• Korean Journal of Radiology
• /
• 제22권12호
• /
• pp.1964-1973
• /
• 2021

Objective: To investigate the diagnostic performance of CT fractional flow reserve (CT-FFR) for myocardial bridging-related ischemia using dynamic CT myocardial perfusion imaging (CT-MPI) as a reference standard. Materials and Methods: Dynamic CT-MPI and coronary CT angiography (CCTA) data obtained from 498 symptomatic patients were retrospectively reviewed. Seventy-five patients (mean age ± standard deviation, 62.7 ± 13.2 years; 48 males) who showed myocardial bridging in the left anterior descending artery without concomitant obstructive stenosis on the imaging were included. The change in CT-FFR across myocardial bridging (ΔCT-FFR, defined as the difference in CT-FFR values between the proximal and distal ends of the myocardial bridging) in different cardiac phases, as well as other anatomical parameters, were measured to evaluate their performance for diagnosing myocardial bridging-related myocardial ischemia using dynamic CT-MPI as the reference standard (myocardial blood flow < 100 mL/100 mL/min or myocardial blood flow ratio ≤ 0.8). Results: ΔCT-FFR_systolic (ΔCT-FFR calculated in the best systolic phase) was higher in patients with vs. without myocardial bridging-related myocardial ischemia (median [interquartile range], 0.12 [0.08-0.17] vs. 0.04 [0.01-0.07], p < 0.001), while CT-FFR_systolic (CT-FFR distal to the myocardial bridging calculated in the best systolic phase) was lower (0.85 [0.81-0.89] vs. 0.91 [0.88-0.96], p = 0.043). In contrast, ΔCT-FFR_diastolic (ΔCT-FFR calculated in the best diastolic phase) and CT-FFR_diastolic (CT-FFR distal to the myocardial bridging calculated in the best diastolic phase) did not differ significantly. Receiver operating characteristic curve analysis showed that ΔCT-FFR_systolic had largest area under the curve (0.822; 95% confidence interval, 0.717-0.901) for identifying myocardial bridging-related ischemia. ΔCT-FFR_systolic had the highest sensitivity (91.7%) and negative predictive value (NPV) (97.8%). ΔCT-FFR_diastolic had the highest specificity (85.7%) for diagnosing myocardial bridging-related ischemia. The positive predictive values of all CT-related parameters were low. Conclusion: ΔCT-FFR_systolic reliably excluded myocardial bridging-related ischemia with high sensitivity and NPV. Myocardial bridging showing positive CT-FFR results requires further evaluation.

• 유통과학연구
• /
• 제12권4호
• /
• pp.85-92
• /
• 2014

Purpose - This study conducted empirical research on non-financial corporations listed on the stock exchange from 2001 to 2010, focusing on the effects of corporate governance on real earnings management of corporations. In particular, this study examined primarily the impact of the largest shareholder who could use earnings management to pursue his own self-interest, and foreign investors who played a checking role against the largest shareholders. The study also reviewed the relationship between corporate governance and earnings management while also considering corporate growth. Research design, data, and methodology - As for the measurements of real earnings management, abnormal operating cash flow and abnormal production cost were utilized. As for the independent variables, share ratio of the largest shareholder and affiliate person (M) and share ratio of foreign investors (FT) were leveraged. This study excluded those organizations that had changed their fiscal years, those that had not submitted an audit report, corporations under supervision, delisted corporations, corporations that had changed their business type, and so on, from the non-financial corporations out of the publicly traded corporations whose fiscal year ended in December from 2001 to 2010 in addition, KIS values were utilized for the corporate financial data in the study. To verify whether management structure and growth had an impact on real earnings management of a corporation through empirical analysis, a multiple regression analysis model was applied. Result - First, as a result of the analysis, the share ratio (M) of the largest shareholder and affiliate person was found to have a significant positive correlation with abnormal cash flow from operations(ACF) and abnormal production cost (APD). When controlling the growth, the share ratio (M) of the largest shareholder and affiliate person was found to have an insignificant correlation with abnormal cash flow from operations(ACF) but a significant correlation with abnormal production cost (APD). Second, foreign ownership (FT) was found to have a significant positive correlation with abnormal cash flow from operations(ACF) and abnormal production cost (APD) at the confidence level of 1 percent when not including the growth dummy. When controlling the growth, foreign ownership (FT) was found to have a significant negative correlation with abnormal cash flow from operations (ACF) and with abnormal production cost (APD). Conclusion - The results imply that the largest shareholder is closely related to earnings management through real activities regardless of corporate growth. It is also possible to determine from these results that foreign investors are related to earnings management through real activities when not considering corporate growth, but that they would reduce earnings management in the case of considering the growth. Thus, this study verified along with the existing studies that foreign investors were conducting the control function on controlling shareholders.

• 한국산학기술학회논문지
• /
• 제14권5호
• /
• pp.2315-2321
• /
• 2013

본 연구는 혈류에 의한 조영제 peak time을 산출하는 새로운 방법을 개발하여 기존의 수식에 의한 부작용을 최소화 하고, 대체할 수 있는 새로운 검사법을 제시하고자 하였다. 시험적조영제주입법을 이용하여 CE MRA를 검사한 환자 127명을 대상으로, 기존의 수식에 의해 산출된 조영제 peak time이 조영제 주입 후 혈류에 의한 영상화 범위의 어느 뇌혈관 측정값과 일치하는지 각 뇌혈관의 조영제 inflow time과 peak time을 측정하였다. 연구결과, 유의수준 0.05에 대한 4개의 집단 간 차이가 존재하였으나 집단 1에서 수식에 의해 산출된 조영제 peak time과 S상 정맥동의 조영제 inflow time이 통계적으로 유의한 차이가 없어 일치하였으며, Bland Altman plot를 시행한 결과 일치도가 상당히 높은 것을 확인할 수 있었다. 따라서 본 연구의 혈류에 의한 새로운 방법을 적용한다면, 부작용 가능성을 최소화하고, 영상의 질은 유지하면서, 쉽고 빠르게 적용할 수 있어, 기존의 수식에 의해 산출된 조영제 peak time을 대체 할 수 있으리라 사료된다.

• 한국환경보건학회:학술대회논문집
• /
• 한국환경보건학회 2004년도 International Conference Global Environmental Problems and their Health Consequences
• /
• pp.193-196
• /
• 2004

To evaluate the acute effects of fine particles on pulmonary function, a longitudinal study was conducted. This study was carried out for the schoolchildren (3rd and 6th grades) living in Beijing, China. Children were asked to record their daily levels of peak expiratory flow rate using portable peak flow meter (mini-Wright) for 40 days. The relationship between daily PEFR and fine particle levels was analyzed using a mixed linear regression models including gender, height, the presence of respiratory symptoms, and daily average temperature and relative humidity as extraneous variables. The total number of students participating in this longitudinal study was 87. Daily measured PEFR was in the range of $253{\sim}501L/min$. On the daily basis, a PEFR measured in the morning was shown to be lower than that measured in the evening (or afternoon). The daily mean concentrations of $PM_{10}$ and $PM_{2.5}$ over the study period were $180.2\;{\mu}g/m^3$ and $103.2\;{\mu}g/m^3$, respectively. The IQR (inter-quartile range) of $PM_{10}$ and $PM_{2.5}$ were $91.8\;{\mu}g/m^3$ and $58.0\;{\mu}g/m^3$. Daily mean PEFR was regressed with the 24-hour average $PM_{10}$ (or $PM_{2.5}$) levels, weather information such as air temperature and relative humidity, and individual characteristics including gender, height, and respiratory symptoms. The analysis showed that the increase of fine particle concentrations was negatively associated with the variability in PEFR. The IQR increments of $PM_{10}$ or $PM_{2.5}$ (at 1-day time lag) were also shown to be related with 1.54L/min (95% Confidence intervals -2.14, -0.94) and 1.56L/min (95% CI -2.16, -0.95) decline in PEFR.

• Journal of Welding and Joining
• /
• 제33권5호
• /
• pp.47-52
• /
• 2015

In this study, it was tried to analyze the effects of welding parameters on the weld penetration and aspect ratio when a STS316L pipe was welded in a horizontal position by GTAW. Experiments were systematically designed using a L18 orthogonal array, and the effects of welding parameters were statistically analyzed by ANOVA(Analysis of Variance). The shielding gas type has the largest effect on both the penetration and aspect ratio. The welding current type and shielding gas flow rate have a little effect on the penetration, whereas the electrode tip angle has a little effect on the aspect ratio. When welded at a selected welding condition, which is composed of He shielding gas, pulse current of 300/45 A, electrode tip angle of 90o, and shielding gas flow rate of 30 l/min, the estimated interval at least 95 % confidence was $1.99{\pm}0.18mm$ for the penetration and $0.31{\pm}0.04$ for the aspect ratio. From the confirmation experiments, the average penetration and aspect ratio were well agreed with the estimation as 1.96 mm and 0.30, respectively. Additionally, the effects of the welding speed and welding current on the penetration and aspect ratio were experimented and analyzed by linear regression. The penetration was linearly increased with the decrease of the welding speed and with the increase of the welding current, but the aspect ratio showed a tendency to a little decrease with the increase of both the welding speed and current.

• 한국환경보건학회:학술대회논문집
• /
• 한국환경보건학회 2003년도 Challenges and Achievements in Environmental Health
• /
• pp.183-186
• /
• 2003

To evaluate the effect of air pollution on respiratory health in children, we conducted a longitudinal study in which children were asked to record their daily levels of peak expiratory flow rate using potable peak flow meter (mini-Wright) far 4 weeks. The relationship between daily PEFR and ambient air particle levels was analyzed using a mixed linear regression models including gender, age in you, weight, the presence of respiratory symptoms, and relative humidity as an extraneous variable. The daily mean concentrations of PM$\_$10/ and PM$\_$2.5/ over the study period were 64.9$\mu\textrm{g}$/㎥ and 46. l$\mu\textrm{g}$/㎥, respectively. The range of daily measured PEFR in this study was 170-481 l/min. Daily mean PEFR was regressed with the 24-hour. average PM$\_$10/ (or PM$\_$2.5/) levels, weather information such as air temperature and relative humidity, and individual characteristics including sex, weight, and respiratory symptoms. The analysis showed that the increase of air particle concentrations was negatively associated with the variability in PEFR. We estimated that the IQR increment of PM$\_$10/ or PM$\_$2.5/ were associated with 1.5 l/min (95% Confidence intervals -3.1, 0.1) and 0.8 l/min (95% Cl -1.8, 0.1) decline in PEFR. Even though this study shows negative findings on the relationship between respiratory function and air particles, it is worth noting that the findings must be interpreted cautiously because exposure measurement based on monitoring of ambient air likely results in misclassification of true exposure levels and this is the first Korean study that PM$\_$2.5/ measurement is applied as an index of air particle quality.

• Journal of Advanced Marine Engineering and Technology
• /
• 제32권6호
• /
• pp.869-876
• /
• 2008

A thermocompressor is the equipment which compresses a vapor to a desired discharge pressure. Since it was first used as the evacuation pump for a surface condenser, it has been widely adopted for energy saving systems due to its high working confidence. In the present study, the geometrical analysis of the shape between the jet nozzle and the diffuser inlet, the drag force was calculated by means of the integrated equation of motion and the computational fluid dynamic (CFD) package called FLUENT. The computer simulations were performed to investigate the effects by the various suction flow rates, the distance from jet nozzle outlet to the diffuser inlet and the dimensions of the diffuser inlet section through the iterative calculation. In addition, the results from the CFD analysis on the thermocompressor and the experiments were compared for the verification of the CFD results. In the case of a jet nozzle, the results from the CFD analysis showed a good agreement with the experimental results. Furthermore, in this study, a special attention was paid on the performance of the thermocompressor by varying the diffuser convergence angle of $0.0^{\circ}$, $0.5^{\circ}$, $1.0^{\circ}$, $2.0^{\circ}$, $3.5^{\circ}$ and $4.5^{\circ}$. With the increase of the diffuser convergence angle. the suction capacity was improved up to the degree of $1.0^{\circ}$ while it was decreased over the degree of $1.0^{\circ}$.

• 한국물환경학회지
• /
• 제22권5호
• /
• pp.856-864
• /
• 2006

For estimating the minimum discharge to maintain a river, low flow analysis is required and long term runoff records are needed for the analysis. However, runoff data should be estimated to run a hydrologic model for ungaged river basin. For the reason, parameter estimation is crucial to simulate rainfall-runoff events for those basins using Tank model. In this study, only runoff data recorded for dry season are used for parameter estimation, which is different to other methods based on runoff data recorded for wet and dry seasons. The Harmony Search algorithm is used to determine the optimum parameters for Tank model. The coefficient of determination ($R^2$) is served as the objective function in the Harmony Search. In cases that recorded data are insufficient, the recording interval is changed and Empirical CDF is adopted to analyze the estimated parameters. The suggested method is applied to Yongdam dam, Soyanggang dam, Chungju dam and Seomjingang dam basins. As results, the higher $R^2s$ are obtained when the shorter recording interval, the better recorded data quality, and the more rainfall events recorded along with certain rainfall amount is. Moreover, when the total rainfall is higher than the certain amount, $R^2$ is high. Considering the facts found from this study for the low flow analysis, it is possible to estimate the parameters for Tank model properly with the desired confidence level.

• Journal of Menopausal Medicine
• /
• 제24권3호
• /
• pp.163-168
• /
• 2018

Objectives: To investigate the rate of postoperative urinary retention (POUR) and identify the risk factors for this complication in women who underwent transvaginal uterosacral suspension surgery. Methods: A retrospective chart review was conducted for 75 women who underwent transvaginal uterosacral suspension surgery with vaginal hysterectomy, repair of cystocele, and levator myorrhaphy with/without transobturator anti-incontinence surgery. POUR was defined as a need for continuous intermittent catheterization on the third day subsequent to removal of the urethral indwelling catheter. Results: Acute POUR was reported in 18 women (24.0%). Thirty-six of the 75 patients (48.0%) had undergone anti-incontinence surgery. Crude analysis revealed significant association between the following variables and the risk of POUR: hypertension, the lower average flow rate in the pressure-flow study (PFS), greater post-void residual (PVR) urine volume in PFS, and PVR >30% of the total bladder capacity (TBC) in PFS. In the logistic regression analysis, PVR >30% of the TBC in PFS was identified as the only significant predictor of POUR (odds ratio, 15.4; 95% confidence interval, 2.5-90.9; P = 0.003). Conclusions: The PVR >30% of the TBC in PFS was identified as the only predictive factor of acute POUR in women who underwent transvaginal uterosacral suspension surgery.

• Tuberculosis and Respiratory Diseases
• /
• 제87권2호
• /
• pp.165-175
• /
• 2024

Background: The prevalence of small airway dysfunction (SAD) in patients with chronic obstructive pulmonary disease (COPD) across different ethnicities is poorly understood. This study aimed to estimate the prevalence of SAD in stable COPD patients. Methods: We conducted a cross-sectional study of 196 consecutive stable COPD patients. We measured pre- and post-bronchodilator (BD) lung function and respiratory impedance. The severity of COPD and lung function abnormalities was graded in accordance with the Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines. SAD was defined as either difference in whole-breath resistance at 5 and 19 Hz > upper limit of normal or respiratory system reactance at 5 Hz < lower limit of normal. Results: The cohort consisted of 95.9% men, with an average age of 66.3 years. The mean forced expiratory volume 1 second (FEV₁) % predicted was 56.4%. The median COPD assessment test (CAT) scores were 14. The prevalence of post-BD SAD across the GOLD grades 1 to 4 was 14.3%, 51.1%, 91%, and 100%, respectively. The post-BD SAD and expiratory flow limitation at tidal breath (EFL_T) were present in 62.8% (95% confidence interval [CI], 56.1 to 69.9) and 28.1% (95% CI, 21.9 to 34.2), respectively. COPD patients with SAD had higher CAT scores (15.5 vs. 12.8, p<0.01); poor lung function (FEV₁% predicted 46.6% vs. 72.8%, p<0.01); lower diffusion capacity for CO (4.8 mmol/min/kPa vs. 5.6 mmol/min/kPa, p<0.01); hyperinflation (ratio of residual volume to total lung capacity % predicted: 159.7% vs. 129%, p<0.01), and shorter 6-minute walk distance (367.5 m vs. 390 m, p=0.02). Conclusion: SAD is present across all severities of COPD. The prevalence of SAD increases with disease severity. SAD is associated with poor lung function and higher symptom burden. Severe SAD is indicated by the presence of EFL_T.