• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제30권4호
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• pp.292-300
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• 2004

Orbital blowout fractures are common consequence to blunt periorbital trauma. Pure orbital blowout fractures first occur at the weakest point of the orbital wall. Computed tomography(CT) is recognized to be the best imaging technique to evaluate orbital fractures. The extent and location of a blowout fractures in the CT scan were noted to have an effect on the clinical outcome. In the early posttraumatic period, the presence of significant enophthalmos is difficult to detect because of orbital edema. Early surgical intervention may improve the ultimate outcome because open reconstruction becomes more difficult if surgery is delayed. In this study, we evaluated isolated blowout fractures of the orbital floor by region-of-interest measurements from CT scans and their relationship to ophthalmologic findings. Six patients of the medial orbital wall fractures, eleven patients of the inferior orbital wall fractures, nineteen of the medial and the inferior orbital wall fractures confirmed by CT scan, were evaluated. The area of fracture and the volume of the displaced orbital tissue were determined from CT scan using linear measurements. Each of the calculated values for the area and the volume were compared with the degree of the enophthalmos, the diplopia, and the eyeball movement limitation to determine whether there was any significant relationship between them. The fracture area and the volume of the herniated orbital tissue were significantly positively correlated with the enophthalmos and the ocular motility limitation and not correlated with the diplopia. For the enophthalmos of 2mm or greater, the mean fracture area was 3.55{\pm}1.25cm^2$ and the volume of the herniated orbital tissue was $1.74{\pm}0.97cm^3$; for less than 2mm enophthalmos, $1.43{\pm}0.99cm^3$ and $0.52{\pm}0.49cm^3$, respectively. The enophthalmos of 2mm can be expected with $2.92cm^2$ of the fracture area and $1.40cm^3$ of the herniated orbital tissue. In conclusion, the enophthalmos of 2mm or more, which is a frequent indication for surgery. It can be expected when area of fracture is $2.92cm^2$ or more, or the volume of herniated orbital tissue is $1.40cm^3$ or more. And the CT scan using linear measurements has an application in the assessment of patients with blowout fractures and provides useful information in the posttraumatic evaluation of orbital fractures.

• 한국구조물진단유지관리공학회 논문집
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• 제19권4호
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• pp.109-115
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• 2015

본 연구는 SIFCON 형태의 고성능 강섬유보강 시멘트 복합체의 섬유혼입률에 따른 휨실험을 수행하였고, 실험결과를 바탕으로 휨성능을 평가하였다. 슬러리를 충전하는 형태로 일반 섬유보강시멘트와 달리 높은 섬유혼입률을 확보할 수 있는 장점을 가지고 있다. 주요 실험 변수는 섬유혼입률 8.0%, 7.5%, 7.0%, 6.5% 및 6.0% 이며, 각 변수에 대한 휨강도 및 휨인성 특성을 분석하였다. 그 결과, 높은 섬유혼입률로 인하여 초기균열 발생 이후에도 계속적으로 하중이 증가하였으며, 최대강도 이후 충분한 잔류강도를 확보하였다. 또한 최대 50MPa 수준의 높은 휨강도를 발현하였으며, 섬유혼입률에 따른 휨강도 및 휨인성은 비례하여 증가하는 경향으로 나타났다.

• Hip & pelvis
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• 제34권1호
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• pp.18-24
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• 2022

Purpose: The aim of this study was to determine whether there is a correlation between the type and stability of intertrochanteric fractures caused by low-energy trauma and gluteus muscle volume. Materials and Methods: A total of 205 elderly (>65 years) patients with intertrochanteric fractures caused by low-energy trauma treated from January 2018 to December 2020 were included in this study. The mean age of patients was 81.24 years (range, 65-100 years). Fractures were classified according to the Jensen modification of the Evans classification. The cross-sectional area of the contralateral gluteus muscle (minimus, medius, and maximus) was measured in preoperative axial computed tomography slices. An analysis and comparison of age, body mass index (BMI), weight, height, and the gluteus muscle area in each fracture type group was performed. Results: In the uni-variable analysis, statistically significant taller height was observed in patients in the stable intertrochanteric fracture (modified Evans 1 and 2) group compared with those in the unstable intertrochanteric fracture (modified Evans 3, 4, and 5) group (P<0.05). In addition, significantly higher BMI-adjusted gluteus muscle area (gluteus muscle area/BMI) was observed for the stable intertrochanteric fracture group compared with the unstable intertrochanteric fracture group except for the BMI-adjusted gluteus minimus area (P=0.112). In multivariable analysis, only the BMI-adjusted gluteus maximus (P=0.042) and total gluteus areas (P=0.035) were significantly higher in the stable group. Conclusion: Gluteal muscularity around the hip, especially the gluteus maximus, had a significant effect on the stability of intertrochanteric fractures.

• 한국세라믹학회지
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• 제32권11호
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• pp.1227-1232
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• 1995

Effect of heating rate on the microstructure of the silicon nitride ceramics has been investigated. The specimens with composition of 92Si3N4-6Y2O3-2Al2O3 (in wt%) were sintered at 176$0^{\circ}C$ under 127 kPa for 3h in N2 atmosphere at various heating rates from 1 to 10$0^{\circ}C$/min. The grain size of larger than 2${\mu}{\textrm}{m}$ and less than 1${\mu}{\textrm}{m}$ were measured and compared for the specimens. Regardless of heating rate, grain size of all the specimens showed bimodal distributions and the fracture toughness remained in the range of 5.53~5.72 MPa.m1/2. However, the aspect ratio of the grains of diameter above 2${\mu}{\textrm}{m}$ increased with the heating rate while their grain size and volume fraction decreased.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제20권4호
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• pp.373-378
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• 1998

In the midfacial fracture, the orbital region presents many additional complication unique to the orbit. Among them are ectropion, entropion, lid ptosis, injury to the lacrimal apparatus, diplopia or the late development of enophthalmos. The residual problem confronting the surgen is usually enophthalmos or diplopia. Enophthalmos becomes cosmetically obvious at 3mm and if more severe it can interfere with vision from obstruction by the orbital rim. In this clinical situation, many patients prefer the simpler intraorbital volume expansion to the more complex orbital osteotomy. In general, except in mild cases of enophthalmos, the procedure of choice is osteotomy and repositioning for zygoma fracture and volume augmentation for blow-out fracture. Late treatment is performed by volume augmentation based on the CT findings behind the axis of the globe. Inferiorly placed grafts elevate the globe, posterior superior grafts move the globe anterior and medially positioned grafts push the globe laterally. In this two cases, the patients who has stable orbitozygomatic rim, the use of calvarial bone grafts more than 3 areas around intraorbital content, we corrected late enophthalmos combined with diplopia. As result, the first patient had 2mm advance in exophthalmometric check with improvement of the diplopia gradually. The second patient had 1.5mm advance with correction of vertical ocular dystopia and cosmetically good results respectively.

• Journal of the Korean Data and Information Science Society
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• 제11권2호
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• pp.189-199
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• 2000

불연속면의 분석은 방향성 데이터로서 적은 표본을 가지고 암반의 전체를 추론해야 하는 문제를 갖고 있다. 실험실에서 분석된 표본은 시추공에 의하여 분석된 데이터이므로 그 크기가 제한되어 있어, 거대한 암석을 분석하는 것은 대단히 어렵다. 따라서 이런 표본을 이용하여 거대한 암석의 대표 방향성, 집락 정도, 불연속면의 간격, 암석의 크기를 결정하는 연장성에 관하여 가정된 분포 하에서 계산하고, 이를 이용하여 암석의 분포형태를 관찰할 수 있는 확률 절리망을 그리는 알고리즘을 연구한다. 그리고 실제 불연속면 데이터를 적용하여 이들을 구하고 확률절리망을 작성한다.

• 소성∙가공
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• 제25권6호
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• pp.402-408
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• 2016

A manufacturing technology of carbon fiber composites with thermoplastic polymer pellets and continuous woven fiber was investigated using a compression molding process. To secure the impregnation of resin into the porosity of fabric the composite specimens were prepared with general injection-molding grade polypropylene pellets and low viscosity polycarbonate pellets. Tensile tests of polypropylene and polycarbonate composites were performed. Polycarbonate composites showed higher fracture strength than that of polypropylene composites because of the difference of matrix properties. However, the increase rate of strength was lower than that of polypropylene composites due to the difference of coherence between matrix and reinforcement. To investigate the effect of carbon fiber volume fraction on the fracture strength variation polypropylene composites with different volume fraction were compression molded and tensile tests were performed together. It was shown that the fracture strength of the polypropylene composites increased by 3.2, 5.4 and 6.9 times with the increase of carbon fabric volume fraction of 0.256, 0.367, and 0.480, respectively.

• 한국해양공학회지
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• 제5권2호
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• pp.58-66
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• 1991

Not only difference of fatigue crack growth and propagation behavior resulted from the grain size, the hardness ratio and volume fraction in M.E.F. dual phase steel composed of martensite in hard phase and ferrite in soft phase, but also the effects of the plastic constraint were investigated by fracture mechanics and microstructural method. The main results obtained are as follows: 1) The fatigue endurance of M.E.F. steel increases with decreasing the grain size, increasing the ratio of hardness and volume fraction. 2) The initiation of slip and crack occures faster as the stress level goes higher. These phenomena result from the plastic constraint effect of the second phase. 3) The crack propagation rate in the constant stress level is faster as the grain size gets larger, the ratio of hardness lower and volume fraction smaller.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1998년도 추계학술대회 논문집
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• pp.273-278
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• 1998

In this paper, basic micro-mechanical properties of unidirectional CFRP composite shell such as bonding strength, fiber volume fraction and void fraction are measured and tensile strength test is performed with a fixture. And then fracture surfaces are observed by SEM. In case of basic micro-mechanical properties, bonding strength is reduce with decreasing of radius of each ply in a shell for the effect of residual stress, fiber volume fraction is smaller than plate, and void fraction is vise versa. For these reason, tensile strength of shell is smaller than plate fabricated with same prepreg. For failure mode shell has many splitted part along its length, and it is assumed that this phenomenon is caused by the difference of bonding strength for residual stress.

• 콘크리트학회지
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• 제6권1호
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• pp.131-141
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• 1994

본 실험적 연구는 강섬유의 길이와 혼입율이 콘크리트의 파괴인성과 강도에 미치는 영향을 고찰하기 위하여 수행되었다. 강섬유의 길이(30,60mm)와 혼입율(0.0, 0.5, 1.0, 1.5, 2.0%)을 달리한 노치를 가진 강섬유보강콘크리트 보를 제작하여 3점 휨시험을 하였으며, 그 실험결과로부터 파괴에너지, CMOD 및 휨강도 등을 구하였다. 또한 파괴에너지로부터 콘크리트의 파괴인성을 평가하였다. 연구결과, 콘크리트의 파괴인성과 강도는 전반적으로 강섬유의 혼입율이 증가할수록 증가하였으며 강섬유의 길이는 휨강도에는 큰 영향을 주었으나 파괴인성과 압축강도에는 거의 영향을 주지않았다. 또한 강섬유의 분산성, 시공연도 및 굵은골재의 최대치수 등을 고려할 때, 콘크리트의 파괴인성과 강도측면에서 강섬유의 혼입율은 1.0%정도가 최적이라 판단되며, 그길이가 긴 경우 약간 유리하였다.