• Computers and Concrete
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• v.21 no.6
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• pp.705-715
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• 2018

This paper presents an experimentally investigation pertinent to the mechanical properties of rubberized mortar (RM) with styrene-butadiene rubber (SBR). The SBR were used with constant water-to-cement ratio of 0.485 and two different volume proportion of SBR particles were utilized as aggregates. One types of SBR particles with fineness modulus of 4.951 were utilized 0%, 10%, and 20% of aggregate volume. Effectiveness of SBR replacement ratio, curing and aging effect on the compressive strength, flexural strengths as well as load-displacement. Compressive and flexural strength of concrete were investigated at the end of 28-days and 56-days age. Obtained results demonstrated that utilization of SBR reduced the flexural strength of SBR mortar at the earlier curing age while SBR increased. Moreover, mechanical properties of mortar mentioned above were significantly affected by the water cure timing with an increasing proportion of the replacement level of SBR.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.04a
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• pp.45-46
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• 2022

In this study, ultrasonic pulse velocity is compared on non-sintered hwangto concrete(NHTC) and normal concrete(NC) at ages. Strength of specimens set up 30MPa. Cement is replaced with 15 and 30% non-sintered hwangto. UPV is tested at 1, 3, 7, 28, 56, 91 days. As a result, UPV increases as the age and strength increase, but decreases as the non-sintered hwangto replacement increases. Although ultrasonic pulse velocity of NHTC was 72% lower than NC, after that, difference tends to decrease

• Computers and Concrete
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• v.17 no.3
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• pp.423-433
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• 2016

After the industrial of steelmaking by-products are processed properly, they can be used in civil engineering, not only as a substitute for natural resources and to reduce costs, but also to provide environmental protection. This study used different amounts (10%, 20%, 30%, 40%,and 50%) of desulphurization slag to replace natural fine aggregates in ready-mixed soil materials, and tested the physical and fresh properties (slump, slump flow, tube flow, initial setting time, and bleeding) and hardened properties (compressive strength, ball drop, ultrasonic pulse velocity) of the materials. The variations between the performances of the materials with different mix proportions were discussed. When desulphurization slag is used in RMSM, the workability can be enhanced obviously significantly. When the replacement of desulphurization slag is 50%, the slump flow is increased by 110mm compared with the control group, and the initial setting time increases as the replacement increases, because of bleeding. When the replacement is 10% and 20%, the compressive strength at various ages is higher than that of the control group. When the replacement is 10%, the compressive strength at 7 days is higher than that of the control group by 60%, and the ultrasonic pulse velocity is proportional to the compressive strength, which increases with age and decrease as the replacement increases. An appropriate replacement can effectively accelerate construction, and allow projects to be finished ahead of schedule; therefore, an appropriate replacement, is applicable for ready-mixed soil materials.

• Journal of Chest Surgery
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• v.19 no.1
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• pp.108-115
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• 1986

During 12 years period from 1974 to 1985, 76 valve replacement procedures were performed at Seoul National University Hospital in 67 pediatric patients aging up to 15 years [mean 12.3 years] and it was 7.3% of total valve replacement procedures in same period. Sixty seven patients were composed of 44 males and 23 females. Of the 67 patients, 43 patients had acquired valve lesions and 24 patients congenital valve lesions. Sixty cases received single valve replacement, 7 cases double or triple valve replacement and 9 cases redo-valve replacement. Sixty seven patients received 84 valves [65 bioprosthetic valves and 19 prosthetic valves by] 76 operations, Sixty three of 65 bioprosthetic valves had been replaced before 1983 and 15 of 19 prosthetic valves in recent 2 years. Eleven patients [14.6%] died within one month post-operatively and 8 patients [10.5%] during the follow-up period with the overall mortality rate of 25.1%. There were early post-operative complication of 23 cases [30.3%] and late post-operative complication of 27 cases [35.3%] with the total complication rate of 65.8%. In 58 patients received bioprosthetic valves, there were 14 cases of restenosis of replaced valves. Of the 14 cases of bioprosthetic valve restenosis, 8 cases received redo-valve replacement procedures without mortality in 1 5/12-5 years after initial operation but 4 cases died without reoperation and 2 cases lost during follow-up. The overall mortality and complication rate were still high but they markedly decreased during recent 2 years. So, in spite of its containing many problems, valve replacement in children is becoming safe and useful procedure in whom valve reconstructive procedures are impossible.

• Journal of Chest Surgery
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• v.44 no.6
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• pp.399-405
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• 2011

Background: Left ventricular (LV) hypertrophy caused by aortic valve stenosis (AS) leads to cardiovascular morbidity and mortality. We sought to determine whether aortic valve replacement (AVR) decreases LV mass and improves LV function. Materials and Methods: Retrospective review for 358 consecutive patients, who underwent aortic valve replacement for degenerative AS between January 1995 and December 2008, was performed. There were 230 men and 128 women, and their age at operation was $63.2{\pm}10$ years (30~85 years). Results: There was no in-hospital mortality, and mean follow-up duration after discharge was 48.9 months (2~167 months). Immediate postoperative echocardiography revealed that LV mass index and mean gradient across the aortic valve decreased significantly (p<0.001), and LV mass continued to decrease during the follow-up period (p<0.001). LV ejection fraction (EF) temporarily decreased postoperatively (p<0.001), but LV function recovered immediately and continued to improve with a significant difference between preoperative and postoperative EF (p<0.001). There were 15 late deaths during the follow-up period, and overall survival at 5 and 10 years were 94% and 90%, respectively. On multivariable analysis, age at operation (p=0.008), concomitant coronary bypass surgery (p<0.003), lower preoperative LVEF (<40%) (p=0.0018), and higher EUROScore (>7) (p=0.045) were risk factors for late death. Conclusion: After AVR for degenerative AS, reduction of left ventricular mass and improvement of left ventricular function continue late after operation.

• Journal of Chest Surgery
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• v.44 no.2
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• pp.131-136
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• 2011

Background: We evaluated the surgical results and predictors of long-term survival in patients who underwent coronary artery bypass grafting (CABG) at the time of an aortic valve replacement (AVR) due to aortic stenosis. Materials and Methods: Between January 1990 and December 2009, 183 consecutive patients underwent CABG and concomitant aortic valve replacement for aortic stenosis. The mean follow-up period was $59.8{\pm}3.3$ months and follow-up was possible in 98.3% of cases. Predictors of mortality were determined by Cox regression analysis. Results: There were 5 (2.7%) in-hospital deaths. Follow-up of the in-hospital survivors documented late survival rates of 91.5%, 74.8%, and 59.6% at 1, 5, and 10 postoperative years, respectively. Age (p<0.001), a glomerular filtration rate (GFR) less than 60 mL/min (p=0.006), and left ventricular (LV) mass (p<0.001) were significant predictors of mortality in the multivariate analysis. Conclusion: The surgical results and long-term survival of aortic valve replacement with concomitant CABG in patients with aortic stenosis and coronary artery disease were acceptable. Age, a GFR less than 60 mL/min, and LV mass were significant predictors of mortality.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2006.05a
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• pp.147-153
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• 2006

Photocatalyst reaction has limit of its usage because application range mostly centered on atmosphere purification area. Thus, it is true that an alternative plans are necessary to increase usage of $TiO_2$ as photocatalyst material. (1) The result of flow felt according to $TiO_2$ replacement rate has shown that both of anatase type and rutile type over 12% deviated from desired flow, $110{\pm}5mm$. Consequently, the range below 9% will be suitable when the anatase type $TiO_2$ if used for functional additives if workability is considered. (2) After compressive strength test, replacement rate 6-9% is estimated as suitable range if $TiO_2$ is used as compressive strength material. Rutile type and anatase type are suitable for in early-age strength and long-age strength respectively. (3) It was revealed that bending strength was dramatically decreased when replacement rate was increased. The main reason were the increase of $TiO_2$ doesn't influence hydration reaction and the decrease of bending strength. (4) The result from the water purification properties test using ion-chromatograhpy has shown that the condition with anatase type $TiO_2$ was normally better than rutile type on the same replacement rate.

• Journal of Chest Surgery
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• v.52 no.2
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• pp.61-69
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• 2019

Background: Scarce data have been reported on the efficacy of concomitant atrial fibrillation (AF) ablation in patients undergoing bioprosthetic valve replacement. Methods: From 2001 and 2014, 146 consecutive patients ($69.3{\pm}9.4years$, 84 females) who underwent bioprosthetic heart valve replacement concomitant with AF ablation were assessed. We evaluated long-term rhythm and valve-related outcomes. Results: During 49.1 months of follow-up (interquartile range, 22.5-96.8 months), 7 in-hospital and 49 (6.7% per person-year) post-discharge deaths occurred. The thromboembolic event-free survival rate at 5 years was $79.2%{\pm}3.5%$. The freedom from AF recurrence rate at 5 years was $59.8%{\pm}4.9%$. Multivariate analysis showed that old age (hazard ratio [HR], 1.06; 95% confidence interval [CI], 1.02-1.11; p=0.002), previous cardiac operation (HR, 3.01; 95% CI, 1.22-7.43; p=0.02), and a large left atrial (LA) dimension (HR, 1.02; 95% CI, 1.00-1.05; p=0.045) were significantly associated with AF recurrence. Conclusion: The overall long-term clinical outcomes in these predominantly elderly patients undergoing AF ablation concomitantly with bioprosthetic valve replacement were satisfactory; however, AF recurrence was frequent. Older age, a history of prior cardiac surgery, and large LA size were associated with an increased risk of AF recurrence.

• Journal of dental hygiene science
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• v.18 no.1
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• pp.9-17
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• 2018

The purpose of this study was to investigate the relationship between hormone replacement therapy (HRT) and periodontal disease in postmenopausal women using data from the 4th and 5th Korea National Health and Nutrition Examination Survey. A total of 5,482 postmenopausal women aged 45~75 years were included as study subjects in the final analysis. The HRT group comprised 1,035 postmenopausal women who had received HRT for at least one month, and the non-HRT group comprised 4,447 postmenopausal women who did not receive HRT. The chi-square test was used to confirm the bivariate relationship between the variables. Multinomial logistic regression analysis was used to adjust for covariance (age, education, family income, body mass index, age of menopause, alcohol, smoking, dental visit <1 per year, use of oral care products, and frequency of tooth brushing per day). After adjusting for all covariates, HRT was found to be associated with periodontal disease. In particular, the relationship between HRT and periodontal disease was more evident in older women and women younger than 45 years of menopausal age. The relationship between HRT and periodontal disease was stronger in women who brushed their teeth less than 3 times per day, women without regular oral examination, and women who did not use oral hygiene products. The results of this study confirmed the importance of actively considering hormone therapy when determining policy recommendations for postmenopausal women. Especially, health programs such as HRT, regular dental examination, and oral care are needed for older women who have undergone premature menopause.

• Journal of Korean Foot and Ankle Society
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• v.18 no.4
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• pp.195-201
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• 2014

Purpose: The purpose of this study is to develop guidelines for clinical trial of the total ankle replacement system for premarket approval. Materials and Methods: We selected and analyzed nine peer-reviewed articles whose quality had been proven in a previous phase. Two investigators extracted parameters for guideline criteria, including number of cases, patient age, follow-up period, failure rate, radiographic osteolysis rate, residual pain rate, and percentage of satisfaction. In addition, the inclusion and exclusion criteria were analyzed and developed. Results: Eight level IV studies and one level II study were included. The average number of cases was 159 cases and the mean patient age was 63.5 years. The mean follow-up period was 4.2 years, ranging from two to nine. The average failure rate of total ankle replacement in mid- to long-term follow-up was approximately 13% (2%~32.3%). The rate of osteolysis was approximately 18%. Residual pain was common (21.4%~46%), but overall patient satisfaction was approximately 85.6% (67.5%~97%). Conclusion: The results could be used as criteria for designing the clinical studies, such as number of cases, patient age (over 60 years), and follow-up period (minimum two years). The clinical scoring system and 36-item short form health survey (SF-36) was the most commonly used method for clinical evaluation for total ankle arthroplasty. In addition, the overall results, including failure rate, osteolysis rate, and patient satisfaction, could be used as a parameter of guidelines for premarket approval.