• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2005.03a
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• pp.18-25
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• 2005

Stochastic ground-motion method is adopted to simulate horizontal PGA values for the offshore Uljin earthquake recorded at nationwide seismic stations. For this purpose, the Fourier spectra are calculated at every stations based on comprehensive results of wave propagation and site effect which were previously revealed through inversion process applied to large accumulated spectral D/B. In addition, the apparent source spectrum of the offshore Uljin earthquake is estimated by removing the path and site response from the observed spectra. The distance dependent time-duration model is revised by iteratively fitting the PGA values generated by using the raw spectra data to the observed PGA data. The stochastic ground-motion method predicts the observed PGA values within a error of ${\sigma}_{log10}=0.1$. Transfer functions of a site relative to another site are estimated based on the error residual of the inversion results and used to convert PGA values at multiple stations to expected PGA values at a reference station of TJN. The converted PGA values can be used as basic data to evaluate the ground-motion attenuation relations developed for seismic hazard analysis that concerns the large damaging earthquakes.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2006.03a
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• pp.70-77
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• 2006

Stress drops of Brune's single-corner ${\omega}^2$ source model were estimated for the earthquakes (2.0$M3.5{\sim}4.0$ and increase up to $M4.5{\sim}5.0$ above which the level of the stress drop could be assumed to be flat or decrease according to whether the rupture process accompanies buried fault or surface rupturing. The converted data of corner frequency and seismic moment were nicely fitted to the relation of $M_0{\propto}f^3$ but show systematically higher corner frequencies for $M_0>10^15$ Nm. This relationship enables systematic evaluation of a scaling relation between magnitude and stress drop. The inverted level of the stress drop is comparable to the recent studies conducted domestic and abroad. A result of lower stress drop estimated by Jun(1991) is supposed to be due to the use of low frequency spectra and existence of two-comer source model around the Korean Peninsula.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• v.4 no.2
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• pp.148-154
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• 2001

Purpose: Ingested foreign bodies present a common clinical problem. It is well known that most of them pass uninterrupted through the gastrointestinal tract. We evaluated the role of endoscopy and Foley catheter for removal of foreign bodies in the gastrointestinal tract. Methods: We investigated retrospectively 60 cases with foreign bodies in the gastrointestinal tract. They had been treated at Wonju Christian Hospital, Yonsei University of Korea, from January, 1996 through December, 1999. Results: The age of the patients ranged from 7 months to 13 years. Patients under 5 years were 57 cases (97%) and there was no significant difference in sex (M : F=1.07 : 1). 45 cases of the patients had no symptom. The most common foreign bodies were coins (43 cases). The most common location was esophagus (31 cases). The number of foreign body removal using flexible endoscopy and Foley catheter was 22 (36.7%) and 18 (30.0%) cases, respectively. In 18 cases (30.0%), foreign bodies passed spontaneously. Only 1 case (1.7%), curtain pin impaction at ileocecal region, required surgery. Conclusion: Early foreign body removal from esophagus and stomach is recommended to lessen the morbidity and complication. Fluoroscopic foley catheter technique and flexible endoscopy for removal of esophageal foreign bodies in children is safe and effective.

• Advances in pediatric surgery
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• v.13 no.2
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• pp.127-134
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• 2007

Meckel's diverticulum is the most common congenital anomaly of gastrointestinal tract in children. The incidence of complicated Meckel's diverticulum is about 4 %. The major complications of Meckel's diverticulum are bleeding, intussusception, obstruction and perforation. The aim of this study was to investigate the clinical manifestations and the role of laparoscopic surgery in complicated Meckel's diverticulum in children. We retrospectively reviewed the medical records of 19 patients with complicated Meckel's diverticulum who underwent operation at Asan Medical Center between Jan. 1990 and Apr. 2007. Male to female ratio was 11:8, and median age was 1 year (1 day-13 years). The most frequent symptom was hematochezia (68%), followed by irritability or abdominal pain (16%), vomiting (11%), and abdominal distension (5%). Two operative procedures were performed; small bowel resection with anastomosis (68%) and diverticulectomy (32%). The operation proven complications of the Meckel's diverticulum were bleeding (68%), intussusception (16%), perforation (11%) and obstruction (5%). Ectopic tissues found by postoperative pathologic examination were gastric (84%) and pancreatic (11%). Hospital stay after laparoscopic operation for bleeding Meckel's was 5 days (median) and average first postoperative feeding was 1.5 days. On the contrary, hospital stay for open surgery was 7 days and first feed was 3 days. In summary, the most common compliation of Meckel's diverticulum in children was bleeding and ectopic gastric tissues were present in 84%. Laparoscopic procedure seemed to be useful for diagnosis as well as for definitive treatment.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.3
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• pp.417-422
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• 2019

Hemodynamically unstable pelvic fractures show a remarkably high mortality rate of 40% to 60%. However, their standard of care remains controversial. We report here a case of a 78-year-old woman who was admitted to the Emergency Department with pelvic pain following a fall. Based on pelvic radiography, she was diagnosed with an unstable pelvic fracture. Her blood pressure was 60/40 mmHg, and owing to her unstable vital signs, emergency angiography was performed without computed tomography (CT). Both internal iliac arteries were embolized without sub-branch selection for prompt control of pelvic bleeding. Following embolization, her vital signs were stabilized. Subsequent CT revealed free intra-abdominal air, suggesting bowel perforation had occurred and necessitating emergency laparotomy. An approximately 1 cm-sized free perforation of the small intestine was identified intraoperatively, and primary closure was performed. A retroperitoneal hematoma identified intraoperatively was not explored further because it was a non-expanding and non-pulsatile mass. The patient was admitted to the Intensive Care Unit and transferred to the general ward on postoperative day 3. In this case, the hemodynamically stable pelvic fracture with bowel perforation was successfully and safely treated by prompt angioembolization without conducting CT.

• The Journal of Engineering Geology
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• v.5 no.1
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• pp.21-29
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• 1995

Among the index properties of granite and andesite, the relation between porosity and water content is highly correlated, but specific gravity, porosity and water content have loW relation with P wave velocity and their relationship showed dispersed zone type. With raising the temperature, Brazilian tensile strength was not changed remarkably, but decreased near $100^{\circ}C$. After the strength increased at $150^{\circ}C$, it decreased near $200^{\circ}C$ in granite. In andesite, however, the strength was increased up to $200^{\circ}C$, and then decreased. The variations of P wave velocity at each temperature zone are similar to those of tensile strength.

• The Journal of Engineering Geology
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• v.19 no.3
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• pp.277-285
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• 2009

In order to assess the fault behavior by the geometric analysis of fault slip, the study area between Yangsan city and Shinkwang-myon, Pohang city along the strike of the Yangsan fault is divided into 5 domains($A{\sim}E$ domains) based on the strike change of main fault, the type of fault termination, the cyclic variation of fault zone width, deformation pattern of fault rocks and angular deviation of secondary shears. And, we would apply the relationship between the mode of fault sliding and the resultant deformation texture obtained from previous several experimental studies of simulated fault gouge to the study of the Yangsan fault. To understand sliding behavior of the fault we measured the data of fault attitude and fault slip, and analyzed relationships between the main fault and secondary Riedel shear along the Yangsan fault. The sliding behavioral patterns in each section were analyzed as followings; the straight sections of A, D and E domains were analyzed as the creeping section of stably sliding. In contrast, the curved section of B domain was analyzed as the locked section of stick-slip movement.

• The Journal of Engineering Geology
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• v.3 no.1
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• pp.1-20
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• 1993

In this study, laboratory direct shear tests on 37 core specimens of gneiss were performed to examine the characteristics of shear behavior on fractures by using a portable direct shear box. The multi-stage shear testing method was used and normal stress applied to specimens ranges from 5.60 to $25.67kg/\textrm{cm}^2$. On the basis of test results, the empirical equations for the shear strength on fractures were suggested. The methanical parameters that can influence the shear behavior were derived and compared between each parameter. The values of shear stiffness have a trend showing rapid increase with the increase of normal stress and joint roughness coeffident, and the average value of secant shear stiffness for all specimens is about $110.68kg/\textrm{cm}^3$ under the range of normal stress applied in this test In addition, the relationship between the length of specimen and shear stiffness is inversely correlated due to the size effect. Therefore, even the specimens with the same joint roughness coeffident show the trend of decreasing shear stiffness in case of the specimens being the longer length.

• The Journal of Engineering Geology
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• v.23 no.3
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• pp.217-225
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• 2013

We carried out geometrical, kinematic, and geomechanical analyses on a lineament (the Imgok fault) near Gangneung, observed in ASTER images and aerial photographs, and field surveys. Earthquake focal mechanism solutions, used to estimate the present-day stress state, revealed that the direction of maximum compression is approximately N$70^{\circ}$E and that the stress condition is in favor of either strike-slip or reverse movement on the fault. The strike of the fault is not ideal for slip under the present-day stress field and thus the fault has a low slip tendency. However, the fault may be able to slip if the frictional coefficient (${\mu}$), representing the resistance of the fault to slip, is sufficiently low (e.g., ${\mu}$ < 0.25).

• The Journal of Engineering Geology
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• v.5 no.2
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• pp.129-138
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• 1995

To elucidate the effects of flow rate on the hydraulic fracturing property of andesite, the hydraulic fracturing tests were conducted under three flow rates. As the tests are conducted with 1ml/min, 2ml/min and 3 ml/min under the constant axial load of 40 kN, the breakdown pressures of andesite seem to be constant as 163kg/cm$^2$. The hydraulic fracturing tests were carried out under the temperatures of five stages to elucidate the effects of temperature variation on hydraulic fracturing property of granite. As the tests are carried out under the constant flow rate of 1.7ml/min, with the axial load of 40kN, the breakdown pressures of granite are 168kg/cm$^2$ at room temperature, and 124kg/cm$^2$ at 20$0^{\circ}C$. The breakdown pressure decreases about 25% than that of room temperature with increasing the temperature. Under the controlled flow rates, the initiation pressures of the microcracks of granite are well coincided with the breakdown pressures and these results are also confirmed by the levels of acoustic emission.