• 대한의용생체공학회:의공학회지
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• 제25권6호
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• pp.531-536
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• 2004

외고정장치를 이용한 골절 치료에서, 골절 부위에서의 절골편간 운동은 골절의 치유과정에 다양한 영향을 미친다고 알려져 있고, 이 미세 운동은 외고정장치-절골편 시스템의 강성과 밀접한 관련이 있다. 그렇기 때문에 최적의 골절 치유 과정을 부여하기 위하여 외고정장치 시스템의 구성 인자와 강성과의 연관성에 대한 이해가 필요하다. 본 연구에서는 장골 골절의 외고정술에 대한 유한요소 해석에서 외고정장치 시스템의 구성인자가 시스템 강성에 미치는 영향을 조사하였다. 이를 위하여, 시스템 정렬, 재료 비선형성, 조인트 유연성 및 가골형성 등을 해석 인자로 선정하였다. 개발된 유한요소 모델은 실험 결과와 유사한 시스템 강성을 나타내었고, 조인트 유연성 및 재료 비선형성의 고려는 시스템 강성 결과를 더욱 정확하게 반영하였다. 시스템 비정렬상태, 조인트 유연성 및 재료 비선형성은 시스템 강성의 감소를, 그리고 골절 부위의 가골형성은 시스템 강성의 증가를 나타내었다. 본 연구 결과는 외고정술시 시스템 강성을 증가시키기 위한 프레임 구성이나 기구 설계 등의 도구로 사용될 수 있을 것으로 기대된다.

• 대한인간공학회지
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• 제19권2호
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• pp.15-31
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• 2000

The aim was to evaluate the prevailing ergonomic and psychosocial conditions regarding low back injury in an automobile assembly system. This study consisted of two parts. In the first part of the study, analytic biomechanical model and NIOSH guidelines were applied to evaluate risk levels of low back injury for automobile assembly jobs. Total of 246 workers were analysed. There were 20 jobs having greater back compressive forces than 300kg at L5/S1. Also, there were 44 jobs over Action Limit with respect to 1981 NIOSH guidelines. This might in part be explained by the ergonomic conditions of the company analysed generally being good, with a relatively low duration of 'combined' extreme work posture. The relationship between psychosocial factors and low back injury was examined in the second part of the study. It has recently been recognized that overall reaction to working conditions was influenced by a range of factors, some of which were physical and some psychosocial. The psychosocial environment surrounding the work place may contribute to the perception of risk and eventual ill-health. A battery of questionnaires concerning the psychosocial stress based on PWI(Psychosocial Well-being Index) and musculoskeletal pain symptoms at low back was completed by 246 workers at the same plant. Results showed that 207 out 246 workers experienced the symptoms and 27 workers were diagnosed as patients. Two groups(low stressed, high stressed) based on PWI score had no significant relationships with both symptoms and results of diagnosis. However, sensitivities for symptoms and diagnosis by PWI were 91.3% and 92.6% respectively. Finally, relationships between physical work load and psychosocial stress were analysed. Specifically, some postural factors {vertical deviation angle of forearm, horizontal deviation angle of upperarm, vertical deviation angle of thigh, etc) were highly correlated with psychosocial stress. The results illustrated that PWI scores were associated with some physical workloads. However, psychosocial stress levels couldn't be well related with the pain symptom as well as the actual incidence of low back injury since pain or discomfort regarding low back injury were more complex than that of other musculoskeletal disorders.

• 한국운동역학회지
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• 제25권1호
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• pp.39-47
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• 2015

Objective : The purpose of this study was to investigate the velocity conversion coefficient and invariance for the optimal phase ratio on the performance of the women's triple jump. Methods : Three-dimensional kinematic data were obtained from the three finalists of the women's triple jumper competition at the 2011 Daegu IAAF World Championships. Computer simulations were performed using the biomechanical model of the triple jump to optimize the phase ratio for the longest actual distance for all athletes with altered velocity conversion coefficients. Results : Top elite triple jumpers showed better technical consistency at the phase ratio. Also, no consistent relationship was observed between the loss in horizontal velocity and the gain in vertical velocity across supporting the three phase. In addition, regardless of the magnitude A1, all athletes were optimized with jump-dominated technique. Finally, as the magnitude of A1 increased, the athletes showed better performance. The obtained overall distance jumped showed the longest actual distance when the optimal phase ratio was transferred from hop-dominated to jump-dominated(the step ratio was 30%~31%), and when the optimal phase ratio was transferred from balanced to jump-dominated(the step ratio was 27%~29%). Conclusion : Future studies need to be conducted in order to explore the active landing motion and the inclination angle of the body with the velocity conversion coefficient simultaneously at each supporting phase.

• 한국의학물리학회지:의학물리
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• 제2권2호
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• pp.161-173
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• 1991

앉은 자세에서 동적 작업을 수행하는 6명의 실험대상자에 작용하는 관절 모멘트에 대해 통계학적인 해석을 수행하였다. 본 연구에서는 곧게 앉은 자세에서 1kg의 물체를 오른손에 들고 가슴 앞쪽에서 어깨 높이로 물체를 왕복으로 움직이는 작업에 대하여 미시간대학 생체역학 실험실에서 얻은 실험자료를 사용하였다. 각 실험대상자에게 동일한 작업을 3 번씩 수행하게 하여 얻은 자료를 기초로 3 차원 생체역학 모델을 사용하여 손목, 팔꿈치, 어깨관절, 세번째 요추관절, 고관절, 무릎 및 발목과 같은 주요 관절에 작용하는 모멘트를 계산하였다. 관절 모멘트의 실험대상자 사이의 차이와 수행 사이의 차이를 고찰하기 위하여 선형상관계수와 이원분산분석을 적용하였다. 세번째 요추관절에서 가장 큰 크기의 모멘트가 작용하였고 가장 큰 변화량을 나타내었으며, 모멘트와 본 연구에서 시도한 모멘트의 차원을 갖는 량 사이에 선형적인 상관관계를 찾을 수 없었으며, 각 관절에 작용하는 모멘트의 최대값과 변화량은 3번의 수행 사이에서 통계학적으로 동일하지만 6 명의 실험대상자 사이에는 통계학적으로 동일하지 않다는 결과를 얻었다.

• 대한의용생체공학회:의공학회지
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• 제29권6호
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• pp.451-456
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• 2008

Total knee arthroplasty(TKA) using computer-assisted navigation has been increased in order to improve the accuracy of femoral and tibial components implantation. Recently, a few clinical studies have reported on the femoral stress fracture after TKA using computer-assisted navigation. The purpose of this study is to investigate the stress concentration around the femoral pin-hole for different pin-hole diameter, the modes of pin penetration by finite element analysis to understand the effects of pin-hole parameters on femoral stress fracture risk. A three-dimensional finite element model of a male femur was reconstructed from 1 mm thick computed tomography(CT) images. The bone was rigidly fixed to a 25 mm above the distal end and 1500 N of axial compressive force and 12 Nm of axial torsion were applied at the femoral head. For all cases, transcortical pin penetration mode showed the highest stress fracture risk and unicortical pin penetration mode showed the lowest stress concentration. Pin-hole diameter increased the stress concentration, but pin number did not increase the stress dramatically. The results of this study provided a biomechanical guideline for pin-hole fracture risk of the computer navigated TKA.

• 대한의용생체공학회:의공학회지
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• 제34권3호
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• pp.111-116
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• 2013

Finite element analysis(FEA) has been extensively applied in the analyses of biomechanical properties of stents. Geometrically, a closed-cell stent is an assembly of a number of repeated unit cells and exhibits periodicity in both longitudinal and circumferential directions. This study concentrates on various parameters of the FEA models for the analysis of drug-eluting biodegradable polymeric stents for application to the treatment of coronary artery disease. In order to determine the mechanical characteristics of biodegradable polymeric stents, FEA was used to model two different types of stents: tubular stents(TS) and helicoidal stents(HS). For this modeling, epigallocatechin-3-O-gallate (EGCG)-eluting poly[(L-lactide-co-${\varepsilon}$-caprolactone), PLCL] (E-PLCL) was chosen as drug-eluting stent materials. E-PLCL was prepared by blending PLCL with 5% EGCG as previously described. In addition, the effects of EGCG blending on the mechanical properties of PLCL were investigated for both types of stent models. EGCG did not affect tensile strength at break, but significantly increased elastic modulus of PLCL. It is suggested that FEA is a cost-effective method to improve the design of drug-eluting biodegradable polymeric stents.

• 대한화장품학회:학술대회논문집
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• 대한화장품학회 2003년도 IFSCC Conference Proceeding Book I
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• pp.192-202
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• 2003

The wrinkles correspond to the most obvious expression of skin ageing and are manifested by changes on the organization and dermal structure. In the extracellular matrix, decreased quantities of collagens and glycosaminoglycans as well as a deterioration of the fibrillary network is noted, result in a reduction of dermal thickness. In addition, the activity of the collagenases increases in contrast to the synthesis of collagen fibers. Nor are cells spared during the aging process. We thus studied and compared the contractile capacity as well as the synthesis capacity of normal human fibroblasts and human fibroblasts obtained from biopsies of forehead wrinkles. The capacity of the fibroblasts to be adhered to the collagen network and to maintain a three-dimensional structure of dermis was studied on a model of equivalent dermis. The metabolic activity was studied by evaluating the capacities of synthesis of collagen I, main component of dermis. Human fibroblasts resulting from the forehead wrinkle contract less the gel of collagen than the normal human fibroblasts and present an activity of biosynthesis of collagen I less important than normal human fibroblasts. These results show that fibroblasts with aging present a deceleration of their metabolic activity and lose their capacity of adhesion to collagen fibers thus limiting the possibility of organizing the dermal tissue. We investigated the potential of an active ingredient able to compensate for the reduction of the metabolic activity and to restore the contractile capacity of fibroblasts obtained from forehead wrinkles. This effect was compared with a reference molecule: the vitamin C.

• The Journal of Advanced Prosthodontics
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• 제6권5호
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• pp.346-350
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• 2014

PURPOSE. Impact forces in implant supported FDP (fixed dental prosthesis) are higher than that of tooth supported FDPs and the compositions used in frameworks also has a paramount role for biomechanical reasons. The aim of this study was to evaluate the flexural strength of two different zirconia frameworks. MATERIALS AND METHODS. Two implant abutments with 3.8 mm and 4.5 mm platform were used as premolar and molar. They were mounted vertically in an acrylic resin block. A model with steel retainers and removable abutments was fabricated by milling machine; and 10 FDP frameworks were fabricated for each Biodenta and Cercon systems. All samples were thermo-cycled for 2000 times in $5-55^{\circ}C$ temperature and embedded in $37^{\circ}C$ artificial saliva for one week. The flexural test was done by a rod with 2 mm ending diameter which was applied to the multi-electromechanical machine. The force was inserted until observing fracture. The collected data were analyzed with SPSS software ver.15, using Weibull modulus and independent t-test with the level of significance at ${\alpha}=.05$. RESULTS. The mean load bearing capacity values were higher in Biodenta but with no significant differences (P>.05). The Biodenta frameworks showed higher load bearing capacity ($F_0=1700$) than Cercon frameworks ($F_0=1520$) but the reliability (m) was higher in Cercon (m=7.5). CONCLUSION. There was no significant difference between flexural strengths of both zirconia based framework systems; and both Biodenta and Cercon systems are capable to withstand biting force (even parafunctions) in posterior implant-supported bridges with no significant differences.

• 구강회복응용과학지
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• 제24권3호
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• pp.253-267
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• 2008

이 연구의 목적은 임플란트 고정체와 지대주간의 직경 차이가 임플란트 지지조직에 발생하는 응력에 미치는 영향을 평가 하는 것이다. 본 연구에는 세 가지 직경(4.0, 5.0, 6.0㎜)의 3i 임플란트 고정체에 지대주의 직경을 달리하여 수복하고, 하중 조건(15, 30 lb)에 따라 임플란트 지지조직에 발생한 응력의 정도와 분포를 광탄성 응력 분석법을 이용하여 비교, 분석하였다. 연구결과 고정체의 직경이 증가할수록, 상부 보철물에 가해지는 하중에 대하여 고정체 변연부의 응력집중이 높게 나타났으며, 상부 보철물의 근원심 폭경을 증가시키는 것이나, 임플란트 고정체의 직경에 비해 작은 지대주를 사용하는 것은 고정체 주위의 응력양상에 영향을 주지 않았다.

• 한국전산유체공학회지
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• 제22권1호
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• pp.15-25
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• 2017

Swirl flow is often found in proximal coronary arteries, because the aortic valves can induce swirl flows in the coronary artery due to vortex formation. In addition, the curvature and tortuosity of arterial configurations can also produce swirl flows. The present study was performed to investigate fractional flow reserve alterations in a post-stenotic distal part due to the presence of pre-stenotic swirl flow by computational fluid dynamics analysis for virtual stenotic models by quantifying fractional flow reserve(FFR). Simplified stenotic coronary models were divided into those with and without pre-stenotic swirl flow. Various degrees of virtual stenosis were grouped into three grades: mild, moderate, and severe, with degree of stenosis of 0 ~ 40%, 50 ~ 60%, and 70 ~ 90%, respectively. In this study, three-dimensional computational hemodynamic simulations were performed under hyperemic conditions in virtual stenotic coronary models by coupling with a zero-dimensional lumped parameter model. The results showed that the influence of pre-stenotic swirl inflow is dominant on FFR alteration in mild stenosis, whereas stenosis is dominant on FFR alteration in moderate/severe stenosis. The decrease in FFR caused by swirl flow is more significant in mild stenosis than moderate/severe stenosis. Biomechanical modeling is useful for clinicians to provide insight for medical intervention strategies. This hemodynamic-based parameter study could play a critical role in the development of a non-invasive imaging-based strategy-support system for percutaneous transluminal angioplasty in cases of mild/moderate stenosis.