• Journal of Chest Surgery
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• v.30 no.7
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• pp.663-669
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• 1997

This is a report on the clinical outcome and hemodynamic profile of the ATSwcardiac valve prosthesis, which is a recently introduced pyrolytic carbon bileaflet prosthesis. We retrospectively reviewed the early outcome of 100 consecutive patients who underwent isolated cardiac valve replacement with the ATS(w prosthesis from October 1994 through June 1996 at our hospital. All patients were evaluated with Doppler echocardiography before discharge from the hospital. The mean age of the patients was 48.6 years(range: 2 to 74). A tota of 124 prosthesis were implanted; 71 mitral, 46 aortic, and 7 tricuspid. The two most frequently used sizes were 27 mm(40.8%) and 29 mm(35.2%) in the mitral position, and 23 mm(30.4%) and 21 mm(28.3%) in the aortic position. There was no early or late death. The total follow-up period was 950 patient-months with 99% follow-up rate. Serious late morbidity occurred in three patients; reoperation in two patients for late rupture of Sinus of Valsava in one and for endocarditis with prosthetic dehiscence in the other, and intracranial hemorrhage due to hypertension in one patient. There has been no thromboembolic complication or structural valval deterioration. In the mitral position, the average values of peak and mean transprosthetic pressure gradients and valve area calculated from pressure half time were 6.9$\pm$2.8 mmHg, 2.6$\pm$ 1.5 mmHg, and 2.7 $\pm$0.8 cm2 respectively. In the aortic position, the peak and mean pressure gradients'were 26.4 $\pm$ 15.9 mmHg and 14.2 $\pm$ 7.9 mmHg. For the mitra prostheses larger than 25-mm size, there was no significant difference among prosthetic sizes in terms of transprosthetic gradients, whereas there was a significant negative correlation between the prosthesis size and the transprosthetic gradients for the aortic valves. The peak and mean Pressere pradients were 52.2 $\pm$ 17.6 tmHg and 26.9$\pm$ 7.4 mmHg across the 19-mm aortic Prostheses, and 27.1 $\pm$ 11.9 mmHg and 13.3$\pm$6.6 mmHg across the 21-mm size. Above results can lead to the conclusion that the early clinical outcome of the ATS valve prosthesis is quite satisfactory, And the hemodynamic characteristics are comparable, if not better, with other bileaflet prostheses.

• Journal of Korea Water Resources Association
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• v.54 no.7
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• pp.535-544
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• 2021

Agricultural water occupies 48% of water demand, and management of agricultural reservoirs is essential for water resources management within agricultural basins. For more efficient use of agricultural water, monitoring the distribution of water resources in agricultural reservoirs and agricultural basins is required. Therefore, in this study, three threshold determination methods (i.e., fixed threshold, Otsu threshold, Kittler-Illingworth (KI) threshold) were compared to detect terrestrial water bodies using Sentinel-1 images for 3 years from 2018 to 2020. The purpose of this study was to evaluate methods for determining threshold values to more accurately estimate the reservoir area. In addition, by analyzing the relationship between the water surface and water storage at the Edong, Gosam, and Giheung reservoirs, water storage based on the SAR image was estimated and validated with observations. The thresholding method for detecting a waterbody was found to be the most accurate in the case of the KI threshold, and the water storage estimated by the KI threshold indicated a very high agreement (r = 0.9235, KGE' = 0.8691). Although the seasonal error characteristics were not observed, the problem of underestimation at high water levels may occur; the relationship between the water surface and the water storage could change rapidly. Therefore, it is necessary to understand the relationship between the water surface area and water storage through ground observation data for a more accurate estimation of water storage. If the use of SAR data through water resources satellites becomes possible in the future, based on the results of this study, it is judged that it will be beneficial for monitoring water storage and managing drought.

• Journal of Chest Surgery
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• v.38 no.7 s.252
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• pp.496-500
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• 2005

There was no difference between the bileaflet mechanical valves on the midterm and longterm clinical outcome. We reviewed the hemodynamic comparison between recently available mechanical valves by Doppler Echocardiography. Material and Method: We retrospectively reviewed 396 postoperative hemodynamic datas (EOA, MDPG, and MSPG) by doppler echocardiography in 345 patients. Mechanical valves from 5 venders (Sorin Bicarbon, SJM, ATS, On-X, and Edward MIRA) were compared. There were 232 valves in mitral position, 162 in aortic, and 2 in tricuspid. Result: There were 178 men (mean age; $50.6\pm13.9$ years old) and 167 women $(52.6\pm,4.6)$. MDPG/EOA of 27 mm in mitral position was Sorin; $4.2\pm1.5 mmHg/3.0\pm0.9cm^2,\;SJM;\;2.3\pm1.2/3.5\pm0.6$. In 29mm, Sorin, SJM, ATS, On-X, MIRA revealed $3.4\pm1.2/3.1\pm0.6,\;3.3\pm1.1/2.7\pm0.4,\;3.8\pm0.8/3.2\pm0.6,\;4.0\pm3.0/3.1\pm0.9,\;2.9\pm0.9/3.0\pm0.8$ In 31mm, Sorin, SJM, ATS, MIRA revealed $3.9\pm1.9/2.9\pm0.6,\;3.5\pm1.2/3.0\pm0.6,\;3.4\pm0.8/2.8\pm0.2,\;3.7\pm1.5/2.7\pm0.7$. In 33mm, Sorin, SJM, MIRA revealed $4.4\pm0.9/2.5\pm0.4,\;3.4\pm1.5/3.3\pm0.5,\;4.7\pm2.4\3.0\pm0.3$. MSPG/EOA of 19mm aortic position was Sorin, SJM, ATS, On-X, MIRA $18.0 mmHg/1.2cm^2,\;25.6\pm8.7/1.1\pm0.3,\;25.9\pm12.6/1.2\pm0.3,\;23.0/1.3,\;27.9\pm7.1/1.2\pm0.1$ in that order. In 21mm, SJM, ATS, On-X, MIRA revealed $18.3\pm6.7/1.5\pm0.5,\;13.7\pm2.1/1.7\pm0.3,\;17.0/1.4,\;17.1\pm5.5/1.8\pm0.5$. In 23mm Sorin, SJM, ATS, On-X, MIRA revealed $14.0\pm4.6/1.7\pm0.6,\;12.8\pm3.2/2.0\pm0.2,\;16.8\pm12.2/2.1\pm0.9,\;14.0/1.5,\;15.0\pm5.5/1,8\pm0.5$. In 25mm, SJM and MIRA revealed $14.0\pm5.1/1.8\pm1.0,\;11.0/2.3$. There was no statistically significant difference in these values between the venders given the same position and size. 2 redo valve replacements were performed, 1 due to severe hemolysis in ATS and 1 due to leaflet immobilization in SJM. Conclusion: Postoperative hemodynamic comparison by doppler echocardiography shows no statistically significant difference between recently available mechanical valves in this country.

• Journal of Chest Surgery
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• v.31 no.7
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• pp.679-683
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• 1998

From June 1995 to May 1997, we have implanted 52 Sorin Bicarbon mechanical valves in 41 patients. They were 16 men and 25 women, and their mean age was 47.4${\pm}$14.8(range; 18∼74 y.o.). 35(27 mm∼31 mm) were in mitral position, 15(19 mm∼25 mm) in aortic position, and 2(31 mm) in tricuspid position. 3 CABGs and a tumor excision were taken concomittantly. 35 patients were primary operation, and 6 were re-do operations. By intraoperative transesophageal doppler echocardiography, transvalvular peak/mean pressure gradient was 6.1${\pm}$2.7/2.4${\pm}$1.4 mmHg in mitral position and 27.6/10.7 mmHg in aortic position. The effective valve opening area in mitral position was 3.2${\pm}$0.6 cm2. Follow-up was total 508.6 patient-months, and mean follw-up was 12.7${\pm}$9.2 months. NYHA class was improved from 2.6${\pm}$0.6 to 1.2${\pm}$0.3 in average postoperatively. During that period, there was no operative death. 2 late non-valve related deaths were occurred. One was died of COPD, and the other was possible acute myocardial infarction. Among 7 postoperative complications, one valve related complication(minimal paravalvular leakage) was noticed. In conclusion, Sorin Bicarbon mechanical valve is believed one of the safe choice in clinical settings. It showed excellent hemodynamic and mechanical functions, and very low postoperative valve related complications in short term clinical experience.

• Korean Journal of Remote Sensing
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• v.40 no.2
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• pp.229-241
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• 2024

With the advancement of big data processing technology using cloud platforms, access, processing, and analysis of large-volume data such as satellite imagery have recently been significantly improved. In this study, the Change Detection Method, a relatively simple technique for retrieving soil moisture, was applied to the backscattering coefficient values of pre-processed Sentinel-1 synthetic aperture radar (SAR) satellite imagery product based on Google Earth Engine (GEE), one of those platforms, to estimate the surface soil moisture for six observatories within the Yongdam Dam watershed in South Korea for the period of 2015 to 2023, as well as the watershed average. Subsequently, a correlation analysis was conducted between the estimated values and actual measurements, along with an examination of the applicability of GEE. The results revealed that the surface soil moisture estimated for small areas within the soil moisture observatories of the watershed exhibited low correlations ranging from 0.1 to 0.3 for both VH and VV polarizations, likely due to the inherent measurement accuracy of the SAR satellite imagery and variations in data characteristics. However, the surface soil moisture average, which was derived by extracting the average SAR backscattering coefficient values for the entire watershed area and applying moving averages to mitigate data uncertainties and variability, exhibited significantly improved results at the level of 0.5. The results obtained from estimating soil moisture using GEE demonstrate its utility despite limitations in directly conducting desired analyses due to preprocessed SAR data. However, the efficient processing of extensive satellite imagery data allows for the estimation and evaluation of soil moisture over broad ranges, such as long-term watershed averages. This highlights the effectiveness of GEE in handling vast satellite imagery datasets to assess soil moisture. Based on this, it is anticipated that GEE can be effectively utilized to assess long-term variations of soil moisture average in major dam watersheds, in conjunction with soil moisture observation data from various locations across the country in the future.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.11
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• pp.724-731
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• 2016

The purpose of this study was to determine what rules or patterns exist when people gaze at a villa savoye, which is probably Le Corbusier's best known building, using eye-movement tracking techniques. Villa savoye was designed, addressing his emblematic "Five Points", such as pilotis, functional roofs, free floor plans, long horizontal windows, and freely-designed facades. This study examined how the villa savoye's facade image is formed in an objective manner. This study selected a total of 56 test subjects, and showed them an image of a villa savoye. Using eye-movement tracking tools, this study recorded where they mostly gazed at when seeing the building. In addition, an experiment was carried out to test the different points of view, relating to visual attention, between the two groups with different levels of knowledge in architecture. To analyze the data, the Gaze Frequency was used as the key indicator. The results showed that the subjects have a higher degree of attention to either the door or window in general than in former studies. The architecture major group showed that they gazed the experiment image more evenly.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.2 s.117
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• pp.158-165
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• 2007

In this paper, the circularly polarized $4{\times}4$ array antenna is proposed for the X-band. A single antenna consists of square patch and unequal cross-aperture coupled feeding. The RHCP(Right Handed Circularly Polarization) is generated by unequal cross-aperture coupled feeding. By reducing space among elements of way antenna from 0.8 ${\lambda}_0$ to 0.45 ${\lambda}_0$, the mounting area of array antenna is miniaturized. The $2{\times}2$ array antenna is designed using sequential rotation feeding network. The good level of gain, axial ratio, and impedance bandwidth are achieved. The $4{\times}4$ array antenna is extended by ${\lambda}/4$ transformer and T-junction power divider. The simulated maximum radiation gain is 15.09 dBi at 10 GHz. The simulated 3 dB Axial Ratio bandwidth is from 9.05 to 10.4 GHz(13.5%). Also the measured impedance bandwidth($VSWR{\leq}2$) of manufactured $4{\times}4$ array antenna is from 8.45 to 11.84 GHz(33.9%). The measured maximum radiation gain is 11.10 dBi at 10 GHz. The measured 3 dB Axial Ratio bandwidth is from 9.42 to 10.47 GHz(10.5%).

• Korean Journal of Optics and Photonics
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• v.10 no.3
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• pp.195-200
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• 1999

We made sharp optical fiber tips with less than 100 nm diameter by using the heating and pulling method with a good repetition and fabricated the photon scanning tunneling microscope (PSTM) using constant intensity mode. The 3-dimensional PZT (Piezoelctric transducer) scanner made of a long PZT tube is consisted of three divided parts, that is, a pair of $\pm$ x and a pair of $\pm$y scanning parts and a z scanning part for the fine approach and scanning. The scanning dimension is 1.43 $\mu\textrm{m}$$\times$1.76 $\mu\textrm{m}$. The height of a optical tip to maintain a constant height within $1/{\lambda}_0$ (${\lambda}_0$ is the incident wavelength) from surface of a specimen to a optical tip is controlled automatically by using the electric feedback circuit. The 3-dimensional shape of standing evanescent waves generated on the surface of a dove prism was measured successfully by using the constant intensity mode PSTM.

• Fire Science and Engineering
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• v.32 no.3
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• pp.51-59
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• 2018

Although a fire curtain plays an important role in preventing smoke from spreading to the auditorium in a theater fire, there has been insufficient research on fire curtains. In this study, to check the accuracy of numerical simulation, for previous experiments using a reduced scale model, a numerical simulation was carried out, and the results were compared with previous experimental data. The fire curtain effect was then predicted numerically. A Fire Dynamics Simulator (FDS) was used, and the natural exhaust vent sizes were set to ~10%, ~5%, and ~1% of the stage floor area. The smoke movement was visualized, and the mass flow rates and temperatures were measured and analyzed. In addition, the law of similarity was used to examine the influence of a fire curtain in a real scale theater fire. Without the fire curtain, the present numerical simulation results were in agreement with the previous experimental data within reasonable accuracy. Meanwhile, the fire curtain affects the mass flow rates through the natural exhaust vent and proscenium opening, as well as the start time of soot outflow to the auditorium. Overall, the present results can be used to develop a fire curtain system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.2
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• pp.644-648
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• 2019

This study examined effects of the wall thermal conductivity coefficients on the thermal fluid phenomenon of a compartment fire. The reduced scale compartment was 0.4 m in width, 0.6 m in length and 0.6 m in height with a fire-board, which has a thermal conductivity coefficient of $0.18W/m{\cdot}K$. The local temperature at a 0.37 m height and the overall heat release rate were measured under the following experiment conditions: a $0.12m^2$ opening area and $0.01m^2$ pool size of a gasoline fire. The numerical results obtained by the Fire Dynamic Simulation were compared with the experimentally measured temperature. The deviations were within 10 % in the period of the steady state for maximum heat release rate (4.8 kW). The numerical results show that the average temperature of the compartment wall decreases by approximately 71 % with increasing thermal conductivity coefficient from $0.1W/m{\cdot}K$ to $100.0W/m{\cdot}K$ on the fixed heat release rate.