• Journal of Korean Society of Transportation
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• v.28 no.5
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• pp.31-41
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• 2010

The objective of this paper is to evaluate production efficiency of the commercial road freight transportation industry using quarterly actual data by individual truck drivers from January 2005 to September 2009. In addition, this study analyzes various impact factors that influence production efficiency, including regulatory factors (e.g., entrust management system and multi-level transactions). For this purpose, this study uses data envelopment analysis and a truncated Tobit model. As a result, production efficiency of the general freight sector is higher than those of the other two sectors. Also, production efficiency in the steel goods sector ranks the highest; meanwhile, production efficiency in the oil goods sector ranks the lowest. In particular, production efficiency indicators of the commercial road freight transportation industry fluctuate with time by a small margin, and have an upward tendency on the whole. Finally, some policy implications are given to promote production efficiency of the commercial road freight transportation industry.

• Industrial Engineering and Management Systems
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• v.12 no.1
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• pp.30-35
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• 2013

Motivated by the emergency scheduling in a transportation network, this paper considers a transportation problem, in which, the truck times and transportation costs are assumed as uncertain variables. To meet the demand in the practical applications, two optimization objectives are considered, one is the total costs and another is the completion times. And then, a multi-objective optimization model is developed according to the situation in applications. Because there are commensurability and conflicting between the two objectives commonly, a solution does not necessarily exist that is best with respective to the two objectives. Therefore, the problem is reduced to a single objective model, which is an uncertain programming with a chance-constrain. After some analysis, its equivalent deterministic form is obtained, which is a nonlinear programming. Based on a stepwise optimization strategy, a solution method is developed to solve the problem. Finally, the computational results are provided to demonstrate the effectiveness of our model and algorithm.

• Journal of applied mathematics & informatics
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• v.24 no.1_2
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• pp.449-460
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• 2007

Several fuzzy approaches can be considered for solving multi-objective transportation problem. This paper presents a fuzzy goal programming approach to determine an optimal compromise solution for the multiobjective transportation problem. We assume that each objective function has a fuzzy goal. Also we assign a special type of nonlinear (hyperbolic) membership function to each objective function to describe each fuzzy goal. The approach focuses on minimizing the negative deviation variables from 1 to obtain a compromise solution of the multiobjective transportation problem. We show that the proposed method and the fuzzy programming method are equivalent. In addition, the proposed approach can be applied to solve other multiobjective mathematical programming problems. A numerical example is given to illustrate the efficiency of the proposed approach.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.12
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• pp.1711-1716
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• 2018

Unlike conventional transmission and distribution lines, catenary system for operating electric railway vehicles are composed of multi-conductor groups (feeder line, contact wire, messenger wire, protection wire) and are used for railway employees, public or passengers in the station yards. Electric shock hazards are exposed and electric shocks such as death or serious injury are occurring in electric railway vehicles, railway high-voltage distribution lines, and catenary system. In order to analyze the types of electric shock accidents on railway by systematic approach method, we modeled 'unsafe behavior classification' method using swiss cheese model. Based on this method, we derived the type of electric shock accidents about railway accidents during the last 5 years by analyzing the frequency of occurrence of human errors and unsafe acts, laws and regulations related to violations, and so on.

• Proceedings of the Korean Society of Computer Information Conference
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• 2020.01a
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• pp.67-68
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• 2020

본 논문에서는 미세먼지 센서와 가스 센서를 이용한 효율적인 스마트 홈 기반 다중 센서 알림 시스템을 제안한다. 시스템은 여러 유형의 홈 센서를 이용하여 효율적으로 미세먼지와 실내의 가스를 탐지 후 실시간으로 애플리케이션을 통해서 사용자에게 탐지 결과를 알려주는 시스템이다. 본 시스템의 경우 기존에 존재하는 미세먼지 센서와 가스 센서를 적용한 측정 시스템에 비해 소액으로 최적의 시스템을 구축할 수 있다. 시스템은 기존의 가스 센서와 다르게 한 번에 다양한 종류의 가스를 탐지해 사용자에게 여러 정보를 제공할 수 있도록 개발하였다.

• Proceedings of the KOR-KST Conference
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• 1999.10a
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• pp.261-266
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• 1999

• Journal of the Korean Society for Aviation and Aeronautics
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• v.18 no.2
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• pp.41-45
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• 2010

It is often misled that Multi Pilot License is introduced by International Civil Aviation Organization for the shortage of pilots. The truth is, however, that the license is focused on efficient training of co-pilots in the airline transportation system which an autopilot system is increasing in the Multi Crew environment. ICAO has been researching on the license since 1982, and made it international standard on 2006. Currently, co-pilots trained under Multi-Crew Pilot License courses are continuously increasing over the world. Although the license has introduced to Korea in September 10, 2009, it has not won popular support yet. This paper will lead people to precise understanding of Multi-Crew Pilot License and suggest its introduction plan.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.17 no.2
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• pp.98-112
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• 2018

Intentional aggressive driving (IAD) is a very dangerous driving behavior that threatens to attack the adjacent vehicles. Most existing studies have focused on the independent driving characteristics of attack drivers. However, the identification of interactions between the offender and the victim is necessary for the traffic safety analysis. This study established multi-agent driving simulation environments to systematically analyze vehicle interactions in terms of traffic safety. Time-to-collision (TTC) was adopted to quantify vehicle interactions in terms of traffic safety. In addition, a exponential decay function was further applied to compare the overall pattern of change in crash potentials when IAD events occurred. The outcome of this study would be useful in developing policy-making activities to enhance traffic safety by reducing dangerous driving events including intentional aggressive driving.

• Journal of Korean Society of Transportation
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• v.20 no.7
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• pp.79-85
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• 2002

In this paper, multilevel models are adopted to identify interactions among household members in trip making behaviors. The multilevel approach is a proper methodology to handle samples, which are extracted from a hierarchical structure universe. PSTP dataset is used in developing models and understand proportion of variations among individuals and household. The results of this study show that for activity participation and travel behavior household level variance is more than 1/4 of person level variance and therefore not negligible. The results confirm the importance of multilevel model in travel behavior analysis.

• Structural Engineering and Mechanics
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• v.82 no.1
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• pp.41-53
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• 2022

We developed an accurate and simple vibration model to calculate the natural frequencies and their corresponding vibration modes for multi-span beam bridges with non-uniform cross-sections. A closed set of characteristic functions of a single-span beam was used to construct the vibration modes of the multi-span bridges, which were considered single-span beams with multiple constraints. To simplify the boundary conditions, the restraints were converted into spring constraints. Then the functional of the total energy has the same form as the penalty method. Compared to the conventional penalty method, the penalty coefficients in the proposed approach can be calculated directly, which can avoid the iteration process and convergence problem. The natural frequencies and corresponding vibration modes were obtained via the minimum total potential energy principle. By using the symmetry of the eigenfunctions or structure, the matrix size can be further reduced, which increases the computational efficiency of the proposed model. The accuracy and efficiency of the proposed approach were validated by the finite element method.