• Journal of Korean Society of Transportation
• /
• v.27 no.4
• /
• pp.115-126
• /
• 2009

The lane-change behavior usually consists of discretionary lane-change and mandatory lane-change types. For the first type, drivers change lanes selectively to maintain their own driving condition and the second type is the case that the drivers must change the current lane, which can occur in recurrent congestion sections like merging and weaving sections. The mandatory lane-change behavior have a great effect on the operation condition of freeway. In this paper, we first generate data such as traffic volumes, speeds, densities, and the number of lane-change within the merging and weaving sections using the data of individual vehicle collected from time-lapse aerial photography. And then, the data is divided into the stable and congested flow by analyzing the speed variation pattern of individual vehicles. In addition, the number of lane-changing from ramp to mainline within every 30-meter interval is investigated before and after traffic congestion at study sites and the distribution of lane-changing at each 30-meter point is analyzed to identify the variation of lane-changing ratio depending on the stable and congested flows. To recognize the effect of mainline flow influenced by ramp flow, this study also analyzes the characteristics of the lane-changing distributions within the lanes of mainline. The purpose of this paper is to present the basic theory to be used in developing a lane-changing model at the merging and weaving sections on freeways.

• KDI Journal of Economic Policy
• /
• v.32 no.2
• /
• pp.1-26
• /
• 2010

This paper empirically examines whether Korean monetary policy is independent of U.S. monetary policy during the post-crisis period in which capital account is liberalized and floating exchange rate regime is adopted and during the pre-crisis period in which capital mobility is restricted and tightly managed exchange rate regime is adopted. Before capital account liberalization, monetary autonomy can be achieved in view of the trillema, even under tightly managed exchange rate regime, as capital mobility is restricted. On the other hand, for the period after capital account liberalization, monetary autonomy can be also achieved in view of the trillema, as exchange rate stability is given up. Securing monetary autonomy, however, may not be easy under liberalized capital account for a small open economy like Korea. Huge capital movements can generate excessive instability in foreign exchange and asset markets. Strengthened international economic linkages may also be another factor to prevent monetary policy from being independent. Using block-exogenous structural VAR model, the effects of U.S. monetary policy shocks on Korean economy are examined. Empirical results show that Korean monetary policy is not independent of U.S. monetary policy for both periods before and after capital account liberalization. For the period after capital account liberalization, Korea does not seem to have implemented floating exchange rate policy in practice, which may lead Korean monetary policy to be dependent on U.S. monetary policy. For the period after capital account liberalization, portfolio flows respond dramatically to the U.S. monetary policy, which may also keep Korean monetary policy from being independent.

• Journal of the Korean Chemical Society
• /
• v.47 no.6
• /
• pp.553-558
• /
• 2003

The crystal structure of $[n-Bu_4N]_2[Mo_6O_{19}]$(TBAM) (n-Bu4N=tetrabutylammonium) has been determined by X-ray crystallography. It crystallizes in the monoclinic system, space group C2/c, with lattice parameters ${\alpha}$=16.314(5), b=17.288(5), c=17.776(4)${\AA}$ ${\beta}$=101.47(3), and Z=4. In $[Mo_6O{19}]^{2-}$ anion, Mo atoms occupy six vertices of octahedron and each Mo atom is coordinated by six oxygen atoms to adopt distorted octahedral coordination geometry. The average bond distance of Mo-Ot (terminal), Mo-Ob (bridged) and Mo-Oc (central) are 1.680 ${\AA}$, 1.931 ${\AA}$ and 2.325 ${\AA}$ respectively. In $[n-Bu_4N]^+$ cation, the N atom possesses a slightly distorted tetrahedral geometry. There are some potential extensive C-H ${\cdots}$ O hydrogen bonds in the lattice, by which connecte molecules and stabilize the crystal structure. Thermogravimetric analysis suggests that thermal decomposition of the title compound includes two transitions and it loses weight at 356.0 and 803.5 $^{\circ}$, respectively, and the residue presumable be $Mo_2O_2$. Accordingly, the title compound has high thermal stability.

• Journal of Korea Water Resources Association
• /
• v.48 no.5
• /
• pp.409-423
• /
• 2015

In this study the very short-term rainfall forecasting and storm water forecasting using the weather radar data were implemented in an urban stream basin. As forecasting time increasing, the very short-term rainfall forecasting results show that the correlation coefficient was decreased and the root mean square error was increased and then the forecasting model accuracy was decreased. However, as a result of the correlation coefficient up to 60-minute forecasting time is maintained 0.5 or higher was obtained. As a result of storm water forecasting in an urban area, the reduction in peak flow and outflow volume with increasing forecasting time occurs, the peak time was analyzed that relatively matched. In the application of storm water forecasting by radar rainfall forecast, the errors has occurred that we determined some of the external factors. In the future, we believed to be necessary to perform that the continuous algorithm improvement such as simulation of rapid generation and disappearance phenomenon by precipitation echo, the improvement of extreme rainfall forecasting in urban areas, and the rainfall-runoff model parameter optimizations. The results of this study, not only urban stream basin, but also we obtained the observed data, and expand the real-time flood alarm system over the ungaged basins. In addition, it is possible to take advantage of development of as multi-sensor based very short-term rainfall forecasting technology.

• Journal of the Korea Society for Simulation
• /
• v.29 no.2
• /
• pp.11-20
• /
• 2020

As the manufacturing environment becomes more complex, traditional simulation models alone are having a lot of difficulties in reflecting real-time manufacturing situations. Although the Digital Twin concept is actively discussed as an alternative to overcome theses issues, many studies are being carried out only in the product design phase. This research presents a Digital Twin-based manufacturing environment framework for applying the Digital Twin concept to the manufacturing process. Twin model that is operated in virtual space, physical system and databases describing the actual manufacturing environment, are proposed as detailed components that make up the framework. To check the applicability of proposed framework, a simple Digital Twin-based manufacturing system was simulated in a conveyor system using Arena software and Excel VBA. Experiment results have shown that the twin model is transmitted real time data from the physical system via DB and were operating in the same time unit. The Excel VBA fitted parameters defined by cycle time based on historical data that real-time and training data are being accumulated together. This study proposes operating method of digital twin model through the simple experiment examples. The results lead to the applicability of Digital twin model.

• Journal of The Korean Association For Science Education
• /
• v.36 no.3
• /
• pp.509-517
• /
• 2016

Previous studies have investigated the similarity between the development of evolutionary explanations and students' conceptual developments on evolution. However, the validity and reliability of the assessment method reflecting the similarity have not been quantitatively examined yet. In addition, no study has examined the conceptual progressions of evolution concept based on contexts although literature has addressed the contextual difference of evolutionary explanation in the history of science. This study examined the validity and reliability of history-of-science-based evolution concept assessment using ordered multiple choice (OMC) methods and Rasch analysis and explored conceptual progression by three contexts (e.g., human, animal, and plant). The evolution concept assessment developed by Ha (2007) was used to examine 1711 elementary, middle, and high school students, and pre- and in-service science teachers' (biology majors and non-majors) evolution concepts. Internal consistency reliability and item response fitness of the OMC method that provide 0- to 4-point scores to creationism, teleology, intentionality, use/disuse, and natural selection respectively met the benchmark based on the Cronbach alpha and MNSQ indices of Rasch analysis. The level of elementary and middle school students' evolution concepts were located between intentionality and use/disuse while the level of high school and non-biology science teachers' evolution concepts were located between use/disuse and natural selection. The conceptual progressions of evolution concepts were differentiated according to three contexts. This study provided the quantitative evidence for the similarity between the development of evolutionary explanations and students' conceptual developments on evolution and suggest new analysis methods (i.e., OMC) of evolution concept assessment.

• CRM연구
• /
• v.4 no.2
• /
• pp.19-29
• /
• 2011

There is a large difference between purchasing patterns in an online shopping mall and in an offline market. This difference may be caused mainly by the difference in accessibility of online and offline markets. It means that an interval between the initial purchasing decision and its realization appears to be relatively short in an online shopping mall, because a customer can make an order immediately. Because of the short interval between a purchasing decision and its realization, an online shopping mall transaction usually contains fewer items than that of an offline market. In an offline market, customers usually keep some items in mind and buy them all at once a few days after deciding to buy them, instead of buying each item individually and immediately. On the contrary, more than 70% of online shopping mall transactions contain only one item. This statistic implies that traditional data mining techniques cannot be directly applied to online market analysis, because hardly any association rules can survive with an acceptable level of Support because of too many Null Transactions. Most market basket analyses on online shopping mall transactions, therefore, have been performed by expanding the co-occurrence criteria of traditional association rule mining. While the traditional co-occurrence criteria defines items purchased in one transaction as concurrently purchased items, the expanded co-occurrence criteria regards items purchased by a customer during some predefined period (e.g., a day) as concurrently purchased items. In studies using expanded co-occurrence criteria, however, the criteria has been defined arbitrarily by researchers without any theoretical grounds or agreement. The lack of clear grounds of adopting a certain co-occurrence criteria degrades the reliability of the analytical results. Moreover, it is hard to derive new meaningful findings by combining the outcomes of previous individual studies. In this paper, we attempt to compare expanded co-occurrence criteria and propose a guideline for selecting an appropriate one. First of all, we compare the accuracy of association rules discovered according to various co-occurrence criteria. By doing this experiment we expect that we can provide a guideline for selecting appropriate co-occurrence criteria that corresponds to the purpose of the analysis. Additionally, we will perform similar experiments with several groups of customers that are segmented by each customer's average duration between orders. By this experiment, we attempt to discover the relationship between the optimal co-occurrence criteria and the customer's average duration between orders. Finally, by a series of experiments, we expect that we can provide basic guidelines for developing customized recommendation systems.

• KSBB Journal
• /
• v.9 no.3
• /
• pp.325-331
• /
• 1994

PGA is formed in a route of CO2 fixation of RuBP catalyzed by RuBPCase, followed by reduction of the PGA by NADH to GAP This reduction is enhanced in an anionic micellar solution(SDS), in which NADH is distributed in the aqueous and the micellar pseudophases in a given ratio. This micellar bounded NADH reacts to PGA, and in higher micellar concentration than $1.25{\times}10^{-2}M$, most of NADH is oxidized to NAD+ by PGA. On the other hand, in the solutions of the positive ionic(CTABr), zwitter ionic(Chaps) and nonionic (Brij and Triton X-100) micelles, the reactions are also enhanced and the concentrations of NADH reach minima with micellar concentrations. Such minima are typical of micellar catalyzed bimolecular reactions, and the fall in concentrations of the reductant followed by a gradual increase is charataristic of reactions of hydrophobic substrates: that is, the reductions of PGA by NADH are sharply enhanced in a range of the lower micellar concentrations, and NADH amounts in ca. $1.25-2.50{\times}10^{-3}M$ micellar solutions are reached to minima, followed by gradual increases of the reductant concentration.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.16 no.4
• /
• pp.439-450
• /
• 2003

Flat plate system has been adopted in many buildings constructed recently because of the advantage of reduced floor heights to meet the economical and architectural demands. Structural engineers commonly use the effective beam width model(EBWM) in practical engineering for the analysis of flat plate structures. However, in many cases, when it is difficult to use the EBWM, it is necessary to use a refined finite element model for an accurate analysis. But it would take significant amount of computational time and memory if the entire building structure was subdivided with finer meshes. An efficient analytical method is proposed in this study to obtain accurate results in significantly reduced computational time. The proposed method employs super elements developed using the matrix condensation technique and fictitious beams are used in the development of super elements to enforce the compatibility at the interfaces of super elements. The stiffness degradation of flat plate system considered in the EBWM was taken into account by reducing the elastic modulus of floor slabs in this study. Static and dynamic analyses of example structures were performed and the efficiency and accuracy of the proposed method were verified by comparing the results with those of the refined finite element model and the EBWM.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.21 no.5
• /
• pp.599-607
• /
• 2015

The purpose of this study is to reproduce long-term wave fields in coastal waters of Korea based on wave hind-casting modelling and discuss its applications. To validate wind data(NCEP, ECMWF, JMA-MSM), comparison of wind data was done with wave buoy data. JMA-MSM predicted wind data with high accuracy. But due to relatively longer period of ECMWF wind data as compared to that of JMA-MSM, wind data set of ECMWF(2001~2014) was used to perform wave hind-casting modelling. Results from numerical modelling were verified with the observed data of wave buoys installed by Korea Meteorological Administration(KMA) and Korea Hydrographic and Oceanographic Agency(KHOA) on offshore waters. The results agree well with observations at buoy stations, especially during the event periods such as a typhoon. Consequently, the wave data reproduced by wave hind-casting modelling was used to obtain missing data in wave observation buoys. The obtained missing data indicated underestimation of maximum wave height during the event period at some points of buoys. Reasons for such underestimation may be due to larger time interval and resolution of the input wind data, water depth and grid size etc. The methodology used in present study can be used to analyze coastal erosion data in conjunction with a wave characteristic of the event period in coastal areas. Additionally, the method can be used in the coastal disaster vulnerability assessment to generate wave points of interest.