• Proceedings of the KOR-KST Conference
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• 2003.02a
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• pp.127-150
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• 2003

This research presents a novel application of static traffic assignment methods, but with a variable time value, for estimating the market share of a high-speed rail (HSR) in the NW-SE corridor of Korea which is currently served by the airline (AR), conventional rail (CR), and highway (HWY) modes. The proposed model employs the time-space network structure to capture the interrelations among all competing transportation modes, and to reflect their supply- and demand-sides constraints as well as interactions through properly formulated link-node structures. The embedded cost function for each network link offers the flexibility for incorporating all associated factors, such as travel time and fare, in the model computation, and enables the use of a distribution rather than a constant to represent the time-value variation among all transportation mode users. To realistically capture the tripmakers' value-of-time (VOT) along the target area, a novel method for VOT calibration has been developed with aggregate demand information and key system performance data from the target area. Under the assumption that intercity tripmakers often have nearly "perfect" travel information, one can solve the market share of each mode after operations of HSR for each O-D pair under the time-dependent demand with state-of-the-art traffic assignment. Aside from estimating new market share, this paper also investigated the impacts of HSR on other existing transportation modes.

• Korean Management Science Review
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• v.23 no.1
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• pp.21-41
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• 2006

Given the growing deployment of mobile offices, we need to understand the fectors which affect their successful use and implementation. We in this paper present a parsimonious model which integrates the IS success model and the TAM. The main feature of the model is that it allows one to explore the role of mobility of mobile office systems in determining the level of system usage and dependence. Although the mobility is the key property of any mobile system, there is little research effort exerted to understand how mobility affects the traditional IS factors such as perceived ease of use and usefulness. In addition to the system usage, this model also uses dependence as the dependent variable. This is expected to provide richer understanding of the study context. We collected survey data from 1,614 field service workers of a major domestic electronic company. They use PDAs to retrieve information regarding the specifics of the customer service requests and to report what has been done for each service job. The results from SEM analysis show that mobility improves the perceived ease of use which then leads the field service workers to depend more on the PDA systems. Interestingly enough, however, the workers' satisfaction does not cause more frequent use of the system.

• Geomechanics and Engineering
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• v.36 no.3
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• pp.247-258
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• 2024

Tailings are waste materials of mining operations, consisting of a mixture of clay, silt, sand with a high content of unrecoverable metals, process water, and chemical reagents. They are usually discharged as slurry into the storage area retained by dams or earth embankments. Poor knowledge of the hydro-mechanical behaviour of tailings has often resulted in a high rate of failures in which static liquefaction has been widely recognized as one of the major causes of dam collapse. Many studies have dealt with the static liquefaction of coarse soils in saturated conditions. This research provides an extension to the case of silty tailings in unsaturated conditions. The static liquefaction resistance was evaluated in terms of stress-strain behavior by means of monotonic triaxial tests. Its dependency on the preparation method, the volumetric water content, the void ratio, and the degree of saturation was studied and compared with literature data. The static liquefaction response was proved to be dependent mainly on the preparation technique and degree of saturation that, in turn, controls the excess of pore pressure whose leading role is investigated by means of the relationship between the -B Skempton parameter and the degree of saturation. A preliminary interpretation of the static liquefaction response of Stava tailings is also provided within the Critical State framework.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.6
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• pp.2148-2167
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• 2021

The proliferation of the Internet of Things (IoT) technologies and applications, especially the rapid rise in the use of mobile devices, from individuals to organizations, has led to the fundamental role of secure wireless networks in all aspects of services that presented with many opportunities and challenges. To ensure the CIA (confidentiality, integrity and accessibility) security model of the networks security and high efficiency of performance results in various resource-constrained applications and environments of the IoT platform, DDO-(data-driven operation) based constructions have been introduced as a primitive design that meet the demand of high speed encryption systems. Among of them, the TMN-family ciphers which were proposed by Tuan P.M., Do Thi B., etc., in 2016, are entirely suitable approaches for various communication applications of wireless mobile networks (WMNs) and advanced wireless sensor networks (WSNs) with high flexibility, applicability and mobility shown in two different algorithm selections, TMN64 and TMN128. The two ciphers provide strong security against known cryptanalysis, such as linear attacks and differential attacks. In this study, we demonstrate new probability results on the security of the two TMN construction versions - TMN64 and TMN128, by proposing efficient related-key recovery attacks. The high probability characteristics (DCs) are constructed under the related-key differential properties on a full number of function rounds of TMN64 and TMN128, as 10-rounds and 12-rounds, respectively. Hence, the amplified boomerang attacks can be applied to break these two ciphers with appropriate complexity of data and time consumptions. The work is expected to be extended and improved with the latest BCT technique for better cryptanalytic results in further research.

• Journal of Advanced Navigation Technology
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• v.24 no.6
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• pp.527-532
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• 2020

Seoul terminal maneuvering area (TMA) that includes Incheon International Airport (ICN) and Gimpo International Airport is a very congested airspace with around 1,000 daily flights and the airspace blocked at the boundary between Incheon flight information region (FIR) and Pyongyang FIR. Consequently, with frequency radar vectorings, separation assurance in this airspace is complicated thus resulting in higher controller workload. In this paper, the conflict and collision risks in Seoul TMA are analyzed using recorded ADS-B data for past three years. Using the recorded trajectories, original flight plan procesures and routes are reconstructed and the risks are quantified using detect and avoid well clear (DWC) metric that is developed for large unmanned aircraft system. The region west of ICN was found to be the highest risk area regardless of the runway directions. In addition, merge and crossing points between procedures displayed relatively high risks.

• Asia pacific journal of information systems
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• v.19 no.2
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• pp.73-94
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• 2009

The general aspects for the future warfare shows that the concept of firepower and maneuver centric warfare has been replacing with that of information and knowledge centric warfare. Thus, some developed countries are now trying to establish the information systems to perform intelligent warfare and innovate defense operations. The C4I(Command, Control, Communication, Computers and Intelligence for the Warrior) systems make it possible to do modern and systematic war operations. The basic idea of this study is to investigate how TAM(Technology Acceptance Model) can explain the acceptance behavior in military organizations. Because TAM is inadequate in explaining the acceptance processes forcomplex technologies and strict organizations, a revised research model based upon TAM was developed in order to assess the usage of the C4I system. The purpose of this study is to investigate factors affecting the usage of C4I in the Korean Army. The research model, based upon TAM, was extended through a belief construct such as self-efficacy as one of mediating variables. The self-efficacy has been used as a mediating variable for technology acceptance, and the variable was included in the research model. The external variables were selected on the basis of previous research. The external variables can be classified into following: 1) technological, 2) organizational, and 3) environmental factors on the basis of TOE(Technology-Organization-Environment) framework. The technological factor includes the information quality and the task-technology fitness. The organizational factor includes the influence of senior colleagues. The environmental factor includes the education/train data. The external variables are considered very important for explaining the behavior patterns of information technology or systems. A structured questionnaire was developed and administrated to those who were using the C4I system. Total 329 data were used for statistical data analyses. A confirmatory factor analysis and structured equation model were used as main statistical methods. Model fitness Indexes for measurement and structured models were verified before all 18 hypotheses were tested. This study shows that the perceived usefulness and the self-efficacy played their roles more than the perceived ease of use did in TAM. In military organizations, the perceived usefulness showed its mediating effects between external variables and dependent variable, but the perceived ease of use did not. These results imply that the perceived usefulness can explain the acceptance processes better than the perceived ease of use in the army. The self-efficacy was also used as one of the three mediating variables, and showed its mediating effects in explaining the acceptance processes. Such results also show that the self-efficacy can be selected as one possible belief construct in TAM. The perceived usefulness was influenced by such factors as senior colleagues, the information quality, and the task-technology fitness. The self-efficacy was affected by education/train and task-technology fitness. The actual usage of C4I was influenced not by the perceived ease of use but by the perceived usefulness and selfefficacy. This study suggests the followings: (1) An extended TAM can be applied to such strict organizations as the army; (2) Three mediation variables are included in the research model and tested at real situations; and (3) Several other implications are discussed.

• Korean Journal of Construction Engineering and Management
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• v.15 no.6
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• pp.26-34
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• 2014

Highway construction is a combination of linear, repetitive, and highly equipment intensive operations. Various types of construction equipment are deployed to ensure undisrupted performance of construction, and thus productivity improvement and cost-saving can be achieved through well-thought-out planning. The selection of construction equipment is dependent upon construction sequence, site conditions, and construction methods. In the process of planning, management should consider various types of construction methods per each type of construction operation. Also, management should map out proper construction equipment operation plan that takes the construction duration and cost measures into consideration. However, limited availability of historic data from the similar types of operations has been a stumbling block to proper construction planning, making the operations performed based upon experience and intuition guided by rules-of-thumb. As a consequence, the planing phase rarely provided an adequate validity in the implementation phase. The researchers developed a process logic for each construction type that management can utilize from early phase of highway construction planning process. Moreover, derived the construction equipment combination optimized for efficiency by using the process simulation technique. The developed method is expected to be useful for the decision-making process that aims to evaluate efficiency of various process plans and to ensure optimal selection of construction equipment for highway construction projects.

• Journal of The Korea Institute of Healthcare Architecture
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• v.19 no.2
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• pp.31-40
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• 2013

Purpose: It seems obvious that the hospital structures become more large-sized and tall-risen in Korea today. Nothing is more influential than the vertical core plan on the movements of various people in such large-tall hospitals. The present paper, therefore, aims to study on the efficient hospital core space paying first attention to patients by analysing the data on relations between/among department layouts of vertical and horizontal movements. Methods: This study sampled representative 14 hospitals and drew their degrees of data importance on the basis of precedented relative studies. This study also analysed their placements on the blueprint and made confirmations of their arrangements through their homepage on line. Actual visits were made to make sure of the spacial connections between/among departments in the hospitals as well. Results: Even in emergency case in need for vertical movements, the central main core spaces are usually used, which is because special vertical transportation systems are not provided. In these cases, the main core spaces are very important for those who have to move vertically and/or horizontally according to the locations and types of main cores. While special lifts or dumbwaiters are prepared to install for the important articles, such as samples of pathology department, most patients should share with regular visitors the elevators not separated visually and spatially from them. Implications: Vertical core plans are greatly dependent on the ward types and hospital styles. This study is hopefully expected to contribute itself to the standard setting-up of comfortable and quick vertical core system operations for patients.

• Korean Management Science Review
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• v.32 no.2
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• pp.91-109
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• 2015

The M&A of firms has been emerged as the effective means of fast diversification and growth in dynamic environment. However, the empirical research about M&A in Korea has not been implemented rich due to the difficulty of obtaining M&A data. In this research, we empirically investigate the relationships among M&A, environment and firms' performance focused on Korean manufacturing firms, understanding the current practice of M&A in Korea. We use the Manufacturing Productivity Panel Survey Data, which are collected by Korea Productivity Center in 2013. The sample size is 575 and the sample is divided into M&A group and non-M&A group. We conduct logit analysis with the independent variables of environment factors (munificence, dynamic, uncertainty), and firms' performance (sales growth, ROS, labor productivity and Inventory turnover), and dependent variable of M&A group or non M&A group. The results show that M&A is closely related to environment feature and firm performance: M&A firms are likely to be the higher munificence and dynamic and the lower sales growth and higher profitability than non-M&A group. In addition, we also examine the characteristics of firms by M&A types (competitors, customer/supplier and firms from unrelated industry). These results imply that if firms confront the pressure of uncertainty (dynamic) and the lower growth, they tend to choose M&A. Futhermore, to profoundly understand the behavior of firms about M&A, it is required to classify the M&A firms by merge types.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.40 no.2
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• pp.13-21
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• 2017

Airline schedules are highly dependent on various factors of uncertainties such as unfavorable weather conditions, mechanical problems, natural disaster, airport congestion, and strikes. If the schedules are not properly managed to cope with such disturbances, the operational cost and performance are severely affected by the delays, cancelations, and so forth. This is described as a disruption. When the disruption occurs, the airline requires the feasible recovery plan returning to the normal operations in a timely manner so as to minimize the cost and impact of disruptions. In this research, an Ant Colony Optimization (ACO) algorithm with re-timing strategy is developed to solve the recovery problem for both aircraft and passenger. The problem consists of creating new aircraft routes and passenger itineraries to produce a feasible schedule during a recovery period. The suggested algorithm is based on an existing ACO algorithm that aims to reflect all the downstream effects by considering the passenger recovery cost as a part of the objective function value. This algorithm is complemented by re-timing strategy to effectively manage the disrupted passengers by allowing delays even on some of undisrupted flights. The delays no more than 15 minutes are accepted, which does not influence on the on-time performance of the airlines. The suggested method is tested on the real data sets from 2009 ROADEF Challenge, and the computational results are compared with the existing ones on the same data sets. The method generates the solution for most of problem set in 10 minutes, and the result generated by re-timing strategy is discussed for its impact.