• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.3
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• pp.35-41
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• 2019

In this study, the fire resistance performance of polymer cement mortars which are used as a representative repair material for section restoration, is evaluated and residual bond strength is measured by considering unity with concrete. According to the evaluation of fire resistance performance of re-emulsification type polymer cement mortars, residual compressive strength was drastically decreased according to heating temperatures with an increase of polymer addition rate, and this seems to be attributable to the application of polymer film. In addition, an explosion phenomenon occurred frequently with an increase of addition rate, so this should be considered when selecting repair materials and processing.

• Radiation Oncology Journal
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• v.7 no.2
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• pp.171-183
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• 1989

A general effect for cell proliferation has been incorporated into Roesch's survival equation (Accumulation Model). From this an isoeffect formula for the low dose-rate regimen is obtained. The prediction for total doses equivalent to 60Gy delivered at the constant dose-rate over 7 days agrees well with the dose-time data of Paterson and of Green, when the parameter ratio A/B (${\approx}{\alpha{\mu}}/2{\beta}\;where\;{\mu}$ is the repair rate) is chosen to be 0.7Gy/h. When a constant proliferation rate and known facts of division delay are assumed, an isoeffect relation between low dose-rate treatment and acute dose-rate treatment can be derived. This formula in the regimens where proliferation is negligible predicts exactly the data of Ellis that 8 fractions of 5 Gy/day for 7 days are equivalent to continuously applied 60Gy over 7days, provided the A/B ratio is 0.7 Gy/h and the $\alpha/\beta$ ratio is 4Gy. Overall agreement between the clinical data and the predictions made by the formula at the above parameter values suggests that the biologcal end points used as the tolerance level in the studies by Paterson, Green, and Ellis all agree and they are not entirely the early effects as generally assumed. The absence of dose-rate effects observed in the mouse KHT sarcoma can better be explained in terms of a large value for the A/B ratio. Similarly, the same total dose used independently of the dose-rate to treat head and neck tumors by Pierquin can be justified.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.7
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• pp.551-558
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• 2016

Reduction of welding residual stress is very important in the railway industry, but calculating its distribution in structures is difficult because welding residual stress formation is influenced by various parameters. In this study, we developed a finite element model for simulating the repair welding process to recover a surface damaged rail, and conducted a series of parametric studies while varying the cooling rate and the duration of post weld heat treatment (PWHT) to find the best conditions for reducing welding residual stress level. This paper presents a three-dimensional model of the repair welding process considering the phase transformation effect implemented by the ABAQUS user subroutine, and the results of parametric studies with various cooling rates and PWHT durations. We found that heat treatment significantly reduced the residual stress on the upper rail by about 170 MPa.

• Clinics in Shoulder and Elbow
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• v.6 no.2
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• pp.161-166
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• 2003

Purpose: To evaluate the usefulness of arthroscopic repair that was related with full thickness rotator cuff tear and assess clinical result. Materials and Methods: Twenty-one cases of arthroscopically repaired full thickness tear of rotator cuffs were studied. Between October 1998 to July 2002 we have analysed 21 repairs of FTRCT the average age 54(42∼74) years old, mean follow-up was 24(12∼41) months We analyzed the results statistically by paired t-test. Results: Postoperative VAS of pain improved average 7.2 to 1.9, UCLA score improved 13.9 to 31.9, ADL improved 11.5 to 25.5 respectively(all, p<0.001). Eighty-seventh ％ of the patients showed excellent St good results at the final follow-up. The satisfied rate was 90.5%(19cases). Conclusions: Arthroscopic repair in full thickness rotator cuff tear is effective surgical methods.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.43 no.1
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• pp.61-69
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• 2020

Systems such as database and socal network systems have been broadly used, and their unexpected failure, with great losses and sometimes a social confusion, has received attention in recent years. Therefore, it is an important issue to find optimal maintenance plans for such kind of systems from the points of system reliability and maintaining cost. However, it is difficult to maintain a system during its working cycle, since stopping works might incur users some troubles. From the above viewpoint, this paper discusses minimal repair maintenance policy with periodic replacement, while considering the random working cycles. The random working cycle and periodic replacement policies with minimal repair has been discussed in traditional literatures by usually analyzing cases for the nonstopping works. However, maintenance can be more conveniently done at discrete time and even during the working cycle in real applications. So, we propose that periodic replacement is planned at discrete times while considering the random working cycle, and moreover provide a model in which system, with a minimal repair at failures between replacements, is replaced at the minimum of discrete times KT and random cycles Y. The average cost rate model is used to determine the optimal number of periodic replacement.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2862-2867
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• 2008

High-temperature components of gas turbine operated for certain period of time can be reused by being repaired or rejuvenated. In case of the gas turbine combustion liners, the biggest and the most important one in the high-temperature components, come in a repair shop after operated for 8,000 or 12,000 hours according to the model and go through the repair and rejuvenation in order to be reused. A stated combustion liner is the first channel which has the combustion gas reached a nozzle from a fuel nozzle. Materials and coating properties of old and new model combustion liners were investigated. To repair these components after the visual inspection, the coatings of combustion liners were removed and then FPI(Fluorescent Penetrant Inspection), a kind of the NDI(Non-Destructive Inspection), was conducted. Damage patterns and the number of the damaged components were classified and analyzed based on data provided from the visual inspection over a long period of time. Focusing on the difference between old model and new model combustion liners, we analyzed the damage distribution and changes and consequently concluded that new model combustion liner would increase repair rate.

• Journal of the Korea Safety Management & Science
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• v.23 no.3
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• pp.27-33
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• 2021

The purpose of this study is to present a novel indicator for analyzing machine failure based on its idle time and productivity. Existing machine repair plan was limited to machine experts from its manufacturing industries. This study evaluates the repair status of machines and extracts machines that need improvement. In this study, F-RPN was calculated using the etching process data provided by the 2018 PHM Data Challenge. Each S(S: Severity), O(O: Occurence), D(D: Detection) is divided into the idle time of the machine, the number of fault data, and the failure rate, respectively. The repair status of machine is quantified through the F-RPN calculated by multiplying S, O, and D. This study conducts a case study of machine in a semiconductor etching process. The process capability index has the disadvantage of not being able to divide the values outside the range. The performance of this index declines when the manufacturing process is under control, hereby introducing F-RPN to evaluate machine status that are difficult to distinguish by process capability index.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.32 no.2
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• pp.117-128
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• 2006

Free flap transplantation with microvascular anastomosis has been successfully performed by development of surgical technique, materials and postoperative monitoring equipments of flap. But success rate of microvascular anastomosis is influenced by various factors, and failure rate is about 5-10%. The most influential factor for success rate is surgical technique and other factors that influence failure of microvascular anastomosis are ischemic time of free flap, thrombus formation of anastomosis region and vascular spasm. Many studies has been published in microvascular anastomosis with histologic effect for irrigating solution. But local irrigation solution has been used clinically in microvascular anastomosis, the comparison with each solution, microhistological study for endothelial cell repair and vascular patency has not been reported. The heparin which is anti-thrombotic agent, and urokinase which is fibrinolytic agent are used for this study. Vascular patency and thrombus formation in experimental micro-arterial anastomosis, and endothelial repair were observed with histologic analysis, scanning electron microscopy, transmission electron microscopic examination. The results were obtained as follows: 1. In vascular patency test in 30 minute and 7 days after micro-arterial anastomosis, equal effects of good vascular patency were obtained in group of local irrigation with heparin and urokinase. 2. In thrombus formation in 7 days after micro-arterial anastomosis, equal effects of minimal thrombus formation were obtained in group of local irrigation with heparin and urokinase. 3. In toluidin blue staining in 7 days after micro-arterial anastomosis, local destruction of endothelial cell and inner elastic lamina were seen and endothelial repair was not seen. 4. In scanning electron microscope examination in 7 days after micro-arterial anastomosis, endothelial cell was not seen in peripheral to suture materials, thrombus associated fibrin network was observed. 5. In transmission electron microscope examination in 7 days after micro-arterial anastomosis, inflammatory cell was seen within smooth muscle cells in site of endothelial cell destruction, smooth muscle cell around suture material were arranged irregularly, some collagenous change were seen. From the results obtained in this study, same results of good vascular patency and anti-thrombotic effect of heparin and urokinase were obtained as a local irrigation solution, and repair of endothelial cell was not seen in 7 days after micro-arterial anastomosis.

• The Korean Journal of Zoology
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• v.23 no.3
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• pp.115-123
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• 1980

The rates of escision repair at various doses and times after MNNG treatment in CHO cells were compared with the frequencies of chromosome aberrations to determine a possible relation between there two types of biological phenomena, and the results obtained were as follows: 1. the MNNG-induced excision repair was dose-dependent in te ranges between $0.5 \\times 10^-5$M. The maximum rate of excision repair was occurred in the cells soon after the treatment. The rates were then gradually decreased and appeared about 66% of 0 hour at 24 hours. 2. The rates of chromosome aberrations induced by MNNG was the highest at 6 hours, in which majority were chromatid deletions. The rates of chromatid deletions decreased, whereas chromatid exchanges increased with time, resulting is about equal rates at 24 hours after treatment. 3. The rates of excision repair at different times after MNNG treatment were roughly related to the total breaks per cell. The rates, however, did not show any relation to either chromatid exchanges or deletions. These results may suggest that excision repair may not be directly related to chromosome aberrations in MNNG treated CHO cells.

• Proceedings of the PSK Conference
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• 2000.10a
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• pp.133.3-134
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• 2000