• Korean Journal of Applied Biomechanics
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• v.17 no.2
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• pp.113-121
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• 2007

The purpose of this study was to determine the effect of three different plates($0^{\circ}$, $10^{\circ$}, $20^{\circ}$)under heels on the lower limb muscles and erector spinae during squat exercise. Ten high school korean traditional wrestling players(age: $18.5{\pm}0.7$, weight: $1972.2{\pm}128.5N$, height: $177.8{\pm}6.0cm$, weight of barbell: $1004.5{\pm}132.4N$) performed squat exercise using three different tilting plates under heels at a cadence of 40beats/sec with 80% one repetition maximum load. Surface electrodes were placed on the participants' left and right erector spinae, and rectus femoris, vastus medialis, vastus lateralis, tibialis anterior, biceps femoris, medial gastrocnemius, and lateral gastrocnemius in the right lower extremity. One S-VHS camcorder(Panasonic AG456, 60fields/s) was placed 10m to the side of the participant. To synchronize the video and EMG data, a synchronization unit was used for this study. Average and Peak IEMG values were determined for each participant. For each variable, a one-way analysis of variance was used to determine whether there were significant differences among three different tilting plates under heels. When a significant difference was found in plates type, post hoc analyses were performed using the Tukey procedure. A confidence level of p<.05 was used to determine statistical significance. As a result of this study, maximum nEMG values of the tibialis anterior in $0^{\circ}$ plates was significantly higher than the corresponding values for the other plates during the knee extension. This increased activation in the tibialis anterior muscle indicates an increase in displacement of center of gravity of body. It is very likely that additional muscle activation are needed to stop the forward and backward movement. The results also showed that muscular activities of quadriceps femoris and erector spinae were decreased with increasing angle of plates. This suggests that increasing angle of plate may help to sustain the balance and posture of squat exercise. It is considered that very few significant differences were found among three different plates($0^{\circ}$, $10^{\circ}$, $20^{\circ}$) since elite players with much experience in squat exercise, were chosen as a participant of this study. In order to obtain meaningful results regarding the tilting angle of heel plates in squat exercise, kinetic and 3D kinematic analysis will be needed in the future study.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2000.09a
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• pp.67-75
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• 2000

The numerical simulation of Brazilian fracture toughness test is carried out using PFC code and the influence parameters are analyzed such as shape of loading plane, size of Brazilian disc and unit panicle of model, loading angle and loading rate. The flattened Brazilian disc is adopted for applying uniform load. The range of loading angle(2$\alpha$) necessary to induce the tensile crack at disc center and to obtain the load-displacement curve giving the critical load for the stable crack propagation is shown as 20$^{\circ}$~40$^{\circ}$. In condition that the loading angle is 20$^{\circ}$, the mode-I fracture toughness is evaluated almost constant in the range of particle size less than I mm and loading rate less than 0.01 mm/s. This range of influence parameters seems appropriate condition for the tensile crack initiation at disc center and the control of stable crack propagation, which can give the reliance in evaluation of fracture toughness by Brazilian test.

• Tunnel and Underground Space
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• v.10 no.3
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• pp.320-328
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• 2000

The numerical simulation of Brazilian fracture toughness test is carried out using PFC code and the influence parameters are analyzed such as shape of loading plane, size of Brazilian disc and unit particle of model, loading angle and loading rate. The flattened Brazilian disc is adopted for applying uniform load. The range of loading angle(2$\alpha$) necessary to induce the tensile crack at disc center and to obtain the load-displacement curve giving the critical load for the stable crack propagation is shown as 20°∼40°. In condition that the loading angle is 20°, the mode-I fracture toughness is evaluated almost constant in the range of particle size less than 1 mm and loading rate less than 0.01㎜/s. This range of influence parameters seems appropriate condition for the tensile crack initiation at disc center and the control of stable crack propagation, which can give the reliance in evaluation of fracture toughness by Brazilian test.

• Korean Journal of Applied Biomechanics
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• v.24 no.3
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• pp.201-207
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• 2014

This study investigated the center of mass and lower extremity kinematic patterns between carved and basic paralell turn during alpine skiing. Six experienced skiers (age: $20.67{\pm}4.72yrs$, body mass: $72.67{\pm}7.15kg$, height: $171.00{\pm}5.51cm$) participated in this study. Each skier were asked to perform carved and basic paralell turn on a $22.95^{\circ}$ groomed slope. Each turn was divided into the initiation phase, steering phase 1 and 2. The results of this study show that the carved turn spent significantly less running time than basic paralell turn at all three phases (p<.05). Also vertical displacement of the center of mass was significantly greater in carved turn at all three phases, whereas inward leaning angle of the center of mass was significantly greater in carved turn at the steering phase 1 and 2 (p<.05). Bilateral knee and hip joint angle were significantly greater in basic paralell turn at the initiation phase and the steering phase 2 (p<.05). On the other hand, left knee and hip joint angle were significantly greater in basic paralell turn at the steering phase 1 (p<.05). In order to perform successful carved turn, we suggest that skiers should coordinate bilateral knee and hip joint angles to adjust the center of mass, depending on three ski turn phases.

• Journal of radiological science and technology
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• v.40 no.1
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• pp.63-70
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• 2017

The purpose of this study was compare to the patient setup deviation of two different type thermoplastic immobilization masks for glottis cancer in the intensity-modulated radiation therapy (IMRT). A total of 16 glottis cancer cases were divided into two groups based on applied mask type: standard or alternative group. The mean error (M), three-dimensional setup displacement error (3D-error), systematic error (${\Sigma}$), random error (${\sigma}$) were calculated for each group, and also analyzed setup margin (mm). The 3D-errors were $5.2{\pm}1.3mm$ and $5.9{\pm}0.7mm$ for the standard and alternative groups, respectively; the alternative group was 13.6% higher than the standard group. The systematic errors in the roll angle and the x, y, z directions were $0.8^{\circ}$, 1.7 mm, 1.0 mm, and 1.5 mm in the alternative group and $0.8^{\circ}$, 1.1 mm, 1.8 mm, and 2.0 mm in the alternative group. The random errors in the x, y, z directions were 10.9%, 1.7%, and 23.1% lower in the alternative group than in the standard group. However, absolute rotational angle (i.e., roll) in the alternative group was 12.4% higher than in the standard group. For calculated setup margin, the alternative group in x direction was 31.8% lower than in standard group. In contrast, the y and z direction were 52.6% and 21.6% higher than in the standard group. Although using a modified thermoplastic immobilization mask could be affect patient setup deviation in terms of numerical results, various point of view for an immobilization masks has need to research in terms of clinic issue.

• Restorative Dentistry and Endodontics
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• v.18 no.2
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• pp.291-316
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• 1993

Restorative procedures can lead to tooth fracture due to the relatively small amount of the remaining tooth structure. It is essential to prevent fractures by having a clear concept of the designs for cavity preparations. Among the several parameters in cavity designs, profound understanding of isthmus width factor would facilitate selection of the appropriate cavity preparation for a specific clinical situation. In this study, MO amalgam cavity were prepared on maxillary first premolar and filled with amalgam. Three dimensional, model with 1365 8-node brick elements was made by serial photographic method. In this model, isthmus was varied in width at 1/4, 1/3, 1/2 and 2/3 of intercuspal width and material properties were given for three element groups, i.e., enamel, dentin and amalgam. A load of 500 N was applied vertically on amalgam and enamel. In case of enamel loading, 2 model (with and without amalgam) was compared to consider the possibility of play at the interface between tooth material and amalgam. These models were analyzed with three dimensional finite element method. The results were as follows: 1. The stress was concentrated on the facio-pulpal line angle and distal marginal ridge of the cavity. 2. With the increase of the isthmus width, the stress spread around the facio-pulpal line angle and the area of stress concentration moved toward the proximal box. 3. In case of narrow isthmus width, the initiation point of crack would be in the area of isthmus corner of the cavity, and with the increase of the isthmus width, it would move toward the proximal box and at the same time the possibility of crack increase at the distal marginal ridge. 4. The direction of crack progressed outward and downward from the facio-pulpal line angle, and with the increase of the isthmus width, it approximated vertical direction. At the marginal ridge, it occurred in vertical direction. 5. It would be favorable to make the isthmus width narrower than a third of the intercuspal width, and to cover the cusp if isthmus width were wider than half of the intercuspal width. 6. It is necessary to apply the possibility of play to the finite element analysis.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.14 no.3
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• pp.217-227
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• 1992

The purpose of this paper is to investigate changes in soft tissue in 22 patients treated by vertical ramus osteotomy and sagittal split ramus osteotomy for the correction of mandibular prognathism. 22 individuals, 12 males and 10 females, were selected from the patients with mandibular prognathism at the Department of Oral and Maxillofacial Surgery, Colledge of Dentistry, Kyung Hee University. Patient were analyzed with cephalogram taken 1 week before and at least 6 weeks after surgery under the same condition. Measurements were made constructed hard tissue and sop tissue points located on each before-and-after film tracing. Comparision were made of these figures to estimate the amount that the soft tissue followed the hard tissue structures in each surgical procedure : ratio of sop and hard tissue changes were formulated. The results were as follows. 1. The horizontal changes of Pogs and Bs as a ratio of the horizontal changes of Pog and B point were 1.02 and 1.16 respectively. 2. One millimeter of posterior changes at Pog resulted in 0.86mm of posterior change at Li and 0.09mm of posterior change at Ls. The greatest amount of sop tissue change occurred at Pogs, with substantially less posterior displacement at Bs, even less at Li and at least at Ls. 3. The ratio of LI to Li was 1:0.81 and the ratio of LI to Ls was not significant.(1 : 0.17) 4. The ULA(Cm-Sn-Ls) and the relative lower lip projection (LLP) was incnease4 but the relative upper lip projection (ULP) was slightly decreased 5. The angular change of the upper lip inclined angle (Ls-Sn/ANS-PNS) and lower lip inclined angle(Li-Pogs/Me-Go) expressed as a ratio of the posterior change of Pog were 0.57 and 0.20 respectively. 6. The ratio of the lower anterior facial height change of the soft tissue(Sn-Mes) to the hard tissue(ANS-Gn) were 0.78 and and the ratio of vertical height changes of the hard tissue and sop tissue to the posterior change of the Pog were 0.18 and 0.19 respectively. 7. The sop tissue angular change of facial convexity(G-Sn-Pogs) expressed as a ratio of the angular change of the hard tissue angle of facial convexity(N-A-Pog) was 1.24.

• Archives of Hand and Microsurgery
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• v.23 no.4
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• pp.239-247
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• 2018

Purpose: We investigated occurrence of reduction loss after extension block (EB) Kirschner wire fixation or additional interfragmentary fixation (AIF) and clinical results including extension lag of the distal interphalangeal joint for treating bony mallet finger. Methods: Forty-six patients were included with a mean follow-up of 28 months (range, 12-54 months). Twenty-seven patients were treated with EB K-wire fixation (Group A) while 19 patients were treated with AIF (Group B). We checked radiologic factors, such as amount of articular involvement, volar subluxation, mallet fragment angle, reduction loss, range of motion including extension lag, and functional outcomes using Crawford's criteria. Results: Reduction loss occurred in eight patients (17%). Differences in mean extension lag, age, preoperative volar subluxation and mallet fragment angle between patients with reduction loss and those with reduction maintaining were significant. However, there were no significant differences in gender, hand dominance, amount of articular involvement, AIF, or further flexion between reduction loss and reduction maintaining. As for patterns of displacement, there was a significant relationship between gap or step-off and extension lag. Using Crawford's evaluation criteria, functional outcomes were excellent in 31, good in 10, fair in 3, and poor in 2 patients. Conclusion: Reduction loss should be careful in older age, smaller mallet fragment angle and preoperative volar subluxation.

• Journal of the Korean Geotechnical Society
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• v.39 no.12
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• pp.93-102
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• 2023

Despite recent modifications to building structural standards emphasizing the seismic stability of building foundations, the current design focus remains solely on vertical support, resulting in insufficient consideration of horizontal loads during earthquakes. In this study, we evaluated the dynamic behavior of inclined tripod micropiles (ITMP), which provide additional seismic resistance against horizontal and vertical loads during earthquakes. A comparison of the dynamic characteristics, such as acceleration, displacement, bending moment, and axial force, of ITMP with a 15° installation angle and normal vertical micropiles with a 0° installation angle was performed using dynamic centrifuge model tests. Results show that under moderate seismic loads, the proposed ITMP exhibited lower acceleration responses than the vertical micropiles. However, when subjected to a long-period strong seismic excitation, such as sine (2 Hz), ITMP showed greater responses than the vertical micropiles in terms of acceleration and settlement. These results indicate that the use of ITMP reduces the amplif ication of short-period (high-f requency) contents compared with the use of vertical micropiles. Therefore, ITMP can be used to enhance seismic performance of structures.

• Korean Journal of Applied Biomechanics
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• v.12 no.2
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• pp.51-63
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• 2002

This study sought to identify the kinematic characteristics at entrance to the straight course from the curvilinear course in the 200m-track game. For this purpose, this study was conducted for 4 sprinters by setting the 10m-section combined from the curvilenear track to the straight course and shooting them with the camcorder. It was set up to include all the sections of analysis by using the framework of the control point knowing the coordinate of the space and actual analysis was conducted on the motion showing the best records by conducting it for each subject five times. As a result, the following conclusion was drawn: It was found that the subjects showed the average stride of 4.5${\pm}$0.41 times at the 10-meter section and the required time of 1.42${\pm}$0.04sec. They showed the ratio average stride to height of 1.25${\pm}$0.20% and the average speed of 7.06${\pm}$0.19m/s. The displacement in the center of gravity of the human body at the section combined from the curvilinear course to the straight course was moving along the inward course of the curvilinear course, and the displacement of the leg located at the outward direction(right) was found to be larger than that of the leg located at the inward direction(left). In the speed of the left and right hand segments, it was found that the speed of the right hand located in the outward direction was faster than that of the left hand located at the inward, and it was found that the subjects progressed in the curvilinear course. The subjects showed the larger angle of the shoulder joint when the upper arm was located in the forward direction than when the it was located in the backward direction. In the curvilinear course, they showed the lower value of the lateral angle of the trunk when the right foot located at the outward direction left the ground than when the left foot located at the inward direction left the ground. And it was found that the lateral angle of the trunk became lower with approaching the straight course.