• Journal of the Korean earth science society
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• v.42 no.2
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• pp.164-174
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• 2021

The study examines the shearing and crushing characteristics of land-derived subaqueous granular materials in a gravel-bed river. A series of large-sized ring shear tests were performed to examine the effect of shear time and shear velocity on the shear stress characteristics of aquarium gravels with a 6-mm mean grain size. Three different shear velocities (i.e., 0.01, 0.1, and 1 mm/sec) were applied to measure the shear stress under the drained (long-term shearing) and undrained (short-term shearing) conditions. Different initial shear velocities, i.e., 0.01→0.1→1 mm/sec and 0.1→0.01→1 mm/sec, were considered in this study. The test results show that the grain crushing effect is significant regardless of drainage conditions. The shear stress of coarse-grained materials is influenced by initial shear velocities, regardless of the drainage conditions. In particular, particle breakage increases as grain size increases. The shearing time and initial shear velocity are the primary influencing factors determining the shear stress of gravels. The granular materials may be broken easily into particles through frictional resistance, such as abrasion, interlocking and fracture due to the particle-particle interaction, resulting in the high mobility of granular materials in a subaqueous environment.

• Journal of the Korean Geotechnical Society
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• v.26 no.3
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• pp.35-45
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• 2010

The mechanism of load transfer by punching shear in pile-supported embankments is investigated. Based on the geometric configuration of the punching shear observed in sand fills on soft ground, a theoretical analysis is carried out to predict the embankment loads transferred on a cap beam according to punching shear developed in pile-supported embankments. The equation presented by the theoretical analysis was able to consider the effect of various factors affecting the vertical loads transferred on the cap beam. The reliability of the presented theoretical equation is investigated by comparing it with the results of a series of model tests. The model tests were performed on cap beams, which had two types of width; one is narrow width and the other is wide width. Sand filling was performed through seven steps. Two types of loading pattern were applied at each filling step; one is the long-term loading, in which sand fills at each filling step were kept for 24 hours, the other is the short-term loading, in which sand fills at each filling step were kept for 2 hours. The vertical loads measured in all model tests show good agreement with the ones predicted by the theoretical equation. Finally, the predicted vertical loads also show good agreement with the vertical loads measured in a well-instrumented pile-supported embankment in field, where cap beams were placed on too wide space.

• The Journal of the Convergence on Culture Technology
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• v.10 no.1
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• pp.165-170
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• 2024

'K-contents' is in the spotlight worldwide. As the prefix 'K' became popular, interest in K-food(Korean food) also increased. Various studies on K-contents are being conducted, but research on K-food is still very limited. References and articles about K-food are mainly limited to the overseas expansion, marketing status, and sales of domestic brands, and a few research papers deal with only cases of a specific brand's overseas expansion. This paper aims to analyze how K-food is represented in TV unscripted shows and TV series produced in Korea and what their effects are through empirical works. Among the unscripted shows based on food, they are estimated that the point of competitiveness as K contents deal with foreigners' Korean food experiences. Representative examples here are the way foreigners who visit Korea experience Korean food as part of their Korean culture experience, or the type of temporarily setting up a restaurant overseas to sell Korean food to local people. However, the problem with such shows are that it lacks long-term appeal because it is based on the 'Gukbbong(a slang term for 'extreme nationalism')' sentiment. The exposure of K-food in K-contents creates a tremendous advertising effect. It is judged that the current status and analysis of K-contents based on K-food can help establish the direction of future program production and the identity of K-food.

• Journal of Korean Society of Disaster and Security
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• v.12 no.2
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• pp.73-82
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• 2019

Recently, as the occurrence frequency of sudden floods due to climate change increased, the flood damage on riverside social infrastructures was extended so that there has been a threat of overflow. Therefore, a rapid prediction of potential flooding in riverside social infrastructure is necessary for administrators. However, most current flood forecasting models including hydraulic model have limitations which are the high accuracy of numerical results but longer simulation time. To alleviate such limitation, data driven models using artificial neural network have been widely used. However, there is a limitation that the existing models can not consider the time-series parameters. In this study the water surface elevation of the Hangang River bridge was predicted using the NARX model considering the time-series parameter. And the results of the ANN and RNN models are compared with the NARX model to determine the suitability of NARX model. Using the 10-year hydrological data from 2009 to 2018, 70% of the hydrological data were used for learning and 15% was used for testing and evaluation respectively. As a result of predicting the water surface elevation after 3 hours from the Hangang River bridge in 2018, the ANN, RNN and NARX models for RMSE were 0.20 m, 0.11 m, and 0.09 m, respectively, and 0.12 m, 0.06 m, and 0.05 m for MAE, and 1.56 m, 0.55 m and 0.10 m for peak errors respectively. By analyzing the error of the prediction results considering the time-series parameters, the NARX model is most suitable for predicting water surface elevation. This is because the NARX model can learn the trend of the time series data and also can derive the accurate prediction value even in the high water surface elevation prediction by using the hyperbolic tangent and Rectified Linear Unit function as an activation function. However, the NARX model has a limit to generate a vanishing gradient as the sequence length becomes longer. In the future, the accuracy of the water surface elevation prediction will be examined by using the LSTM model.

• The Journal of Engineering Geology
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• v.32 no.4
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• pp.697-723
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• 2022

Data-driven models to predict groundwater levels 30 days in advance were developed for 12 groundwater monitoring stations in the middle-Jeju watershed, Jeju Island. Stacked long short-term memory (stacked-LSTM), a deep learning technique suitable for time series forecasting, was used for model development. Daily time series data from 2001 to 2022 for precipitation, groundwater usage amount, and groundwater level were considered. Various models were proposed that used different combinations of the input data types and varying lengths of previous time series data for each input variable. A general procedure for deep-learning-based model development is suggested based on consideration of the comparative validation results of the tested models. A model using precipitation, groundwater usage amount, and previous groundwater level data as input variables outperformed any model neglecting one or more of these data categories. Using extended sequences of these past data improved the predictions, possibly owing to the long delay time between precipitation and groundwater recharge, which results from the deep groundwater level in Jeju Island. However, limiting the range of considered groundwater usage data that significantly affected the groundwater level fluctuation (rather than using all the groundwater usage data) improved the performance of the predictive model. The developed models can predict the future groundwater level based on the current amount of precipitation and groundwater use. Therefore, the models provide information on the soundness of the aquifer system, which will help to prepare management plans to maintain appropriate groundwater quantities.

• The Journal of Industrial Distribution & Business
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• v.9 no.5
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• pp.63-72
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• 2018

Purpose - This work analyzes, in detail, the specification of vector error correction model (VECM) and thus examines the relationships and impact among seven economic variables for USA - balance on current account (BCA), index of stock (STOCK), gross domestic product (GDP), housing price indices (HOUSING), a measure of the money supply that includes total currency as well as large time deposits, institutional money market funds, short-term repurchase agreements and other larger liquid assets (M3), real rate of interest (IR_REAL) and household credits (LOAN). In particular, we search for the main explanatory variables that have an effect on stock and real estate market, respectively and investigate the causal and dynamic associations between them. Research design, data, and methodology - We perform the time series vector error correction model to infer the dynamic relationships among seven variables above. This work employs the conventional augmented Dickey-Fuller (ADF) and Phillips-Perron (PP) unit root techniques to test for stationarity among seven variables under consideration, and Johansen cointegration test to specify the order or the number of cointegration relationship. Granger causality test is exploited to inspect for causal relationship and, at the same time, impulse response function and variance decomposition analysis are checked for both short-run and long-run association among the seven variables by EViews 9.0. The underlying model was analyzed by using 108 realizations from Q1 1990 to Q4 2016 for USA. Results - The results show that all the seven variables for USA have one unit root and they are cointegrated with at most five and three cointegrating equation for USA. The vector error correction model expresses a long-run relationship among variables. Both IR_REAL and M3 may influence real estate market, and GDP does stock market in USA. On the other hand, GDP, IR_REAL, M3, STOCK and LOAN may be considered as causal factors to affect real estate market. Conclusions - The findings indicate that both stock market and real estate market can be modelled as vector error correction specification for USA. In addition, we can detect causal relationships among variables and compare dynamic differences between countries in terms of stock market and real estate market.

• The KIPS Transactions:PartB
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• v.14B no.7
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• pp.531-540
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• 2007

In this research, we proposed a two-phase hybrid stock price forecasting model with cointegration tests and artificial neural networks. Using not only the related stocks to the target stock but also the past information as input features in neural networks, the new model showed an improved performance in forecasting than that of the usual neural networks. Firstly in order to extract stocks which have long run relationships with the target stock, we made use of Johansen's cointegration test. In stock market, some stocks are apt to vary similarly and these phenomenon can be very informative to forecast the target stock. Johansen's cointegration test provides whether variables are related and whether the relationship is statistically significant. Secondly, we learned the model which includes lagged variables of the target and related stocks in addition to other characteristics of them. Although former research usually did not incorporate those variables, it is well known that most economic time series data are depend on its past value. Also, it is common in econometric literatures to consider lagged values as dependent variables. We implemented a price direction forecasting system for KOSPI index to examine the performance of the proposed model. As the result, our model had 11.29% higher forecasting accuracy on average than the model learned without cointegration test and also showed 10.59% higher on average than the model which randomly selected stocks to make the size of the feature set same as that of the proposed model.

• Clinics in Shoulder and Elbow
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• v.14 no.1
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• pp.117-124
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• 2011

Purpose: We reviewed arthroscopic reconstruction among the several treatment options for anterior shoulder instability with a bony Bankart lesion. Materials and Methods: Although open Bankart repair has long been considered the optimal surgical management of anterior shoulder instability, advancements in arthroscopic techniques have led to a recent shift to arthroscopic Bankart repair. However, for cases of a glenoid bony defect, several authors have reported various methods to accurately measure the amount of bony defect. Results: The arthroscopic technique of bony Bankart reconstruction continues to evolve and various methods have followed. To overcome the limitations of single fixation of a Bankart lesion, arthroscopic dual fixation (2 point fixation) has recently been tried to anatomically repair and restore the rigid fixation of a bony fragment. The concept of performing the Bristow-Latarjet transfer procedure under arthroscopy has also recently emerged. However, a large series of cases and long term follow up are required to prove the better results. Conclusion: To obtain a successful outcome for patients with anterior instability with a glenoid bony defect, it is imperative that the surgeon be aware of the accurate status of the bony defect and the intraoperative, postoperative factors associated with the proper treatment of this unstable pathology.

• The Journal of the Acoustical Society of Korea
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• v.34 no.1
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• pp.20-35
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• 2015

Underwater acoustic channel impulse responses (CIR) are influenced by sound speed profile (SSP), and the variation of CIR has significant effects on the performance of underwater acoustic communication systems. A significant change of SSP can occur within a short period, which must be considered during the design of underwater acoustic modems. This paper statistically analyzes the effect of the variation of SSP on the long-range acoustic signal propagation in shallow-water with thermocline using numerical modeling based on the data acquired from JACE13 experiment near Jeju island. The analysis result shows that CIR changes variously according to the SSP and the depth of the transmitter and receiver. We also found that when the transmitter and receiver are deeper, the variation of sound wave propagation pattern is smaller and signal level becomes higher. All CIR obtained in this study show that a series of bottom reflections due to downward refraction and small bottom loss in the shallow water with thermocline can be very important factor for long-range signal transmission and the performance of underwater acoustic communication system in time varying ocean environment can be very sensitive to the variation of SSP even for a short period of time.

• Archives of Plastic Surgery
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• v.38 no.5
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• pp.669-673
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• 2011

Purpose: The authors have conducted a series of anatomic studies on the factors affecting shape of a lower vault in Asian noses. The results of the studies showed that prominence of alar lobule is mainly affected by the volumes of the dilator naris anterior and posterior muscles and the insertions of the dilator naris posterior muscles. However, information on its clinical availability is yet insufficient. The present study was undertaken for clinical purpose to find out the effect of dilator naris muscle resection on the correction of prominent alar lobule. Methods: Six patients who were treated by dilator naris muscle resection with a long-term follow-up of more than 1 year were involved in this study. Rhinoplasties were performed via endonasal approaches with resecting dilator naris anterior and posterior muscles by sharp scissor. The effect of the dilator naris muscle resection on alar prominence was investigated by measuring ratio of the short axis to the long axis of a nostril (SA/LA) pre-and postoperatively. The visual analog scale (VAS) was also used to evaluate satisfaction of patients. An average follow-up time was $15.6{\pm}3.7$ months. Results: Having lost the dilating and lateral pulling effects of the dilator naris muscles, the alar lobule shifted medially and alar lobule shapes improved. SA/LA significantly improved (preoperatively $0.71{\pm}0.11$ and postoperatively $0.58{\pm}0.08$; $p$ <0.05). The VAS score was also increased postoperatively (preoperatively $3.2{\pm}1.8$ and postoperatively $8.7{\pm}1.2$; $p$ <0.05). A mild degree of hyperpigmented scar was noted in one alar lobule. Otherwise, there was no case of postoperative complication. Conclusion: Our results suggest that prominent alar lobule could be modified by resecting the attachment of the dilator naris muscles. This maneuver removes the function of dilator naris muscles, then may produce a more aesthetically acceptable alar lobule shape.