• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.11
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• pp.1-8
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• 2011

In this paper, we study receiver design issue to apply the OFDM based WLAN specification, such as 802.11p, to the communications in high speed mobile environment, e.g., for the ICT based railroad control on a train having its speed up to 300 km/hr. To successfully apply the existing WLAN specifications without modifying its transmission format, the performance at the receiver will solely depends on the channel estimation performance if we ignore the affect of frequency offset With a speed of multiple hundred km/hr, the channel estimation using only the preamble will not provide enough precision since the channel changes so fast. Therefore, in this paper, taking the high mobility into account, we focus on the design of decision directed channel estimation and equalization techniques and perform simulations to evaluate and compare their performances and to finally confirm the applicability of the existing WLAN specification to the systems with very high mobility.

• Journal of the Korean Institute of Intelligent Systems
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• v.26 no.6
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• pp.452-457
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• 2016

In this paper, we propose a taxi safety support system using the beacon device to reduce the anxiety and increase the satisfaction of taxi passengers. At first, we design a USB-type low power beacon device that can be easily installed inside a taxi and propose a distance and estimation method using beacon signal strength. Mobile applications for passengers and drivers based on beacon signals are developed. The server operation program for situation recognition, position estimation, risk management and notification of the taxi passenger is also developed. An accident risk management method is proposed using the recognition of getting on and off of the taxi passenger. The proposed methods are verified for applicability and usefulness through practical experiments.

• Journal of the Korean GEO-environmental Society
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• v.20 no.12
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• pp.49-55
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• 2019

Slope failure analysis entails proper understanding of various factors as well as the characteristics of ground conditions, which are difficult to achieve due to technological limits. Despite a number of past studies to clarify possible factors triggering slope failures, the impact of rainfall characteristics and infiltration rate, which are the key to estimation of slope stability in wet condition, on slope failures still remains unclear. This study has estimated permeability against various unit weights of soil based on constant head permeability tests using Jumunjin standard silica sand. One dimensional infiltration tests were conducted to estimate the infiltration capacity and the amount of infiltration taking into account the permeability and rainfall intensity. The applicability of existing empirical equations for the estimation of infiltration to granular soils was verified on the basis of the test results.

• Korean Journal of Remote Sensing
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• v.33 no.5_2
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• pp.631-640
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• 2017

The estimation of rice yield affects the income of farmers as well as the fields related to agriculture. Moreover, it has an important effect on the government's policy making including the control of supply demand and the price estimation. Thus, it is necessary to build the crop yield estimation model and from the past, many studies utilizing empirical statistical models or artificial neural network algorithms have been conducted through climatic and satellite data. Presently, scientists have achieved successful results with deep learning algorithms in the field of pattern recognition, computer vision, speech recognition, etc. Among deep learning algorithms, the SSAE (Stacked Sparse AutoEncoder) algorithm has been confirmed to be applicable in the field of forecasting through time series data and in this study, SSAE was utilized to estimate the rice yield in South Korea. The climatic and satellite data were used as the input variables and different types of input data were constructed according to the period of rice growth in South Korea. As a result, the combination of the satellite data from May to September and the climatic data using the 16 day average value showed the best performance with showing average annual %RMSE (percent Root Mean Square Error) and region %RMSE of 7.43% and 7.16% that the applicability of the SSAE algorithm could be proved in the field of rice yield estimation.

• Journal of Korea Water Resources Association
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• v.50 no.1
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• pp.37-53
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• 2017

Pan evaporation has been used as an indirect method for the estimation of reservoir evaporation. Therefore, in this study, pan evaporation estimation equations using only temperature data were suggested in the case that available meteorological data is limited. A formula for estimating the pan evaporation were suggested by comparing estimated pan evaporation with measured pan evaporation in 12 study areas in Korea. The suggested pan evaporation equations were verified in 44 study areas by comparing not only with temperature-based equations but also with equations using other meteorological data (temperature, wind speed, relative humidity, and sunshine duration). The study results indicate that the suggested equations in this study provide much better pan evaporation estimates, compared with other temperature-based equations. Overall, the suggested equations provide appropriate pan evaporation estimates in most of 56 study areas. Therefore, the suggested equations using only temperature data in this study are considered appropriate for the estimation of pan evaporation in Korea especially in the case that available meteorological data is limited. In the future, using the air temperature and pan evaporation data measured at the reservoir, further research is needed to examine the applicability of suggested equations for the estimation of reservoir evaporation.

• Journal of Oral Medicine and Pain
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• v.39 no.2
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• pp.69-77
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• 2014

Purpose: It aims to verify the applicability of existing age estimation methods derived from data of foreign population groups to Korean population groups. Moreover it is to suggest a new way applicable to practical age estimation on the basis of newly calculated regression formulae from data of Korean population groups and develop a subsidiarily applicable method to the existing method. Methods: Ratio of pulp cavity to dental crown was calculated by measuring the height and width of dental crowns and pulp cavities at the cervical line from 4,034 first and second upper molars, first and second upper premolars, first and second lower molars and first and second lower premolars on both left and right sides of 400 patients who had been treated in Dental Hospital of Yonsei University College of Dentistry, and regression equations were derived from the values of the ratio. Results: The equation with correlation coefficients the highest among females was as follows: age=$107.96-75.684{\times}{\sharp}17$ TCHI-$53.741{\times}{\sharp}26$ TCVI-$40.664{\times}{\sharp}45$ TCVI-$56.307{\times}{\sharp}46$ TCVI. Randomized anohter Korean female subjects (n=20) are applicated to the new equation. Mean of error of estimate is 10.322 years, standard deviation is 12.852 years. Minimum of error of estimate is 1.018 years, maximum is 21.365 years Conclusions: The error range of age estimation was found to be slightly wider when the existing regression formulae of Drusini were applied to Korean population groups. Also age estimation in females using the ratio of pulp cavity to dental crown measured with the length and width of dental crowns and pulp cavities from maxillomandibular molars was observed to have the highest reliability in the research. However, we consider that advanced equations of regression are needed to apply to both molars and premolars of males and females in the future.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.7 no.6
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• pp.701-708
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• 2017

The construction cost is estimated based on the drawings at the design stage and constructor will find efficient construction methods for budgeting and budgeting appropriate to the budget. Accurate quantity estimation and budgeting are critical to determining whether the project is profitable or not. However, since this process is mostly performed depending on manpower or 2D drawings, errors are likely to occur and The BIM(Build Information Modeling) program, which can be automated, is very expensive and difficult to apply in the field. In this study, 3D architectural modeling was performed using SketchUp which is a 3D modeling software and suggest a methodology for Quantity Estimation. As a result, 3D modeling was performed effectively using 2D drawings of buildings. Based on the modeling results, it was possible to calculate the difference of the quantity estimation by 2D drawing and 3D modeling. The research suggests that the 3D modeling using the SketchUp and the calculation of the quantity can prevent the error of the conventional 2D calculation method. If the applicability of the research method is verified through continuous research, it will contribute to increase the efficiency of architectural modeling and quantity Estimation work.

• Journal of the Korean Society of Safety
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• v.32 no.1
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• pp.115-120
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• 2017

The aim of this study is to develop construction safety and health management cost prediction model using support vector machine (SVM). To this end, theoretical concept of SVM is investigated to formulate the cost prediction model. Input and output variables have been selected by analyzing the balancing accounts for the completed construction project. In order to train and validate the proposed prediction model, 150 data sets have been gathered from field. Effects of SVM parameters on prediction accuracy are analyzed and from which the optimal parameter values have been determined. The prediction performance tests are conducted to confirm the applicability of the proposed model. Based on the results, it is concluded that the proposed SVM model can effectively be used to predict the construction safety and health management cost.

• Korean Journal of Computational Design and Engineering
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• v.21 no.4
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• pp.443-452
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• 2016

This paper proposes a method for expensive black box optimization using radial basis functions (RBFs). The proposed algorithm is a computational strategy that uses a RBF model approximating the expensive black box function to predict an optimum. First, a RBF-based approximation technique is introduced and a sampling plan for estimation of the black box function is described. Then the proposed algorithm is explained, which presents the pseudo-codes for implementation and the detailed description of each step performed in the optimization process. In addition, numerical experiments will be given to analyze the performance of the proposed algorithm, by investigating computation accuracy, number of function evaluations, and convergence history. Finally, geometric distance problem as application example will be also presented for showing the algorithm applicability to different engineering problems.

• Wind and Structures
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• v.23 no.5
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• pp.385-403
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• 2016

The across-wind dynamic loads on L-shaped tall buildings with various geometric dimensions were investigated through a series of wind tunnel testing. The lift coefficients, power spectral densities and vertical correlation coefficients of the across-wind loads were analyzed and discussed in details. Taking the side ratio and terrain category as key variables, empirical formulas for estimating the across-wind dynamic loads on L-shaped tall buildings were proposed on the basis of the wind tunnel testing results. Comparisons between the predictions by the empirical formulas and the wind tunnel test results were made to verify the accuracy and applicability of the proposed formulas. Moreover, a simplified procedure to evaluate the across-wind dynamic loads on L-shaped tall buildings was derived from the proposed formulas. This study aims to provide a simple and reliable way for the estimation of across-wind dynamic loads on L-shaped tall buildings.