• Earthquakes and Structures
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• v.7 no.6
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• pp.1283-1301
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• 2014

Ground motion modification is extensively used in seismic design of civil infrastructure, especially where few or no recorded ground motions representative of the design scenario are available. A site in Los Angeles, California is used as a study site and 28 ground motions consistent with the design earthquake scenario are selected. The suite of 28 ground motions is scaled and modified in the time domain (TD) and frequency domain (FD) before being used as input to a bilinear SDOF system. The median structural responses to the suites of scaled, TD-modified, and FD-modified motions, along with ratios of he modified-to-scaled responses, are investigated for SDOF systems with different periods, strength ratios, and post-yield stiffness ratios. Overall, little difference (less than 20%) is observed in the peak structural accelerations, velocities, and displacements; displacement ductility; and absolute accelerations caused by the TD-modified and FD-modified motions when compared to the responses caused by the scaled motions. The energy absorbed by the system when the modified motions are used as input is more than 20% greater than when scaled motions are used as input. The observed trends in the structural response are predominantly the result of changes in the ground motion characteristics caused by modification.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.6
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• pp.205-212
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• 2003

This paper may provide a basic design data for the safer car seat mechanism and the quality of the material used by finding out the passenger's dynamic behavior when protected by seat belt during collision. A computer simulation with finite element method is used to accomplish this objective. At first, a detailed geometric model of the seat is constructed using CAD program. The formation of a finite element from a geometric data of the seat is carried out using Hyper-Mesh that is the commercial software for mesh generation and post processing. In addition to seat modeling, the finite element model of seat belt and dummy is formed using the same software. Rear impact analysis is accomplished using Pam-Crash with crash pulse. The part of the recliner and right frame is under big stress in rear crash analysis because the acceleration force is exerted on the back of the seat by dummy. The stress condition of the part of the bracket is checked as well because it is considered as an important variable on the seat design. Front impact model which including dummy and seal belt is analyzed. A Part of anchor buckle of seat frame has high stress distribution because of retraction force due to forward motion of dummy at the moment of collision. On the basis of the analysis result, remodeling and reanalysis works had been repeatedly done until a satisfactory result is obtained.

• Journal of The Korean Society of Integrative Medicine
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• v.7 no.3
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• pp.1-9
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• 2019

Purpose : To find out how action observation training for chronic stroke patients affects their balance and body control abilities in the posture seated in the rehabilitation of stroke. Methods : This study was conducted on 30 subjects who were diagnosed with stroke. The group conducted motion observation training through video clips, while the control group only conducted physical training, and the general physical therapy was performed equally by both counties. The static balance was measured using Biorescue and the dynamic balance was measured using Modified Functional Reach Test (MFRT), Postural Assessment Scale for Stroke, and Trunk Impairment Scale. Results : Static balance showed statistically significant difference in foot pressure (p<.05) as a result of comparison between pre and post exercise training. Dynamic balance was statistically significant (p>.05) as a result of comparing pre and post differences using modified functional reach test. The trunk control ability was statistically significant (p>.001). Comparison between the results of before and after motion observation training showed a statistically significant difference. Conclusion: This study confirmed that exercise training in sitting position was effective for static, dynamic balance ability and trunk control ability of hemiplegic patients due to stroke. These results suggest that the use of motion monitoring in stroke patients may have a positive impact on the diversity and function of rehabilitation.

• Korean Journal of Applied Biomechanics
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• v.34 no.1
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• pp.34-44
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• 2024

Objective: This study aimed to investigate how the movements occurring during the follow-through phase after releasing an arrow among elite compound archers, are associated with the arrow impact points on the target. Method: Nine elite archers performed consecutive compound archery shooting under conditions identical to actual competitions using their own bows and equipment. Motion capture system and force platform were utilized to record the changes in joint positions and center of pressure, respectively. Principal component analysis was employed to identify the patterns in which multidimensional joint positions and COP changes were organized with horizontal and vertical coordinates of arrow impact points. Subsequently, correlation analysis quantified the relationship between individual variables and the coordinates of arrow impacts on the target. Results: We found a common organizational pattern in which the two axes of the impact point coordinates were grouped into the first two principal components. The movements of the upper and lower limbs following release exhibited opposite patterns in the anterior-posterior axis, with significant correlations observed between the arrow impact points of the horizontal axis and the left shoulder, right elbow, left hip, and both knees. Additionally, the lateral movements induced by the reaction force upon arrow release showed significant associations with the vertical coordinates of the impact points. Particularly, the correlations between the movements of the left shoulder and elbow, as well as the bilateral hip and right knee, were consistently observed among all participants. Conclusion: These findings implied that the post-release movements could significantly influence the trajectory and impact points of the arrows in compound archery. We suggest that a consistent and controlled movement during the follow-through phase may be more beneficial for optimizing shooting accuracy and precision rather than minimizing movements.

• 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.

• The Journal of Advanced Prosthodontics
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• v.14 no.2
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• pp.88-95
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• 2022

PURPOSE. This study investigated the accuracy of full-arch intraoral scans obtained by various scan strategies with the segmental scan and merge methods. MATERIALS AND METHODS. Seventy intraoral scans (seven scans per group) were performed using 10 scan strategies that differed in the segmental scan (1, 2, or 3 segments) and the scanning motion (straight, zigzag, or combined). The three-dimensional (3D) geometric accuracy of scan images was evaluated by comparison with a reference image in an image analysis software program, in terms of the arch shape discrepancies. Measurement parameters were the intermolar distance, interpremolar distance, anteroposterior distance, and global surface deviation. One-way analysis of variance and Tukey honestly significance difference post hoc tests were carried out to compare differences among the scan strategy groups (α = .05). RESULTS. The linear discrepancy values of intraoral scans were not different among scan strategies performed with the single scan and segmental scan methods. In general, differences in the scan motion did not show different accuracies, except for the intermolar distance measured under the scan conditions of a 3-segmental scan and zigzag motion. The global surface deviations were not different among all scan strategies. CONCLUSION. The segmental scan and merge methods using two scan parts appear to be reliable as an alternative to the single scan method for full-arch intraoral scans. When three segmental scans are involved, the accuracy of complete arch scan can be negatively affected.

• Journal of the Society of Naval Architects of Korea
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• v.56 no.2
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• pp.103-108
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• 2019

A new state-of-the-art sloshing research equipment has developed to perform the model test of LNG tanks for the safer design of LNG cargo containment system in violent sloshing phenomena. This sloshing test system has developed by the Samsung Ship Model Basin (SSMB) and thoroughly verified. The accuracy of the motion of hexapods equipment for the excitation of a model tank has been verified. The maximum displacement in six degrees of freedom, harmonic motions of various frequencies, and irregular motions in wave conditions are measured and compared with input signals. In order to confirm the reliability of the post-processing program for measured impact pressure, the post-processed results were compared with those of the reference institute. A benchmarking sloshing test using 1/50 scale model of 160K LNGC tank was conducted for the verification of the whole testing system. The partial filing levels were considered. As a result of the experiment, it is confirmed that the results are in good agreement with those of the reference institute.

• Journal of Ocean Engineering and Technology
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• v.7 no.1
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• pp.33-55
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• 1993

선수충격파의 문제를 푸는데 있어서 Boundary Integral Method(BIM)의 여러가지 수치 해석방법이 검토되었으며, 특히 여러가지 Time stepping scheme, Green function, far-field 조건등에 따른 수치해석안정성과 정확성의 상관관계가 연구되었다. von Neumann 안정성해석과 matrix 안정성해석 등을 이용한 선형 안정성해석을 기초로하여, 수치해석방법의 안정성 여부를 체계적으로 조사할 수 있는 parameter(Free Surface Stability number)를 설정하고, 이 parameter의 변화에 따른 비선형 운동해석을 연구하였다. 그 결과 비선형성이 심하지 않은 기진파의 경우에서는 비선형 운동해석의 수치해석 안정성의 선형 수치해석 안정성과 큰 차이가 없음을 알 수 있게 된다.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.28 no.3
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• pp.89-99
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• 2022

Background: The purpose of this study was to investigate the effects of physical therapy intervention with local vibration on the physical function of patients with traumatic patella fractures. Methods: This study recruited 6 subjects who had suffered traumatic patella fractures. The study was conducted for an average of 12.8 weeks. Before the treatment (2 weeks post-surgery), they were evaluated using the numeric pain rating scale (NPRS), the Korean-version of the impact of event scale-revised (IES-R-K), pressure pain threshold (PPT), range of motion (ROM) of the knee joint, and the Korean knee injury and osteoarthritis outcome score (K-KOOS) and were reevaluated after 7 and 12 weeks, post-surgery. This study was conducted according to ORIF Patella Fracture Post-Operative Rehabilitation Protocol after applying local vibration. The protocol consists of Phases 1~5 and this study has been applied from phase 2. Results: A comparison of the performance of the participants before and after the intervention showed a decrease in NPRS (9.83±.41→4.83±.98), IES-R-K (68.67±2.73→23.83±2.40), and K-KOOS (Function, Daily living: 70.5±5.96→34.0±3.35, Function, Sports and Recreational activities: 22.83±2.32→10.77±1.37, Quality of Life: 19.33±7.33→7.33±.52) scores. And the ROM (Knee flexion: 30.0±4.47°→128.73±3.6°, Knee extension: -6.83±2.48°→-1.33±1.03°) and PPT (9.67±.52kg/cm²→22.44±2.33kg/cm²) scores increased. Conclusion: These results show that physical intervention with local vibration using a Blackroll® booster and head can help to improve pain, physical function, and psychological status. Also, it was possible to select interventions depending on the patient's condition and the desired goal, using physical intervention with the Blackroll® booster technique.

• PNF and Movement
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• v.21 no.1
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• pp.37-45
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• 2023

Purpose: Whiplash-associated disorder is often caused by external impact, such as a car accident, and it involves acceleration and deceleration of the flexion and extension of the neck. The purpose of this study is to determine whether the combination of cyrotherapy and a joint mobilization intervention in patients with acute whiplash-associated disorder is effective for pain, cervical range of motion (ROM), and muscle tone in the neck muscles. Methods: In this study, 20 patients with acute whiplash-associated disorder were randomly assigned to two groups. Group A was treated with cyrotherapy for 5 minutes, while group B was treated with cyrotherapy and a joint mobilization intervention. In both groups, visual analogue scale (VAS), neck disability index (NDI), cervical ROM, and muscle tone values were measured pre- and post-intervention. Results: According to the VAS values, both groups showed significant differences pre- and post-intervention (p<0.05), and in both groups, NDI was significantly decreased pre- and post-intervention (p<0.05). Finally, in terms of muscle tone, both groups showed significant changes before and after the intervention (p<0.05). Conclusion: These results showed that cryotherapy and joint mobilization can be effective interventions in patients with whiplash-associated disorder. In addition, to improve the ROM of the cervical joint and reduce NDI, the combination of cryotherapy and joint mobilization is considered more effective than the single intervention of cryotherapy.