• Journal of Korean Society of Coastal and Ocean Engineers
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• v.26 no.3
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• pp.174-183
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• 2014

Seabed beneath and near coastal structures may undergo large excess pore water pressure composed of oscillatory and residual components in the case of long durations of high wave loading. This excess pore water pressure may reduce effective stress and, consequently, the seabed may liquefy. If liquefaction occurs in the seabed, the structure may sink, overturn, and eventually increase the failure potential. In this study, to evaluate the liquefaction potential on the seabed, numerical analysis was conducted using the expanded 2-dimensional numerical wave tank to account for an irregular wave field. In the condition of an irregular wave field, the dynamic wave pressure and water flow velocity acting on the seabed and the surface boundary of the composite breakwater structure were estimated. Simulation results were used as input data in a finite element computer program for elastoplastic seabed response. Simulations evaluated the time and spatial variations in excess pore water pressure, effective stress, and liquefaction potential in the seabed. Additionally, the deformation of the seabed and the displacement of the structure as a function of time were quantitatively evaluated. From the results of the analysis, the liquefaction potential at the seabed in front and rear of the composite breakwater was identified. Since the liquefied seabed particles have no resistance to force, scour potential could increase on the seabed. In addition, the strength decrease of the seabed due to the liquefaction can increase the structural motion and significantly influence the stability of the composite breakwater. Due to limitations of allowable paper length, the studied results were divided into two portions; (I) focusing on the dynamic response of structure, acceleration, deformation of seabed, and (II) focusing on the time variation in excess pore water pressure, liquefaction, effective stress path in the seabed. This paper corresponds to (II).

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.26 no.3
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• pp.160-173
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• 2014

Seabed beneath and near coastal structures may undergo large excess pore water pressure composed of oscillatory and residual components in the case of long durations of high wave loading. This excess pore water pressure may reduce effective stress and, consequently, the seabed may liquefy. If liquefaction occurs in the seabed, the structure may sink, overturn, and eventually increase the failure potential. In this study, to evaluate the liquefaction potential on the seabed, numerical analysis was conducted using the expanded 2-dimensional numerical wave tank to account for an irregular wave field. In the condition of an irregular wave field, the dynamic wave pressure and water flow velocity acting on the seabed and the surface boundary of the composite breakwater structure were estimated. Simulation results were used as input data in a finite element computer program for elastoplastic seabed response. Simulations evaluated the time and spatial variations in excess pore water pressure, effective stress, and liquefaction potential in the seabed. Additionally, the deformation of the seabed and the displacement of the structure as a function of time were quantitatively evaluated. From the results of the analysis, the liquefaction potential at the seabed in front and rear of the composite breakwater was identified. Since the liquefied seabed particles have no resistance to force, scour potential could increase on the seabed. In addition, the strength decrease of the seabed due to the liquefaction can increase the structural motion and significantly influence the stability of the composite breakwater. Due to limitations of allowable paper length, the studied results were divided into two portions; (I) focusing on the dynamic response of structure, acceleration, deformation of seabed, and (II) focusing on the time variation in excess pore water pressure, liquefaction, effective stress path in the seabed. This paper corresponds to (I).

• Pediatric Infection and Vaccine
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• v.4 no.1
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• pp.126-132
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• 1997

Measles outbreak in the world was decreased since measles vaccine had been introduced. Although vaccination rate is high, measles was not eradicated and measles reappeared among vaccinated children. We measured measles-specific antibody from the vaccinated and unvaccinated groups who had experienced apparent measles in the Seongnam city in 1993. The results were as follows. 1) The data included total 126 children (M:F=1 : 1). Age distribution of measles outbreak revealed 6 children in 5yr, 11 in 6yr, 20 in 7yr, 39 in 8yr, 22 in 9yr, 11 in 10yr, 11 in 11yr, and 6 in 12yr. 2) MMR vaccination rate was 78.6%(99/126) in the children who had experienced measles. Positive rate of measles-specific IgM Ab was 80.8% (80/99) among the vaccinated group and among 9E.6.% (25/27) the unvaccinated. 3) Positive rate of measles-specific IgG Ab was 90.9% (90/99) among MMR-vaccinated group, and 85.2% (23/27) in unvaccinated group. In conclusion, measles-specific IgM antibody have been detected more than 1 month in most patients. The relatively high proportion of measles-specific IgM positivity may mean primary vaccine failure. To booster the antibody titers and to prevent measles epidemic in school-aged children, revaccination of measles should be considered.

• Journal of Chest Surgery
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• v.38 no.10 s.255
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• pp.680-684
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• 2005

Background: With the increasing age of the population, coronary artery bypass grafting in the elderly patients is becoming common. Off-pump coronary artery bypass grafting (OPCAB) has been proven to be less morbidity and to facilitate early recovery. The elderly patients may have benefits by avoiding the adverse effects of the cardiopulmonary bypass. The purpose of this study is to evaluate our results of OPCAB in elderly patients. Material and Method: A retrospective chart review was carried out for 12 patients aged over 80 years who underwent isolated OPCAB from January 2001 and March 2004. Data were collected risk factors for disease, extent of coronary disease, and in-hospital outcomes. Postoperative graft patiency was evaluated in 9 patients by multi-slice computed tomography. Result: Eleven patients had triple vessel disease or left main disease. Four patients were suffered from preoperative CVA, and 4 patients had chronic obstructive pulmonary disease. Two patients had myocardial infarction (MI), among them 1 patient was suffered from pulmonary edema after preoperative MI. There was no perioperative death, perioperative MI, and no ventricular arrhythmia. Also there was no perioperative stroke and renal failure. But there was one deep sternal infection who recovered by treating of muscle flap. Atrial fibrillation was newly developed in 1 patient, but was well controlled by medication. Mean intubation time was $15.9\pm4.4(8\~20hrs)$ hrs and mean ICU stay was $2.9\pm0.8(2\~4 days)$ days. Mean hospital day was $21.6\pm14.3(13\~56 days)$ days. Postoperative mean CK-MS was $11.3\pm14.1\;ng/mL$. Early postoperative graft patency rate was $100\%(24/24)$. Follow-up was completed in all patients. In this time, there was no patients with angina or death. Conclusion: The results of this study suggest that OPCAB reduces morbidity and favors hospital outcomes. Therefore, OPCAB is safe, reasonable and might be preferable operative strategy in elderly patients.

• Journal of Chest Surgery
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• v.37 no.9
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• pp.749-754
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• 2004

Off-pump coronary artery bypass grafting (Off-Pump CABG) has been proven to have less morbidity and to facilitate early recovery. High-risk surgical patients may have benefitted by avoiding the adverse effects of the cardiopulmonary bypass. We compared the effectiveness of Off-Pump CABG with that of coronary artery bypass using cardiopulmonary bypass (On-Pump CABG) in high-risk patients. Material and Method: 682 patients (424 Off-Pump CABG and 258 On-Pump CABG) underwent isolated coronary artery bypass grafting between January 2001 and June 2003. Patients who were considered high risk were selected High risk is defined as the presence of one or more of nine adverse prognostic factors. Data were collected from 492 patients in Off-Pump CABG and 100 in On-Pump CABG for risk factors, extent of coronary disease, and in-hospital outcomes. Result： Off-Pump CABG group and On-Pump CABG group did not show differences in their preoperative risk factors. We used more arterial grafts in Off-Pump CABG group (p < 0.05). Postoperative results showed that operative mortality (0.5% in Off-Pump CABG versus 2.0% in On-Pump CABG), renal failure (2.6% in Off-Pump CABG versus 7.0% in On-Pump CABG), and perioperative myocardial infarction (1.5% in Off-Pump CABG versus 1.0% in On-Pump CABG) did not differ significantly. However, Off-Pump CABG had shorter mean operation time (p<0.05), lower mean CK-MB level (p <0.05), lower rate of usage of inotropics (p < 0.05), shorter mean ventilation time (p <0.05), lower perioperative stroke (0% versus 2.0%), and shorter length of stay (p < 0.05) than On-Pump CABG. On-Pump CABG had more distal grafts (p<0.05) than Off-Pump CABG. Although Off-Pump CABG and On-Pump CABG did not show statistical differences in mortality and morbidity was more frequent in CABG. Conclusion: Off-Pump CABG reduces morbidity and favors hospital outcomes. Therefore, Off-Pump CABG is safe, reasonable and may be a preferable operative strategy for high-risk patients.

• Journal of Chest Surgery
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• v.35 no.12
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• pp.862-870
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• 2002

The surgical results of the patients with single ventricle(SV) associated with total anomalous pulmonary venous connection(TAPVC) has been reported with high mortality and morbidity due to their morphologic and hemodynamic complexity. A retrospective review was undertaken to report the outcome of the first-stage palliative surgery in our institution and to determine the factors influencing early death. Material and Method: Between January 1987 and June 2002, 39 patients with SV and TAPVC underwent surgical intervention with or without TAPVC repair. Age at operation ranged from 1day to 10.7months (median age, 2.4month), and 29 patients were male. Preoperative diagnosis included 20 right-dominant SV, 15 SV with endocardial cushion defect, 3 left-dominant SV, and 1 tricuspid atresia. The pulmonary venous connection was supracardiac in 22, cardiac in 5, infracardiac in 11, and mixed in 1, Obstructed TAPVC was present in 11. First-stage palliative surgery was performed in 37. Repair of TAPVC, either alone or in association with other procedures, was performed during the initial operation in 31. Univariate and multivariate analyses were performed to analyze the risk factors influencing the operative death. Result: A mean follow-up period of survivors was 34.3 $\pm$ 43.0(0.53 ~ 146.2)months. Overall early operative mortality was 43.6%(17/39). The causes were low cardiac output in 8, failure of weaning from cardiopulmonary bypass in 3, sepsis in 2, pulmonary hypertensive crisis in 1, pulmonary edema in 1, pneumonia in 1, and postoperative arrhythmia in 1. Risk factors influencing early death in univariate analysis were body weight, surgical intervention in neonate, obstructive TAPVC, preoperative conditions including metabolic acidosis, and need for inotropic support, TAPVC repair in initial operation, operative time, and cardiopulmonary bypass(CPB) time. In multivariable analysis, body weight, age at initial operation, surgical intervention in neonate, preoperative conditions including metabolic acidosis, need for inotropic support and CPB time were the risk factors. Conclusion: In this study, we demonstrated that the patients with SV and TAPVC had high perioperative mortality. Preoperative poor condition, young age, the length of operative and CPB time, the presence of obstructive TAPVC had been proven to be the risk factors. This fact suggests that the avoidance of unnecessarily additional procedures may improve the surgical outcomes of the first-stage palliative surgery. However further observation and collection of the data is mandatory to determine the ideal surgical strategy.

• Journal of Chest Surgery
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• v.42 no.3
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• pp.324-330
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• 2009

Background: The long term patency of the free saphenous vein graft, which is the most commonly used conduit, anastomosed to the ascending aorta has been reported to be lower than that of arterial grafts. We evaluated early clinical outcome and the angiographic patency of the saphenous vein composite graft based on the left internal thoracic artery, and compared these results with those of using arterial composite grafts. Material and Method: From September 2006 to October 2008, 419 patients underwent off-pump coronary revascularization. Among those, 295 patients (70.4%) were revascularized using composite grafts (group I: saphenous vein composite graft, n=71, group II: arterial composite graft, n=224). The clinical results were compared between the 2 groups. Early postoperative coronary angiograms were performed in all the patients. ($1.6{\pm}1.6$ days) Result: The number of the distal anastomosis per patient was $3.5{\pm}1.0$ and $3.1{\pm}0.8$ in group I and II, respectively (p=.002). The operative mortality (n=2, 0.7%) and postoperative complications such as atrial fibrillation (n=73, 24.7%), perioperative myocardial infarct (n=6, 2.0%), acute renal failure (n=6, 2.0%), reoperation for bleeding (n=5, 1.7%), cerebrovascular accident (n=3, 1.0%), and mediastinitis (n=1, 0.3%) were not related with the use of saphenous vein graft. Early coronary angiograms revealed a 96.9% (126/130) for the saphenous vein grafts and a 98.8% (479/485) for the composite graft in group II (p=.231). Conclusion: Our data suggested that a saphenous vein graft might be used as analtemative conduit to the arterial graft for constructing a composite graft, as based on our early clinical and angiographic results. Further study is required to establish the long-term efficacy of using a saphenous vein as a composite graft.

• Journal of Chest Surgery
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• v.38 no.3 s.248
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• pp.204-213
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• 2005

In spite of the improvement in the quality of artificial heart valves and surgical techniques, the incidence of the complications following valve replacement is still high. We reviewed the clinical results of the valve replacements peformed in Korean University Anam Hospital during the last 26 years. Material and Method: The data of 571 patients who received valve replacement between December 1976 and December 2003 were reviewed. Result: There were 304 cases of MVR which was the most common procedure performed. There were 122 cases of AVR, and 111 cases of AVR with MVR. Among the 47 patients who received redo operation 38 cases were redo cases including 31 cases of MVR. $32.5\%$ of the patients who had tissue valve replacement had second valve replacement with 10.2 $\pm$ 3.9 years interval. $24.3\%$ (139/571) of the patients developed valve related complications and cerebral infarction was the highest in frequency. Atrial fibrillation was related with increased complication rates and the mechanical valve replaced group had higher hemorrhagic complication rate than tissue valve replaced group. The operative mortality was $3.68\%$ and the most common cause of the failure was low output syndrome. The operative mortality was higher in the patient group who had valve replacement before the year 1990. The patient group who had mechanical valve replacement had higher operative mortality rate th;3n the tissue valve group. The 5-year survival rate was $92.2\%$ and 10 year survival rate was $85.7\%$. Conclusion: The operative mortality of valve replacement has been improved. The mechnical valve replaced patients had higher hemorrhagic complication rate than the tissue valve replaced patients and more tissue valve replaced patients received redo valve replacement.

• Journal of the Korea Concrete Institute
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• v.26 no.4
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• pp.429-440
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• 2014

Since the World Trade Center and Pentagon attacks in 2001, terror, military attack, or man-made disaster caused impact, explosion, and fire accident have frequently occured on civil infrastructures. However, structural behavior researches on major Prestressed Concrete (PSC) infrastructures such as bridges, tunnels, Prestressed Concrete Containment Vessel (PCCVs), and LNG tanks under extreme loading are significantly lacking. Especially, researches on possible secondary fire scenarios after terror, bombing, collision of vehicles and vessels on concrete structures have not been performed domestically where most of the past researches related to extreme loadings on structures focused on an independent isolated extreme loading scenario. Due to the outcry of public concerns and anxiety of potential terrorist attacks on major infrastructures and structures, a study is urgently needed at this time. Therefore, in this study, the bi-directional prestressed concrete $1400{\times}1000{\times}300mm$ panels applied with 430 kN prestressing force using unbonded prestressing thread bars were experimentally evaluated under impact, fire, and impact-fire combined loadings. Due to test site restrictions, impact tests were performed with 14 kN impactor with drop heights of 10m and 3.5 m to evaluate impact resistance capacity. Also, fire and impact-fire combined loading were tested using RABT fire loading curve. The measured residual strength capacities of PSC and RC specimens applied with impact, fire, impact-fire combined loadings were compared with the residual strength capacity of undamaged PSC and RC specimens for evaluation. The study results can be used as basic research data for related research areas such as protective design and numerical simulation under extreme loading scenarios.

• Clinical and Experimental Pediatrics
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• v.51 no.6
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• pp.584-596
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• 2008

Purpose : This study was conducted to investigate treatment compliance and related factors in pediatric patients. Methods : Three hundred and fifty-five patients diagnosed with various acute diseases at a teaching hospital or clinic in October 2003 were enrolled. Data were analyzed using the Health Belief Model, which includes items on self-efficacy and family assistance. Results : The study found that 62.9% of pediatric patients adhered faithfully to agreed-upon hospital revisits, 41.6% complied with dose timings instructions, 65.8% precisely took medication, and 27.2% complied with all of these requirements. According to ${\chi}^2$ test analysis, the factors found to be related to therapeutic compliance (the taking of medicines requested) were; susceptibility, severity, benefit, barriers, mother's self-efficacy, and family assistance (P<.05). Multiple logistic analysis and path analysis showed that susceptibility, severity, barriers, and mother's self-efficacy were related to therapeutic compliance (P<.05). Moreover, mother's self-efficacy was identified as the most important factor. Conclusion : To improve therapeutic compliance among pediatric patients, parental education is necessary, and a health care professional must take a thorough history of how the medication was taken before it is assumed that treatment failure is attributable to the medication prescribed. Furthermore, the type of device recommended for dosing should be determined by clinicians. In addition, it is important that pediatric medications be discussed in relation to their palatability and internal acceptability.