• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.4
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• pp.579-586
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• 2018

Short-term prediction of travel speed has been widely studied using data-driven non-parametric techniques. There is, however, a lack of research on the prediction aimed at urban areas due to their complex dynamics stemming from traffic signals and intersections. The purpose of this study is to develop a hybrid approach combining ensemble empirical mode decomposition (EEMD) and artificial neural network (ANN) for predicting urban travel speed. The EEMD decomposes the time-series data of travel speed into intrinsic mode functions (IMFs) and residue. The decomposed IMFs represent local characteristics of time-scale components and they are predicted using an ANN, respectively. The IMFs can be predicted more accurately than their original travel speed since they mitigate the complexity of the original data such as non-linearity, non-stationarity, and oscillation. The predicted IMFs are summed up to represent the predicted travel speed. To evaluate the proposed method, the travel speed data from the dedicated short range communication (DSRC) in Daegu City are used. Performance evaluations are conducted targeting on the links that are particularly hard to predict. The results show the developed model has the mean absolute error rate of 10.41% in the normal condition and 25.35% in the break down for the 15-min-ahead prediction, respectively, and it outperforms the simple ANN model. The developed model contributes to the provision of the reliable traffic information in urban transportation management systems.

• Journal of the Korean Geographical Society
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• v.49 no.3
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• pp.405-422
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• 2014

Two important issues in hedonic model are to specify accurate model and delineate submarkets. While the former has experienced much improvement over recent decades, the latter has received relatively little attention. However, the accuracy of estimates from hedonic model will be necessarily reduced when the analysis does not adequately address market segmentation which can capture the spatial scale of price formation process in real estate. Placing emphasis on improvement of performance in hedonic model, this paper tried to segment real estate markets in Gangnam-gu and Jungrang-gu, which correspond to most heterogeneous and homogeneous ones respectively in 25 autonomous districts of Seoul. First, we calculated variable coefficients from mixed geographically weighted regression model (mixed GWR model) as input for clustering, since the coefficient from hedonic model can be interpreted as shadow price of attributes constituting real estate. After that, we developed a spatially constrained data-driven methodology to preserve spatial contiguity by utilizing the SKATER algorithm based on a minimum spanning tree. Finally, the performance of this method was verified by applying a multi-level model. We concluded that submarket does not exist in Jungrang-gu and five submarkets centered on arterial roads would be reasonable in Gangnam-gu. Urban infrastructure such as arterial roads has not been considered an important factor for delineating submarkets until now, but it was found empirically that they play a key role in market segmentation.

• Journal of the Korean Society of Visualization
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• v.9 no.4
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• pp.47-53
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• 2011

A water driven ejector loop was designed and constructed for air absorption. The used ejector was horizontally installed in the loop and annular water jet at the throat entrained air through the circular pipe placed at the center of the ejector. Wide range of water flow rate was provided using two kinds of pumps in the loop. The tested range of water flow rate was 100${\ell}$ /min to 1,000 ${\ell}$/min. Two-phase flow inside the ejector loop was simulated by CFD analysis. Homogeneous particle model was used for void fraction prediction. Water and air flow rates and pressure drop through the ejector were automatically recorded by using the LabView based data acquisition system. Flow characteristics and air bubble velocity field downstream of the ejector were investigated by two-phase flow visualization and PIV measurement based on bubble shadow images. Overall performance of the two-phase ejector predicted by the CFD simulation agrees well with that of the experiment.

• The Journal of Asian Finance, Economics and Business
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• v.7 no.12
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• pp.941-949
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• 2020

This study aims to investigate the factors which impact the possibility of Environmental Management Accounting (EMA) implementation in automobile companies in Vietnam. A survey was carried out with automobile enterprises' managers, getting 198 usable respondents, with data and theoretical model analyzed by using SPSS with EFA method. Results indicated that in Vietnamese automobile enterprises, the possibility of EMA implementation was driven by elements including motivation to reduce production costs, reactions to environmental issues, compliance to legislation, procedures and processes in the working environment which they are in business. The government and professional institutions should play a vital role in promoting EMA practices by issuing specific guidelines and continuous training. Besides, tax authorities should apply the favor policies such as tax incentives to stimulate interest enterprises to implement EMA. However, this study's results only reflect about 63.7% of the impact to the implementation of EMA in Vietnamese automotive enterprises, so there are still some other factors that should be found out in the future researches. This is the first attempt to systematically analyze enterprises' perception and willingness to apply EMA in Vietnamese automobile industry. This study contributes to not only the existing empirical literature of EMA but also enterprises' managers in Vietnam and other transitional economies.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.35C no.4
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• pp.21-29
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• 1998

As silicon geometry shrinks into deep submicron and the operating speed icreases, higher accuracy is required in the analysis of the propagation delays of the gates and interconnects in an ASIC. In this paper, the driving characteristics of a CMOS gate is represented by a gatedriver model, consisting of a linear resistor $R_{dr}$ and an independent ramp voltage source $V_{dr}$ . We drivered $R_{dr}$ and $V_{dr}$ as the functions of the timing data representing gate driving capability and an effective capacitance $C_{eff}$ reflecting resistance shielding effect by interconnet circuits. Through iterative applications of these equations and AWE algorithm, $R_{dr}$ , $V_{dr}$ and $C_{eff}$ are comuted simulataneously. then, the gate delay is decided by $C_{eff}$ and the interconnect circuit delay is determined by $R_{dr}$ and $V_{dr}$ . this process has been implemented as an ASIC timing analysis program written in C language and four real circuits were analyzed. In all cases, we found less than 5% of errors for both of gate andinterconnect circuit delays with a speedup factor ranging from a few tens to a few hundreds, compared to SPICE.SPICE.

• Journal of The Korean Association of Information Education
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• v.9 no.3
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• pp.407-416
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• 2005

Considering teaching methods for computer education is a must for effectively instructing students of knowledge and skills on computers. In this paper, we adopts STAD Cooperative Learning method, among many others, in order to reduce any burden teachers and learners may have. As a result, it finds out that practical training based on STAD Cooperative Learning is very effective in enhancing students' abilities for ICT data collection and manipulation. The teaching model driven out as a result of this study, will be a good example for teaching models in many computer-related departments. In the future, more studies on teaching models will have to take place for more effective teaching of computer courses.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.3
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• pp.164-172
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• 2004

This paper presents the comparison results of some kinds of control method in circumstance of eccentric load. The plant to be controlled is a computed tomography(CT) driven by a permanent magnet synchronous motor. In a CT system, many units are attached on the rotationally part of a gantry such as x-ray tube, detector, heat exchanger, and data acquisition unit etc. Therefore keeping many components to balance which have different weight is not easy; this is inescapable problem in the all CT systems. To solve this problem against eccentric load, some kinds of control method have been compared and analysed by using protype CT. From the experimental results it is vilified that the CT drive system with model reference control method indicates higher speed regulation ability regardless of variable eccentric weight and uncertain position, and also in the limit condition of constant eccentric weight and fixed position, the compensation method with sinusoidal form is a strong candidate in view of speed ripple reduction.

• MALSORI
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• no.65
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• pp.93-103
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• 2008

In this paper, we propose a method for optimizing a multiple pronunciation dictionary used for modeling pronunciation variations of non-native speech. The proposed method removes some confusable pronunciation variants in the dictionary, resulting in a reduced dictionary size and less decoding time for automatic speech recognition (ASR). To this end, a confusability measure is first defined based on the Levenshtein distance between two different pronunciation variants. Then, the number of phonemes for each pronunciation variant is incorporated into the confusability measure to compensate for ASR errors due to words of a shorter length. We investigate the effect of the proposed method on ASR performance, where Korean is selected as the target language and Korean utterances spoken by Chinese native speakers are considered as non-native speech. It is shown from the experiments that an ASR system using the multiple pronunciation dictionary optimized by the proposed method can provide a relative average word error rate reduction of 6.25%, with 11.67% less ASR decoding time, as compared with that using a multiple pronunciation dictionary without the optimization.

• Geomechanics and Engineering
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• v.20 no.4
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• pp.345-358
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• 2020

Numerous studies have repeatedly demonstrated the efficiency of using skirts to increase the bearing capacity and to reduce settlement of shallow foundations subjected to static loads. However, no efforts have been made to study the efficiency of using these skirts to reduce settlement produced by machine vibration, although machines are very sensitive to settlement and the foundations of these machines should be designed properly to ensure that the settlement produced due to machine vibration is very small. This research has been conducted to investigate the efficiency of using skirts as a technique to reduce the settlement of a strip foundation subjected to machine vibration. A two-dimensional finite element model has been developed, validated, and employed to achieve the aim of the study. The results of the analyses showed that the use of skirts reduces the settlement produced due to machine vibration. However, the percentage decrease of the settlement is remarkably influenced by the density of the soil and the frequency of vibration, where it rises as the frequency of vibration increases and declines as the soil density rises. It was also found that increasing skirt length increases the percentage decrease of the settlement. Importantly, the results obtained from the analyses have been utilized to derive new dynamic impedance values that implicitly consider the presence of skirts. Finally, novel design equations of dynamic impedance that implicitly account to the effect of the skirts have been derived and validated utilizing a new intelligent data driven method. These new equations can be used in future designs of skirted strip foundations subjected to machine vibration.

• The Journal of Asian Finance, Economics and Business
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• v.7 no.9
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• pp.477-488
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• 2020

This study provides the empirical testing to test the influences of contemporary leadership styles (i.e., transactional and transformational) on job satisfaction and customer satisfaction as the mediating variable between job satisfaction and customer loyalty. The approach utilized in this study was a quantitative research design using a survey model. The participants of this study were recruited from 160 front-liners in the airline's industry in Indonesia. This study employed 160 front liners (flight attendants, reservation/ticketing, and check-in-counter officers) who worked in Branch Office/General Sales Agent of Indonesian commercial airlines. The studied airlines serve domestic routes based at Soekarno-Hatta International Airport. Furthermore, the data were examined the four developed hypotheses by using Structural Equation Modeling (SEM). The primary results are: First, in the context of job satisfaction, both leadership styles (i.e., transactional and transformational) have similar influences; Second, job satisfaction affects customer satisfaction positively and significant, Third, customer loyalty is driven by passengers' satisfaction when they are utilizing the airline services. The findings imply that the working-role encouragement is essential to maximize the productivity of front-liners to serve their customer well. This research supports on developing the general knowledge based on leadership styles in the context of the airline's industry in managing the human resources strategically.