• Journal of the Korean Geotechnical Society
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• v.25 no.10
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• pp.99-110
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• 2009

In order to provide the design criteria, the characteristics of consolidation for soft ground improvement have been investigated using the field banking test performed by the vertical drain method at the northern container section in Busan New Port. Field test results indicated that the estimated degree of consolidation in design stage decreased by about 7% compared with the measured one. This difference is attributed to the fact that the conservative geological properties were applied with relatively high amount of maximum clay mixture ratio during the design stage. Based on this findings, another laboratory oedometer test was implemented to consider various combination of mixture ratio. It was found that the consolidation degree increased in accordance with the increase of sand/silt mixture ratio. Also, the proportion of 10%, 50%, and 40% for sand, silt, and clay, respectively, was observed as the best combination of mixture ratio to the actual measurement, which is very similar to the average grain size distribution in the banking test area. Therefore, it is suggested that the overall geological characteristics as well as the grain size distribution should be considered in design stage to improve the soft ground that contains mixture of sand, silt, and clay.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.390-390
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• 2020

자연재해 중 홍수의 경우 단기간에 발생하며, 큰 인명 및 금전적 피해를 가져오는 재해이다. 1970년~2017년 국내 홍수 피해 분석결과 사상자(총 8,152명)는 점차 줄어드는 추세를 보이지만, 반대로 피해액(총 17조5,000억원)은 증가하는 것으로 나타났다(wamis, 국가수자원관리종합정보시스템). 이러한 국내 홍수 피해를 최소화하기 위해서는 각 유역 또는 지역별 특성을 고려한 홍수 취약성 평가가 필요하다. 홍수 취약성은 대상 지역의 기상, 지형, 인문학적 상황에 따라 상이하게 나타나며, 홍수 취약성을 평가하는 인자의 선정 또한 매우 중요하다. 따라서 본 연구에서는 홍수 피해 자료와 홍수 인자간의 인과관계를 분석하여 홍수 취약성 지표 선정 및 취약성 평가를 실시하였다. 홍수 취약성 평가를 위해 홍수 피해 자료와 대상 인자간의 상관성 분석을 통해 상관계수 값이 상대적으로 높게 나온 인자를 선정하였다. 대상 인자는 크게 기상학적 인자, 지형학적 인자, 사회·인문학적 인자로 구분하였다 선정된 인자 간 서로 높은 상관성을 보일 시 공선성이 존재함을 의미하며, 이러한 공선성을 방지하기 위해 VIF (Variance Inflation Factor, 분산팽창계수)를 통한 공선성 검토를 적용하였다. 또한 각 인자 간 에는 서로 다른 단위 및 범위를 가진다. 이러한 경우 특정 인자들의 증감을 취약성 평가에 반영하기에 어려움이 있으며, 유역별 평가 시 신뢰성이 낮아진다. 따라서 Re-scaling 방법을 통해 각 인자의 단위 및 범위를 표준화 후 동일가중치 법을 적용하였다. 본 연구에서는 전체 유역 중 홍수피해가 가장 크게 발생하는 낙동강 태화강 유역을 연구 대상 지역으로 선정하였다. 태화강은 도심지의 중심부를 흐르는 하천이며, 산지의 고도가 높은 지형적 특성을 가지고 있어 홍수에 대한 취약성이 높은 것으로 나타났다(wamis, 국가수자원관리종합정보시스템). 태화강 유역 홍수 취약성 평가결과 유역별 기상, 지형, 인문학적 특성에 따라 홍수 취약성이 높게 나타나는 결과를 보였다. 이와 같은 결과는 유역 내 도심지 비율, 인구밀도, 토지피복 특성에 의한 것으로 주로 지형학적 인자로 인해 취약성이 높게 나타났다. 본 연구에서 활용한 홍수 취약성 평가 방법은 향후 홍수피해 대책 수립에 사용될 수 있을 것으로 판단된다.

• Journal of The Korean Astronomical Society
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• v.56 no.2
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• pp.213-224
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• 2023

Type II solar radio bursts show frequency drifts from high to low over time. They have been known as a signature of coronal shock associated with Coronal Mass Ejections (CMEs) and/or flares, which cause an abrupt change in the space environment near the Earth (space weather). Therefore, early detection of type II bursts is important for forecasting of space weather. In this study, we develop a deep-learning (DL) model for the automatic detection of type II bursts. For this purpose, we adopted a 1-D Convolution Neutral Network (CNN) as it is well-suited for processing spatiotemporal information within the applied data set. We utilized a total of 286 radio burst spectrum images obtained by Hiraiso Radio Spectrograph (HiRAS) from 1991 and 2012, along with 231 spectrum images without the bursts from 2009 to 2015, to recognizes type II bursts. The burst types were labeled manually according to their spectra features in an answer table. Subsequently, we applied the 1-D CNN technique to the spectrum images using two filter windows with different size along time axis. To develop the DL model, we randomly selected 412 spectrum images (80%) for training and validation. The train history shows that both train and validation losses drop rapidly, while train and validation accuracies increased within approximately 100 epoches. For evaluation of the model's performance, we used 105 test images (20%) and employed a contingence table. It is found that false alarm ratio (FAR) and critical success index (CSI) were 0.14 and 0.83, respectively. Furthermore, we confirmed above result by adopting five-fold cross-validation method, in which we re-sampled five groups randomly. The estimated mean FAR and CSI of the five groups were 0.05 and 0.87, respectively. For experimental purposes, we applied our proposed model to 85 HiRAS type II radio bursts listed in the NGDC catalogue from 2009 to 2016 and 184 quiet (no bursts) spectrum images before and after the type II bursts. As a result, our model successfully detected 79 events (93%) of type II events. This results demonstrates, for the first time, that the 1-D CNN algorithm is useful for detecting type II bursts.

• Journal of The Korean Association For Science Education
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• v.26 no.4
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• pp.527-536
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• 2006

This study investigated the components of science teacher professionalism, the meaning of PCK (Pedagogical Content Knowledge), examples of science PCK, and complementary measures that should be taken to improve teacher professionalism. Six science teachers recommended by their colleagues explained that the science teacher's professionalism (or professional knowledge) consists of science content knowledge, knowledge about teaching, knowledge about learners, and improvement efforts. Science teachers' definition of PCK, which is the professional knowledge that members of the wider society expect teachers to possess, is the teacher's materialized knowledge that aims at students' understanding and PCK is the accumulated know-how of teachers as they strive to make their teaching comprehensible by students. Science teachers also contended that teachers as professionals need to complement an accountability system, acknowledgement of continuous self-developmental efforts, collegiality, and securing validity in the teacher employment test. The teachers argued that the societal recognition of teaching professionalism is essential for a high quality teaching. Suggestions for how to improve science teaching professionalism are also discussed.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.13 no.3
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• pp.280-285
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• 2008

Manganese nodule abundance estimated based on operation of a Free Fall Grab(FFG) needs to be corrected to make up for its incomplete recovery of nodule, because FFGs can not recover all the nodules distributed on seabed. The correction factor for nodule abundance was proposed as 1.29 and 1.13 in 1994 and 2002, respectively, mainly based on the analyses of seabed images. In this study we collected manganese nodules using both FFG and Box Corer(BC) at same stations to examine the accuracy of the previous correction factors. It was found that the nodule recovery of the BC was 1.4 times greater than that of the FFG at the same sampling station, suggesting the necessity of re-evaluation of the previously proposed correction factor for FFG. More extensive sampling and improvement of image analysis method are required to improve the precision of nodule abundance correction factor for FFG.

• Korean Journal of Environment and Ecology
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• v.38 no.1
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• pp.79-89
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• 2024

The purpose of this study was to evaluate the area adjustment criteria and methods of the feasibility study of national park plans by applying them to Hallyeohaesang National Park. As a result of the ecological-based assessment used to identify the adjustment target areas, the ecological-based assessment Grades I and II that can be considered for inclusion were analyzed as 10.0% and 40.4%, respectively. Grade V, which can be considered for release, was 9.9%. As a result of the inclusion and release suitability assessment, the area subject to inclusion was 35.150 km² (3.669 km² on land and 31.481 km² at sea), and the area subject to release was 0.071 km² on land. When local governments and residents request the release of a park area for public interest or convenience, the release can be considered as long as the total area does not change, which is called a mutual exchange. The release area determined by mutual exchange was 10.386 km². It was 146 times the area determined by the suitability assessment for release. Matching the areas released by the mutual exchange with the ecological-based assessment, 70.6% (7.321 km²) was in Grades I and II, which can never be released. As a result, it was determined that the area adjustment of the feasibility study of Hallyeohaesang National Park was based on a very limited application of the results of the ecological-based assessment or the release suitability assessment. Also, mutual exchange was the key to area adjustment of the feasibility studies of national parks.

• Tunnel and Underground Space
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• v.34 no.5
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• pp.461-476
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• 2024

As the paradigm of urban development has recently changed to development of underground space, the road tunnels and railway tunnels are increasing to relieve traffic congestion. This technical notes is related to the development of underground spaces using NATM (New Austrian Tunneling Method). Limitations of conventional 2D blasting pattern design method were analyzed, and BIM-based automatic design method was developed to overcome them. Since it was developed to facilitate modeling of all safety facilities along a alignment using coordinates and GIS data, it can overcome the limitations of the number of safety facilities that can be considered and time required for conventional design. In the conventional design, the results of borehole test blasting were used to predict the blasting impact. However, the developed technology is possible to recalculate by applying the measurement results obtained from actual tunnel blasting, enabling rapid re-evaluation of the blasting impact on all safety facilities during construction, leading economical design. As a result of applying it to GTX-A5 and 6 sites, it took about 5 minutes, which is 1/480 compared to the conventional design method. In addition, the construction cost was reduced by about 8 billion won/km and the period was reduced by about 41 days/km. It is expected to be used as technical basis for calculating the optimal blasting pattern in the BIM-based design and construction management process.

• Journal of Wind Energy
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• v.13 no.4
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• pp.26-41
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• 2022

Three similarities (i.e., geometrical similarity, kinematic similarity and dynamic similarity) between a prototype and model must be satisfied to perform an experiment for a floating offshore wind turbine (FOWT). For dynamic similarity, most of the model tests in ocean engineering basins are performed based on the Froude number, so the scale effect for the wind turbine of an FOWT occurs by different Reynolds numbers between the prototype and model. In this study, various model test techniques for overcoming the scale effect of the wind turbine part of the FOWT are investigated. Firstly, model test techniques using simple approaches are reviewed, and the advantages and disadvantages of the simple approaches are summarized. Secondly, the model test techniques in recent projects that apply improved approaches are introduced including advantages and disadvantages. Finally, new approaches applying digitalization are reviewed, and the characteristics of the new approaches are introduced.

• Korean Circulation Journal
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• v.54 no.11
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• pp.743-756
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• 2024

Background and Objectives: Although various cardiac parameters on echocardiography have clinical importance, their measurement by conventional manual methods is time-consuming and subject to variability. We evaluated the feasibility, accuracy, and predictive value of an artificial intelligence (AI)-based automated system for echocardiographic analysis in patients with ST-segment elevation myocardial infarction (STEMI). Methods: The AI-based system was developed using a nationwide echocardiographic dataset from five tertiary hospitals, and automatically identified views, then segmented and tracked the left ventricle (LV) and left atrium (LA) to produce volume and strain values. Both conventional manual measurements and AI-based fully automated measurements of the LV ejection fraction and global longitudinal strain, and LA volume index and reservoir strain were performed in 632 patients with STEMI. Results: The AI-based system accurately identified necessary views (overall accuracy, 98.5%) and successfully measured LV and LA volumes and strains in all cases in which conventional methods were applicable. Inter-method analysis showed strong correlations between measurement methods, with Pearson coefficients ranging 0.81-0.92 and intraclass correlation coefficients ranging 0.74-0.90. For the prediction of clinical outcomes (composite of all-cause death, re-hospitalization due to heart failure, ventricular arrhythmia, and recurrent myocardial infarction), AI-derived measurements showed predictive value independent of clinical risk factors, comparable to those from conventional manual measurements. Conclusions: Our fully automated AI-based approach for LV and LA analysis on echocardiography is feasible and provides accurate measurements, comparable to conventional methods, in patients with STEMI, offering a promising solution for comprehensive echocardiographic analysis, reduced workloads, and improved patient care.

• Journal of radiological science and technology
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• v.31 no.2
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• pp.129-134
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• 2008

Purpose: We examined the roles of Ultrasonography conductors by analyzing the results of tissue biopsy of complex cystic masse under the guidance of breast US. Objects and methods: This study was performed to a group of 178 who showed breast US indicating complex cystic masses among 342 patients who were definitely diagnosed by tissue biopsies and operations in our hospital from June 30th, 2003 to June 30th, 2007. The evaluation of tissues around, calcification, the distribution state of blood flow were excluded from the analysis subjects and logic 200 made by GE corporation and gun for core biopsy(Kimal corp., K7/MBD23) were used in this study. Results: The biopsy results of 178 subjects showed FCC (fibrocystic change)(n=56 : 31.4%), Fibrosis (n=41 : 23.0%), Fibroadenoma (n=20 : 11.2%), Epithelial hyperplasia (n=17 : 9.6%), Carcinoma (n=15 : 8.4%), Fibroadipose (n=8 : 4.5%), Sclerosing adenosis (n=7 : 3.9%), Duct ectasia (n=5 : 2.8%), Papiloma (n=5 : 2.8%), and Fat necrosis (n=1 : 0.6%), Hemangioma (n=1 : 0.6%), Abscess (n=1 : 0.6%), Dystrophic calcification(n=1 : 0.6%). Conclusion: The US showed that the results of the tissue biopsy of complex cystic masses were mostly carcinoma(8.4%). Most of them were benign and only 9.6% of epithelial hyperplasia which has high progression rate into malignant tumors epidemically showed malignancy. Most of them were included in the spectrum of fibrous cystic nodule. Even though these results are confirmed, further studies are required. As a result, a nodule which is not certified by US should be right to take the tissue biopsy, but if it's difficult due to patients or another reasons, re-check tests in three months are required. And systemic ultrasonography evaluation should be well recognized to conduct more careful and specific tests.