• Nuclear Engineering and Technology
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• 제54권11호
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• pp.4072-4083
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• 2022

Ultrasonic impact treatment (UIT) is carried out on the Ni-based alloy stainless steel pipe gas tungsten arc welding (GTAW) girth weld, the differences of microstructure, microhardness and shear strength distribution of the joint before and after ultrasonic shock are studied by microhardness test and shear punch test. The results show that after UIT, the plastic deformation layer is formed on the outside surface of the Ni-based alloy overlayer, single-phase austenite and γ type precipitates are formed in the overlayer, and a large number of columnar crystals are formed on the bottom side of the overlayer. The average microhardness of the overlayer increased from 221 H V to 254 H V by 14.9%, the shear strength increased from 696 MPa to 882 MPa with an increase of 26.7% and the transverse average residual stress decreased from 102.71 MPa (tensile stress) to -18.33 MPa (compressive stress), the longitudinal average residual stress decreased from 114.87 MPa (tensile stress) to -84.64 MPa (compressive stress). The fracture surface has been appeared obvious shear lip marks and a few dimples. The element migrates at the fusion boundary between the Ni-based alloy overlayer and the austenitic stainless steel joint, which is leaded to form a local martensite zone and appear hot cracks. The welded joint is cooled by FA solidification mode, which is forming a large number of late and skeleton ferrite phase with an average microhardness of 190 H V and no obvious change in shear strength. The base metal is all austenitic phase with an average microhardness of 206 H V and shear strength of 696 MPa.

• Geomechanics and Engineering
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• 제29권5호
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• pp.567-582
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• 2022

In the present study, a series of physical experiments and numerical simulations were conducted to investigate the effects of mode I and mixed-mode I/II cracks on the fracture modes and stability of roadway tunnel models. The experiments and simulations incorporated different inclination angle flaws under both static and dynamic loads. The quasi-static and dynamic testing were conducted by using an electro-hydraulic servo control device and drop weight impact system (DWIS), and the failure process was simulated by using rock failure process analysis (RFPA) and AUTODYN software. The stress intensity factor was also calculated to evaluate the stability of the flawed roadway tunnel models by using ABAQUS software. According to comparisons between the test and numerical results, it is observed that for flawed roadways with a single radical crack and inclination angle of 45°, the static and dynamic stability are the lowest relative to other angles of fractured rock masses. For mixed-mode I/II cracks in flawed roadway tunnel models under dynamic loading, a wing crack is produced and the pre-existing cracks increase the stress concentration factor in the right part of the specimen, but this factor will not be larger than the maximum principal stress region in the roadway tunnel models. Additionally, damage to the sidewalls will be involved in the flawed roadway tunnel models under static loads.

• Clinics in Shoulder and Elbow
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• 제27권1호
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• pp.32-38
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• 2024

Background: Open reduction and internal fixation (ORIF) with a locking plate is a popular surgical treatment for proximal humeral fractures (PHF). This study aimed to assess the occurrence of complications in elderly patients with PHF treated surgically using ORIF with a locking plate and to investigate the potential differences between patients treated by shoulder surgeons and non-shoulder surgeons. Methods: A retrospective study was conducted using a single-center database to identify patients aged ≥70 years who underwent ORIF for PHF between January 1, 2011, and December 31, 2021. Data on the Neer classification, follow-up, occurrence of avascular necrosis of the humeral head, implant failure, and revision surgery were also collected. Statistical analyses were performed to calculate the overall frequency of complications according to the Neer classification. Results: The rates of implant failure, avascular osteonecrosis, and revision surgery were 15.7%, 4.8%, and 15.7%, respectively. Complications were more common in patients with Neer three- and four-part fractures. Although the difference between surgeries performed by shoulder surgeons and non-shoulder surgeons did not reach statistical significance, the rate of complications and the need for revision surgery were nearly two-fold higher in the latter group. Conclusions: PHF are highly prevalent in the elderly population. However, the ORIF surgical approach, as demonstrated in this study, is associated with a considerable rate of complications. Surgeries performed by non-shoulder surgeons had a higher rate of complications and a more frequent need for revision surgery. Future studies comparing surgical treatments and their respective complication rates are crucial to determine the optimal therapeutic options. Level of evidence: III.

• 대한치과보철학회지
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• 제41권4호
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• pp.393-404
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• 2003

Statement of problem. Higher incidence of prosthetic complications such as screw loosening, screw fracture has been reported for posterior single tooth implant. So, there is ongoing research regarding stability of implant-abutment interface. One of those research is increasing the implant diameter and prosthetic table width to improve joint stability. In another part of this research, internal conical type implant-abutment interface was developed and reported joint strength is higher than traditional external hex interface. Purpose. The purpose of this study is to compare stress distribution in single molar implant between external hex butt joint implant and internal conical joint implant when increasing the implant diameter and prosthetic table width : 4mm diameter, 5mm diameter, 5mm diameter/6mm prosthetic table width. Material and method. Non-linear finite element models were created and the 3-dimensional finite element analysis was performed to see the distribution of stress when 300N static loading was applied to model at $0^{\circ},\;15^{\circ},\;30^{\circ}$ off-axis angle. Results. The following results were obtained : 1. Internal conical joint showed lower tensile stress value than that of external hex butt joint. 2. When off-axis loading was applied, internal conical joint showed more effective stress distribution than external hex butt joint. 3. External hex butt joint showed lower tensile stress value when the implant diameter was increased. 4. Internal conical joint showed lower tensile stress value than external hex butt joint when the implant diameter was increased. 5. Both of these joint mechanism showed lower tensile stress value when the prosthetic table width was increased. Conclusion. Internal conical joint showed more effective stress distribution than external hex joint. Increasing implant diameter showed more effective stress distribution than increasing prosthetic table width.

• 대한치과보철학회지
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• 제34권2호
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• pp.385-402
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• 1996

The purpose of this study was to analyze how the stability of the implant prostheses and the loosening of the fastening screw was affected when the various types of Hex structure provided for the effect of anti-rotation of the single prostheses were given. Three dimensional finite element model was designed with which the implants with the external hex type of 0.75mm, 1.5mm and the implant with the internal hex type of 0.75mm, 1.5mm and the implant with the external hex type of $15^{\circ}$ tapered shape of 0.75mm were supposed to completely osseointegrate to the mandible. After fininshing the finite element model, the preload of 10N at the fastening screw was applied and then the vertical and $30^{\circ}$ lateral load of 200N was applied respectively at the cusp tips of the prostheses. The following results were obtained : 1. In case of displacement, the amount of displacement was increased at the internal hex type(model C, D) than at the external hex type(model A, B, E) when the vertical and lateral load was applied. 2. Less equivalent stress was represented at the model B with increased external hex height than at the model A when the vertical and lateral load was applied. 3. Much stress was represented at the model E with increased hex angle than at the model A in case of the stress happened to the implant body and the fastening screw when the vertical and lateral load was applied. 4. Much equivalent stress was represented at the model D with deepened internal hex height than at the model C when vertical and lateral load was applied. 5. The least stress was taken at the model B and the most stress was taken at the model D in case of the stress happened to the implant when the vertical and lateral load was applied. 6. The least stress was taken at the model C at the vertical load. And the least stress was taken at the model B at lateral load in case of the stress happened to the fastening screw. As a results of this study, the good lateral stability of prostheses and less stress of the component of implant was taken when the external hex height was increased, and the risk of neck fracture of implant and fastening screw was increased when the internal hex height was deepned because of long screw neck portion and thin implant neck portion.

• Clinical and Experimental Pediatrics
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• 제57권3호
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• pp.140-148
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• 2014

Purpose: Lowe syndrome is a rare, X-linked recessive disorder caused by mutations in the OCRL gene. It involves multiple anatomic systems, particularly the eyes, central nervous system, and kidneys, and leads to profound growth failure and global developmental delay. This study evaluated the clinical and genetic characteristics of Korean patients with Lowe syndrome. Methods: The clinical findings and results of genetic studies were reviewed for 12 male patients diagnosed with Lowe syndrome at a single medical institution. Results: The mean age of the patients at presentation was 2.2 months (range, 0-4 months), although the diagnosis was delayed by a mean of 2.8 years (range, 0-9.7 years). The mean follow-up period was 9.0 years (range, 0.6-16.7 years). Nine mutations in OCRL were identified in 11 patients (92%), with three novel mutations. The main presentation was congenital cataract in both eyes necessitating early cataract removal in the 11 patients with impaired visual acuity. Profound short stature and developmental delay were observed in all patients, and seizures occurred in 50% of the patients. All patients suffered from proximal renal tubular dysfunction, and one patient developed chronic renal failure. Other manifestations included pathologic fracture (50%), cutaneous cysts (42%), and cryptorchidism (42%). However, there was no bleeding tendency, and none of the patients died during the study period. Conclusion: This study describes the clinical and genetic characteristics of Korean patients with Lowe syndrome. The observations are helpful for understanding the natural courses of Lowe syndrome and for appropriate genetic counseling.

• 접착 및 계면
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• 제2권1호
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• pp.9-17
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• 2001

전기저항 측정법과 인장 및 압축 시험을 이용하여, 탄소섬유/에폭시 복합재료의 정화특성과 계면물성을 평가하였다. 계면이 존재하지 않는 탄소섬유 자체만을 사용했을 경우에는 경화 초기와 최종단계의 저항차이는 없었으며, 계면이 존재하는 탄소섬유/에폭시 시편의 경우에는 매트릭스 경화 수축에 의해 저항차가 크게 나타났다. 인장 하충하의 저항 변화 측정에서, 전기증작된 시편은 섬유의 첫 파단에 의해 저항이 무한대로 도달하는 시간이 미처리에 비해 다소 지연되는 현상을 보였다. 인장 및 압축 시험에서 표면처리된 시연은 미처리섬유에 비해 계면전단 강도가 현저히 크게 증가하였다. 인장의 경우, 미처리 섬유에서는 debonding 형태, 그리고 표면처리된 섬유에서는 cone 형태의 판단이 관찰되었다. 압축에서는 부러진 섬유 끝에서 대각선으로 미끄러지는 파단 현상이 두 경우 모두에서 나타났는데, 미처리섬유는 창 끝과 같은 예리한 파단이 일어나며, 전기증착된 섬유는 다소 둔한 판단이 나타났다. 이를 통해 전기증착에 의한 표면처리가 계면접착력과 미세파괴구조에 인장 및 압축하에서 각각 다른 영향을 주는 것을 확인하였다.

• Restorative Dentistry and Endodontics
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• 제31권6호
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• pp.415-426
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• 2006

자가부식 상아질 접착제의 중합 후 시간 경과에 따른 접착강도의 변화를 관찰하고, 중합률의 영향을 평가하고자 하였다. 36개의 상하악 대구치를 Single Bond (SB, 3M ESPE, USA), Clearfil SE Bond (SE, Kuraray, Japan), Xeno-III (XIII, Dentsply, Germany), 및 Adper Prompt (AP, 3M ESPE, USA)를 적용하는 4군으로 나누고, 이를 다시 미세인장접착강도 측정 시점에 따라 22$^{\circ}$C의 증류수에 보관 후 48시간에 측정한 군과 7일 후 측정한 군, 및 접착된 시편을 5000회 열순환을 시행하고 측정한 군으로 나누었다. 모래시계 형태의 접착시편을 제작하여 만능시험기 (Model 4466; Instron Co., USA)로 1 mm/min의 하중속도 하에서 미세인장접착강도를 측정하였다. 접착제의 중합률은 Fourier 변환 적외선 분광법을 이용하여 중합 직후, 48시간, 1주일에 측정하였으며, 주사전자현미경을 이용하여 파절 단면을 관찰하였다. 미세인장접착강도와 중합률 모두 시간의 경과에 따라 유의한 증가를 보였으며, 시간 경과와 재료간에 교호작용이 있었다 (미세인장접착강도, 2-way ANOVA, p = 0.018; 중합률, Repeated Measures ANOVA, p < 0.001) . XIII와 AP의 낮은 미세인장접착강도는 낮은 중합률 때문임을 확인할 수 있었다. 48시간 이후에 SE와 AP에서 접착강도가 증가 되는 것은 중합률과는 관련이 없고, 전자현미경에서 관찰되는 접착제층의 성숙에 따른 취성의 증가가 원인일 가능성이 제기된다.

• Composites Research
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• 제24권6호
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• pp.56-63
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• 2011

본 연구에서는 화석에너지 고갈과 환경문제로 인해 새로운 신재생에너지로 주목 받고 있는 태양전지를 대표적인 경량재료인 복합재료에 적용하기 위해 적절한 태양전지 접착 방법에 대한 연구를 진행하였다. 사용된 태양전지는 후면전극 태양전지로 에너지변환 실험실 효율이 약 24.2%인 태양전지를 사용하였다. 하지만, 실리콘계열 태양전지는 재료의 특성상 깨지기 쉽기 때문에 일반적으로 사용되고 있는 동시경화 접착법 대신 접착제를 이용한 이차 접착법을 사용하였다. 접착재료는 태양전지의 충진재 및 접착제로 사용되고 있는 EVA film 과 프리프레그의 수지인 Resin film, 그리고 탄성 접착제를 이용하여 실험을 진행 하였으며, 태양전지가 접착된 복합재료 시험편에 기계적 하중을 부가하여 접착제 종류별 태양전지의 성능변화를 측정하였다. 또한, 기계적 하중 하에서 실시간으로 태양전지의 성능을 평가할 수 있는 측정장치를 설계하여 접착재료별 파단 시점과 특성을 비교 평가 하였다. 파단면분석을 통해 태양전지 효율 감소원인을 분석하여 고찰하였다. 실험결과 태양전지의 접착방법에 따라서 태양전지의 효율이 크게 영향을 받는다는 것을 파악하였다. 또한, 탄성접착제를 사용한 접착 방법이 가장 높은 태양전지 효율 성능을 보여주고 있음을 확인하였다.

• 지구물리와물리탐사
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• 제10권4호
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• pp.369-376
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• 2007

해수침투가 우려되는 해안지역의 소유역에 설치된 모니터링용 관측정을 이용하여 전기비저항 토모그래피 탐사를 수행하였다. 전기비저항 탐사는 지하 매질의 전기비저항 분포를 통해 지반상태 및 층서구조 등을 밝히는 효과적인 방법이지만, 매질의 전기전도도가 매우 높은 해안지역에서는 신호대 잡음비가 가장 높은 배열법을 사용하는 경우에도 관측정 주변의 전기비저항 특성 파악이 힘들다. 따라서 본 연구에서는 해수침투 관측을 목적으로 설치된 해안지역의 서로 다른 두 곳의 관측정 주변 대수층에 대하여, 신호대 잡음비가 낮아 시추공 주변의 대수층 특성 파악이 어려운 지표 전기비저항 탐사의 한계를 극복하기 위하여 시추공-지표간 전기비저항 토모그래피 탐사를 수행하였다. 탐사자료를 이용한 역산 결과는 각 시추공의 시추 주상도, 전기전도도 검층 및 노말 전기비저항 검층 자료를 이용하여 시추공 주변의 파쇄구간과 비교하여 검증하였다. 또한 이들 중 한 곳의 관측정 주변 대수층에 대하여는, 동일한 탐사 방법을 이용하여 간조와 만조시에 각각 탐사를 실시하였다. 탐사 결과 관측정 주변 대수층에 대하여 높은 해상도의 전기비저항 분포 단면을 획득할 수 있었으며, 조석에 의한 대수층을 통한 해수침투와 관련된 수리특성 파악이 가능함을 확인하였다. 따라서 본 연구에서 사용된 시추공-지표간 전기비저항 토모그래피 탐사 결과를 시추 주상도, 전기전도도 검층 및 노말 전기비저항 검층 결과와 함께 분석하는 경우, 해안지역의 관측정 및 그 주변 대수층의 수리지질 구조를 효과적으로 파악할 수 있는 것으로 나타났다.