• Korean Journal of Applied Biomechanics
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• v.12 no.2
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• pp.33-49
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• 2002

This study was intended to provide basic materials for golf coaching by somatotype by analyzing and comparing the kinematic factors found in each somatotype at the time of golf swing. For this purpose, the somatotype was divided into endomorph, mesomorph and ectomorph in reference to the weight, height and upper arm circumference of each of nine professional golfers. Each of their swing motions was videotaped with the camcorder and their swing motion was analyzed by dividing it into 8 sections. The time required for the swing motion, the displacement of the center of the human body and the rotation angle of the upper body were calculated through the three-dimensional image analysis based on the DLT(Direct Linear Transformation). Based on the findings of this study, the following conclusion was drawn: The endomorphic golfers showed the longest required golf swing time, followed by the mesomorphic golfer and then the endomorphic golfer. The displacement of left-to-right movement was largest in the mesomorphic golfers, followed by the endomorphic golfers the up-to-down displacement was upward at the time of impact and that the endomorphic and mesomorphic golfers raised the sense of stability by maintaining an almost uniform height at the time of impact. As for the rotational angle of the upper body and the rotational angle of the thigh, the upper body and the thigh took a form of rotating earlier in the ectomorphic golfers at the time of impact, who showed a somewhat different characteristics compared to the endomorphic and mesomorphic golfers. It is necessary to investigate the movement of more fundamental forces in presenting the theory related to the kinematic characteristics of this swing by somatotype. Accordingly, it is thought that it is necessary to analyze the center of pressure(COP) using the ground counterforce in the future study.

• Journal of the Korean earth science society
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• v.28 no.2
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• pp.179-186
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• 2007

The response spectrum is one of the important basic materials for the aseismic design. Numerous strong ground motions based on the seismic source characteristics for the earthquakes occurring in the Korean Peninsula were simulated to obtain the response spectra by using the computer program, SMSIM, developed by Boore (2005). Through the extensive review of other study outcomes, the input data for the simulation such as seismic source and attenuation characteristics were selected. The spectra obtained from the simulated ground motions were normalized to 1.0 g of zero period acceleration and compared with the standard response spectrum proposed by the U.S. Atomic Energy Commission (AEC, 1973). In this study, we found that the spectral values for the response spectra appeared to be larger than those of the standard spectrum in the frequency band above roughly 10 Hz. The variation of resulting response spectra was evaluated with the variable stress drops. It was shown that the spectral amplitude of the spectrum for the larger stress drop denotes higher value in the low frequency range.

• Journal of the Korean GEO-environmental Society
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• v.21 no.7
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• pp.5-16
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• 2020

Currently, the seismic design standards have been strengthened due to the occurrence of the Gyeongju and Pohang earthquake, and seismic performance evaluation of existing facilities is being conducted. It aims to secure a seismic performance effect during earthquakes by improving the micro-pile method, which can be constructed in limited confined places while minimizing damage to existing facilities. The improvement method is to construct all the piles in the square-tray-type plate on the top of the pile by constructing the slope pile in the form of an umbrella around the vertical pile, the main pillar. In this paper, the numerical analysis was performed to analyze the horizontal displacement behavior of an umbrella-type micropile for various real-measurement seismic waves in sandy soil. As a result of numerical analysis, the softer the ground, the better the effect of horizontal resistance of umbrella-type micropile. The horizontal displacement reduction effect was pronounced when the embedded depth was 15 m or more at the same ground strength, and it was found to be effective in earthquakes if it was settled on the ground with an N value of 30 or more. The embedded depth and horizontal displacement suppression effect of the micropile was proportional. Generally, the weaker the ground, the greater the displacement suppression effect. Umbrella-type micropile had a composite resistance effect in which the vertical pile resists the moment and inclined pile resists the axial force.

• Korean Journal of Applied Biomechanics
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• v.15 no.2
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• pp.167-183
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• 2005

The purpose of this study was to analyze the kinetical variables of the lower extremity joints when performing uchimata(inner thigh reaping throw) by uke(receiver)'s two posture(shizenhon tai), jigohon tai), by voluntary resistance level(VRL) in judo. The subjects, who were for 3 male Korean national representative judokas(elite group : EG) and 3 male representative judokas of Korean University(non-elite group: NEG), and were filmed 4 DV video cameras(60fields/sec.), that posture of uke were shizenhon-tai (straight natural posture), jigohon-tai(straight defensive posture), VRL of uke was 0%. The selected trials were subject to 3-dimensional film motion analysis and ground reaction force(MRF) analysis. The kinetical variable of this study were temporal, postures( ankle and knee angle of attacking leg), that were computed through video film analysis, MRF at events were obtained from the ground-reaction force analysis by AMTI force plate system. When performing uchi-mata according to each posture and by VRL, from the data analysis and discussion, the conclusions were as follows : 1) Temporal variables : total time-required(TR) when performing uchi-mata was shown EG 0.13sec the shorter than NEG(o.77sec.) in shizenhon-tai. and EG 0.17sec the shorter than NEG(o.76sec.) in jigonhon-tai. Also, all of two groups' jigohon-tai(0.68sec.) were faster than shizenhon-tai(0.71 sec.). 2) The posture variables : The angle of ankle in attacking when performing were plantar flexion in EG, and dorsi flexion in NEG by shizenhon-tai and jigohon-tai posture. The angle of knee in attacking when performing were extension in EG and NEG, but range of extension in EG were larger than in NEG. 3) MRF : Vertical MRF when performing uchi-mata was shown the strongest in the 2nd stage of kake phase(2.23BW) by EG in both posture, and it was same value by NEG(2.23BW), but shizenhon-tai (2.28BW), jigohon-tai(1.64BW), respectively.

• The Journal of Engineering Geology
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• v.17 no.1 s.50
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• pp.1-13
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• 2007

In order to evaluate the local site effects at two town fortress areas in Korea where stone parapets were col-lapsed by historical earthquakes, site characteristics were assessed using site investigations such as borehole drillings and seismic tests. Equivalent-linear site response analyses were conducted based on the shear ways velocity ($V_s$) profiles and geotechnical characteristics determined from site investigations. The study sites are categorized as site classes C and B according to the mean $V_s$ to 30 m ranging from 500 to 850 m/s, and their site periods are distributed in the short period range of 0.06 to 0.16 sec, which contains the natural period of fortress wall and stone parapet. From the results of site response analyses in the study areas, for site class C indicating most of site conditions, contrary to site class B, the short-period (0.1-0.5 sec) and mid-period (0.4-2.0 sec) site coefficients, $F_a$ and $F_v$ specified in the Korean seismic design guide, underestimate the ground motion in short-period band and overestimate the ground motion in mid-period band, respectively, due to the high amplification in short period range, which represent the site-specific seismic response characteristics. These site-specific response characteristics indicate the potential of resonance in fortress walls during earthquake and furthermore could strongly affect the collapse of parapets resulted from seismic events in historical records.

• Korean Journal of Applied Biomechanics
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• v.27 no.4
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• pp.247-255
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• 2017

Objective: The purpose of this study was to investigate the maximum core muscle activation angle according to core-strengthening exercises. Method: Twenty-six young female football players (age: $17.84{\pm}0.80years$, height: $163.08{\pm}5.25cm$, weight: $54.96{\pm}7.41kg$) registered in the Korea Football Association from D High School located in Seoul were the subjects of this research. An electromyogram (Noraxon, USA) was used for monitoring the maximum core muscle contraction activity. Results: The angle for the maximum core muscle strength per core exercise and muscle was the smallest for the upper rectus abdominis in the windshield wiper exercise. The angle of the vastus medialis was significantly the largest. The range of angles at which the maximum strength was observed for each core exercise were as follows: 1) abdominal flutter kicks ($11{\sim}40^{\circ}$), 2) leg raises ($21{\sim}34^{\circ}$), 3) scissors ($45{\sim}66^{\circ}$), 4) knee to elbow sit-ups ($42{\sim}64^{\circ}$), 5) reverse crunches ($9{\sim}40^{\circ}$), 6) butt-ups ($24{\sim}32^{\circ}$), 7) V sit-ups ($5{\sim}24^{\circ}$), 8) windshield wipers ($11{\sim}20^{\circ}$), 9) bird dog ($11{\sim}18^{\circ}$), and 10) raised leg plank ($38{\sim}50^{\circ}$). Conclusion: Four kinds of motion could be classified according to the range of angles at which the core muscles were maximally activated. The first group involves the range of motion that gives the maximum muscle strength when the lower extremity and ground angle was between $5^{\circ}$ and $24^{\circ}$, such as the V sit-ups, windshield wipers, and bird dog. The second group comprised the flutter kicks and reverse crunches at an angle between $9^{\circ}$ and $40^{\circ}$. The third group comprised the leg raise and butt-up exercises at an angle between $21^{\circ}$ and $34^{\circ}$. The fourth group included the scissors, knee to elbow sit-ups, and raised leg plank at an angle between $38^{\circ}$ and $66^{\circ}$. These results may be useful as basic data for core movement and core muscle training according to the purpose of exercise.

• Journal of the Korean GEO-environmental Society
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• v.20 no.7
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• pp.5-10
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• 2019

In recent Gyeongju and Pohang earthquakes, motions that exceed the design ground motion were recorded. This has led to adjustments to the design earthquake intensity in selected design guidelines. An increment in the design intensity requires reevaluation of all associated facilities, requiring extensive time and cost. Firstly, the seismic factor of safety of built concrete retaining walls are calculated. Secondly, the seismic margin of concrete retaining walls is evaluated. The design sections of concrete walls built at power plants and available site investigation reports are utilized. Widely used pseudo-static analysis method is used to evaluate the seismic performance. It is shown that all concrete walls are safe against the adjusted design ground motion. To determine the seismic margin of concrete walls, the critical accelerations, which is defined as the acceleration that causes the seismic factor of safety to exceed the allowable value, are calculated. The critical acceleration is calculated as 0.36g~0.8g. The limit accelerations are significantly higher than the design intensity and are demonstrated to have sufficient seismic margin. Therefore, it is concluded that the concrete retaining walls do not need to be reevaluated even if the design demand is increased up to 0.3g.

• Korean Journal of Applied Biomechanics
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• v.21 no.1
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• pp.1-7
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• 2011

The purpose of this study was to investigate changes in kinetic and kinematic variables associated with an increase in upper body weight. Eighteen healthy male university students($175.96{\pm}4.19\;cm$, $70.79{\pm}8.26\;kg$) participated. Eight motion analysis cameras(Qualysis Oqus 500) and 2 force AMTI platforms(Advanced Mechanical Technologies Inc. OR6-7, US) were used to record motion and forces during the drop landing at a frequency of 120 Hz and 1200 Hz, respectively. QTM software(Qualisys Track Manager) was used to record the data, and the variables were analyzed with Visual 3D and Matlab 2009. For the drop landing, a box of $4{\times}2{\times}0.46\;m$ was constructed from wood. Knee and ankle maximum flexion angle, knee flexion angle, knee and ankle angle at landing, time for maximum ankle flexion after landing, and time for maximum knee flexion after landing were calculated. There was a significant change in the time for maximum and minimum ground force reaction and the time for maximum dorsal flexion after landing(p<.05) with increasing weight. There was no significant change for the hip, knee, and ankle ROM, whereas there was an increase in the angle ROM as the weight increased, in the order of ankle, knee, and hip ROM. This result shows that the ankle joint ROM increased with increasing weight for shock attenuation during the drop landing. There was a trend for greater ankle ROM than knee ROM, but there was no clear change in the ROM of the hip joint with increasing weight. In conclusion, this study shows the importance of ankle joint flexibility and strength for safe drop landing.

• The Journal of Korean Physical Therapy
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• v.22 no.2
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• pp.15-23
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• 2010

Purpose: This study was done to establish reference data for temporo-spatial, kinematic and kinetic parameters for normal Koreans as they age. Methods: Normal adults and children without a previous history of musculoskeletal problems were enrolled in this study. The normal subjects were divided by age into three groups: Group I: children ($11.95{\pm}0.29$ years); Group II: young adults ($23.90{\pm}3.67$ years); Group III: older adults ($71.40{\pm}4.08$ years). The temporo-spatial and kinematic data were measured using 6 MX3 cameras while each subject walked through a 10 m walkway at a self-selected speed. The kinetic data were measured using 2 force plates and were calculated by inverse dynamics. Results: Motion patterns are typically associated with a specific phase of the gait cycle. Our results were as follows: 1. There were significant differences between the different age groups in temporo-spatial parameters such as cadence, double support, time of foot off, stride length, step length, and walking speed. 2. There were significant differences between the groups in kinematic parameters such as range of motion (ROM) of the hip, knee and ankle in the sagittal plane, ROM of the pelvis, hip and knee in the coronal plane and ROM of the pelvis, hip and ankle in the transverse plane. 3. There were significant differences between the groups in kinetic parameters such as joint moments of force, joint mechanical power generation or absorption and ground reaction forces. Conclusion: The results of this study can be utilized (a) as a reference for kinematic and kinetic data of gait analysis in normal Koreans, and (b) as an aide in evaluating and treating patients who have problems relating to gait.

• Korean Journal of Applied Biomechanics
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• v.25 no.1
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• pp.65-76
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• 2015

Objective : The purpose of this study was to analyse the differences in core stability and muscle balance of the pilates Teaser motion according to the surfaces and skills. Methods : There were 10 subjects in this study with 5 being skilled and 5 that were not skilled. The independent variables were surfaces (high elastic & aluminum) and skills (skilled & unskilled). Dependent variables were core stability and muscle balance. Core stability was measured by Force Platform (9872, Switzerland), 3D Imagery (IBS-2000, EXYMA) was used to understand the muscle balance. In order to do the Teaser movement subjects had to lay flat on their back and then lean forward as much as possible and hold the position for 10 seconds. Afterwards, they would lay back down again. A camera (MHS-PM5K, SONY) was used to make 4 phases (take off, recoil forward, holding, recoil backward) during the teaser exercise to analyze movement. In this study quantitative and qualitative analysis was used. For the statistical analysis, 2X2 ANOVA was used to analyze the differences in movement time, X,Y,Z maximum force, center of pressure and angles according to different phases. 2X3 ANOVA was used to analyze the differences in muscle balance via SPSS 18.0. Results : Soft. Elastic mat had a longer holding time, lower Fx/ Fy/ Fz, shorter Fx trajectory, larger angle and shorter gaps in muscle balance than a hard surface in skilled subjects. This was because the mat can help to recruit and then sustain core fine muscles during holding time in the Teaser movement.