• Polymer(Korea)
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• v.29 no.5
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• pp.433-439
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• 2005

The copolymers were prepared by the emulsion copolymerization of fluoroalky lacrylate-stearylacrylate-m-isopropenyl-${\alpha},\;{\alpha}'$-dimethylbenzyl isocyanate (TMI) in order to obtain water repellent polymers. The respective copolymerization rates of the three monomers considerably depended upon the use of the nonionic emulsifier and the nonionic-cationic mixed emusifier, and the optimum conditions were obtained. The particle sizes of the copolymers were in the range of 105 to 222nm. The particle sizes of the copolymers prepared by the use of the mixed emulsifiers were smaller than those of the copolymers prepared by the use of the nonionic emulsifier. The reactions of both TMI-N-methyl acetamide and TMI-cellobiose did not take place. However, the reaction of TMI-n-butylamine occurred. The water contact angles before and after washing three times for nylon and poly(ethylene terephthalate) (PET) fabrics coated with the copolymer prepared by the use of mixed emulsifier were about $139^{\circ}\;and\;133^{\circ}$ Therefore, the copolymer showed good durable repellency for nylon and PET.

• Polymer(Korea)
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• v.28 no.4
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• pp.314-320
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• 2004

Soluble aromatic polyimides bearing 4-(4-oxyalkyleneoxystyryl)- pyridines (ethylene and hexylene) as photoreactive side groups were synthesized and characterized. The photoreactive polymers were soluble in various polar organic solvents and their films were easily formed by solution casting. The photoreactivities of the polymers in the film state were approximately 64% at an exposure energy of 1.5 J/$\textrm{cm}^2$. Transmittances of the polymer films were about 85% after annealing at 20$0^{\circ}C$. Therefore, these polymers can be evaluated to be photoreactive polyimides with good transparency and solubility. The dichroic ratios of the polymers with ethylene and hexylene groups as the alkylene spacers were 0.023 and 0.026, respectively. The order parameters of 4'-pentyl-4-bipheny1carbonitrile as a liquid crystal (LC) in the film cells of the former and latter polymers were 0.50 and 0.52, respectively. These results indicate that the polymers show the effect of alkylene spacer on the photoalignments. The LC in the film cells of the polymers was perpendicularly oriented to the electric vector of the linear polarized UV light (LPUVL).

• Journal of the Korean Institute of Gas
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• v.2 no.1
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• pp.7-13
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• 1998

In this study, for the safety performance of LNG storage tank, the fracture toughness in X-grooved weld HAZ(heat-affected zone) of $9\%$ Ni steel was evaluated qualitatively and quantitatively, and the relation with the change in microstructure was analyzed. The toughness assessment was peformed through the modified CTOD test proposed for thick weldment with X-groove. Additionally, microstructures of HAZ were evaluated by OM, SEM and XRD. From the results, HAZ toughness of SMA(shielded metal arc)-welded $9\%$ Ni steel decreased as the evaluated region approached the fusion line. The decrease in toughness was apparently caused by the increase in the fraction of coarse-grained zone within HAZ. On the other hand, toughness drop with decreasing test temperature in F.L.(fusion line) ${\~}$F.L.+3mm was larger than that in F.L.+5mm${\~}$F.L.+7mm region due to the fact that in the former regions, retained austenite had poor stability.

• Journal of the Society of Disaster Information
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• v.18 no.4
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• pp.908-921
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• 2022

Purpose: As the connection between physical and non-physical structures in cities is expanding and becoming more complex, the risk of complex disaster which causes damage in a complex way is increasing. Preparing for these complex disasters, it is important to preemptively identify and manage disasters that can develop into complex disasters. Therefore, this study analyzes the disaster types studied as complex disasters by analyzing the trends of domestic and international studies related to complex disasters, and presents the direction of complex disaster management in the future. Method: We first established co-occurrence networks between disaster types based on 993 articles related to complex disasters published in disaster-related journals for the last 20 years (2002-2021). Then, through network analysis, domestic and international complex disaster research trends were compared and analyzed. Result: Research on complex disasters related to storm and flood damage, infrastructure failure and fire was high in domestic studies, and it was analyzed that research on complex disasters related to earthquakes and landslides has recently increased. However, in international studies, the proportion of studies on infrastructure failure along with storm and flood damage and earthquake was high, and various types of disasters such as tsunami and drought appeared. Conclusion: The results of this study are expected to increase the understanding of the trends in complex disaster research and provide suggestions of domestic complex disaster research in the future.

• The Journal of the Acoustical Society of Korea
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• v.28 no.1
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• pp.10-18
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• 2009

A moving surface vessel generates a ship wake which contains a cloud of micro-bubbles with radii ranging between $8{\sim}200{\mu}m$. Such micro-bubbles can be detected by active sonar system for more than ten minutes depending on the size and speed of the surface vessel. In this paper, a reverberation model for the ship wake is presented. The developed model consists of the acoustic scattering model due to the distribution of the micro-bubbles and the kinematic model for the moving active sonar. The acoustic scattering model is based on the volume integration, where the volume scattering strengths are obtained from the spatial distribution of micro-bubbles. Since the directivity and look-direction of active sonar are important factors for moving active sonar, the kinematic model utilizes the Euler transformation to obtain the relative motion between the global and local coordinates. In order to verify the developed model, a series of sea experiment was executed in September 2007 to obtain the spatial-temporal distribution of a bubble cloud, and analyzed to be compared with the simulation results.

• Journal of agricultural medicine and community health
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• v.30 no.2
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• pp.137-149
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• 2005

Objectives and Methods: This study was performed to investigate the etiologic bacterial, viral and protozoal organisms for the diarrhea from hospitals in Chungnam area from January to December in 2004. Total of 787 fecal samples were collected and examined. Results and Conclusions: In test for enteropathogenic bacteria, total of 79 cases out of 787 samples from hospitals showed positive isolation. Among 79 positive samples, 27 cases were confirmed as Salmonella spp.. 20 cases as pathogenic E. coli, 18 cases as Clostridium perfringens, 6 cases as Staphylococcus aureus, 4 cases as Shigella spp. and 4 cases as Vibrio parahaemolyticus. In test for enteropathogenic virus, 190 cases out of 787 samples from hospitals showed positive reaction. Among 190 samples, 115 cases were confirmed as rotavirus, 55 cases as norovirus, 5 case as astrovirus, 4 case as rotavirus & norovirus, 3 cases as adenovirus, 2 case as rotavirus & astrovirus. In test for enteropathogenic protozoa, 6 cases out of 787 samples from hospitals showed positive result. Among 6 samples, 5 cases were confirmed as Entamoeba histolytica and 1 cases as Giardia lamblia. When we classified the positive results by the age of the patients, the highest isolation rate was noted in a group of age under 10 and over 60 for bacterial, viral and protozoal pathogens. Especially, patient below age of 5 showed high positive rate. When we classified the positive results by the time, pageathogenic bacteria were isolated throughout the year, and the highest frequency was noted in August. On the other hand, pathogenic viruses were detected more frequently during the colder season from December to April. Antimicrobial susceptibility test for the isolated bacteria resulted as follows; Salmonella strains showed high drug resistance rates against ampicillin, chloramphenicol, tetracycline, nalidixic acid, ticarcillin. Shigella strains showed high drug resistance rates against ampicillin, trimethoprim/sulfamethoxazole, chloramphenicol, tetracycline, ampicillin/sulbactam, ticarcillin. Pathogenic E. coli strains showed high drug resistance rates against ampicillin, cephalothin, gentamicin, tetracycline, nalidixic acid, ampicillin/sulbactam, ticarcillin.

• Journal of Chest Surgery
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• v.36 no.7
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• pp.497-503
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• 2003

Pulmonary aspergillosis usually results from the colonization of the existing lung lesions by chronic pulmonary diseases, such as tuberculosis. Most cases of pulmonary aspergilloma have been treated surgically for many years because it is a potentially life-threatening disease causing massive hemoptysis. Here we reviewed our results from the last 10 years. Material and Method: We reviewed 31 cases surgically treated from Aug. 1992 to Jul. 2002. retrospectively. This investigation is designed to illustrate the peak age incidence, sex ratio, chief complaints, preoperative study, anatomic location of operative site, postoperative pathologic finding and postoperative complications. Result: The peak age Incidence laid in the 3rd and 4th decade of 20 cases (64.5%). The most common complaint was hemoptysis in 27 cases (87.1%). The 31 cases had a history of treatment with anti-tuberculous drugs under impression of pulmonary tuberculosis. The 19 cases (61.3%) showed the so-called “Air-meniscus sign” on the preoperative chest X-ray. In the 31 cases (100%) on the chest computed tomography. as a preoperative diagnostic modality, positivity was shown in 37.9%, 83.3% was shown on the fungus culture of sputum for Aspergillus, serum immunodiffusion test for A. fumigatus, respectively. The anatomical location of aspergilloma was mainly in the upper lobe in 19 cases (61.3%) and the majority of cases were managed by lobectomy. The postoperative pathologic findings showed that 31 cases (100%) were combined with tuberculosis. The postoperative complications include empyema, prolonged air leakage, remained dead space, postoperative bleeding and these numbers of cases is 3 cases (9.7%), 2 cases (6.45%), 2 cases (6.45%), 1 case (3.23%), respectively. one case was died postoperatively due to massive beeding, and asphyxia. Conclusion: Compared with the previous study, there is no significant difference in results. Preoperative chest computed tomography and immunodiffusion test were more commonly available and showed high positivity. Operations often became technically difficult because of pleural space obliteration, indurated hilar structures, and poor expansion of the remaining lung, which were more prominent in the patients with complex aspergillosis. In such cases, medical treatments and interventional procedures like bronchial artery embolization are preferred. However, cavernostomy is also recommanded with few additional morbidity because of its relatively less invassiveness. Early surgical intervention is the recommended management for patients with simple aspergilloma considering the Row surgical mortality and morbidity in recent days.

• Journal of Chest Surgery
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• v.43 no.6
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• pp.635-641
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• 2010

Background: Radiofrequency endovenous ablation of incompetent saphenous vein has gaining popularity over the conventional ligation and stripping as a minimally invasive technique. The latest version of radiofrequency endovenous catheter, $VNUS^{\circledR}Colosure$ fast VNUS medical Technologies, San Jose, CA, adopted a segmental ablation system, instead of continous pullback, is designed to reduce treatment time in comparison with the previous model $VNUS^{\circledR}Colosure$ plus VNUS medical Technologies, San Jose, CA. The purpose of this study is to compare the difference between two endovenous radiofrequency ablation systems in terms of treatment efficacy and complication rates. We analyze the initial efficacy and complication rates of $VNUS^{\circledR}Colosure$ fast with $VNUS^{\circledR}Colosure$ plus. Material and Method: Between June 2006 and August 2009, $VNUS^{\circledR}Colosure$ plus was performed to treat varicose vein on 59 limbs in 41. patients and $VNUS^{\circledR}Colosure$ fast was performed on 76 limbs in 67 patients. We retrospectively compared in both group with sex, mean treatment time, mean treatment diameter, conjugated treatment, and complications after the procedure. Result: All patient were symptomatic and diagnosed as varicose vein and underwent level 2 clinical classification with color duplex scan. The mean treatment time for the great saphenous vein was significantly less with $VNUS^{\circledR}Colosure$ fast ($17.0{\pm}6.5min$) than $VNUS^{\circledR}Colosure$ plus ($62.7{\pm}9.8min$). There was no significant difference in 1 yr closure rate between groups (p=0.32). Minor complications such as skin burn, thrombophlebitis, ecchymosis, hematoma, cellulitis, tenderness, and there were not different between the groups. Conclusion: Both $VNUS^{\circledR}Colosure$ fast and $VNUS^{\circledR}Colosure$ plus are effective methods of endovenous saphenous ablation. $VNUS^{\circledR}Colosure$ fast is superior to the previous model with less treatment time preserving compatible efficacy and complications. The efficacy of $VNUS^{\circledR}Colosure$ fast for long term closure rate remains to be established.

• Journal of Chest Surgery
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• v.37 no.9
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• pp.742-748
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• 2004

The On-X valve was recently introduced. It was the aim of this study to assess the safety and feasibility from the data derived from 28 patients who underwent aortic and/or mitral valve replacement with this prosthesis in National Medical Center. Material and Method： From May 1999 and May 2003, a series of 28 consecutive patients who had been implanted with 32 On-X prosthesis were reviewed, The operative procedure comprised of 12 MVR, 10 AVR and 6 DVR. The study followed the guidelines of AATS/STS. Mean follow-up was 27 months (total 04 patient-years). Result: Early ($\leq$30 days) mortality was 7.44% (2/28) and no late mortality occurred in the study. Total actuarial freedom from mortality at 2 years was 92.86$\pm$4.87% for all cases, 100% for MVR, 90$\pm$9.49% for AVR, and 83.3$\pm$1.52% for DVR. Thromboembolic event occurred in 2 MVR patients and that was the only complication; therefore, the linearized incidence of valve related complications was 3.17%/ patient-years for all cases and 6.5%/patient-years for MVR and the actuarial freedom from valve related complications at 2 years was 84.85$\pm$10.75%. Preoperatively, 24 (85.71%) patients were in NYHA functional class III or IV but postoperatively, 25 (89,29%) patients were in NYHA functional class I or II. The levels of hemoglobin, hematocrit, serum LDH, reticulocyte rate and indirect bilirubin were all within normal range at postoperative 3 month. In mitral position, the peak gradient was 6.1$\pm$1.8 mmHg and the mean gradient was 3.0$\pm$0.6 mmHg and EOA were 2.54$\pm$0.56 $m^2$, 2.39$\pm$0.73 $m^2$, 2.34$\pm$0.55 $m^2$, 2.40$\pm$0.63 $m^2$ at 27 mm, 29 mm, 31 mm, 33 mm respectively. In aortic postion, the peak gradient was 21.1 $\pm$14.12 mmHg and the mean gradient was 12.3$\pm$6.52 mmHg. Conclusion: Since there was no significant difference in the postoperative mortality, valve related complications and echocardiographic hemodynamic data compared to standard bileaflet design and since there was an improvement in the NYHA functional class and normal values of hemolytic indicators, it can be assumed that On-X valve is safe and feasible. However, accumulation of cases and long-term follow-up of this patient group is needed to establish this result.

• Journal of Chest Surgery
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• v.37 no.9
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• pp.762-767
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• 2004

With the developement of non-invasive surgical techeniques, coronary artery bypass graft without cardiopulmonary bypass has become popular. We compared the preoperative risk factors and in-hospital outcomes of patients having off-pump CABG with these having on-pump CABG. Material and Method： From January 2001 to June 2003, 87 patients underwent CABG. Thirty-sin patients underwent on-pump CABG, fifty-one patients under-went off-pump CABG. Preoperative risk factors, extent of coronary disease, operative time, postoperative endotracheal intubation time, duration of ICU stay & hospital stay, the amount of bleeding and postoperative levels of cardiac enzymes were compared in both groups, Result: The were no differences in their sex ratios, ages, preoperative risk factors, preoperative Ml, Canadian classes, extent of coronary artery diseases and, echocardio-graphic ejection fraction between Off-pump CABG and On-pump CABG groups. Off-pump CABG group had significantly lower mean operative time (270$\pm$79.3 min vs 372$\pm$142.2 min, p＜0.001), mean ventilation time (17.1$\pm$13.4 hr vs 24.3$\pm$17.8 hr) and CK-MB level (8,9$\pm$18.7 IU/L vs 25.7$\pm$8.4 IU/L) than on-pump CABG groups, On-pump CABG group had more distal grafts (2.2$\pm$0.5 vs 1.7$\pm$0.71 than Off-pump CABG groups did. There were no differences in their postoperative complications and outcomes including amount of postoperative bleeding for 24 hrs, reoperation for bleeding control, mean in-hospital days, postoperative infection, renal failure and neurologic complications between Off-pump CABG and On-pump CABG groups. Conclusion: This study showed that patients who underwent Off-pump CABG had less operation time & intubation time and lower CK-MB level; however, they also have less distal graft. Even though CABG without CPB provided satisfactory results, more clinical experience & longer follow-up is required.