• Clinics in Shoulder and Elbow
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• 제18권2호
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• pp.75-79
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• 2015

Background: This retrospective comparative study aims to evaluate the surgical outcomes and complications of two surgical methods for simple fractures of the humeral shaft; minimally invasive anterior plating and open reduction combined with internal fixation. Methods: A total of 26 patients with humeral shaft simple fractures, who had surgery between June 2009 and September 2013 and were followed-up at least 12 months, were included in our analysis. They were divided into two groups; group 1 comprised of 12 patients who underwent minimally invasive anterior plating and group 2 comprised of 14 patients who underwent an open reduction and internal fixation. The clinical outcomes, radiological results, and complications were compared and analyzed. Results: We found that bone union was achieved in all patients, and the mean union periods were $20.7{\pm}3.34$ and $20.3{\pm}3.91$ weeks for groups 1 and 2, respectively. In most patients, we found that shoulder and elbow functions were recovered. At 12 months post-operation, we found that the Korean Shoulder Scoring system, the University of California at Los Angeles score and Mayo elbow performance score were $91.4{\pm}7.97$, $33.4{\pm}1.15$, and $90.8{\pm}2.23$ for group 1, and $95.2{\pm}1.53$, $33.3{\pm}1.43$, and $90.17{\pm}1.85$ for group 2. In terms of complications, we found that 2 patients had radial nerve palsy after open reduction and internal fixation, but all cases spontaneously resolved within 6 months. Complications such as infection and loss of fixation were not reported. Conclusions: Both minimally invasive anterior plating and open reduction with internal fixation produced satisfactory outcomes in the treatment of simple fractures of the humeral shaft.

• 한국세라믹학회지
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• 제41권1호
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• pp.1-8
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• 2004

The microstructural features and mechanical behavior of directionally solidified $(Y_2O_3)ZrO_2/Al_2O_3$ eutectic fibers after extended beat treatment in oxidizing environment were investigated. The fiber was grown continuously by an Edge-defined Film-fed Growth (EFG) technique. The microstructure was characterized using X-Ray Diffraction (XRD) and Scanning Electron Microscopy(SEM). The microstructure of the fiber in the as-fabricated state consists of highly oriented colonv and fine lamellar microstructure along the fiber axis. Tensile strength of the $(Y_2O_3)ZrO_2/Al_2O_3$ eutectic fiber remained unchanged with heat treatment at temperatures between $1200^{\circ}C$ and $1500^{\circ}C$ up to 300h. The weibulls modulus remained fairly constant after extended thermal exposure. The fracture toughness and crack propagation behavior were investigated. The fracture toughness ($K_{1C}$) of the $(Y_2O_3)ZrO_2/Al_2O_3$ eutectic fiber in the as-fabricated state were measured to be 3.6 ${\pm}$ 0.5 MPa${\cdot}m^{1/2}$ by an indentation technique and 2.2 ${\pm}$ 0.2 MPa${\cdot}m^{1/2}$ by assuming elliptical flaw of a semi-infinite solid, respectively. The $(Y_2O_3)ZrO_2/Al_2O_3$ eutectic fiber showed a radial (Palmqvist) crack type and exhibited an orthotropic crack growth behavior under 100 g load.

• Clinics in Shoulder and Elbow
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• 제12권2호
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• pp.159-166
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• 2009

목적: 압박 긴장대 방법을 이용한 작은 구상 돌기 골절의 견고한 고정과 주관절의 조기 운동을 통한 기능의 향상 및 그 결과를 분석하고자 한다. 재료 및 방법: 주관절 내측접근법으로 K-강선과 철선을 이용하여 고정된 8예의 구상돌기 골절을 대상으로 하였다. 분류상 8예 모두 Regan-Morrey type 2였으며 O'Driscoll 분류12)로는 tip형(subtype 2)가 예, anteromedial 형 (subtype 2, 1예 그리고 subtype 3, 2예)3예였다. 동반 손상으로는 측부인대 파열이 6예, 요골두 및 경부골절이 4예였으며 모두 함께 치료하였다. 술 후 5~7일간의 고정 치료 후 경첩 보조기 (hinge brace)을 착용한 상태에서 술후 6주까지 능동적 운동을 허용하였다. 술 후 통증의 여부, 관절 운동 범위, Mayo elbow performance score(MEPS)을 이용한 기능적 평가 방법을 이용하여 치료 결과를 분석하였다. 평균 11 (6~28)개월 추시 하였으며 척골 신경 증상에 대해서도 함께 조사하였다. 결과: 모든 구상돌기 골절은 내고정용 도구의 실패 없이 모두 유합되었다. 평균 2.2 (2~4)개의 K-강선이 사용되었다. 관절운동 범위에 대해 신전은 평균 $3^{\circ}(0^{\circ}\sim25^{\circ})$, 굴곡는 평균 $137^{\circ}(130^{\circ}\sim140^{\circ})$, 회내전은 평균 $69^{\circ}(45^{\circ}\sim90^{\circ})$, 회외전은 $78^{\circ}(45^{\circ}\sim90^{\circ})$이였다. MEPS는 평균 96 (65~100) 이였다. 척골 신경 증상은 terrible triad 1예에서 첫 수술 (index operation)후 요골두를 절제하고 내측 측부 인대의 기능 부전이 있는 1예에서 관찰되었다. 결론: 쉽게 구할 수 있으며 가격이 저렴한 K-강선과 철선을 이용한 압박 긴장대 방법은 충분히 견고하여 조기에 능동적 운동을 허용할 수 있어 주관절의 기능 향상을 가져올 수 있었다. 이 방법은 특히 다발성 소형 구상 돌기 골절의 경우 유용한 하나의 고정 방법으로 생각된다.

• 폴리머
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• 제38권3호
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• pp.351-357
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• 2014

위장관 종양 조직이 스텐트 내로 성장하는 것을 방지하는 피막형 스텐트가 개발되어 널리 사용되고 있으나 위산에 의한 막의 분해로 인해 스텐트 폐쇄나 파손이 있다. 이에 본 연구에서는 위산 환경하에서 막의 성분과 재질 농도에 따른 피막형 스텐트의 물성 변화와 안정성을 살펴보고자 하였다. 스텐트 막의 재질은 실리콘과 폴리우레탄을 사용하였고, 각각의 농도를 15%, 18%, 20%로 하여 제작된 스텐트를 pH 1.2 산성 용액에서 18주 동안 3주 간격으로 변화를 관찰하였다. 피막을 분석한 결과 동일 농도에서 비교하였을 때 실리콘이 폴리우레탄보다 두껍고 균일하게 코팅되었다. 인공 위액에 의한 폴리우레탄 피막의 분해가 실리콘 피막에 비해 심하였다. 반경 방향 팽창력의 크기는 실리콘 피막이 폴리우레탄 피막에 비해 상대적으로 컸다. 반경 방향 팽창력과 변형 회복력 모두 인공 위액에서의 침잠 기간이 경과함에 따라 점차 감소하였고, 폴리우레탄 피막 스텐트에서 감소율이 더 컸다. 결론적으로 실리콘 피막이 폴리우레탄에 비해 위산에 대해 안정성이 높음을 알 수 있었다.

• 한국지반공학회논문집
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• 제22권11호
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• pp.55-64
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• 2006

터널과 같은 지하 공동 굴착을 위한 발파로 주변에 손상이 발생하였을 경우, 암반의 역학적 및 수리적 불안정성을 유발하기 때문에 암반의 최종손상영역의 예측은 매우 중요하다 그러나 복잡한 발파거동으로 인해 손상영역을 적절히 예측하는 데에는 상당한 어려움이 따르고 있다. 이러한 어려움을 효과적으로 해결하기 위해 발파하중을 응력파와 가스압으로 분리한 많은 연구가 진행되었다. 응력파는 발파공 주위에 분쇄환(crushing annulus)과 파쇄균열대(fracture zone)를 형성시키며, 상당시간 지속되는 준정적인 가스는 파쇄균열대의 닫힌 균열내부에 침투하여 균열을 다시 진행시키는 역할을 하게 된다. 즉, 가스압은 최종적으로 암반에 손상을 가하는데 기여를 한다. 따라서 본 논문은 이러한 가스압에 의해 생성되는 균열의 최종 진행 길이를 예측함으로써 발파로 인한 최종 손상영역을 간단하게 예측할 수 있는 방법을 제시하고자 한다. 이를 위해 균질한 무한 탄성평면에서 발파공 주위에 대칭으로 형성되는 방사균열을 모델로 사용하였다. 이 모델에서 균열이 진행할 수 있는 조건과 가스의 질량이 일정하다는 두 가지 조건을 사용하였다. 그 결과 응력확대계수는 균열이 진행할수록 감소하여 최종균열의 길이를 산정하였으며, 또한 발파공에 작용하는 압력도 감소하는 것을 확인하였다.

• Journal of Mechanical Science and Technology
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• 제19권9호
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• pp.1761-1772
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• 2005

In blood flow passing through the mechanical heart valve (MHV) and elastic blood vessel, hemolysis and platelet activation causing thrombus formation can be seen owing to the shear stress in the blood. Also, fracture and deformation of leaflets can be observed depending on the shape and material properties of the leaflets which is opened and closed in a cycle. Hence, comprehensive study is needed on the hemodynamics which is associated with the motion of leaflet and elastic blood vessel in terms of fluid-structure interaction. In this paper, a numerical analysis has been performed for a three-dimensional pulsatile blood flow associated with the elastic blood vessel and curved bileaflet for multiple cycles in light of fluid-structure interaction. From this analysis fluttering phenomenon and rebound of the leaflet have been observed and recirculation and regurgitation have been found in the flow fields of the blood. Also, the pressure distribution and the radial displacement of the elastic blood vessel have been obtained. The motion of the leaflet and flow fields of the blood have shown similar tendency compared with the previous experiments carried out in other studies. The present study can contribute to the design methodology for the curved bileaflet mechanical heart valve. Furthermore, the proposed fluid-structure interaction method will be effectively used in various fields where the interaction between fluid flow and structure are involved.

• 대한기계학회논문집A
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• 제21권10호
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• pp.1571-1579
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• 1997

The development of a new material which should be continuously use under severe environment of very high temperature has been urgently requested. For the development of such super-heat resistant materials, the main problem is not only to make the superior thermal barrier properties but also to actively release thermal stress. So, a new concept of functionally graded material(FGM) has been proposed to overcome this problem. A composition and microstructure of FGM are varied continuously from place to place in ways designed to provide it with the maximum function of mitigating the induced thermal stress. So, FGM can be applied in the aerospace, the electronic and the medical field, etc.. In this study, thermal stress analysis of sintering PSZ/NiCrAlY graded material was conducted theoretically using a finite-element program. The temperature condition was sintering temperature assuming a cooling-down process up to room temperature. Fracture damage mechanism was anlayzed by the parameters of residual stress. It could be known that FGM provided with the function of mitigating the induced thermal stress.

• 한국세라믹학회지
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• 제41권7호
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• pp.503-507
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• 2004

The importance of porous ceramics has been increasingly recognized and adequate strength of porous ceramics is now required for structural applications. Porosities of porous ceramics act as flaws in inner volume and outer surface which result in severe strength degradation. The effect of pore structure, however, on strength and reliability of porous ceramics has not been clearly understood. We investigate the relationship between pore structure and mechanical properties using a sphere indentation on bilayer structure, porous ceramic top layer with soft polymer substrate. Porous alumina and silica were prepared to characterize the isolated pore structure and interconnected pore structure, respectively. The porous ceramic with 1mm thickness were bonded to soft polycarbonate substrate and then fracture strengths were estimated from critical loads for radial cracking of porous ceramics during sphere indentation from top surface. This simple and reproducible technique provides Weibull modulus of strength of porous ceramics with different pore structure. It shows that the porous ceramics with isolated pore structure have higher strength and higher Weibull modulus as well, than those with interconnected pore structure even with the same porosity.

• Nuclear Engineering and Technology
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• 제49권8호
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• pp.1740-1747
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• 2017

To investigate allowable peak cladding temperature and hoop stress for maintenance of cladding integrity during interim-dry storage and subsequent transport, zirconium alloy cladding tubes were hydrogen-charged to generate 250 ppm and 500 ppm hydrogen contents, simulating spent nuclear fuel degradation. The hydrogen-charged specimens were heated to four peak temperatures of $250^{\circ}C$, $300^{\circ}C$, $350^{\circ}C$, and $400^{\circ}C$, and then cooled to room temperature at cooling rates of $0.3^{\circ}C/min$ under three tensile hoop stresses of 80 MPa, 100 MPa, and 120 MPa. The cool-down specimens showed that high peak heat-up temperature led to lower hydrogen content and that larger tensile hoop stress generated larger radial hydride fraction and consequently lower plastic elongation. Based on these out-of-pile cladding tube test results only, it may be said that peak cladding temperature should be limited to a level < $250^{\circ}C$, regardless of the cladding hoop stress, to ensure cladding integrity during interim-dry storage and subsequent transport.

• 센서학회지
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• 제25권1호
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• pp.35-40
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• 2016

Pulse diagnosis is one of the representative diagnostic methods in Oriental medicine. In this study, a pulse pressure sensor array coated with silicone, which includes 6 piezo-resistive sensors and 1 thermistor, is fabricated for pulse measurement. It is necessary to coat the pulse sensor array with silicone to avoid the fracture or damage of pressure sensors when the sensor is in contact with the skin and a constant pressure is applied. However, the silicone coating on the pulse sensor array can cause signal interference among the sensors in the pulse sensor array. The interference number (IN), a calculation for expressing the degree of interference among channels, is changed according to the silicone thickness on the pulse sensor array. The IN is increased by a thick silicone coating, but the fabrication error, an important index for the mass production of the sensor array, is reduced by the thickness of the silicone coating. We propose that the thickness of the silicone on the pulse sensor array is an important consideration for the performance of the fabricated sensor and manufacturing repeatability.