• Journal of Biosystems Engineering
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• v.2 no.1
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• pp.33-48
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• 1977

Transporting agricultural products and the other material by the two-wheel-tractor (power-tiler)and trailer system may be one of its most widely used farming functions.The safety and hitching load for all the previaling performing conditions may be the general concern over the operation of the tiller-trailer system. In this study, a mathematical model to determine the static and dynamic forces excerting on the hitch point were developed . Based on the analysis of the model and the field measurements. the limiting hitching load and critical slope were analyzed. The results of the study are summarized as follows ; 1) The limit angle of slope land for the safety steering that two-wheel tractor-single axle trailer system was able to transport agricultural products was the direct angle (${\gamma}$) = 8 ; the cross angle$\beta$) 15 ; and it was decreased in accordance with the increase of carrying load ($W_4). 2) The critical velocity for safe operation in case of running on downward hill road was about 1.08m/sec. 3) The limiting carrying load for the safe steering was W$_4$=600kg. The degree of the safe steering for different braking methods was given in order as follows ; Simulataneous braking the tractor and trailer , braking the trailer only, and braking tractor only. 4) Among the three components of impact loads excerting on the hitch point, the component in the lateral direction ($P_{Vy}$) was near zero in spite of increase of hitching load ($W_4) , while the components in the other two mutually perpedicular directions ($P_{Vx}$ and ($P_{Vz}$) ) had larger values in horizontal plane than those in the slope lands. 5) Moment of forces on the lateral direction (M$y$) had the largest value among the three components of impact moment acting on the hitch point, however all the components were sharply increased in accordance with the increase of hitching loads ($W_4. Three components of the moment were the negative values.

• Korean Journal of Applied Biomechanics
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• v.13 no.3
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• pp.133-149
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• 2003

The purposes of present study were to determine the major check-points of golf swing from the review of previous studies, and to suggest additional information on the teaching theory of golf. The golf swing motion of 6 male and female elite university golf players were filmed with 16mm Locam II high speed cameras at the speed of 200f/s, and variables such as time, displacement, angle, velocity were calculated and analyzed by 3D Cinematography using DLT method. The results were: 1. Differences were shown in the ratio of weight distribution on the feet, cocking angle, take-back velocity, club-head velocity at impact depending upon the physical characteristics and club used for swing. 2. Time for the down-swing and impact were $0.27{\sim}0.29s$ in men and $0.29{\sim}0.32s$ in women, which was 1/3 of the time for the back-swing. Women showed longer total swing time than men because of longer time in back-swing, follow-through and finish. 3. Men showed larger range of motion in shoulder and knee joints than women, on the other hand women showed larger range of motion in hip joint than men. 4. Cocking motion and right elbow flexion were occurred at the top of back-swing and cocking release was occurred at the moment of impact. Maximum rotations of shoulder and hip joints were found between the top of back-swing and down-swing phase. 5. Women showed lower back-swing velocity than men, and men showed higher club velocity(men: $38.2{\sim}38.6m/s$, women: $35.1{\sim}36.4m/s$) than women.

• Korean Journal of Applied Biomechanics
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• v.13 no.2
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• pp.101-114
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• 2003

The purpose of this study was to examine the major kinematicak variance to Increase the club head velocity during the driver swing two PGA prp-golfers utilizing 3-dimensional Image analyzing linear velocity of the club-head during the impact quantiatively. To achive these purpose, two high speed camera in 120 field/s and one high-speed camera in 500 field/s were used in this study. The program made by Younghoo Kwon(1944) was used to analysis the digitalization of reference point, digitalization of joint venter, synchronization, calculation of 3-Dimensional coordinate by DLT method, and smoothing. Through this study, the conclusions are as follow. 1. During the drivel swing, in the percentile of the total time, two pro-golfer showed 0.925, 0.929 second from adress to top-swing, 0.236, 0.929 second from top-swing to impact. 2. During the driver swing, in the displacement of the center of the body, two pro-golfer showed 45.3, 45.23% from adress, 44.3, 44.24% front impact. 3. In the velocity variance, The maximum club-head velocity two pro-golfer showed 43.36, 43.24m/s respectively the down swing. The ball velocity showed 63.12, 63.06m/s. 4. In the rotational angle of the shoulder joint. two pro-golfer showed $-13.5,-13.53^{\circ}$, during the back swing respectively. Two subject adressed opening status og upper body. 5. In the rotational angle of the right knee angle showed $156.3,154.7^{\circ}$ from the adress.

• Journal of the Korean Applied Science and Technology
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• v.36 no.3
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• pp.789-796
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• 2019

The purpose of this study was to compare kinematic variables between elite golfer and novice during golf putting. 23 elite golfers and 19 novice were participated, and SAM Putt was used to collect kinematic variables. To identify main effect and interaction effect, it was performed Two-way Mixed ANOVA at a significant level of a .05. Elite and novice group, follow-through was significantly different and indicated main effect between distance and skill level. Impact, backswing, and loft angle were significantly different and showed main effect between skill level. Also, backswing rhythm and impact timing were significantly different and indicated main effect between skill level. Therefore, minimizing the movement of the wrist and keeping the putting strike rhythm may improve the putting ability.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.9
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• pp.839-847
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• 2011

This paper proposes a new guidance law for increasing the lethality of munitions. The well known PNG (Proportional Navigation Guidance) is inadequate for the munitions because of some weaknesses. Even if the munition does not have the impact point error, the acceleration command is non zero because the line-of-sight changes at all times in flight. Therefore, we use a difference between a target and an impact point. This proposed guidance law is similar to PNG in the form, but this guidance law concentrates a correction rate of flight path angle instead of the LOS (Line of Sight) rate. The correction of flight path angle is defined as the amount of impact point error. This impact point error can be calculated by neural networks rapidly. Finally, we show that the simulation results prove the suitability of this law.

• The Journal of the Korean dental association
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• v.50 no.9
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• pp.566-573
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• 2012

Purpose : This study evaluated the impact of the presence and aspect of mandibular third molars to the mandible angle fracture or condyle fractures in Korean. Materials and Methods : A retrospective study was designed for patients attending the division of Oral and Maxillofacial Surgery, Kang-dong sacred heart hospital for treatment of mandibular fracture from January 2006 to September 2010. The primary variable was the presence of mandibular third molar and the secondary variable was the aspects of third molar impaction. Mandibular third molars were classified by the impaction depth and the available space as Pell & Gregory system. Outcome variables were the presence of mandibular angle fracture or condyle fracture. Also the source of trauma, age, sex were studied. Hospital charts, radiographs were used for study. Statistic analysis was done with descriptive statistics, the X2-test, linear-by-linear association. P value under 0.05 was considered significant statistically. Results : The number of involved patients was 86. The ratio of male to female patients was about 9:1 for angle fracture and 7:3 for condyle fracture. The most common source of trauma was assault for angle fracture and fall down for condyle fracture. The presence of mandibular third molar increased frequency of angle fracture and decreased condyle fracture with larger impaction depth. But available space of mandibular third molar did not show high association with angle or condyle fractures. Conclusion: Preventive extraction of mandibular third molar is recommended for patients with high risk of angle fracture. Male patients at their third decade or martial artists, police officer could be the case. But it is not recommended for patients with low risk of angle fracture and high risk of condyle fracture relatively. Elder female patients without any symptom on their third molar could be the case.

• Korean Journal of Applied Biomechanics
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• v.16 no.3
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• pp.85-94
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• 2006

The purpose of this study was to analyze the kinematics variables of during forehand stroke by stance patterns. Eight high school tennis players were chosen for the study, who have never been injured for last six months, in Busan. They performed horizontal swing and vertical swing that it was done each five consecutive trial in the condition of square, open and semi-open stance. It was filmed by 6 video camera and used with 3-dimensional motion analyzer system. The following kinematic variables were analyzed in relation to angle of segment( shoulder, hip and knee joint). The conclusion were as follow: 1. The angle of hip joint represented at impact that horizontal swing was not significant difference by stance patterns but vertical swing was increased in open stance than square and semi-open stance. 2. The angle of both knee was not significant difference between all stance types and swing patterns. 3. The angle of shoulder, hip and knee joint rotation showed that open stance was increased than square and semi-open stance in all swing types and event.

• 한국전산유체공학회:학술대회논문집
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• 2009.04a
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• pp.191-195
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• 2009

A parametric study for for the water entry of a two dimensional symmetric wedge with deadrise angle of 10 degrees was carried out to find out the most dominant parameter. Water entry problem with constant velocity is simplified as the stationary wedge in the way of the upcoming water surface. The calculated impact loads showed that the effect of the viscosity was not so important in this problem. For a given grid system a suitable time step size can be found. The most sensitive parameter was found to be the grid size.

• Ocean Systems Engineering
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• v.7 no.3
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• pp.179-193
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• 2017

Dynamic response analysis of offshore triceratops with stiffened buoyant legs under impact and non-impact waves is presented. Triceratops is relatively new-generation complaint platform being explored in the recent past for its suitability in ultra-deep waters. Buoyant legs support the deck through ball joints, which partially isolate the deck by not transferring rotation from legs to the deck. Buoyant legs are interconnected using equally spaced stiffeners, inducing more integral action in dispersing the encountered wave loads. Two typical nonlinear waves under very high sea state are used to simulate impact and non-impact waves. Parameters of JONSWAP spectrum are chosen to produce waves with high vertical and horizontal asymmetries. Impact waves are simulated by steep, front asymmetric waves while non-impact waves are simulated using Stokes nonlinear irregular waves. Based on the numerical analyses presented, it is seen that the platform experiences both steady state (springing) and transient response (ringing) of high amplitudes. Response of the deck shows significant reduction in rotational degrees-of-freedom due to isolation offered by ball joints. Weak-asymmetric waves, resulting in non-impact waves cause steady state response. Beat phenomenon is noticed in almost all degrees-of-freedom but values in sway, roll and yaw are considerably low as angle of incidence is zero degrees. Impact waves cause response in higher frequencies; bursting nature of pitch response is a clear manifestation of the effect of impact waves on buoyant legs. Non-impact waves cause response similar to that of a beating phenomenon in all active degrees-of-freedom, which otherwise would not be present under normal loading. Power spectral density plots show energy content of response for a wide bandwidth of frequencies, indicating an alarming behaviour apart from being highly nonlinear. Heave, being one of the stiff degrees-of-freedom is triggered under non-impact waves, which resulted in tether tension variation under non-impact waves as well. Reduced deck response aids functional requirements of triceratops even under impact and non-impact waves. Stiffened group of buoyant legs enable a monolithic behaviour, enhancing stiffness in vertical plane.

• Korean Journal of Applied Biomechanics
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• v.12 no.2
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• pp.207-214
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• 2002

The purpose of this study was to examine the putter head movement during the putting strokes. Highly skilled 5 golfers(less than 3 handicaps) and 5 novice golfers(having no golf experience) participated in this study. A target distance was 3 m. Movements of the putter head were recorded at 60 Hz with two video cameras(1/500 shutter speed). The results showed that the angle of the clubface of expert golfers was almost 1 degree, but the novice golfers were more than 6 degrees. Expert golfers moved their hands faster than the head movement, therefore the clubface was not opened during impact. However, the novice golfers moved their hands slower than the head movement, therefore the clubface was opened during impact. The ratio of input and output angles of total movement was 1:3-4, however, the ratio of input and output angles of impact zone was 1:2. The angle of normal vector of expert golfers was less than the angle of normal vector of novice golfers.