• Journal of Energy Engineering
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• v.29 no.3
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• pp.25-33
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• 2020

In this study, flow and structural computational analysis were performed to investigate the structural safety of the lightweight butterfly valve disc designed by topology optimization. After flow analysis, as the opening angle increased, the flow coefficient increased non-linearly and showed a gentle slop. When the opening angle was 12 degree, the cavitation could be predicted. After FE analysis, all FE von-Misses stresses of the lightweight disc were smaller than the yield strength of the material, and all FE maximum deformations were also smaller than the conservative deformation of the previous study. Ultimately, it was confirmed that the structural safety of the lightweight valve disc based on computational analysis is effective.

• Journal of the Korea Institute of Military Science and Technology
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• v.2 no.2
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• pp.148-156
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• 1999

The thermal postbuckling and vibration characteristics of cylindrical composite panel subject to thermal loads are analyzed using finite elements. The von-Karman nonlinear displacement-strain relation based on the layerwise theory is applied to consider large deflections due to thermal loads. Cylindrical arc-length method is used to take into account the snapping phenomena. Thermal snapping and vibration characteristics are investigated for various structural parameters such as thickness ratio, shallowness angle and boundary conditions. The present results show that thermal snapping changes the mode shapes as well as static deformations.

• Journal of Chest Surgery
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• v.38 no.9 s.254
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• pp.595-600
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• 2005

Background: Colchicine with its immunosupressive properties has been used with benefcial effects in autoimmune disease, such as Gout, etc. Whether colchicine, by virtue of the above property, could attenuate the process of cardiac allograft rejection in the rats is investigated in this report. Material and Method: We compared the untreated group (Control, n=6), Cyclosporin A group (10 mg/kg, daily, n=20), and Colchicine derivative group (Colchicine 40 ${\mu}g$/kg, n=20) of cardiac allografts in the rats. Result: In the untreated control group (n=6), all of 6 rats showed rejection within 3 weeks after cardiac allograft. In the cyclosporin A group (n=20), cyclosporin A (10 mg daily oral dose) was administered at a 10 mg daily oral dose and promoted long-term survival (over 100 days). The cyclosporin A group had one mortality at the 18th post-operative day due to infection. Furthermore, in the Colchicine derivatives group (n=20) with a daily IP (Intra Peritoneum) dose (40 ug/kg/day), we observed long-term survival.(> 100 days), except for one rat that died of an anesthetic problem (respiratory failure) at the 9th post-operative day. Conclusion: Experiments have also been performed to evaluate whether the effect of colchicine derivatives allowed prolonged survival of cardiac allografts compared with the cyclosporin A administration group in the rats.

• Journal of Chest Surgery
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• v.38 no.5 s.250
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• pp.371-376
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• 2005

Background: Retrospective study was carried out on patients with primary spontaneous pneumothorax with the aim of determining if conventional thoracoscopic wedge resection is superior to modified transaxillary minithoracotomy with thoracoscopy in the surgical treatment. Material and Method: 160 patients, aged 14 to 35 years with primary spontaneous pneumothorax were involved in this study. Patients were assigned to two groups by surgical technique; Conventional thoracoscopic wedge resection (group A; n=80) and modified transaxillary minithoracotomy with thoracoscopy (group B; n=80). Apical pleural abrasion & talc poudrage were performed in all cases. This study evaluated the following factors: duration of operation, days of analgesics used after operation, number of no air leak on the first postoperative day, duration of indwelling chest tube, hospital stay, postoperative complications, chronic chest pain (during follow-up) and resumption of normal activity. Relapses (ipsilateral recurrence after discharge) during follow-up periods were evaluated. Result: No significant differences were found in any of the factors studied in either group. Conclusion: Conventional thoracoscopic wedge resection and modified transaxillary minithoracotomy with thoracoscopy offer similar results in the surgical treatment of primary spontaneous pneumothorax. The rate of complication is low and the level of pain is acceptable without long-term sequele. Therefore, modified transaxillary minithoracotomy with thoracoscopy method appears as a valuable alternative surgical technique.

• The Journal of Engineering Geology
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• v.20 no.1
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• pp.47-60
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• 2010

This study is focused on the analysis of tunnel behavior to estimate the stability on tunnel design. An estimation method was proposed as a hybrid consideration, which contains the displacement analysis by 3D numerical simulation, the maximum displacement obtained after field measurement, and an assessment of tunnel stability using a deformation analysis proposed by Sakurai(1988, 1997). The points of case study by Sakurai(1988, 1997) were replotted considering his analysis. From the new analysis of the tunnel case study, the trend line for analyzed points is analogized, which curve is divided into stable, unstable and failure zone. To evaluate the estimation method, a special shape of railway tunnel was selected, which are the Inchon international airport rail way connected to subway line 9 in Gimpo, Korea. The point s of upper and below track on the Inchon international airport rail way were satisfied to the stability of tunnel after reinforcing. Also the points shows the higher apparent Young's modulus, which resulted from improvement on shear strength by the micro silica grouting and the supporting of umbrella method. Therefore, if new analysis used, proper tunnel reinforcing method could be selected according to tunnel strain and geological property.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.7
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• pp.891-897
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• 2013

In this study, the compressive deformation behaviors of aluminum alloy under high strain rates were investigated by means of a SHPB test. An acoustic emission (AE) technique was also employed to monitor the signals detected from the deformation during the entire impact by using an AE sensor connected to the specimen with a waveguide in real time. AE signals were analyzed in terms of AE amplitude, AE energy and peak frequency. The impacted specimen surface and side area were observed after the test to identify the particular features in the AE signal corresponding to the specific types of damage mechanisms. As the strain increased, the AE amplitude and AE energy increased whereas the AE peak frequency decreased. It was elucidated that each AE signal was closely associated with the specific damage mechanism in the material.

• Journal of Korean Society of Steel Construction
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• v.18 no.6
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• pp.783-792
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• 2006

This study investigates developments in a prestressing method using the thermal-expanded cover-plates that increases the load-carrying capacity of structures by installing it on upper or lower flanges in case that huge flexural stiffness according to the increase in span length or load are required of steel structure, such as rolled H-beam or built-up beam. This method applies multi-stepwise contraction forces generated by the contraction of cover plates as prestressing forces after joining the cover plate applied by multi-stepwise thermal expansion that was applied to induce prestressing to structures. To perform a theoretical investigation of the prestressing force applied to a structure due to the thermal expansion and induce a multi-stepwise prestressing method using multi-stepwise thermal distribution, this study proposes a theoretical heat transfer solution for the multi-stepwise thermal distribution of cover plates and analyzes the effect of a multi-stepwise prestressing method using the multi-stepwise thermal expansion.

• Elastomers and Composites
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• v.34 no.1
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• pp.11-19
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• 1999

Rebound, storage and loss modulus, and tan ${\delta}$ were investigated on cured rubbers with various ratios of sulfur to accelerator and the volume fraction of carbon black in the cured rubbers. The rebound was increased as the sulfur to accelerator ratio and the volume fraction of carbon black decreased. The storage modulus decreased as the loading of carbon black and the strain increased regardless of the cure systems. The network structure formed by filler-filler interaction was destroyed above 6% strain regardless of the loading of carbon black, because constant storage modulus was shown at the higher strain than 3% for $40{\sim}50phr$ loading of carbon black and at the higher strain than 6% for 60 phr and above loading of carbon black. Little effect on loss modulus was found at the low loading of carbon black, but the peak of loss modulus was shown at 1% strain as the loading of carbon black was increased. Tan ${\delta}$ increased as the loading of carbon black and the strain were increased regardless of the cure system, and maximum tan ${\delta}$ was shown at 2% strain regardless of the loading of carbon black.

• Journal of the Korean Geotechnical Society
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• v.22 no.8
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• pp.33-42
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• 2006

Geosynthetics reinforced soil (GRS) walls with a flexible wall face allow deformation. GRS walls constructed on the weak ground change in both horizontal earth pressures on wall faces and the tensile stress of geosynthetics, affecting the backfill in time until the deformation of the backfill and the foundation is completed. However, there are few studies that were done to measure and analyze the horizontal earth pressures and geosynthetics deformation on GRS walls constructed on the soft ground for a long period of time. Two field GRS walls in this study are constructed on a shallow layer of a weak foundation to measure and analyze geostynthetics deformation, horizontal earth pressures, and pore water pressures for the duration of approximately 16 months. Strain gauges are used to measure geosynthetics deformation; this study specifically suggests a new method of measuring nonwoven geotextile using strain gauges. Most geosynthetics deformation occurred within a month after the construction of GRS walls. The maximum deformation measured for approximately 16 months appeared as follows: nowoven geotextile: 6.05%, woven geotextile: 2.92%, and geogrid: 2.33%. Pore water pressures on the GRS wall can be ignored; however, horizontal earth pressures on the bottom and the upper part of the wall face appear larger than earth pressures at rest.

• Journal of the Korean Geotechnical Society
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• v.23 no.9
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• pp.17-28
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• 2007

Urban tunnels are usually important in terms of prediction and control of surface settlement, gradient and ground displacement. This paper has studied the application of strain softening analysis to predict deformation behavior of an urban NATM tunnel. The applied strain softening model considered the reduction of shear stiffness and strength parameter after yielding with strain softening effects of a given material. Measurements of surface subsidence and ground displacement were adopted to monitor the ground behavior resulting from the tunneling and to modify tunnel design. The numerical analysis results produced a strain distribution, deformational mechanism and surface settlement profile, which are in good agreement with the results of case study. The approach of strain softening modeling is expected to be a good prediction method on the ground displacement associated with NATM tunneling at shallow depth and soft ground.