• 한국산학기술학회논문지
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• 제16권3호
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• pp.2012-2019
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• 2015

본 연구의 목적은 세 가지 가방 휴대 방법에 따라 세 가지 가방의 무게를 달리하여 보행하는 동안 신체의 압력중심점의 변위와 보행률의 변화를 분석하고자 2013년 6월 3일부터 2014년 1월 20일까지 시행하였다. 38명의 건강한 성인(평균 연령: $26.10{\pm}5.32$세, 연령 범위: 22-30세)이 본 연구에 참여하였다. 첫 번째 조건은 한쪽 어깨에 가방을 메고 보행하였고, 두 번째 조건은 한쪽으로 가로질러 가방을 메고 걸었으며, 세 번째 조건은 양쪽 어깨에 가방을 메고 걸었다. 보행의 운동 형상학적 변수와 보행 시 압력중심점의 변위를 측정하기 위하여 3차원 동작분석기와 지면 반력기를 사용하였다. 각 세 가지 조건에 모든 대상자가 참가하였고, 모든 대상자는 각각 세 가지 조건에서 3kg, 5kg, 7kg의 무게를 지닌 가방을 휴대하여 6m를 걸었다. 본 연구 결과, 양쪽 어깨로 가방을 메고 걸을 때 3kg, 5kg, 7kg의 가방의 무게에 따라 전-후 및 내측-외측 방향의 압력중심점과 보행률 변수에서 통계학적으로 유의한 차이가 있었다. 따라서 양쪽 어깨에 가방을 메고 걷는 것이 다른 조건보다 더 효율적으로 보행할 수 있을 것으로 사료된다.

• Journal of Korean Neurosurgical Society
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• 제60권6호
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• pp.611-619
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• 2017

Objective : In addition to bone bridging inside a cage or graft (intragraft bone bridging, InGBB), extragraft bone bridging (ExGBB) is commonly observed after anterior cervical discectomy and fusion (ACDF) with a stand-alone cage. However, solid bony fusion without the formation of ExGBB might be a desirable condition. We hypothesized that an insufficient contact area for InGBB might be a causative factor for ExGBB. The objective was to determine the minimal area of InGBB by finite element analysis. Methods : A validated 3-dimensional, nonlinear ligamentous cervical segment (C3-7) finite element model was used. This study simulated a single-level ACDF at C5-6 with a cylindroid interbody graft. The variables were the properties of the incorporated interbody graft (cancellous bone [Young's modulus of 100 or 300 MPa] to cortical bone [10000 MPa]) and the contact area between the vertebra and interbody graft (Graft-area, from 10 to $200mm^2$). Interspinous motion between the flexion and extension models of less than 2 mm was considered solid fusion. Results : The minimal Graft-areas for solid fusion were $190mm^2$, $140mm^2$, and $100mm^2$ with graft properties of 100, 300, and 10000 MPa, respectively. The minimal Graft-areas were generally unobtainable with only the formation of InGBB after the use of a commercial stand-alone cage. Conclusion : ExGBB may be formed to compensate for insufficient InGBB. Although various factors may be involved, solid fusion with less formation of ExGBB may be achieved with refinements in biomaterials, such as the use of osteoinductive cage materials; changes in cage design, such as increasing the area of polyetheretherketone or the inside cage area for bone grafts; or surgical techniques, such as the use of plate/screw systems.

• 대한기계학회논문집A
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• 제41권5호
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• pp.361-366
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• 2017

컴퓨팅 아키텍처와 응용 소프트웨어 기술의 발달로 최근에는 근사가 아닌 실제 물리계 모사라는 컴퓨터 시뮬레이션의 궁극 목표가 현실 이슈로 대두되고 있다. 본 논문에서는 미국 정부 주도 슈퍼컴퓨팅 기반 다물리 시뮬레이션 사업의 결과물로 나온 일리노이 대학의 일리노이 록스타라는 유체-구조-연소 연성 해석툴을 활용하여 충격파관 내의 금속판의 미소 시간 운동을 전산모사하고 기존 실험, 해석들과 비교하는 연구를 수행하였다. 전산유동해석은 정렬격자를 기반으로 하였고 구조해석은 대변형 선형탄성을 가정하였다. 또한 강한 연계 시간적분법이 적용된 알고리즘의 고도화로 인해 충격파 내 금속패널에 관한 높은 수준의 실험-계산 상관성을 보였다. 본 연구의 제한적인 검증연구를 확장하여 해석환경 내 추가 모듈들의 검증작업들과 코드개선을 통해 오픈소스 기반 연구개발 도구로서 활용할 예정이다.

• Journal of Oral Medicine and Pain
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• 제21권2호
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• pp.393-405
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• 1996

This study was performed to investigate the effects of changes of head posture and cervical spine shape on the mandibular resting or clenching electromyographic(EMG) activity in anterior temporalis(TA), masseter(MM), sternocleidomastoid muscle(SCM) and trapezius insertion(TI). 30 patients with Temporomandibular Disorders(TMDs) participated in this study. EMG activity($\mu$V) at rest and clenching was observed in four head postures, namely natural head posture(NHP), forward head posture(FHP), upward head posture(UHP), and downward head posture(DHP). For taking in upward or downward head posture head was inclined 10$^{\circ}$ upward or downward and CROM$^\textregistered$(cervical-range-of motion, Performance attainment Inc., USA) was used to maintain same posture during the procedure, and BioEMG$^\textregistered$ (Bioelectromyograph, Bioresearch Inc., USA) was used to record EMG activity in the above four muscles at eight locations on both sides. The recorded EMG activity($\mu\textrm{V}$) were compared and analyzed by cervical spine shape such as the head position from plum line, cervical curvature, and cervical inclination. Head position from plum line was measured in vertical plate calibrated with cm scale, comical curvature by radius was measured with adjustable curved ruler, and cervical inclination by cervical vertebrae tangent(CVT)was measured in lateral cephalograph. The results obtained were as follows : 1. Mean value of head position from plum line, cervical curvature, and cervical inclination were 4.8cm, 26.7cm, and 86.6$^{\circ}$, respectively, And There were no correlationship among these items. 2. For resting EMG activity by head posture, the value in anterior temporalis was higher at FHP than at DHP, the value in masseter was higher at FHP than at NHP, and DHP, the value in sternocleidomastoid muscle was higher at UHP than at NHP, and the value in trapezius insertion was higher at FHP and DHP than, NHP and UHP. The clenching EMG activity, however, did not show any difference by head posture. 3. Comparison of resting and clenching EMG activity between higher and lower groups by head position from plum line, cervical curvature, and cervical inclination did not show any significant difference. From this result, the author concluded that the cervical spine shape had not significantly affected to EMG activity in usual patients with TMDs.

• 대한치과보철학회지
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• 제33권4호
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• pp.780-806
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• 1995

The purpose of this study was to describe the application of 3D finite element analysis to determine resultant stresses on the bone anchored fixed prosthesis, implants and supporting bone of the mandible according to fixture numbers and load conditions. 4 or 6 fixtures and the bone anchored fixed prosthesis were placed in 3D finite element mandibular arch model which represents an actual mandibular skull. A $45^{\circ}$ diagonal load of 10㎏ was labiolingually applied in the center of the prosthesis(P1). A $45^{\circ}$ diagonal load of 20㎏ was buccolingually applied at the location of the 10mm or 20mm cantilever posterior to the most distal implant(P2 or P3). The vertical distribution loads were applied to the superior surfaces of both the right and the left 20mm cantilevers(P4). In order that the boundary conditions of the structure were located to the mandibular ramus and angle, the distal bone plane was to totally fixed to prevent rigid body motion of the entire model. 3D finite element analysis was perfomed for stress distribution and deflection on implants and supporting bone using commercial software(ABAQUS program. for Sun-SPARC Workstation. The results were as follows : 1. In all conditions of load, the hightest tensile stresses were observed at the metal lates of prostheses. 2. The higher tensile stresses were observed at the diagonal loads rather than the vertical loads 3. 6-implants cases were more stable than 4-implants cases for decreasing bending and torque under diagonal load on the anterior of prosthesis. 4. From a biomechanical perspective, high stress developed at the metal plate of cantilever-to-the most distal implant junctions as a consequence of loads applied to the cantilever extension. 5. Under diagonal load on cantilever extension, the 6-implants cases had a tendency to reduce displacement and to increase the reaction force of supporting point due to increasing the bendign stiffness of the prosthesis than 4-implants cases. 6. Under diagonal load on cantilever extension, the case of 10mm long cantilever was more stable than that of 20mm long cnatilever in respect of stress distribution and displacement. 7. When the ends of 10mm or 20mm long cantilever were loaded, the higher tensile stress was observed at the second most distal implant rather than the first most distal implant. 8. The 6-implants cases were more favorable about prevention of screw loosening under repeated loadings because 6-implants cases had smaller deformation and 4-implants cases had larger deformation.

• Clinics in Shoulder and Elbow
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• 제8권2호
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• pp.97-104
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• 2005

Purpose: To report the results of surgical treatment of comminuted fractures of distal humerus and to identify factors that affect the results. Materials and Methods: Thirty-two patients who were treated with open reduction and internal fixation for comminuted fracture of distal humerus were enrolled. According to the AO classification, A2.3 was 1 case, A3.2, 2 cases, A3.3, 8 cases, B1.3, 1 case, B2.3, 1 case, C2.2, 5 cases, C2.3, 4 cases, C3.2, 3 cases and C3.3, 7 cases. As fixation technique, 17 cases were fixed by double plates, 4 cases by only K-wires, 4 cases by only screws, 3 cases by K-wires and screws and 4 cases by one plate and screws. The mean age at the time of the operation was 49 years(range, $19{\sim}77$ years). The mean follow-up period was 16 months(range, $8{\sim}51$ months). Results: At the last follow-up, the mean maximum flexion was $116.4^{\circ}\;(range,\;85{\sim}140^{\circ})$ and the mean loss of terminal extension was $11.8^{\circ}\;(range,\;0{\sim}40^{\circ})$. The average Mayo elbow performance score was $91.4^{\circ}\;(range,\;55{\sim}100^{\circ})$. Overall 29 cases(91%) showed good to excellent results. The mean range of motion of extraarticular and intraarticular fracture group was $105.5^{\circ}\;(range,\;65{\sim}140^{\circ})$ and $104^{\circ}\;(range,\;55{\sim}140^{\circ})$, respectively. The average elbow score of both groups was$93^{\circ}\;(range,\;70{\sim}100^{\circ})$ and $90.7^{\circ}\;(range,\;55{\sim}100^{\circ})$. Over 90% showed more than good results. 30 cases(94%) showed complete bony union but two cases, nonunion. One case of the nonunion cases underwent replating with bone graft as revision surgery and total elbow arthroplasty was performed in the other case. At the last follow-up, 27 patients(84.4%) showed subjective satisfaction. Conclusion: Open reduction and internal fixation with appropriate surgical technique for comminuted fractures of distal humerus showed good results, which were not affected by age at the time of operation, fixation methods and anterior transposition of the ulnar nerve. Transolecranon approach may be considered as good choice for intraarticular comminuted fractures of distal humerus.

• 해양환경안전학회지
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• 제20권3호
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• pp.304-311
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• 2014

In this study, to apply hydrogen energy to ship engine and to generate effective hydrogen production, we investigated the effects of high temperature $H_2SO_4$ feed rate and cooling water rate to pump parts with fixed frequency needed to reciprocate motion and a simulation was conducted at each condition. In the fixed frequency and cooling water inlet flow rate of 0.5 Hz and 3.9 kg/s, we changed the high temperature $H_2SO_4$ flow rate to 47.46 kg/s (it is 105 % of 45.2 kg/s), 49.72 kg/s (110 %), and 51.98 kg/s (115 %). Also, at 0.5 Hz and 45.2 kg/s of frequency and high temperature $H_2SO_4$ flow, the thermal hydraulic analysis was performed at the condition of 95 % (3.705 kg/s), 90 % (3.51 kg/s), and 85 % (3.315 kg/s). In overall simulation cases, the physical properties of materials are more influential to the temperature increase in the pump part rather than the changes on the feed rate of high temperature $H_2SO_4$ and cooling water. A continuous operation of pump was also capable even if the excess feed of high temperature $H_2SO_4$ of about 15 % or the less feed of cooling water of about 15 % were performed, respectively. When the increasing feed of high temperature $H_2SO_4$ of up to 5 %, 10 %, and 15 % were compared with base flow (45.2 kg/s), the deviation of time period rose to a certain temperature and ranged from 0 to 4.5 s in the same position (same material). In case of cooling water, the deviation of time period rose to a certain temperature and ranged from 0 to 5.9 s according to the decreasing feed changes of cooling water at 5 %, 10 %, and 15 % compared to a base flow (3.9 kg/s). Finally, the additional researches related to the two different materials (Teflon and STS for Pitch and End-plate), which are concerned about the effects of temperature changes to the parts contacting different materials, are needed, and we have a plan to conduct a follow-up study.

• 한국지반환경공학회 논문집
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• 제21권7호
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• pp.5-16
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• 2020

현재 경주지진 및 포항지진 발생으로 내진설계기준이 강화되어 기존 시설물에 대한 내진성능평가를 실시하고 있다. 기존 시설물의 피해를 최소화하면서 국한된 협소한 장소에서 시공이 가능한 마이크로파일공법을 개선하여 지진 시 내진성능효과를 확보하고자 한다. 개선방법은 주 기둥인 연직말뚝 주변에 우산형태로 경사말뚝을 시공하여 말뚝 상부의 사각접시형 플레이트에서 말뚝을 모두 일체화하는 것이다. 본 논문에서는 수치해석으로 사질토지반에서 다양한 지진파에 대해 우산형 마이크로파일의 수평변위 거동을 분석하였다. 수치해석 결과, 지반이 연약할수록 우산형 마이크로파일의 수평저항력의 효과가 우수하였다. 경사말뚝의 근입심도에 따른 분석결과, 동일한 지반강도에서 근입심도가 15m 이상일 경우에 수평변위 저감 효과가 뚜렷했으며, N치 30 이상의 지반에 정착하면 지진 시에 효과가 있는 것으로 확인되었다. 마이크로파일의 근입심도와 수평변위 억제효과가 비례하였으며, 대체적으로 지반이 약할수록 변위억제 효과가 컸다. 우산형 마이크로파일은 수직말뚝이 모멘트에 대한 저항을 하고, 경사말뚝이 축력에 대한 저항을 하는 복합저항효과가 있었다.

• 한국운동역학회지
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• 제24권2호
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• pp.173-180
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• 2014

The purpose of this study was to investigate the effect of combined exercise on injury risk factors of lower extremity during landing. Ten sports talented athletes participated in this study. Sports talented athletes participated in a combined exercise (sports talented exercise, coordination) for 16 weeks. A three-dimensional motion analysis was performed using eight infrared cameras (sampling rate of 100 Hz), one force plate, and electromyography system (sampling rate of 1000 Hz) during landing. Kinetic, and kinematics analysis including average impulsive force, angle of lower extremity, vertical stiffness, onset of muscle activation were calculated by Matlab2009a software. Paired t-test was performed at alpha=.05. The average impulsive force in landing phase was not statistically significant (t=-.748, p=.474). The hip joint angle was more decreased in post test compared to pre test (E1: t=2.682, p=.025, E2: t=5.609, p=.000, E3: t=2.538, p=.032). The knee joint (E1: t=-.343, p=.739, E2: t=1.319, p=.220, E3: t=.589, p=.570) and ankle joint (E1: t=.081, p=.937, E2: t=.784, p=.453, E3: t=.392, p=.704) angle were tended to decrease after combined exercise. The vertical stiffness was tended to decrease after combined exercise (t=1.972, p=.080). Onset of quadriceps femoris (t=.698, p=.503) and medial gastocnemius (t=1.858, p=.096) were tended to be faster than biceps femoris (t=-.333, p=.747) after combined exercise. Although thses findings were not statistically significant except on a hip joint angle, risk factors of lower extremity such as joint angle, vertical stiffness and onset of quadriceps femoris, medial gastrocnemius were positively changed after the combined exercise but an additional training for improved onset of biceps femoris would be required in the future.

• 한국운동역학회지
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• 제31권4호
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• pp.276-282
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• 2021

Objective: To investigate effects of Fibular Repositioning Taping (FRT) on lower extremity joint stiffness and angle during drop-landing. Method: Twenty-eight participants (14 healthy, 14 with chronic ankle instability [CAI]) performed drop-landings from a 60 cm box; three were performed prior to tape application and three were performed post-FRT. Three-dimensional kinematic and kinetic data were collected using an infrared optical camera system (Vicon Motion Systems Ltd. Oxford, UK) and force-plate (AMTI, Watertown, MA). Joint stiffness and sagittal angle of the ankle, knee, and hip were analyzed. Results: The hip [Healthy: p<.05; M ± SD: 29.43 ± 11.27 (pre), 33.04 ± 12.03 (post); CAI: p<.05; M ± SD: 31.45 ± 9.70 (pre), 32.29 ± 9.85 (post)] and knee [Healthy: p<.05; M ± SD: 53.44 ± 8.09 (pre), 55.13 ± 8.36 (post); CAI: p<.05; M ± SD: 53.12 ± 8.35 (pre), 55.55 ± 9.81 (post)] joints demonstrated significant increases in sagittal angle after FRT. A significant decrease in joint angle was found at the ankle [Healthy: p<.05; M ± SD: 56.10 ± 3.71 (pre), 54.09 ± 4.31 (post); CAI: p<.05; M ± SD: 52.80 ± 6.04 (pre), 49.86 ± 10.08 (post)]. A significant decrease in hip [Healthy: p<.05; M ± SD: 1549.16 ± 517.53 (pre), 1272.48 ± 646.73 (post); CAI: p<.05; M ± SD: 1300.42 ± 595.55 (pre), 1158.27 ± 550.58 (post)] and knee [Healthy: p<.05; M ± SD: 270.12 ± 54.07 (pre), 239.13 ± 64.70 (post); CAI: p<.05; M ± SD: 241.58 ± 93.48 (pre), 214.63 ± 101.00 (post)] joint stiffness was found post-FRT application, while no difference was found at the ankle [Healthy: p>.05; M ± SD: 57.29 ± 17.04 (pre), 59.37 ± 18.30 (post); CAI: p>.05; M ± SD: 69.15 ± 17.63 (pre), 77.24 ± 35.05 (post)]. Conclusion FRT application decreased joint angle at the ankle without altering ankle joint stiffness. In contrast, decreased joint stiffness and increased joint angle was found at the hip and knee following FRT. Thus, participants utilize an altered shock absorption mechanism during drop-landings following FRT. When compared to previous research, the joint kinematics and stiffness of the lower extremity appear to be different following FRT versus traditional ankle taping.