wind force and current force on the engine power were investigated.

Development of Smart Speed Bump Using Non-newtonian Fluid (비뉴턴 유체를 이용한 스마트 과속방지턱 소재 개발)

  • Jung, Injun;Kim, Eunjung;Yu, Woong-Ryeol;Na, Wonjin
    • Composites Research
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    • v.35 no.4
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    • pp.277-282
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    • 2022
  • In this study, a smart material applicable to speed bumps was developed using low-cost starch and waterbased suspensions, and their properties were investigated. Viscosity and shear stress according to the shear rate was measured by a rheometer to observe shear thickening behavior according to starch concentration. The shear thickening phenomenon and applicability to speed bumps were identified macroscopically via drop weight test and bike driving test, measuring the vibration after impact with a driving speed of 5-25 km/h. As a result of the viscosity measurement, shear thickening occurred after the shear thinning region at the beginning, and the critical strain causing the shear thickening phenomenon decreased as the concentration of starch increased. Also, the viscosity and shear stress increased significantly with the increase of the starch concentration. As a result of the drop weight test and the bike driving test, the suspension was changed to a solid-like state in a short time, and the impact energy was absorbed in the fluid. The shear thickening phenomenon easily occurred as the concentration of the fluid and the applied impact (velocity) increased. Therefore, it can be proposed the development of a smart speed bump material that operates in the range of 5-25 km/h with a Non-Newtonian fluid based on water and starch.

A Study on the Embodiment of a Transfer Case with High-Speed Reduction of the Planetary Gear Type Applied to Big Industrial Vehicles (대형 산업 차량에 적용되는 유성기어형 고감속 중간변속기 구현에 관한 연구)

  • Lee, Won-Kyu;Park, Se-Myoung
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.14 no.6
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    • pp.14-20
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    • 2015
  • A high-speed reduction transfer case is usually employed by an excavator, wheel loader, or bulldozer. When powerful torque is required in the case of climbing steep roads or towing heavy equipment, the high-speed reduction mode of the gearbox is used. Generally, a transfer case using a spur gear type with a speed reduction system has a speed reduction ratio of 1 to 1 or 2 to 1. However, the structure of a transfer case achieved at a high speed of 1 to 1 and a low speed of 4.5 or under 5.5 to 1 with the speed reduction by use of a planetary gear type with a speed reduction system was proposed in this study. By employing a planetary gear type with a speed reduction system, the compact structure of the transfer case was achieved, and the impact or the partial defect of gear teeth was eliminated.

The Impact of Water Depth and Speed on Lower Muscles Activation During Exercise in Different Aquatic Environments

  • Gyu-sun, Moon
    • International Journal of Internet, Broadcasting and Communication
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    • v.16 no.2
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    • pp.169-178
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    • 2024
  • This study aimed to investigate the effects of water depth and speed on the activation of lower muscles during squat exercises, utilizing electromyography(EMG). It involved ten male participants in there. Participants performed 30 squats over a minute at a speed of 60bpm and maximum speed squats until exhaustion within a minute. The Integrated electromyography(iEMG) readings for the rectus femoris showed statistically significant differences due to water depth and speed, with a significant interaction effect between depth and speed during squat exercises. The iEMG readings for the biceps femoris also showed statistically significant differences, with a significant interaction effect between depth and speed during squat exercises. The iEMG readings for the gastrocnemius showed statistically significant differences according to water depth and speed. However, the interaction effect of water depth and speed during squat exercises did not show a statistically significant difference. In contrast, the iEMG readings for the tibialis anterior demonstrated statistically significant differences, with a statistically significant interaction effect during squats. These findings suggest that water depth and speed positively influence the activation patterns of lower muscles. Therefore, appropriately tailored aquatic exercises based on water depth for individuals with musculoskeletal discomfort, including the elderly or those with physical impairments, can effectively reduce physical strain and enhance balance, as well as physical and perceptual aspects. It is concluded that such exercises could provide a safer and more effective method of exercise compared to ground-based alternatives.

A Study on the Impact Pressure of a Falling Body upon a Free Surface Water (자유수면에 낙하하는 물체의 충격압력 변화에 관한 연구)

  • Lee, Jong-Boong
    • Journal of the Korean Society of Industry Convergence
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    • v.4 no.3
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    • pp.295-304
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    • 2001
  • The hydrodynamic impact problem was studied from 1929 to recent. Especially, Impact pressure is important for the design of the ships and offshore structure and spacecrafts, and under weapons. A ship traveling at high speed or in heavy sea has its bow and bottom damaged by high pressure caused by impact with and detachment from the water surface. Considerable impact may also occur when large waves hit the cross member or deck plate of an offshore structure within the splash zone. Many engineering cases require consideration of impact pressure, the movement of objects and change of the flow field. This study was obtained the pressure distribution of a falling body that is deadrise angle 0 and deadrise angle 5 upon a water surface by the experiment with the impact machine. The theoretical equation was obtained the air region and the interface and the water region which devide 3 parties between the body and the water surface for an investigation of the complete phenomena. Pressure distributions and histories compare favorably with available experimental data. The numerical results are similar to the experimental results for the impact force type with Fo(1+cosπt/tc).

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Evaluation of Impact Resistance of Hybrid Fiber Reinforced Cementitious Composites Subjected to Thermal Stress (열응력을 받은 하이브리드 섬유보강 시멘트 복합체의 내충격성능 평가)

  • Han, Seung-Hyeon;Kim, Gyu-Yong;Lee, Yae-Chan;Eu, Ha-Min;Park, Jun-Young;Nam, Jung-Soo
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2023.05a
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    • pp.145-146
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    • 2023
  • In this study, the effect of hybrid fiber reinforcement on the residual strength and impact resistance of high-strength cementitious composites exposed to high temperatures was investigated. A cementitious composites was manufactured in which 0.15 vol% of polypropylene fiber (PP) and 1.0 vol% of smooth steel fiber (SSF) were double-mixed, and a residual strength test was conducted while thermal stress was applied by heating test, and then a high-velocity impact test was performed. In the case of general cementitious composites, the rear surface is damaged due to explosion and low tensile strength during high temperature or impact, while hybrid fiber reinforced cementitious composites can repeatedly absorb and distribute stress until multiple fibers are damaged to suppress the propagation of impact and resistance to explosion. Therefore, this study analyzed the residual strength of cementitious composites exposed to high temperatures depending on whether hybrid fibers were mixed or not, and collected research data on fracture behavior through high-speed impact tests to evaluate impact resistance and mechanical properties.

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Impact Properties of S-2 Glass Fiber Composites with Multi-axial Structure (다축 구조 S-2 유리섬유 복합재의 충격 특성)

  • Song, S.W.;Lee, C.H.;Byun, J.H.;Hwang, B.S.;Um, M.K.;Lee, S.K.
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2005.04a
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    • pp.71-75
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    • 2005
  • For the damage tolerance improvement of conventional laminated composites, stitching process have been utilized for providing through-thickness reinforcements. 2D preforms were stacked with S-2 glass plain weave and S-2 glass MWK (Multi-axial Warp Knit) L type. 3D preforms were fabricated using the stitching process. All composite samples were fabricated by RTM (Resin Transfer Molding) process. To examine the damage resistance performance the low speed drop weight impact test has been carried out. For the assessment of damage after the impact loading, specimens were examined by scanning image. CAI (Compressive After Impact) tests were also conducted to evaluate residual compressive strength. Compared with 2D composites, the damage area of 3D composites was reduced by 20-30% and the CAI strength showed 5-10% improvement.

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A Study on Frequency Characteristics of Impact Induced Damage Signals of Composite Laminates as the Incident Angle of an FBG sensor (복합재 충격손상신호의 FBG센서 입사각도에 따른 주파수분포 특성에 관한 연구)

  • Bang, Hyung-Jun;Song, Ji-Yong;Kim, Chun-Gon
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2005.04a
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    • pp.235-239
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    • 2005
  • In this research, we investigated the frequency characteristic of low-velocity impact induced damage signals on graphite/epoxy composite laminates using high-speed fiber Bragg grating(FBG) sensor system. Appling the FBG sensors to damage assessment, we need to study the response of FBG sensors as the damage signals of the different incident angles because FBG shows different directional sensitivity. In order to discriminate an impact induced damage signal from that of undamaged case, drop impacts with different energies were applied to the composite panel with different incident angle to the FBG sensor. Finally, detected impact signals were compared using frequency distributions of wavelet detail components in order to find distinctive signal characteristics of composites delamination.

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A Study on the Signal Transmissibility of High Frequency Crash Pulse according to the Car Structure Difference (차체 구조 차이에 따른 충돌 고주파 신호 전달성 연구)

  • Park, Dongkyou
    • Transactions of the Korean Society of Automotive Engineers
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    • v.21 no.6
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    • pp.8-15
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    • 2013
  • Wide range frequency pulses occur in a car crash test. Until now, low frequency under 400Hz has been used to determine an airbag deployment criteria. Also, FIS (Front Impact Sensor) has been used to detect the crash pulse in early stage. Nowadays, technology to determine an airbag delpoyment criteria by using a high frequency crash pulse without FIS is being focused on. In this paper, the signal transmissibility of high frequency pulse for two different cars was studied. Also, signal transfer test of high frequency pulse was done by using a high speed ball impact. Signal runtime of the frontal impact is compared with that of the side impact. The signal transmissibility difference due to the car structure difference was discussed and structure change for improving the signal transmissibility was proposed.