• Korean Journal of Applied Biomechanics
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• v.21 no.5
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• pp.529-540
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• 2011

The purpose of this study was to evaluate the kinematic characteristics of $5^{th}$ and $6^{th}$ hurdle clearances during the final of the 110-m hurdles at the IAAF World Championships, Daegu 2011. To this end, the hurdling motions of the top 4 ranked male hurdlers in the competition were analyzed. A total of 12 cameras were used to record their motions, with a sampling frequency of 120 Hz. The cameras were calibrated using $11{\times}2{\times}1\;m$ control objects that covered all of the lanes (1st~8th lanes). After analyzing all the data, we arrived at the following results. In the take-off phase, all athletes revealed similar take-off times (CT), and similar distances from the take-off to hurdleto (L1) and hurdle to landing (L2). In particular, Turner, ranked $3^{rd}$, had an inconsistent L2 and may need further training to correct it. In the flight phase, Richardson, ranked $1^{st}$, showed the longest flight distance, whereas Xiang, who was ranked $2^{nd}$, showed the highest CG height from the hurdle. For the step patterns, to increase the pitch frequency, Richardson and Xiang used shorter 3-step lengths than Turner and Oliver.

• Korean Journal of Applied Biomechanics
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• v.27 no.1
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• pp.9-18
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• 2017

Objective: The purpose of this study was to identify kinematic variables that govern successful performance and judges' scores and to establish correlative relationships among those of Yurchenko layout with a full twist in female vaults. Method: Four video cameras with sampling rate of 60 Hz collected 32 motion data of Yurchenko vaults from twenty-two female participants (age: $18.6{\pm}3.6years$, height: $153.0{\pm}6.5cm$, mass: $44.7{\pm}7.3kg$) during national competition. Posting processing and calculations of kinematic variables were performed in Kwon 3D XP and $Matlab^{(R)}$ programs. Correlation and regression analyses were applied to find the relationships between the obtained scores and kinematic variables. Deterministic model (Hay & Reid, 1988) was used to investigate the strength of correlative relationships among kinematic variables. Results: The obtained scores from the judges' decision were mainly affected by post-flight peak height, horse contact time, knee angle at landing, and horse takeoff angle. Strong blocking during horse contact was required to get successful performance and obtain high scores. Modified deterministic model showed that round-off entrance and takeoff angles and resultant velocity of the center of mass (CM) during the roundoff phase were the starting variables affecting performance in the following kinematics. Knee angle at landing, a highly influential variable on the obtained point, was only determined by judges' decision without significant correlative relationship with previous kinematic variables. Conclusion: The obtained scores highly depended on kinematic variables of post-flight and horse contact phases that were affected by those from the previous phases including round-off postures and resultant velocity of the body center of mass.

• Korean Journal of Applied Biomechanics
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• v.26 no.1
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• pp.71-82
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• 2016

Objective: The purpose of this study was to investigate kinematic comparisons of Tsukahara vault in gymnastics between a top-level athlete and sublevel collegiate athletes in order to obtain information on key biomechanical points for successful Tsukahara vaults. Methods: An Olympic gold medalist (height, 160 cm; weight, 52 kg; age, 25 years) and five sublevel collegiate gymnasts (height, $168.2{\pm}3.4cm$; weight, $59.6{\pm}3.1kg$; age, $23.2{\pm}1.6years$) participated in this study. They repeatedly performed Tsukahara vaults including one somersault. Fourteen motion-capturing cameras were used to collect the trajectories of 26 body markers during Tsukahara vaults. Event time, displacement and velocity of the center of mass, joint angles, the distance between the two hands on the horse, and averaged horizontal and vertical impact forces were calculated and compared. Results: The top-level athlete showed a larger range of motion (ROM) of the hip and knee joints compared to sublevel collegiate athletes during board contact. During horse contact, the top-level athlete had a narrow distance between the two hands with extended elbows and shoulders in order to produce a strong blocking force from the horse with a shorter contact time. At the moment of horse take-off, reactive hip extension of the top-level athlete enhanced propulsive take-off velocity and hip posture during post-flight phase. Conclusion: Even though a high velocity of the center of mass is important, the posture and interactive action during horse contact is crucial to post-flight performance and the advanced performance of Tsukahara vaults.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.30 no.3
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• pp.28-37
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• 2022

Obstacle Limitation Surface (OLS) is conceptual surface establishing the airspace around aerodromes to be maintained from obstacles to ensure safe aircraft operations. Despite advances in the technologies for aircraft, navigation systems and the development of new flight procedures, the criteria defining OLS have not been amended since its initial establishment, resulting in the overestimation of areas for height restriction. As there were requests to examine OLS at the 12th Air Navigation Conference and the 38th ICAO Assembly, the research on the OLS revision began in earnest and ICAO has proposed Obstacle Free Surface (OFS) and Obstacle Evaluation Surface (OES) as an alternative of the existing OLS. OFS is surfaces where obstacles shall not be permitted, and OES is ones where obstacles be evaluated with an aeronautical study and could be permitted under some conditions. The purpose of this study is to preemptively assess the efficiency and safety of OFS and OES by applying them to the second runway (15L/33R) of Incheon International Airport. The results show that OFS and OES are capable of serving the instrument flight procedure safely with a smaller obstacle clearance area compared to the existing OLS.

• Geomechanics and Engineering
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• v.31 no.6
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• pp.573-582
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• 2022

The geometry of the gravity-type anchorage changes depends on various factors such as the installation location, ground type, and relationship with the upper structure. In particular, the anchorage geometry embedded in the ground is an important design factor because it affects the pull-out resistance of the anchorage. This study examined the effect of four parameters, related to anchorage geometry and embedded ground conditions, on the pull-out resistance in the gravity-type anchorage through two-dimensional finite element analysis, and presented a guide for major design variables. The four parameters include the 1) flight length of the stepped anchorage (m), 2) flight height of the stepped anchorage (n), 3) the anchorage heel height (b), and 4) the thickness of the soil (e). It was found that as the values of m increased and the values of n decreased, the pull-out resistance of the gravity-type anchorage increased. This trend is related to the size of the contact surface between the anchorage and the rock, and it was confirmed that the value of n, which has the largest change rate of the contact surface between the anchorage and the rock, has the greatest effect on the pull-out resistance of the anchorage. Additionally, the most effective design was achieved when the ratio of the step to the bottom of the anchorage (m) was greater than 0.7, and m was found to be an important factor in the pull-out resistance behavior of the anchorage.

• The Korean Journal of Air & Space Law and Policy
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• v.35 no.2
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• pp.225-246
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• 2020

More than technical or academic matter, mitigation of height restriction around airports is about up-dating out-dated policies that have not kept up with rapidly developing aircraft and air traffic control technologies. Above all, instead of calling out 'flight safety' that the public do not comprehend, it is important to examine and carry out measures that can protect people's right of property. MOLIT(Ministry of Land, Infrastructure, and Transport) after reviewing ICAO's Obstacle Limitation Surface TF, made an announcement to provide further plans that would apply to contracting states from 2026. However, residents of redevelopment areas near Kimpo international airport asserted that MOLIT's policy overlooks the reality of the redevelopment zone. ICAO, UN's specialized agency for civilian aviation, recommends in Annex 14, 4.2.4 that contracting states conduct an aeronautical study to determine the flight safety of horizontal surface(45m), excluding approach surface, and to mitigate height restrictions if no threat is found. Numerous countries including the United States have been following this recommendation and have been able to effectively protect people's right of property, whereas the South Korean government have not following it so far. The number of height restriction mitigation cases in the recent three months (2019. 7. 15~10. 14.) FAA of the United States have allowed after conducting an aeronautical study reaches 14,706. Japan and Taiwan also reconstruct airspace around airports in metropolitan areas in order to protect people's right of property. Just as the United States is following, MLIT should follow ICAO's recommendation in Annex 14. 4.2.4(Vol. 1. Airport Construction / Operation) and protect people's right of property by first applying aeronautical studies to the horizontal surface(45m) of flight safety zones until the specifics of ICAO's 2026 TF materialize.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.6
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• pp.2689-2708
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• 2016

Multi-camera systems which integrate two or more low-cost digital cameras are adopted to reach higher ground coverage and improve the base-height ratio in low altitude remote sensing. To guarantee accurate multi-camera integration, the geometric relationship among cameras must be determined through platform calibration techniques. This paper proposed a combined two-step platform calibration method. In the first step, the static platform calibration was conducted based on the stable relative orientation constraint and convergent conditions among cameras in static environments. In the second step, a dynamic platform self-calibration approach was proposed based on not only tie points but also straight lines in order to correct the small change of the relative relationship among cameras during dynamic flight. Experiments based on the proposed two-step platform calibration method were carried out with terrestrial and aerial images from a multi-camera system combined with four consumer-grade digital cameras onboard an unmanned aerial vehicle. The experimental results have shown that the proposed platform calibration approach is able to compensate the varied relative relationship during flight, acquiring the mosaicing accuracy of virtual images smaller than 0.5pixel. The proposed approach can be extended for calibrating other low-cost multi-camera system without rigorously mechanical structure.

• Korean Journal of Applied Biomechanics
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• v.14 no.1
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• pp.1-12
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• 2004

The purpose of this study is to provide training materials for practical use by investigating the kinematical variables of the successful landing by the type of the salto backward such as Tuck, Pike. For this study, the subjects are 4 male national gymnasts using 3-dimensional cinematographic method. Based on the results of this study, the conclusions are drawn as follows. 1. In flight phase, Tuck and Pike show fast extension after completing minimum angle of hip joint passing through the peak. It is very important factor to control body with gaining time before landing while decreasing the velocity of flight rotaion. 2. In Landing phase, the angles of each joint for successful landing are shown as $92deg{\sim}100deg$ for knee angle, $52deg{\sim}57deg$ for hip angle, and $56deg{\sim}70deg$ for shoulder angle. 3. Tuck and Pike dramatically decrease the height of COG, and horizontal/vertical velocity of COG from TD to LD. Also, it is shown that the knee angle, the hip angle and the shoulder angle decrease drastically. On the other hand, the angular velocity of trunk rotation shows negative direction and due to this, the angle of trunk rotation is shown as re-flexion.

• Korean Journal of Applied Biomechanics
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• v.23 no.1
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• pp.19-24
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• 2013

The aim of the study was a quantitative analysis of elite athlete's $540^{\circ}$ Dwihuryeochagi and effects of ground movements to the jumping height and kicking velocity. Eleven elite players(Taekwondo demonstration team) participated in this study. In order to get the kinetic and kinematic variables, ten Vicon cameras and a force plate were used. Foot segment velocity(FSV), vertical ground reaction force(GRF), impulse, ground time(GT) in phase 1, trunk angular velocity(TAV), vertical center of gravity(COG), flight time(FT) in phase 2 and kicking leg segment velocity(KSV) in phase 3 were measured and analyzed. Results indicated that there were similar patterns of variables among phases between subjects. Non-significant correlation(r=.145) between flight time(FT) and impulse was found. Also non-significant correlation(r=.119) between center of gravity(COG) and impulse was found. In conclusions, there were similar strategies in phase 1, phase 2, and phase 3 between subjects.

• Spatial Information Research
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• v.15 no.4
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• pp.363-370
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• 2007

This study has been carried for the development of the basic algorithm of helicopter navigation system based on TRN (Terrain Referenced Navigation) with information input from the GPS. The helicopter determines flight path due to Origination-Destination analysis on the Cartesian coordinate system of 3-D DTM. This system shows 3-D mesh map and the O-D flight path profile for the pilot's acknowledgement of the terrain, at first. The system builds TCF (terrain clearance floor) far the buffer zone upon the surface of ground relief to avid the ground collision. If the helicopter enters to the buffer zone during navigation, the real-time warning message which commands to raise the body pops up using Matlab menu. While departing or landing, control of the height of the body is possible. At present, the information (x, y, z coordinates) from the GPS is assumed to be input into the system every 92.8 m of horizontal distance while navigating along flight path. DTM of 3" interval has been adopted from that which was provided by ChumSungDae Co., Ltd..