• 한국압력기기공학회 논문집
• /
• 제8권2호
• /
• pp.7-13
• /
• 2012

A spacer grid which is one of the most important structural components in a pressurized water reactor fuel is an interconnected array of slotted grid straps, welded at the intersections to form an egg-crate structure. The spacer grid is required to not only protect fuel rods stably but also have sufficient lateral crush strength for the sake of enabling shut-down of the nuclear reactor during abnormal operating environments. Then, the lateral crush strength of the spacer grid is closely related with welding quality of the spacer grid. Previous research on the crush strength analysis of the spacer grid had been performed using only parent material properties. In this study, to investigate the effect on the crush strength of the spacer grid when used mechanical properties in weld zone instead of parent material properties, crush strength analysis considering mechanical properties in weld zone obtained from the instrumented indentation technique was performed and compared the results with the previous research.

• 에너지공학
• /
• 제24권4호
• /
• pp.55-62
• /
• 2015

It is expected that the size of welding defect affects the mechanical performance of welded medium density polyethylene (MDPE) pipe joints. In this study, butt fusion welded MDPE pipe joints with a single spherical or planar defect of various sizes were studied using experimental crush testing and also by finite element method. The crush test showed that the mechanical performance of crush was not affected by the size and geometry of a single welding defect when the defect size was increased to 45% of the pipe's wall thickness. The simulation results indicated that the effect of the single welding defect on the Von Mises stress distribution near the defect explained the reason of the test results.

• 국제물리치료학회지
• /
• 제3권1호
• /
• pp.345-355
• /
• 2012

This study purposed to examine the effect of low power laser on pain response and axonal regeneration. In order to prepare peripheral nerve injury models, we crushed the sciatic nerve of Sprague-Dawley rats and treated them with low power laser for 21 days. The rats were divided into 4 groups: normal group(n=10); control group(n=10) without any treatment after the induction of sciatic nerve crush injury; experimental group I(n=10) treated with low power laser(0.21$mJ/mm^2$) after the induction of sciatic nerve crush injury; and experimental group II(n=10) treated with low power laser(5.25$mJ/mm^2$) after the induction of sciatic nerve crush injury. We measured spontaneous pain behavior(paw withdrawal latency test) and mechanical allodynia(von Frey filament test) for evaluating pain behavioral response, and measured the sciatic function index for evaluating the functional recovery of peripheral nerve before the induction of sciatic nerve crush injury and on day 1, 7, 14 and 21 after the induction. After the experiment was completed, changes in the H & E stain and toluidine blue stain were examined histopathologically, and changes in MAG(myelin associated glycoprotein) and c-fos were examined immunohistologically. According to the results of this study, when low power laser was applied to rat models with sciatic nerve crush injury for 21 days and the results were examined through pain behavior evaluation and neurobehavioral, histopathological and immunohistological analyses, low power laser was found to affect pain response and axonal regeneration in both experimental group I and experimental group II. Moreover, the effect on pain response and axonal regeneration was more positive in experimental group I to which output 0.21$mJ/mm^2$ was applied than in experimental group II to which 5.25$mJ/mm^2$ was applied.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2004년도 추계학술대회 논문집
• /
• pp.616-621
• /
• 2004

In this paper, the crush characteristics of a tilting train express (TTX) M-car design are evaluated with a head-on collision scenario. Its body shell is divided into three parts - front end, middle section, and rear end. For each part, crush-force relation is evaluated numerically through 3-dimensional shell element analysis with LS-DYNA. TTX's embody structure is a hybrid type structure made of steel and composite materials. Composite sandwich panels are modeled as layered shells whose layers have different material properties. And a damage material model is used to consider the effect of stiffness degradation during deformation. The crush characteristics obtained from these calculations will be used as material modeling data of full-rake collision analyses.

• The Journal of Korean Physical Therapy
• /
• 제17권3호
• /
• pp.391-401
• /
• 2005

The purpose of this study was to investigate the effect of electrical stimulation(EST) on MAP2(Microtubule Associated Protein 2) expression in cerebral cortex following sciatic nerve crush injury in rats. Twelve Sprague-Dawley adult female rats, six for control and six for experimental, were anesthetized and their sciatic nerves were crushed. The electrical stimulation (EST) was applicated with 3 Hz for 10 minuties in a day for muscles innervated sciatic nerve. The MAP2 expression in cerebral cortex was identified from immunohistochemistry against MAP2. The result of this study were as follow: 1) In control group, MAP2 immunoreactive neurons were observed but there no significant increase for 3 days. 2) MAP2 immunoreactive neurons were increased markably in experimental group than control group. 3) MAP2 immunoreactive neurons were increased markably after applicating with EST in sciatic nerve crush injury induced group from 2nd day. This study showed that the application of EST for muscles after sciatic nerve crushed injury made MAP2 immunoreactive neurons in the cerebral cortex increased. Therefore, the electrical stimulation on the peripheral site, denervated muscle, may facilitate MAP2 expression in the cerebral cortex.

• International Journal of Automotive Technology
• /
• 제8권2호
• /
• pp.193-201
• /
• 2007

The present paper deals with the application of the explicit finite element code, PAM-CRASH, to simulate the crash behavior of steel thin-walled tubes with various cross-sections subjected to axial loading. An isotropic elastic, linear strain-hardening material model was used in the finite element analysis and the strain-rate sensitivity of mild steel was modeled by using the Cowper-Symonds constitutive equation with modified coefficients. The modified coefficients were applied in numerical collapse simulations of 11 types of thin-walled polygon tubes: 7 convex polygon tubes and 4 concave polygon tubes. The results show that the thin hexagonal tube and the thick octagonal tube showed relatively good performance within the convex polygon tubes. The crush strengths of the hexagonal and octagonal tubes increased by about 20% and 25% from the crush strength of the square tube, respectively. Among the concave tubes, the I-type tube showed the best performance. Its crush strength was about 50% higher than the crush strength of the square tube.

• 대한기계학회논문집A
• /
• 제36권12호
• /
• pp.1663-1668
• /
• 2012

가압경수로 핵연료의 구조부품인 지지격자체는 홈이 있는 격자 스트랩들을 끼우고, 끼워진 교차부위를 용접한 구조물이다. 원자로 비정상 운전중에 원자로의 긴급정지가 가능하도록 하기 위해 지지격 자체는 충분한 횡방향 충격강도를 갖도록 설계되어야 한다. 지지격자체의 횡방향 충격강도 해석에 대한 예전의 연구는 모재의 물성치만을 사용하여 수행되었다. 본 연구에서는 지지격자체 용접부에 모재 물성치를 사용하는 대신 용접물성치를 사용할 경우에 지지격자체 횡방향 충격강도에 미치는 영향을 조사하였다. 계장형 압입시험법으로부터 얻은 용접물성치를 용접부에 적용한 해석을 수행하였고, 그 해석 결과를 예전 연구결과와 비교하였다.

• Maxillofacial Plastic and Reconstructive Surgery
• /
• 제29권2호
• /
• pp.132-140
• /
• 2007

This study compared the histological patency rates of anastomoses of the femoral artery. Twelve rabbits weighing about 2 kg were studied. Both the right and left femoral arteries were cut. The control group had no damage to the vessel, saline irrigation, and micro-anastomosis. Experimental group I had a crush injury to the vessel, saline irrigation, and micro-anastomosis. Experimental group II had a crush injury, saline irrigation, 100 U/ml heparin irrigation, and micro-anastomosis. Experimental group III had the same treatment as experimental group II plus the systemic application of 100 U/kg heparin iv. The histological patency rates were compared. The patency rates of the control group 30 min and 3 days after the anastomosis were 100 and 83%, respectively. The respective rates for experimental groups I and II 30 min and 3 days after the anastomosis were 100% in all cases. The respective rates in experimental group III were 100 and 83%. In this study, no significant correlation was observed between the patency rate and the effects of local irrigation or the systemic application of heparin on the microvascular anastomosis of the rabbit femoral artery. However, the patency rate tended to decrease concomitantly with an increase in surgery time. Increased bleeding was observed after the systemic application of heparin. Obvious damage to the crush-injured vascular endothelium was detected on histologic examination of the micro-anastomosed area. In addition, some vessels subjected to crush injury contained thrombi attached to the vascular endothelium. No preventive effect of heparin on thrombus formation was observed.

• 한국균학회지
• /
• 제24권4호통권79호
• /
• pp.322-328
• /
• 1996

왕호장근(Reynoutria sachalinensis)은 국내에서 자라는 마디풀과에 속하는 다년생 잡초로써 단위 면적당 Biomass가 매우 높으므로 버섯재배의 첨가 기질로써 이용가능성을 시험하였다. 대조구인 malt extract agar보다 왕호장근 1/4 희석 배지에서 느타리 균사 생장이 우수하였으며 1/8 희석 배지에서는 대조구보다 3배나 균사생장이 빨랐으며 균총의 밀도도 매우 높았다. 또한 느타리 균사가 왕호장근 한천배양기의 최적 산도 및 희석비율을 알아본 결과 pH 6.5, 희석비율 1/8이 느타리 균사생장에 가장 적합하였다. 왕호장근, 톱밥 및 미강를 각각 혼합하여 균사생장을 비교하여 본 결과 왕호장근을 넣은 배지에서 느타리 생강이 우수하게 나타났으며 1.5 내지 2배의 균사생장을 보였다. 왕호장근 한천배양기의 희석비율 l/4, 1/8와 pH 4.5, 6.5, 8.5에서 느타리 균사와 Trichoderma sp.의 대칭배양에서 산도 및 희석농도와 관계없이 느타리 균사생장이 월등하게 나타났으며 Trichoderma sp.의 균사생장을 억제하였다. 왕호장근, 톱밥, 미강을 혼합하여 종균 제조시 톱밥+왕호장근 10%+미강 10%의 배지에서 균사활착이 대조구보다는 4내지 5일 빨랐으며 2배 이상의 균사생장을 보였고 균사의 밀도도 가장 우수하였다.

• 한국디자인학회:학술대회논문집
• /
• 한국디자인학회 1998년도 봄 학술대회 발표논문집 디자인 학 연구
• /
• pp.58-59
• /
• 1998