• 대한골관절종양학회지
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• 제5권1호
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• pp.17-22
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• 1999

Over 60 cases were enlisted, but only 31 cases among 24 patients were eligible with a minimum follow-up of 1 year and complete medical documents with imaging data. There were 18 boys and 6 girls, and 7 patients had bilateral lesions. The age of the patients ranged from 2 to 20 years(mean:10.5 years). At their first visit, most lesions had a highly characteristic location and radiographic appearance of radiolucent lesion(s) ranging from 1 to 3cm, except for one case of 5.5 cm in the posteromedial comer of distal femoral metaphysis. The margins were generally well-defined, although some were ill-defined. After reviewing our cases from the viewpoint of clinical course and radiographic patterns, we divided these lesions into two types. Type I is the osteolytic lesion excavated into the posteromedial aspect of the distal femur without cortical defect; and type II is the buldged out lesion of the femur with cortical irregularity into the surrounding soft tissues. Both types have distinctive clinical courses. Type I lesions were easy to make a definite diagnosis with plain radiographs alone, but in type II, it was sometimes very difficult to differentiate it from malignant tumors or chronic localized osteomyelitis. For this lesion, Gd-enhanced MRI was the most effective method for differential diagnosis. In this study, biopsy was not necessary to confirm the diagnosis. Clinical symptoms of type I were very minor or even absent. Many of them were accidentally found after minor trauma around the knee joint. Clinical symptoms disappeared far earlier than radiographical lesions. No treatment such as restriction of activity or drugs was necessary. For type II, the clinical symptoms were more accentuated and lasted longer, and it was necessary to restrict the activity for a certain period in many cases. However, all were self-limited.

• The Korean Journal of Pain
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• 제13권2호
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• pp.242-246
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• 2000

Radiofrequency medial branch neurotomy is an effective way of controlling pain in the posterior compartment of the spine such as the facet joint, and the interspinous ligament. However, it is difficult to determine the exact location of the medial branch. Up until now we have relied on sensory response provoked by 50 Hz stimulation. The responses elicited using this method are quite subjective and can originate from sources other than the medial branch such as the periosteum, the intermediate or lateral branch. We need a confirmed indicator to locate the medial branch reliably. We applied 2 Hz stimulation under 0.4 volts to locate the medial branch and elicited a motor response. Twitching of multifidus and muscles around the SI joint was observed. The observation of these muscles provides a much more reliable method for confirmation of the medial branch. We have treated 45 chronic nonspecific low back pain patients using radiofrequency medial branch neurotomy with this method of confirming the medial branch.

• 한국해양공학회지
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• 제6권2호
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• pp.21-34
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• 1992

The behavior of fatigue crack growth in the single spot welded joint of zinc galvanized steel sheets was studied experimentally and analytically based on fracture mechanics. Axial tension fatigue tests were carried out with the BSxGAB specimen that the bare plane(GAB) of monogalvanized steel sheet was spot welded to the double thickness bare steel sheet(BS), and with the GAxGAB specimen that the galvanized plane (GA) was spot welded to the equal thickness bare plane (GAB) 1. The relation between maximum stress intensity factor, K sub(max) and the number of cycles to failure, N sub(f) has shown a linear relation on log-log plot in the spot weld of the zinc galvanized steel sheet. 2. The fatigue strength of BSxGAB specimens is about 23% higher than that of GAxGAB specimens at the fatigue strength of $1\times10^6$ cycles. And the fatigue life of BSxGAB specimens at the same load range increases 6~9 times higher than that of GAxGAB specimens. 3. The general tendency at the angle of bending($\theta$) in an applied load has changed rapidly at the initial 20% of its life. After then, it has changed slowly. The change at the angle of bending has increased linearly as the load range increases. 4. It has shown a linear relation between the location ratio of initiation ${\gamma}$ and fatigue life $N_f$ on the semi-log graph paper. Here $\gamma$ means that the crack distance between main crack and sub-crack, 2L is divided by the nugget diameter, 2r. $\gamma=a{\cdot}log N_f+n$ (where a and n are material constant.)

• 한국멀티미디어학회논문지
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• 제11권11호
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• pp.1575-1591
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• 2008

본 논문에서는 스테레오 카메라로부터 신체 중 발의 3차원 가상 모델을 실시간으로 합성할 수 있도록 동작을 검출하는 새로운 방법을 제안한다. 발에 가상 모델을 같은 위치에 합성하려면 관절의 움직임을 일정하게 추적하는 움직임 검출 과정이 필수적이다. 복잡한 움직임 속에서의 정확한 정합 이 기술이 해결해야 할 가장 중요한 문제이다. 본 논문에서는 두 가지 형태의 마커 그룹을 사용한 동적 정합을 제안한다. 바닥의 평면 정보는 발과 3차원 가상 발 모델의 관계를 조정하고 발의 자세와 위치를 측정한다. 발의 회전은 발등의 중심 골격에 따라 부착한 두 개의 마커(Marker) 그룹을 사용하여 추정했다. 이 논문에서는 제안한 시스템을 직접 구현하고, 다양한 실험을 통해 시스템에 적용된 각 알고리즘의 정확도를 측정했다.

• Imaging Science in Dentistry
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• 제36권4호
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• pp.199-206
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• 2006

Purpose: The purpose of this study was to evaluate comparison of static MRI and pseudo-dynamic (cine) MRI in temporomandibular joint (TMJ) disorder patients. Materials and Methods: In this investigation, 33 patients with TMJ disorders were examined using both conventional static MRI and pseudo-dynamic MRI. Multiple spoiled gradient recalled acquisition in the steady state (SPGR) images were obtained when mouth opened and closed. Proton density weighted images were obtained at the closed and open mouth position in static MRI. Two oral and maxillofacial radiologists evaluated location of the articular disk, movement of condyle and bony change respectively and the posterior boundary of articular disk was obtained. Results: No statistically significant difference was found in the observation of articular disk position, mandibular condylar movement and posterior boundary of articular disk using static MRI and pseudo-dynamic MRI (P<0.05). Statistically significant difference was noted in bony changes of condyle using static MRI and pseudo-dynamic MRI (P<0.05). Conclusion: This study showed that pseudo-dynamic MRI didn't make a difference in diagnosing internal derangement of TMJ in comparison with static MRI. But it was considered as an additional method to be supplemented in observing bony change.

• 대한골관절종양학회지
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• 제9권2호
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• pp.212-216
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• 2003

결절종으로 인한 총 비골 신경 마비는 매우 드문 예에서 보고되고 있지만, 잘 알려져 있는 질환이다. 결절종으로 인한 비골 신경 포착을 보이는 자기 공명 영상 소견에 대하여 3편이 보고되어 있다. 본 증례에서는 진단을 위해 초음파, 자기 공명 영상, 근전도, 신경전도 검사 및 조직 검사를 시행하였다. 비골 경부 주변의 관상 구조는 자기 공명 영상 소견 상 특징적으로 T2 강조영상에서 고신호를 보이면서 상부 경비골 관절의 아래 부분까지 종축으로 뻗어있는 소견을 보였다. 비골 신경을 노출시키고 결절종에 대해 병소내 절제술을 시행하였다. 수술 후에도 마비 증상이 지속되었으나, 수술 후 4개월부터 점차적으로 마비의 회복소견을 보이기 시작했고 술 후 7개월에 완전한 회복을 보였다. 본 증례에서 자기 공명 영상은 낭종의 범위, 위치, 기원을 밝혀 내는데 도움을 주었고, 외과적 절제술로 좋은 결과를 얻을 수 있다.

• 한국정밀공학회지
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• 제13권2호
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• pp.76-83
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• 1996

We have developed the unconventional robot arm which is composed of the two main parts, one is a ball screw and the other is a robot arm. The dynamic systems of the robot arm and ball screw are unstable systems coupled with each other. The ball screw mechanism is unstable system but controllable system. The robot arm's dynamics is quasi stable system when ball screw's angular position is zero, else, unstable system. Our system has the duality between stability and controllability at the view point of control. This duality causes difficulty to control of the robot arm using normal control law. We have investigated the location of the characteristic roots of the dynamic equation. And we have found out that the best condition for the control of the arm is quasi stable state. In this paper, we have proposed multiple control laws which are consist of three components to guarantee the stability and controllability simultaneously. The computer simulations were carried out based on VSC about the angular position control of the robot arm, and it is confirmed that the good performances could be obtained by using new controller.

• 대한관절경학회지
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• 제15권2호
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• pp.121-124
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• 2011

Hill-Sachs 병변은 견관절 탈구 환자에서 가장 흔히 보이는 병변으로 상완골두의 후외방 골결손으로 지칭된다. 처음 탈구되는 환자에서도 관찰될 수 있으며, 탈구가 진행될 될수록 진행하여 탈구의 수와 Hill-Sachs 병변의 관찰정도는 비례관계가 있는 것으로 알려져 있다. Hill-Sachs 병변의 위치와 유무는 견관절 불안정성에 중요한 의미를 띄는 것으로 이해되고 있다. 저자들은 재발성 전방 견관절 탈구 환자에서 동반된 이중 Hill-Sachs 병변1례를 경험하였기에 문헌 고찰과 함께 보고하는 바이다.

• 한국강구조학회 논문집
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• 제14권2호
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• pp.385-394
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• 2002

현재, 국내에서 사용되고 있는 고강도강은 SM570 강재만이 극히 일부분 사용되고 있으며, 그 이상의 고강도강의 사용은 국내의 강교량에는 전무한 실정이다. 본 연구에서는 국내 장대교량 및 일반교량에서의 고강도강 적용의 활성화를 위해 고강도강재인 SM570 강재와 아직 교량에는 적용된 살계가 없는 POSTEN80 강재를 대상으로 횡방향 맞대기 용접연결부의 피로특성을 분석, 평가하였다. 이를 위해 소형시험편을 제작하여 일정진폭하중하에서의 인장 피로시험을 실시하였으며, 피로균열의 발생 및 진정양상, 기존의 연구결과와 비교, 분석하였다. 또한, 모재의 정적 인장강도와 판두께가 용접연결부의 피로강도에 미치는 영향을 분석하고 피로강도를 평가하므로서 고강도강인 SM570과 POSTEN80 강재의 피로특성과 에 따른 횡방향 맞대기 용접연결부에 대한 피로설계기준 제정을 위한 기초 자료를 제시하였다.

• Steel and Composite Structures
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• 제35권3호
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• pp.439-447
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• 2020

This paper presents two sets of full three-dimensional thermoelastic finite element analyses of superimposed thermo-mechanically loaded Spar Wingskin Joints made with laminated Graphite Fiber Reinforced Plastic composites. The study emphasizes the influence of residual thermal stresses and material anisotropy on the inter-laminar delamination behavior of the joint structure. The delamination has been pre-embedded at the most likely location, i.e., in resin layer between the top and next ply of the fiber reinforced plastic laminated wingskin and near the spar overlap end. Multi-Point Constraint finite elements have been made use of at the vicinity of the delamination fronts. This helps in simulating the growth of the embedded delamination at both ends. The inter-laminar thermoelastic peel and shear stresses responsible for causing delamination damage due to a combined thermal and a static loading have been evaluated. Strain energy release rate components corresponding to the Mode I (opening), Mode II (sliding) and Mode III (tearing) of delamination are determined using the principle of Virtual Crack Closure Technique. These are seen to be different and non-self-similar at the two fronts of the embedded delamination. Residual stresses developed due to the thermoelastic anisotropy of the laminae are found to strongly influence the delamination onset and propagation characteristics, which have been reflected by the asymmetries in the nature of energy release rate plots and their significant variation along the delamination front.