• Analytical Science and Technology
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• v.13 no.4
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• pp.504-510
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• 2000

The impurity profiles from the raw materials of glycyrrhizin were performed by the high performance liquid chromatography (HPLC)/electrospray ionization (ESI)- mass spectrometry (MS). For the HPLC experiment, a $C_{18}$($3.9{\times}300mm$, $10{\mu}m$) column was used and the mobile phase was acetic acid/$H_2O$ (1:10):acetonitrile=3:2 with a flow rate of 0.8 ml/min. The effluent was splitted into the ratio of 50:1 and went into the ESI-MS. Three to six impurities were found and informed of the identification of the structure of the impurities by ESI-MS. And the structures of impurities were suggested to a hydroxy-glycyrrhizin which is added with hydroxy group (-OH) in the glycyrrhetic acid moiety and a reduced-glycyrrhizin which the position of 12 of the glycyrrhetic acid moiety is reduced. The purities of the standard materials were about 90%.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.6
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• pp.2593-2600
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• 2013

The main purpose of this study is to carry out the performance evaluation of Ultra-light Fixed Wing UAV(Unmanned Aerial Vehicle) photogrammetry which is being, currently, applied for various fields such as cultural assets, accident survey, military reconnaissance work, and disaster management at home and abroad. Firstly, RMSE estimation of Aerial Triangulation (AT) are within approximately 0.10 cm in position (X, Y). And through the comparison of parcel's boundary points coordinates by terrestrial surveying and by UAV photogrammetry, the analysis shows that RMSE are shifted approximately 0.174~0.205 m in X-direction, 0.294~0.298 m in Y-direction respectively. Lastly, parcel's area by orthophoto of UAV photogrammetry and by that of cadastre register has been shown the difference by 0.118 m2. The results presented in this study is just one case study of orthophoto accuracy assessment of Ultra-light fixed wing UAV photogrammetry, hereafter various researches such as AT, direct-georeferencing, flight planning, practical applications, etc. should be necessary continuously.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.5 no.1
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• pp.47-52
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• 2011

The functional loot orthoses, when wearing shoes, are in the direct contact with bottom of foots to improve and recover the correctness of abnormal lower limb musculoskeletal imbalance and the primary role of foot and also, it can act to keep the balance and weight of body and support the weakened region, so that it is very helpful to keep body balance for the standing position. In this paper, it was researched that foot orthoses which is accommodable for the function of impact absorption including the gait stability affect on the balanced performances of body in according to the formation and the material of foot part. Taking into account the balanced performances by using the sway velocity, the estimation and comparison of the effects on the balanced performances by each formation and material for foot orthoses was evaluated into significant values(p<0.006) in only the eye-opening posture with Firm state, In this posture, the static process performed by each foot formation reveals in order of normal foot(p<0.010), flat foot(p<0.000) and hollow foot(p<0.003) and then, on the base of each formation of foot part, the result that analyze the effects of the materials of foot orthoses on the balance performance appeared showing that soft materials is more effective on the normal foot and, on the other hand, rigid materials is more effective in balancing on flat foot and hollow foot.

• Journal of the Korean Geotechnical Society
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• v.29 no.6
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• pp.5-17
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• 2013

Slug tests can be adopted to estimate hydraulic conductivity of the slurry trench wall backfill for its abilities to reflect the in-situ performance of the construction. A comprehensive three-dimensional numerical model is developed to simulate the slug test in a slurry trench wall considering the presence of bentonite cake on the interface boundaries between the wall and the surrounding soil formation. Influential factors such as wall width (i.e., proximity of wall boundary), well deviation, vertical position of well intake section, compressibility of wall backfill, etc. are taken into account in the model. A series of simulation results are examined to evaluate the bentonite cake effect in analyzing practical slug test results in the slurry trench wall. The results show that the modified line-fitting method can be used without any correction factor for the slug test in the slurry trench wall with the presence of bentonite cake. A case study is reanalyzed with the assumption of existing bentonite cake. The results are compared with the previously reported results by the approaches assuming no bentonite cake (constant-head boundary) or upper-bound solution (no-flux boundary). The case study demonstrates the bentonite cake effect and the validity of the modified line-fitting method in the estimation of the hydraulic conductivity of the slurry wall backfill.

• Journal of Korean Society of Forest Science
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• v.107 no.2
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• pp.184-192
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• 2018

In this study was implemented to develop tree stem weight prediction equation of Larix kaempferi in central region by selecting a standard site, taking into account of diameter and position of the local trees. Fifty five sample trees were selected in total. By utilizing actual data of the sample trees, 11 models were compared and analyzed in order to estimate four different kinds of weights which include fresh weight, ovendry outside bark weight, ovendry inside bark weight and merchantable weight. As to estimate its weight, the study has classified its model according to three parameters: DBH, DBH and height, and volume. The optimal model was chosen by comparing the performance of model using the fit index and standard error of estimate and residual distribution. As a result, the formula utilizing DBH (Variable 1) is $W=a+bD+cD^2$ (3) and its fit index was 90~92%. The formula for DBH and height (Variable 2) is $W=aD^bH^C$ (8) and its fit index was 97~98%. In summation, Variable 2 model showed higher fitness than Variable 1 model. Moreover, fit index of formula for total volume and merchantable volume (W=aV) showed high rate of 98~99%, as well as resulting 7.7-17.5 with SEE and 8.0-10.0 with CV(%) which lead to predominately high fitness in conclusion. This study is expected to provide information on weights for single trees and furthermore, to be used as a basic study for weight of stand unit and biomass estimation equations.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.10
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• pp.581-588
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• 2020

This study examined a brake pad wear compensation method for an Electro-Mechanical Brake (EMB) using the braking test device. A three-phase Interior Permanent Magnet Synchronous Motor (IPMSM) was applied to drive the actuator of an EMB. Current control, speed control, and position control were used to control the clamping force of the EMB. The wear compensation method was performed using a software algorithm that updates the motor model equation by comparing the motor output torque current with a reference current. In addition, a simple first-order motor model equation was applied to estimate the output clamping force. The operation time to the maximum clamping force increased within 0.1 seconds compared to the brake pad in its initial condition. The experiment verified that the reference operating time was within 0.5 seconds, and the maximum value of the clamping force was satisfied under the wear condition. The wear compensation method based on the software algorithm in this paper can be performed in the pre-departure test of rolling stock.

• Journal of Navigation and Port Research
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• v.43 no.3
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• pp.172-178
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• 2019

Although the needs for providing resilient PNT information are increasing, threats due to the intentional RFI or space weather change are challenging to resolve. eLoran, which is a terrestrial navigation system that use a high-power signal is considered as a best back-up navigation system. Depending on the user's environment in the eLoran system, the user may use one of E-field or H-field antennas. H-field antenna, which has no restriction on setting stable ground and is relatively resistant to noise of general electronic equipment, is composed of two loops, and shows anisotropic gain pattern due to the different measurement at the two loops. Therefore, the H-field antenna's phase estimation value of signal varies depending on its direction even at the static environment. The error due to the direction of the signal should be eliminated if the user want to estimate the own position more precisely. In this paper, a method to compensate the error according to the geometric distribution between the H-field antenna and the transmitting station is proposed. A model was developed to compensate the directional error of H-field antenna based on the signal generated from the eLoran signal simulator. The model is then used to the survey measurement performed in the land area and verify its performance.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.7
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• pp.430-439
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• 2019

In this study, a nonlinear impact analysis was performed to evaluate the safety and damage of an eco-pillar debris barrier with a hollow cross-section, which was proposed to improve constructability and economic efficiency. The construction of concrete eco-pillar debris barriers has increased recently. However, there are no design standards concerning debris barriers in Korea, and it is difficult to find a study on performance evaluations in extreme environments. Thus, an analysis of an eco-pillar debris barrier was done using the rock impact speed, which was estimated from the debris flow velocity. The diameters of rocks were determined by ETAG 27. The impact position, angles, and rock diameter were considered as variables. A concrete nonlinear material model was applied, and the estimation of damage was done by ABAQUS software. As a result, the damage ratio was found to be less than 1.0 at rock diameters of 0.3 m and 0.5 m, but it was 1.39 when the diameter was 0.7 m. This study could be used as basic data on impact force in the design of the cross section of an eco-pillar debris barrier.

• The Journal of the Acoustical Society of Korea
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• v.43 no.1
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• pp.29-38
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• 2024

The Matched Field Processing (MFP) is an estimation method for a source range and depth based on the prediction of sound propagation. However, as the frequency increases, the prediction inaccuracy of sound propagation increases, making it difficult to estimate the source position. Recently proposed, the Frequency-Difference Matched Field Processing (FD-MFP) is known to be robust even if there is a mismatch by applying a frequency-difference autoproduct extracted from the auto-correlation of a high frequency signal. In this paper, in order to evaluate the performance of the FD-MFP using a horizontal line array, simulations were conducted in the environment of the East Sea of Korea. In the area of Bottom Bounce (BB) and Convergence Zone (CZ) where detection of a sound source is possible at a long range, and the results of localization were analyzed. According to the the FD-MFP simulations of horizontal line array, the accuracy of localization is similar or degraded compared to the conventional MFP due to diffracted field and mismatch of sound speed. There was no clear result from the simulations conforming that the FD-MFP was more robust to mismatch than the conventional MFP.

• Journal of Intelligence and Information Systems
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• v.16 no.2
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• pp.19-32
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• 2010

Volatility plays a central role in both academic and practical applications, especially in pricing financial derivative products and trading volatility strategies. This study presents a novel mechanism based on generalized autoregressive conditional heteroskedasticity (GARCH) models that is able to enhance the performance of intelligent volatility trading systems by predicting Korean stock market volatility more accurately. In particular, we embedded the concept of the volatility asymmetry documented widely in the literature into our model. The newly developed Korean stock market volatility index of KOSPI 200, VKOSPI, is used as a volatility proxy. It is the price of a linear portfolio of the KOSPI 200 index options and measures the effect of the expectations of dealers and option traders on stock market volatility for 30 calendar days. The KOSPI 200 index options market started in 1997 and has become the most actively traded market in the world. Its trading volume is more than 10 million contracts a day and records the highest of all the stock index option markets. Therefore, analyzing the VKOSPI has great importance in understanding volatility inherent in option prices and can afford some trading ideas for futures and option dealers. Use of the VKOSPI as volatility proxy avoids statistical estimation problems associated with other measures of volatility since the VKOSPI is model-free expected volatility of market participants calculated directly from the transacted option prices. This study estimates the symmetric and asymmetric GARCH models for the KOSPI 200 index from January 2003 to December 2006 by the maximum likelihood procedure. Asymmetric GARCH models include GJR-GARCH model of Glosten, Jagannathan and Runke, exponential GARCH model of Nelson and power autoregressive conditional heteroskedasticity (ARCH) of Ding, Granger and Engle. Symmetric GARCH model indicates basic GARCH (1, 1). Tomorrow's forecasted value and change direction of stock market volatility are obtained by recursive GARCH specifications from January 2007 to December 2009 and are compared with the VKOSPI. Empirical results indicate that negative unanticipated returns increase volatility more than positive return shocks of equal magnitude decrease volatility, indicating the existence of volatility asymmetry in the Korean stock market. The point value and change direction of tomorrow VKOSPI are estimated and forecasted by GARCH models. Volatility trading system is developed using the forecasted change direction of the VKOSPI, that is, if tomorrow VKOSPI is expected to rise, a long straddle or strangle position is established. A short straddle or strangle position is taken if VKOSPI is expected to fall tomorrow. Total profit is calculated as the cumulative sum of the VKOSPI percentage change. If forecasted direction is correct, the absolute value of the VKOSPI percentage changes is added to trading profit. It is subtracted from the trading profit if forecasted direction is not correct. For the in-sample period, the power ARCH model best fits in a statistical metric, Mean Squared Prediction Error (MSPE), and the exponential GARCH model shows the highest Mean Correct Prediction (MCP). The power ARCH model best fits also for the out-of-sample period and provides the highest probability for the VKOSPI change direction tomorrow. Generally, the power ARCH model shows the best fit for the VKOSPI. All the GARCH models provide trading profits for volatility trading system and the exponential GARCH model shows the best performance, annual profit of 197.56%, during the in-sample period. The GARCH models present trading profits during the out-of-sample period except for the exponential GARCH model. During the out-of-sample period, the power ARCH model shows the largest annual trading profit of 38%. The volatility clustering and asymmetry found in this research are the reflection of volatility non-linearity. This further suggests that combining the asymmetric GARCH models and artificial neural networks can significantly enhance the performance of the suggested volatility trading system, since artificial neural networks have been shown to effectively model nonlinear relationships.