• Journal of Korea Water Resources Association
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• v.34 no.5
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• pp.449-458
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• 2001

In order to verify the numerical model, which was developed to simulate the behavior of the two-phase fluid flow in a single fracture, the characteristic equation of relative permeability was incorporated into the developed numerical model, and the computed results were compared with the experimental results of the model test. As results of the sensitivity analysis on the roughness and the aperture size of fracture, the gas velocity was inversely proportional to the fracture roughness, and not proportional to the square of aperture size which is usually observed in single phase flow in a single fracture. The numerical model was applied to the underground LPG storage terminal in order to check the field applicability. The simultaneous flow of water and gas in accordance with the operation pressures in a single fracture near cavern was simulated by the model. It was shown that the leaked gas was able to be controlled in a single fracture neither by the pressure of operation nor by that of groundwater in case the fracture became smoother in roughness and smaller in aperture size.

• The Journal of Engineering Geology
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• v.11 no.3
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• pp.279-294
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• 2001

When constructing subsurface structures and drilling wells, the precise hydraulic parameters must be obtained for operating safety and for developing enough quantity of groundwater, respectively. In this study we conducted water injection test at different depths on six boreholes drilled in the granite of Mt. Geumjeong. Hydraulic conductivity was calculated using Moye and Hvorslev methods. The relation between hydraulic conductivity and fracture frequency data obtained from acoustic televiewer and core log was analyzed. From the result, though the correlation coefficient between the hydraulic conductivity and the fracture frequency from acoustic televiewer data is higher than that between the hydraulic conductivity and the fracture frequency from core log data on most of the test holes, the correlation coefficient between the hydraulic conductivity and the fracture frequency from the televiewer data is lower than 0.5. This suggests that the hydraulic conductivity of granite in the study area is influenced not only by the fracture frequency but also by various factors of fracture network such as fracture aperture and length, interconnectivity of fractures, fracture orientation and angle, filling material and so on.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.37 no.4
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• pp.255-263
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• 2011

Introduction: Maxillomandibular fixation (MMF) is essential before surgery under general anesthesia in maxillofacial trauma patients. MMF is used basically to reconstruct the occlusion and occlusal stability to recover the facial shape and oral functions. The arch bar and wire is a traditional method for MMF, but it can not only bring pressure to the periodontal ligaments and teeth but also cause a penetrating injury to the surgeons. Materials and Methods: In this study, 198 patients with an open reduction using a manual reduction without MMF from September 2005 to May 2010 in Dankook University Dental Hospital were subjected to a follow-up evaluation during the postoperative 4 months periods. This study evaluated the incidence of complications according to the condition of the patient (gender, age), the state of bony union of the fracture sites and a numeric rating scale evaluation for postoperative pain scoring. Results: 1. The complications were classified into major and minor according to the seriousness, and the major complication rate was as low as 2.02%. Only 2 cases of re-operations (1.01%) were encountered. In the classification according to the fracture line, plate fracture was observed in both cases of mandibular symphysis fracture, and angle fractures and loosening of two screws were noted in the case of mandibular angle fracture. 2. The complication rate was similar regardless of gender and age. 3. The degree of bony union was satisfactory, and the complication rate was reduced as the bony union improved. 4. More patients complained of pain as the operation time was increased. Conclusion: The use of MMF is not always necessary if a skilled assistant is provided to help manually reduce the fracture site. Compared to other studies of mandibular fracture surgery using MMF, the complication rate was similar using only manual reduction and the patients' discomfort was reduced without MMF.

• Geomechanics and Engineering
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• v.6 no.2
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• pp.153-172
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• 2014

In order to investigate the effect of different perforation angles (the angle between the perforation direction and the maximum horizontal principal stress) on the fracture initiation and propagation during hydraulic fracturing of highly deviated well in oil & gas saturated formation, laboratory experiments of the hydraulic fracturing had been carried out on the basis of non-dimensional similar criteria by using 400^3 $mm^3$ cement cubes. A plane fracture can be produced when the perforations are placed in the direction of the maximum horizontal principal stress. When the perforation angle is $45^{\circ}$, the fractures firstly initiate from the perforations at the upper side of the wellbore, and then turn to the maximum horizontal principal stress direction. When the well deviation angle and perforation angle are both between $45^{\circ}$ and $90^{\circ}$, the fractures hardly initiate from the perforations at the lower side of the wellbore. Well azimuth (the angle between the wellbore axis and the maximum horizontal principal stress) has a little influence on the fracture geometries; however it mainly increases the fracture roughness, fracture continuity and the number of secondary fractures, and also increases the fracture initiation and propagation pressure. Oriented perforating technology should be applied in highly deviated well to obtain a single plane fracture. If the well deviation angle is smaller, the fractures may link up.

• Proceedings of the KWS Conference
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• 1998.10a
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• pp.231-233
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• 1998

• Proceedings of the Korean Nuclear Society Conference
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• 2003.05a
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• pp.253-253
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• 2003

• Proceedings of the Korean Nuclear Society Conference
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• 2002.10a
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• pp.290.2-290
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• 2002

• Proceedings of the Korean Society For Composite Materials Conference
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• 1999.04a
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• pp.71-74
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• 1999

• Proceedings of the Korean Nuclear Society Conference
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• 2001.10a
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• pp.247.1-247
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• 2001

• Proceedings of the Korean Nuclear Society Conference
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• 2001.10a
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• pp.262.1-262
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• 2001