• Journal of Korea Water Resources Association
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• v.53 no.7
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• pp.545-555
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• 2020

A feasibility modeling for potential hydroelectric dam site selection was suggested using 1 sec ASTGTM (ASTER Global Digital Elevation Model) and Terra/Aqua MODIS (Moderate Resolution Imaging Spectroradiometer) derived land use (MCD12Q1) data. The modeling includes DEM pre-processing of peak, sink, and flat, river network generation, watershed delineation and segmentation, terrain analysis of stream cross section and reservoir storage, and estimation of submerged area for compensation. The modeling algorithms were developed using Python and as an open source GIS. When a user-defined stream point is selected, the model evaluates potential hydroelectric head, reservoir surface area and storage capacity curve, watershed time of concentration from DEM, and compensation area from land use data. The model was tested for 4 locations of already constructed Buhang, BohyunMountain, Sungdeok, and Yeongju dams. The modeling results obtained maximum possible heads of 37.0, 67.0, 73.0, 42.0 m, surface areas of 1.81, 2.4, 2.8, 8.8 ㎢, storages of 35.9, 68.0, 91.3, 168.3×10⁶ ㎥ respectively. BohyunMountain and Sungdeok show validity but in case of Buhang and Yeongju dams have maximum head errors. These errors came from the stream generation error due to ASTGTM. So, wrong dam watershed boundary limit the head. This study showed a possibility to estimate potential hydroelectric dam sites before field investigation especially for overseas project.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.2
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• pp.84-95
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• 2014

Recently, as a variety of techniques of CMF (Compressed media filter) that has advantages of high porosity and compressibility have been developed in the U.S. and Japan. Therefore, the interest of intensive wastewater treatment using CMF has grown. This study examined the feasibility of CMF with varying sewage water quality to determine the optimum operating conditions. A preliminary tracer test that investigated the filtering process under various compression and flow rate conditions was performed. In a high compression condition, different porosities were applied to each depth of the column. Therefore, a distinct difference between a theoretical value and results of tracer test was observed. For the TSS (Total suspended solid) removal and particle size distribution of CMF for pre-treatment water under the various compression conditions, the compression ratio of 30 percent as the optimal condition showed greater than 70% removal efficiency. In addition, the compression ratio of >15% was required to remove small-sized particles. Also, an additional process such as coagulation is necessary to increase the removal efficiency for < $10{\mu}m$ particles, since these small particles significantly influence the effluent concentration. Modeling results showed that as the compression rate was increased, TSS removal efficiency in accordance with each particle size in the initial filtration was noticeably observed. The modeling results according to the depth of column targeting $10{\mu}m$ particles having the largest percentage in particle size distribution showed that 150-300 mm in filter media layer was the most active with respect to the filtering.

• Journal of Climate Change Research
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• v.4 no.2
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• pp.105-114
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• 2013

Recently, foreign direct investment of Korea has increased significantly. Foreign direct investment is motivated by various reasons and renewable energy investments in foreign countries can be performed by many causes. Korean companies can enjoy the export of products, related EPC contracts, acquisition of the knowledge of the project management technique, pre-occupying effect of the market and profit itself. Wind power projects have biggest share in the investment amounts among the renewable energy business. So, in this study, one wind farm project was selected and supposed to be invested in China, USA, Germany and UK at the same time and the effect of electricity price, corporate income tax, inflation rate and interest rate of debt were analyzed. The result showed that investing in Germany is most profitable because of the highest electricity price and electricity price and debt interest rate are the most sensitive factors for IRR. This approach would be helpful to make decisions in investing foreign wind power projects.

• Journal of Biosystems Engineering
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• v.26 no.3
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• pp.209-220
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• 2001

This study was carried out to investigate the usability of the used frying oil, which was extracted from soybean, as one of the alternative fuel of a small diesel engine. For the experiment, NO. 2 diesel oil [D], used frying oil [UF], and their volumetric blends were applied and analysis of the properties and compositions of the experimental fuels were conducted. A four cycle diesel engine with single cylinder, water cooling system, maximum output 8.1 ㎾/2,200 rpm was selected and a direct injection chamber and a precombustion chamber were attached alternately. The results obtained were as follows: 1. Engine power (BHP) were increased from 4.13~4.27㎾ to 9.08~9.15㎾ for diesel oil, from 4.05~4.19㎾ to 8.44~8.92㎾ for UF, and from 4.01~4.48㎾ to 8.69~9.16㎾ for blend fuel, as the engine speed increased from 1,000 rpm to 2,200 rpm. The BHP in case of the direct combustion chamber were fluctuated higher than those of the pre-combustion chamber. 2. With the engine speed increased, torque of the engine were increased from 39.50~40.80 N.m to 42.89 N.m, then decreased to 39.44~39.77 N.m for diesel oil, and increased from 38.73~40.04 N.m to 40.12~40.82 N.m then decreased as 36.53~38.76 N.m for UF. Torque of the blend fuels were increased from 38.75~41.76 N.m to 40.47~42.89 N.m then decreased to 37.73~39.78 N.m. There is no significant difference of torque between the type of combustion chambers. 3. The specific fuel consumption of the UF was increased about 20 percent depending on the engine speed variations. And in case of direct injection chamber, about 12 percent lower fuel consumption was observed than that of precombustion chamber. 4. NOx emission of the UF was higher than that of diesel oil at above 1,800rpm of the engine speed. In case of the direct injection chamber, NOx emission was revealed higher about 59 percent than that of the precombustion chamber, depending on the range of the engine speeds. 5. Smoke emission was decreased in case of UF compared with diesel oil on direct injection chamber. When using precombustion chamber smoke emission was a little higher than that of the direct injection chamber were showed at the engine speed range. 6. At all the engine speed range, exhaust gas temperatures were decreased 2~3$^{\circ}C$ for UF used engine compared with those of the diesel oil. The exhaust gas temperature of the direct injection chamber was higher than that of the precombustion chamber by 72$^{\circ}C$. 7. Unburnt materials remained in the cylinder in case of the pre-combustion chamber was smaller and softer than that of the direct combustion chamber. 8. The feasibility of the blend fuel B-1 and B-2 were verified as a direct combustion chamber was attached to the diesel engine, with respect to the power performance of the engine.

• Journal of Biosystems Engineering
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• v.41 no.2
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• pp.126-137
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• 2016

Purpose: The overall objective of this study was to evaluate the vegetation fraction of soybeans, grown under different cropping conditions using an unmanned aerial vehicle (UAV) equipped with a red, green, and blue (RGB) camera. Methods: Test plots were prepared based on different cropping treatments, i.e., soybean single-cropping, with and without herbicide application and soybean and barley-cover cropping, with and without herbicide application. The UAV flights were manually controlled using a remote flight controller on the ground, with 2.4 GHz radio frequency communication. For image pre-processing, the acquired images were pre-treated and georeferenced using a fisheye distortion removal function, and ground control points were collected using Google Maps. Tarpaulin panels of different colors were used to calibrate the multi-temporal images by converting the RGB digital number values into the RGB reflectance spectrum, utilizing a linear regression method. Excess Green (ExG) vegetation indices for each of the test plots were compared with the M-statistic method in order to quantitatively evaluate the greenness of soybean fields under different cropping systems. Results: The reflectance calibration methods used in the study showed high coefficients of determination, ranging from 0.8 to 0.9, indicating the feasibility of a linear regression fitting method for monitoring multi-temporal RGB images of soybean fields. As expected, the ExG vegetation indices changed according to different soybean growth stages, showing clear differences among the test plots with different cropping treatments in the early season of < 60 days after sowing (DAS). With the M-statistic method, the test plots under different treatments could be discriminated in the early seasons of <41 DAS, showing a value of M > 1. Conclusion: Therefore, multi-temporal images obtained with an UAV and a RGB camera could be applied for quantifying overall vegetation fractions and crop growth status, and this information could contribute to determine proper treatments for the vegetation fraction.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.250-254
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• 2002

Intergranular corrosion of austenitic stainless steels is a conventional and momentous problem during welding and high temperature use. One of the major reasons for such intergranular corrosion is so-called sensitization, i.e., chromium depletion due to chromium carbide precipitation at grain boundaries. Conventional methods for preventing sensitization of austenitic stainless steels include reduction of carbon content in the material, stabilization of carbon atoms as non-chromium carbides by the addition of titanium, niobium or zirconium, local solution-heat-treatment by laser beam, etc. These methods, however, are not without drawbacks. Recent grain boundary structure studies have demonstrated that grain boundary phenomena strongly depend on the crystallographic nature and atomic structure of the grain boundary, and that grain boundaries with coincidence site lattices are immune to intergranular corrosion. The concept of "grain boundary design and control", which involves a desirable grain boundary character distribution, has been developed as grain boundary engineering. The feasibility of grain boundary engineering has been demonstrated mainly by thermomechanical treatments. In the present study, a thermomechanical treatment was tried to improve the resistance to the sensitization by grain boundary engineering. A type 304 austenitic stainless steel was pre-strained and heat-treated, and then sensitized, varying the parameters (pre-strain, temperature, time, etc.) during the thermomechanical treatment. The grain boundary character distribution was examined by orientation imaging microscopy. The intergranular corrosion resistance was evaluated by electrochemical potentiokinetic reactivation and ferric sulfate-sulfuric acid tests. The sensitivity to intergranular corrosion was reduced by the thermomechanical treatment and indicated a minimum at a small roll-reduction. The frequency of coincidence-site-lattice boundaries indicated a maximum at a small strain. The ferric sulfate-sulfuric acid test showed much smaller corrosion rate in the thermomechanically-treated specimen than in the base material. An excellent intergranular corrosion resistance was obtained by a small strain annealing at a relatively low temperature for long time. The optimum parameters created a uniform distribution of a high frequency of coincidence site lattice boundaries in the specimen where corrosive random boundaries were isolated. The results suggest that the thermomechanical treatment can introduce low energy segments in the grain boundary network by annealing twins and can arrest the percolation of intergranular corrosion from the surface.

• Clinical and Experimental Pediatrics
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• v.55 no.7
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• pp.232-237
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• 2012

Purpose: With feasibility in the diagnoses of congenital heart disease (CHD) in the antenatal period, we suspect changes have occurred in its incidence. No data have been reported about the current incidence of simple forms of CHD in Korea. We have attempted to assess the recent incidence and characteristics of CHD in the neonatal care unit of a secondary referral medical center. Methods: Medical records of 497 neonatal care unit patients who underwent echocardiography in the past 5 years were reviewed. Preterm infants with patent ductus arteriosus and other transient, minimal lesions were excluded from this study. Results: Although the number of inpatients remained stable, the incidence of simple forms of CHD showed a gradual decrease over the 5-year study period; a markedly low incidence of complex forms was seen as well. CHD was observed in 3.7% full-term and 6.8% pre-term infants. CHD was observed in 152 infants weighing >2,500 g (3.5% of corresponding birth weight infants); 65 weighing 1,000 to 2,500 g (9.3%); and 6 weighing <1,000 g (8.0%). The incidence of CHD was higher in the pre-term group and the low birth weight group than in each corresponding subgroup (P<0.001); however, the incidence of complex CHD in full-term neonates was high. The number of patients with extracardiac structural anomalies has also shown a gradual decrease every year for the past 5 years. Conclusion: Findings from our study suggest that the recent incidence and disease pattern of CHD might have changed for both complex and simple forms of CHD in Korea.

• Journal of Chest Surgery
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• v.33 no.8
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• pp.662-668
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• 2000

Background: Many recent results of clinical trials show that pre-operative concurrent chemoradiotherapy and surgical resection could increase the survival of N2 positive stage IIIA non-small cell lung cancer. This study was performed to assess the feasibility, toxicity, and affect rates of concurrent chemoradiotherapy and surgical resection in N2 positive stage IIIA non-small cell lung cancer. Material and Method: Thirty-one patients who underwent preoperative concurrent chemoradiotherapy for N2 positive stage IIIA non-small-cell lung cancer from May 1997 to April 1999 were entered into the study. Mean age was 61 yrs(43∼70 yrs), There were 24 men and 7 women. The confirmation of N2 disease were achieved through mediastinoscopic biopsy(24) and CT scans(7). Induction was achieved by two cycles of cisplatin and etoposide(EP) plus concurrent chest radiotherapy to 45 Gy. Resections were done at 3 weeks after the complection of preoperative concurrent chemoradiotherapy. Resections were performed in 23 patients, excluding 5 refusals and 3 distant metastasis. Result: All patients were compled the thoracic radiotherapy except one who had distant metastasis. Twenty three patients were completed the planned 2 cycles of EP chemotherapy, and 8 patients were received only 1 cycle for severe side effects(6), refusal(1), and distant metastasis(1). There was one postoperative mortality, and the cause of death was ARDS. Three patients who had neutropenic fever and one patient who had radiation pneumonitis were required admission and treatment. Esophagitis was the most common acute side effect, but relatively well-tolerated in most patients. The complection rate of concurrent chemoradiotherapy was 74%, resection rate was 71%, pathologic complete remission rate was 13.6%, and pathologic down-staging rate was 68%. Conclusion: Morbidity related to each treatment was acceptable and many of the patients have benefited down staging of its disease. Further prospective, preferably randomized, clinical trials of larger scale may be warranted to confirm the actual benefit of preoperative concurrent chemoradiotherapy and surgical resection in N2-positive stage IIIA non-small cell lung cancer.

• Korean Journal of Agricultural and Forest Meteorology
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• v.7 no.2
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• pp.148-155
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• 2005

An accurate prediction of blooming date is crucial for many authorities to schedule and organize successful spring flower festivals in Korea. The Korea Meteorological Administration (KMA) has been using regression models combined with a subjective correction by forecasters to issue blooming date forecasts for major cities. Using mean monthly temperature data for February (observed) and March (predicted), they issue blooming date forecasts in late February to early March each year. The method has been proved accurate enough for the purpose of scheduling spring festivals in the relevant cities, but cannot be used in areas where no official climate and phenology data are available. We suggest a thermal time-based two-step phenological model for predicting the blooming dates of spring flowers, which can be applied to any geographic location regardless of data availability. The model consists of two sequential periods: the rest period described by chilling requirement and the forcing period described by heating requirement. It requires daily maximum and minimum temperature as an input and calculates daily chill units until a pre-determined chilling requirement for rest release. After the projected rest release date, it accumulates daily heat units (growing degree days) until a pre- determined heating requirement for flowering. Model parameters were derived from the observed bud-burst and flowering dates of cherry tree (Prunus serrulata var. spontanea) at KMA Seoul station along with daily temperature data for 1923-1950. The model was applied to the 1955-2004 daily temperature data to estimate the cherry blooming dates and the deviations from the observed dates were compared with those predicted by the KMA method. Our model performed better than the KMA method in predicting the cherry blooming dates during the last 50 years (MAE = 2.31 vs. 1.58, RMSE = 2.96 vs. 2.09), showing a strong feasibility of operational application.

• The Journal of the Korea Contents Association
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• v.18 no.1
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• pp.164-172
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• 2018

This study explores how to implement a learning experience-based professionalism program for a medical students and evaluates its program through effectiveness and usability test. This study aims to provide practical implications for experience-based learning in an undergraduate level. Seventy four first-year medical students enrolled in PDS1(Patient-Doctor-Society 1): professionalism, one-week block (30 hours), one-credit program based on a experience-based learning model. All of the students were given six learning themes and learning resources and supporting tools, and conducted stepwise learning activities; preparation, organization, sharing, reflection and evaluation of experiences. The effectiveness of learning was evaluated by comparing the pre and post results of student's self-assessment on 24 questionnaire items about professionalism. After the course, the students and instructors conducted a usability evaluation of the program through questionnaires or group interviews. Learners' self-assessment results of professionalism such as leadership, self-directed learning, professional attitude, and social accountability all showed significant differences between the pre- and post-test. Satisfaction of the program was distributed to 3.58~3.78 according to items. Instructors and learner interviews confirmed practical usability throughout the course design, implementation and students evaluation. The results of the study showed the feasibility of implementing learning experience-based professionalism program in medical school. This study provides practical implications to develope and evaluate the learning experience-based professionalism program in medical education.