• Proceedings of the KSME Conference
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• 2001.11a
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• pp.442-447
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• 2001

A finite element analysis of end-to-end artery/PTFE anastomosis has been presented in this study to evaluate the distribution of compliance in the vicinity of the anastomosis due to any mismatch in compliance characteristics. But, In these studies it was assumed that the artery and PTFE have the simple cylindrical shape representing the fatty tissue surrounding the coronary artery. And the fatty tissue was considered as the elastic surrounding materials in the finite element analysis. The simulation results were obtained as follows : 1. A fatty tissue was effect to reduce the compliance mismatch in the vicinity of a artery/PTFE anastomosis of different material because a hypercompliant zone become narrorw and a compliance discrepancy decrease between the artery and the PTFE about 70%. And radial direction displacement distribution with respect to distance in the vicinity of a artery/PTFE anastomosis was similiar. 2. The variation of PTFE thckness reduce the compliance mismatch in the vicinity of a artery/PTFE anastomosis about 25%.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.5
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• pp.469-483
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• 2012

The propagation characteristics of a mechanical wave in human soft tissue depend on its elastic properties. Investigation of these propagation characteristics is of paramount importance because it may enable us to diagnose cancer or tumor from the vibration response of the tissue. This paper investigates and compares displacement patterns generated in soft tissue due to several forms of low-frequency vibration sources placed on a surface. Among vibration sources considered are a normal load, tangential load, and antiplane shear load. We derive analytical expressions for displacements in viscoelastic single layers, and calculate displacement patterns in half space and infinite plate type tissue. Also, we simulate the vibration response of a finite-sized tissue using finite element method. The effects of the type of stress, the size and frequency of vibration sources, and medium boundaries on displacement patterns are discussed.

• Journal of the Korean Society of Radiology
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• v.84 no.6
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• pp.1397-1402
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• 2023

Nodular fasciitis is a benign fibroblastic proliferation rarely reported in the breast. We report the case of a 55-year-old woman who presented with imaging findings that resembled a malignancy. Mammography revealed an isodense nodule with partially indistinct margin in the right breast, showing the abnormality score 75% on artificial intelligence. Ultrasonography revealed an oval hypoechoic nodule with microlobulated margin, echogenic halo, increased blood flow, and soft elasticity. After core needle biopsy and excision, nodular fasciitis was diagnosed. Although nodular fasciitis of the breast is rare, it may mimic malignancy; therefore, it should be considered as a differential diagnosis to prevent unnecessary intervention.

• Journal of the Korean Society of Radiology
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• v.84 no.3
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• pp.770-775
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• 2023

Malignant peripheral nerve sheath tumor (MPNST), a rare soft-tissue sarcoma, is most commonly located in the trunk, extremities, and head and neck, but rare in the breast. We report a metastatic breast MPNST in a 27-year-old woman with neurofibromatosis type 1 (NF-1). Chest computed tomography revealed a well-defined, oval, mildly enhancing nodule in the right breast. US revealed a circumscribed, oval, heterogeneous echoic mass with vascularity and intermediate elasticity in the right upper outer breast. The breast mass was excised and diagnosed as MPNST on histopathology evaluation. Although rare, it should be included in the differential diagnosis of breast mass in NF-1 patient.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.1
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• pp.34-41
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• 2003

Finite element analysis of end-to-end artery/PTFE anastomosis recently have been researched. But, these studies were carried out without the compensation for the error of finite element analysis and assumed the artery and PTFE as the simple cylindrical shape in spite of being the fatty tissue which covers the heart. Therefore, we performed the convergency study with respect to increasing the element numbers and considered the fatty tissue as the elastic foundation in the finite element analysis. The results are as fallow ： 1. An anastomosis with the thinner thickness and larger diameter PTFE than artery could reduce the compliance disagreement. 2. A fatty tissue was affected to reduce the compliance mismatch in the vicinity of anastomosis of different material. Therefore a hypercompliant zone become narrorw and a compliance discrepancy decrease between the artery and the PTFE about 70%. And radial displacement with respect to longitudinal direction of an artery and the PTFE anastomosis was similar to a sectional compliance.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.6 no.2
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• pp.81-92
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• 2001

According to analyses of high-resolution seismic profiles (air gun, sparker, and SBP) and a deep-drill core(YSDP 105) in the mid-eastern Yellow Sea, stratigraphic and geoacoustic models have been established and seismo-acoustic modeling has been fulfilled using ray tracing of finite element method. Stratigraphic model reflects seismo-, litho-, and chrono-stratigraphic sequences formed under a significant influence of Quaternary glacio-eustatic sea-level fluctuations. Each sequence consists of terrestrial to very-shallow-marine coarse-grained lowstand systems tract and tidal fine-grained transgressive to highstand systems tract. Based on mean grain-size data (121 samples) of the drill core, bulk density and P-wave velocity of depositional units have been inferred and extrapolated down to a depth of the recovery using the Hamilton's regression equations. As goo-acoustic parameters, the 121 pairs of bulk density and P-wave velocity have been averaged on each unit of the stratigraphic model. As a result of computer ray-tracing simulation of the subsurface strata, we have found that there are complex ray paths and many acoustic-shadow zones owing to the presence of irregular layer boundaries and low-velocity layers.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.121-121
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• 2016

치아는 인체중에서도 혹한 환경에서 부분으로 높은 하중과 타액과 같은 강 부식성 매체로 그 환경이 상상을 초월한다. 즉 반복적으로 가해지는 하중(응력)과 침식을 유발하는 타액과 음식물 등이다. 따라서 치아가 쉽게 파괴되거나 썩는 현상이 나타나게 된다. 이렇게 사용되다가 치아의 역할을 다하게 되면 인공치아를 사용하게 되는데 그 재료가 바로 타이타늄(Ti)이다. 생체매식재로 사용되는 Ti는 반응성이 높아 산소와 쉽게 결합하여 표면에 TiO, $TiO_2$, 및 $Ti_2O_3$와 같은 산화피막을 표면에 형성함으로써 뛰어난 부식저항성과 생체적합성을 가지며 생체에 독성이 없고 탄성계수가 골과 비슷하여 골과 임플란트 경계면에서 응력분산에 유리한 성질 등 물리적, 기계적 성질이 뛰어나 외과용 임플란트 재료로 가장 좋은 재료이다. 금속 임플란트의 생체적합도는 임플란트 재료 자체보다는 생체 내 산화막이 화학적으로 불안정할 때 부식이 발생하게 되고 그 결과 금속이온이 주위로 유리되어 조직반응을 일으키므로 금속의 표면을 덮고 있는 산화막에 의해 좌우된다. Ti는 생체불활성재료로서 매식재료로 사용할 경우 뼈와 잘 융합되는 골유착을 나타내나 골과 화학적결합은 하지 않고 골형성을 적극적으로 유도하지 못함으로 환자의 치유기간이 길어지게 된다. 이러한 이유로 골조직내 임플란트의 접합을 개선하기위한 연구가 이루어져 골과의 결합을 높이기 위해 골유착을 일으키는 Ti에 골성장을 유도하는 뼈성분인 하이드록시 아파타이트(HA)라는 물질을 플라즈마 코팅법을 사용하던가 아니면 Hanks' solution내에서 침적 후 HA도금을 하는 방법 등으로 처리하고 있다. 그러나 플라즈마 코팅법은 고온에서 처리를 행하고 Hanks' solution내에 침적할 경우 Ti표면에 밀착도가 저하되거나 합금의 상변화 등으로 인하여 표면처리 과정 중에서 내식성이 크게 감소될 수 있다. 이러한 여러 가지 코팅법을 통하여 골 유착을 증진시키기 위한 연구는 계속되고 있지만 임상적으로 사용 후 문제가 단시일에 발생되는 것도 아니고 수년이 지나야 나타나게 된다. 이러한 방법으로 코팅을 하게 되면 골과 잘 유착이 되어 자연차아와 같은 기능을 하게 된다. 따라서 이러한 문제를 최소화하는 방법이 나노구조를 표면에 형성시켜 골유착을 쉽게 함으로써 이를 개선할 수 있을 것으로 생각되어 본 강의에서는 임플란트의 문제와 사용되는 재료에 대하여 고찰하여 자연치아를 대체 할 수 있는지 알아보았다.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.1379-1385
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• 2007

In domestic transitional zone design, there is regulation to prevent generation of irregular substructure behaviors that negatively influence in prevention of plasticity settlement on approach section and contact section as well as relieve overall track rigidity by reducing sectional foundation and track stiffness difference, but design guideline that considers dynamic behavior of transitional track in actual service line is very insignificant. Therefore in this study, characteristics of transitional track dynamic behaviors by substructure stiffness are researched and measured dynamic response of transitional track by substructure stiffness in order to prove correlation between substructure and track and calculate elasticity(stiffness) and track load of transitional track by using measurement and formula to provide basic information for developing design guideline considering dynamic behavior of service line transitional track.