• 대한기계학회논문집A
• /
• 제26권4호
• /
• pp.617-624
• /
• 2002

An equation of J-integral for a penny-shaped crack at the end of the fiber embedded in rubber matrix is proposed. The values of J-integral for the specimens with various crack and specimen radius are obtained by FEA(Finite Element Analysis). The dimensional analysis is applied to derive an equation of J-integral as a nonlinear elastic energy release rate. The geometry and deformation calibration function in an equation of J can be expressed in a separated form. The geometry calibration function characterizing the effects of cord and specimen size is expressed in a polynomial form of fourth order. The deformation calibration function characterizes the effect of the overall level of strain. As approaching the infinitesimal strain, the value of the deformation calibration function approaches the results of LEFM(Linear Elastic Fracture Mechanics).

• 대한금속재료학회지
• /
• 제49권11호
• /
• pp.910-915
• /
• 2011

The microstructures and mechanical properties of roll-bonded STS439/Al1050/STS304 clad materials were investigated after an annealing process at various temperatures. Interfacial layer was developed at the STS439/Al1050 and Al1050/STS304 interfaces at $550^{\circ}C$. STS439/Al1050/STS304 clad metals fractured suddenly in a single step and the fracture decreased with increasing annealing temperatures at $450^{\circ}C$. After annealing at $550^{\circ}C$, samples fractured in three steps with each layer fracturing independently. Interfacial layers formed at $550^{\circ}C$ with a high Vickers microhardness were found to be brittle. During tensile testing, periodic parallel cracks were observed at the interfacial reaction layer. Observed micro-void between Al1050 and the interfacial layer was found to weaken the Al1050/reaction layer interface, leading to the total separation between Al1050 and the reaction layer.

• Clinics in Shoulder and Elbow
• /
• 제14권1호
• /
• pp.59-66
• /
• 2011

목적: 견쇄관절의 손상이나 원위 쇄골 골절의 치료에 대해서는 많은 연구가 있으나, 견쇄관절 손상을 동반한 원위 쇄골 골절의 치료에 대해서는 알려진 바가 적다. 저자들은 견쇄관절의 손상을 동반한 원위 쇄골 골절의 수술적 치료 및 결과, 예후를 평가하고자 한다. 대상 및 방법: 견쇄관절의 손상을 동반한 쇄골 외측단에서 2.5 cm 내를 침범한 원위 쇄골 골절로 수술적 치료를 받은 21명 (21예)의 환자를 대상으로 후향적 연구를 시행하였다. 단순 방사선 사진과 CT상 원위 쇄골의 골절선이 견쇄관절로 연장 (5예)되어 있거나, 7 mm 이상의 견쇄관절의 이개 (separation)가 있는 관절내 골절 (9예), 또는 건측과 비교해서 50% 이상 원위 쇄골의 상방전위가 있는 관절내 골절 (7예)을 견쇄관절의 손상이 있는 경우로 분류하였다. Craig 분류상 III형이 16예, V형이 5예였다. 금속판 (9예), 소형나사 (1예), K 강선 및 긴장대 강선 (10예) 및 경 견쇄관절 K 강선 (1예)을 사용하여 골절을 고정하였다. 건측에 비해 100%이상 원위 쇄골의 상방전위가 있었던 1예 및 골편이 작아 고정력이 약하다고 판단된 1예에서 경 견쇄관절(transarticular AC joint) K 강선 고정을 추가적으로 실시하였다. 견봉 쇄골 인대 또는 오구 쇄골 인대의 봉합이나 재건술은 시행하지 않았다. 결과: 21예 중 20예에서 골유합을 얻었으며 골유합까지의 기간은 평균 8.4주이었다. 최종 추시시 5예에서 견쇄관절의 외상성 관절염이 관찰되었고, 4예에서 견쇄관절의 이개가, 2예에서 건측과 비교하여 50% 이하의 상방전위가 남아 있었으나 견쇄관절의 이개 및 상방전위가 술전보다 증가된 예는 없었다. Kona 등의 기준에 따른 기능적 평가상 19예에서 우수, I예에서 양호, 1예에서 보통의 결과를 얻었다. 견쇄관절 손상의 분류에 따른 UCLA 점수는 I형에서 32.6점, II형에서 34점, III형에서 34.1점이었다. 술전 견쇄관절 손상 종류, 술후 잔여 관절의 이개 및 전위, 외상성 관절염의 유무와 임상 결과간에 유의한 연관성은 관찰되지 않았다 (p>0.05). 합병증으로는 K 강선 및 긴장대 강선 고정술로 고정한 1예에서 불유합이 관찰되어 술후 3개월 금속판 고정술 및 골이식술을 시행하여 골유합을 얻었으며, 금속판 고정술을 시행한 1예에서 추시 관찰 중 내고 정물의 이완이 있었으나 추가적인 치료 없이 골절이 유합되었다. 결론: 견쇄관절로 연장된 골절이 있거나 관절내 골절이 있으면서 견쇄관절 간격이 7 mm 이상 벌어진 경우 또는 정상측과 비교하여 50% 이상 원위 쇄골의 상방전위가 있는 견쇄관절의 손상이 동반된 경우라도 원위 쇄골의 정확한 정복과 견고한 내고정을 통해 만족할 만한 결과를 얻었다. 수술 전 견쇄관절의 손상 종류 및 수술 후 경도의 외상성 관절염이나 이개, 상방전위와 임상적 기능 사이에 유의한 연관성은 없었다.

• 동의생리병리학회지
• /
• 제18권5호
• /
• pp.1476-1484
• /
• 2004

Aging is characterized by an age-dependent reduction in bone density. Pronounced bone loss by postmenopausal estrogen deficiency induces a bad effect on dynamic balance of bone metabolism. When the bone density is reduced to the level below the fracture threshold, the risk for fracture is greatly increased. The purpose of this study is to examine what are the effects of the Guisinhwan(GSH : 歸腎丸) on the ovariectomized rat model of postmenopausal osteoporosis. The results of the experiment are as follows: Body weight in control group showed significant increase in comparison with sham, but that in GSH-treated showed no change in comparison with control. The level of serum albumin in control group showed significant decrease in comparison with sham. That in GSH-treated was slightly decreased in comparison with control. The level of serum ALP activity in control group showed significant increase in comparison with sham, but that in GSH-treated was significantly decreased in comparison with control. The level of serum phosphorous, calcium, GOT, GPT, T3 did not significant change among the three groups. The level of serum estrogen in control group showed slightly decreased in comparison with sham, but that in GSH-treated showed no change in comparison with control. The level of serum T4 in control group showed significant increase in comparison with sham, but that in GSH-treated was significantly decreased in comparison with control. Trabecular bone area as well as trabecular thickness in control group showed significant decrease In comparison with sham. Those in GSH-treated showed significant increase in comparison with control. Trabecular number did not significant change among the three groups. Trabecular separation only in GSH-treated showed significant decrease in comparison with control. Osteoclast number in control group showed significant increase in comparison with sham. That in GSH-treated showed significant decrease in comparison with control. Oseoblast surface in control group showed significant increase in comparison with sham, but that in GSH-treated showed no change in comparison with control. According to the above these results, GSH has shown to be capable of preventing and curing osteoporosis caused by old-aged and postmenopause.

• 동의생리병리학회지
• /
• 제16권4호
• /
• pp.788-800
• /
• 2002

Aging is characterized by an age-dependent reduction in bone density. Pronounced bone loss by postmenopausal estrogen deficiency induces a bad effect on dynamic balance of bone metabolism. When the bone density is reduced to the level below the fracture threshold, the risk for fracture is greatly increased. The purpose of this study is to examine what are the effects of the Yuklinzu(YLZ: 毓麟珠) on the ovariectomized rat model of postmenopausal osteoporosis. The results of the experiment are as follows: Body weight in control group showed significant increase in comparison with sham, but that in YLZ-treated showed no change in comparison with control. The level of serum albumin in control group showed significant decrease in comparison with sham. That in YLZ-treated was slightly decreased in comparison with control. The level of serum ALP activity in control group showed significant increase in comparison with sham, but that in YLZ-treated was significantly decreased in comparison with control. The level of serum phosphorous in control group showed significant increase in comparison with sham, but that in YLZ-treated showed no change in comparison with control. The level of serum calcium in control group showed no change in comparison with sham, but that in YLZ-treated was significantly decreased in comparison with control. The level of serum GOT in control group showed no change in comparison with sham, but that in YLZ-treated was significantly decreased in comparison with control. The level of serum GPT did not significant change among the three groups. The level of serum estrogen in control group showed slightly increased in comparison with sham, but that in YLZ-treated showed no change in comparison with control. The level of serum T3 in control group showed no change in comparison with sham, and that in YLZ-treated showed no change in comparison with control. The level of serum T4 in control group showed significant increase in comparison with sham, but that in YLZ-treated was significantly decreased in comparison with control. Mechanical strength of the femur neck in control group showed significant decrease in comparison with sham. That in YLZ-treated showed slightly increased in comparison with control. Trabecular bone area as well as trabecular thickness in control group showed significant decrease in comparison with sham. Those in YLZ-treated showed significant increase in comparison with control. Trabecular number and did not significant change among the three groups. Trabecular separation only in YLZ-treated showed significant decrease in comparison with control. Osteoclast number and oseoblast surface in control group showed significant increase in comparison with sham. Those in YLZ-treated showed slightly decreased in comparison with control. According to the above these results, YLZ has shown to be capable of preventing and curing osteoporosis caused by old-aged and postmenopause.

• Journal of the Korean Wood Science and Technology
• /
• 제44권3호
• /
• pp.415-423
• /
• 2016

원통형 단판적층재는 단판 테이프를 원형 실린더에 감아서 제작된 제품이다. 단판 테이프는 단판을 직사각형으로 제단한 후 섬유 수직방향으로 재봉하여 제작하였다. 단판의 수종과 재봉사의 종류 및 재봉사의 조합을 다르게 제작한 단판테이프로 인장강도 실험이 실시되었다. 라디에타 소나무 단판에 강화 재봉사를 사용하여 재봉선 3줄로 제작한 단판 테이프의 인장강도 성능이 가장 우수하였다. 또한 단판 테이프의 이격 및 끊어짐 현상이 개선되어 원통형 단판 적층재의 작업성이 향상되었다. 원통형 단판적층재는 단판 테이프의 종류와 직물형 유리섬유의 보강 유무 및 단판 적층 수를 다르게 제작하여 낙엽송 원목과 휨강도 성능을 비교 검토하였다. 직물형 유리섬유를 체적비 11%로 보강한 시험편은 휨 파괴계수가 보강하지 않은 시험편보다 65% 향상되었다. 재봉선 2줄 단판 테이프로 제작한 원통형 단판적층재는 단판 테이프 간 Butt joint에서 파단이 발생하였다. 하지만 재봉선 3줄 단판 테이프로 제작한 원통형 단판적층재는 섬유방향으로 파단이 발생하였다.

• 한국작물학회지
• /
• 제43권2호
• /
• pp.77-82
• /
• 1998

Aerenchyma development in rice (Oryza sativa L.) roots is quite important for adaptation to waterlogged or reduced soil conditions. Anatomical observations were carried out to clarify the development of schizogenous and lysigenous aerenchyma in elongating crown roots of rice. The crown roots of 3rd and 4th phytomer were taken from rice plants of the 8th leaf stage grown by hydroponic culture. The schizogenous intercellular spaces in the cortex of crown root tip were observed using a light microscope with semi ultra-thin sections and the lysigenous aerenchyma in mature tissue of crown root were observed using a cryo scanning electron microscope (cryo-SEM) with freezing fracture method. The schizogenous intercellular spaces in the root tip exist obviously in the middle portion of cortical cell layers close to the root-root cap junction, but not in root cap, stele and outer cell layers of cortex. The air spaces were formed at the junction of four neighbouring cells of inner cortex in the transverse sections, and between longitudinal cell layer connected along the root axis. Although many of those spaces were filled with liquid, some spaces seem to exist as air spaces. The lysigenous aerenchyma in the cortex, which hardly filled with liquid, emerged at 3-4 cm segment from the root tip and increased toward the basal region of root axis. The developing process of lysigenous aerenchyma was primarily separation of a radial row of cells caused by the shrinking and collapsing of cortical cells and then formation of septa along the radial cell rows by the fusion of cell wall with each other. These results suggest that the schizogenous and lysigenous aerenchyma playa role as a passage for the movement of oxygen into the root tip region where oxygen is required for respiration.

• 대한치과의사협회지
• /
• 제54권5호
• /
• pp.365-373
• /
• 2016

Purpose: Cemental tear is a specific type of root surface fracture characterized by a complete separation of a cemental fragment along the cementodentinal junction or a partial split within the cementum along an incremental line. It is suggested to be a factor for periodontal or periapical tissue destruction. The aim of this study is to present a diagnosis and treatment of cemental tear associated with periapical lesion with root canal treatment and regenerative periodontal surgery. Treatments: A 60-year-old male who had a history of sports trauma on the mandibular right central incisor about 10 years ago presented with apical cemental tear. Clinical examination showed a slightly dark yellowish discoloration and sinus tract that was located on the apical labial mucosa. The mobility and percussion were also assessed on the diseased tooth and recorded as $Miller^{\circ}{\phi}s$ Class II and tenderness to percussion. The probing depth was within the normal limit (<3 mm). Radiographic examination revealed a radiolucent lesion at the apical area and extended to distal aspect of the tooth along the fragment of cemental tear. After root canal treatment, periapical surgery was performed. The bony defect was exposed and then the detached root fragment was removed. Apical root resection and retrograde filling with Mineral Trioxide Aggregate (MTA) were accomplished and the bony defect was filled with deproteinized bovine bone mineral (DBBM) and covered with biodegradable collagen membrane. Results: After 9-month follow-up, healing of the mandibular right central incisor was uneventful and no swelling, purulence or pain was revealed in the associated area. Probing pocket depth was favorably stable, and the tooth mobility was decreased to the Miller's Class I. Conclusions: Apical cemental tear associated periapical lesion could be successfully treated with removal of the detached cementum in combination with apical surgery and GTR procedure.

• 대한기계학회논문집A
• /
• 제29권5호
• /
• pp.663-670
• /
• 2005

DIN CK35 (JIS S35CK) steels have been used as a material in fuel pump blocks for marine engines. Failures in the inner surface of a drilling hole, due to the initiation of fatigue cracks have been frequently reported. However, the mechanism initiating these cracks and growths has not been clearly diagnosed yet. This study was conducted using a scraped fuel pump block, containing an initiated fatigue crack in the inner surface of a drilling hole. Initially, the cracks and fractured surfaces inside the block were investigated using an optical microscope and a SEM (Scanning Electron Microscope). In addition, microstructure observation, fatigue life test and fatigue crack growth test were performed using a specimen, which was taken from the same block. Results from these tests are summarized as follows; (1) The early crack in the block was supposed to occur inside the inner surface of the drilling hole. (2) The fatigue endurance of this material was about 330 Mpa. (3) The early crack was generated in the cavitations created by the breakdown of a big inclusion, or separation between the big inclusion and the base metal, in which the fundamental ingredients of the inclusion were C, 5, and Mn. (4) In order to prevent these types of failures, the suppression of inclusions inflow by improving the casting process, formation of fine inclusions by applying a heat treatment process, and coating of the surface of the drilling hole were required.

• 한국수소및신에너지학회논문집
• /
• 제26권2호
• /
• pp.120-126
• /
• 2015

Recently, the ever-increasing use of fossil fuels for rapid industrial development and population significantly caused an environment pollution and global warming such as climate change. So research and development of sustainable and eco-friendly energy have been performed. Especially the interest in nuclear fusion fuel was significantly increased from the developed countries. The system of fusion energy production was tritium separation, storage and delivery, and purification. Republic of Korea is in charge of Storage and Delivery System (SDS) in the International Thermonuclear Experimental Reactor (ITER). Welding part of the SDS bottles for storing the tritium is known to be susceptible to hydrogen embrittlement. In this study, conducted a study for the relaxation of the stability and hydrogen embrittlement of the weld area. The hydrogen heat treatment was processed through the Pressure-Composition-Temperature (PCT) device according to the time variation. Also mechanical properties such as impact test and hardness test according to using the alkaline cleaning liquid for hydrogen embrittlement relief and the fracture was observed by scanning electron microscopy (SEM) after the mechanical properties evaluation.