• Journal of Advanced Navigation Technology
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• v.28 no.4
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• pp.420-427
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• 2024

This study proposes a method for utilizing flight and flow - information for a collaborative environment (FF-ICE) for flight plan management based system wide information management (SWIM) technology for the safe and efficient operation of urban air mobility (UAM). SWIM provides a standardized infrastructure for air traffic data, enabling seamless information exchange among various stakeholders. This study purposed flight plan procedures for UAM operation regarding submitting preliminary and filed flight plans, validation and operational evaluation processes, state management, and the roles of each stakeholder. The system developed through the SWIM infrastructure for low-density urban air mobility traffic management. The study are expected to significantly enhance the safety and efficiency of UAM operations through strategic flight plan management methods.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.22 no.3
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• pp.82-86
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• 2014

Modern Air Traffic Management has been shifted from the conventional vector- based clearances to trajectory based operations (TBO) concept which utilizes four-dimensional trajectory based on the internationally interoperable information using Globally Unique Flight Identifier (GUFI). This study reviews the development for TBO-related standards and Flight Information Exchange Model (FIXM), which has been discussed by the ICAO Air Traffic Management Requirements and Performance Panel (ATMRPP). In addition, plans for the next step with TBO and the Republic of Korea's participation on the Mini-Global Demonstration were also introduced.

• Asian Journal of Business Environment
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• v.11 no.4
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• pp.5-16
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• 2021

Purpose: This study aims to investigate the impact of auditor-client traffic convenience on accrual -based and real earnings management of the client firms. Research design, data and methodology: Using a sample of firms listed in Shanghai and Shenzhen Stock Exchanges over the period of 2007 to 2018, this paper empirically investigates the association between auditor-client traffic convenience and earnings management. We use three measures of auditor-client traffic convenience: railway traffic convenience, expressway traffic convenience, and air traffic convenience. The accrual-based earnings management is measured by abnormal accruals estimated by industry and year using the Modified Jones Model. Results: Findings indicate that traffic convenience is conducive to detecting and restraining positive accrual earnings management and real earnings management. After changing the measurement of independent variable and dependent variable, including potential omitted variables, the results are statistically unchanged. Further, the research shows that traffic convenience can not only improve audit quality, but also lead to higher fee premiums. Auditors didn't share with clients the cost reduction benefits caused by traffic convenience. Conclusions: Traffic convenience provides auditors with easy access to the client firms, alleviating the information asymmetry and improving corporate earnings quality. The findings have implications for regulators, audit practitioners and stakeholders.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.11
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• pp.4268-4289
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• 2020

Advanced traffic signal timing method plays very important role in reducing road congestion and air pollution. Reinforcement learning is considered as superior approach to build traffic light timing scheme by many recent studies. It fulfills real adaptive control by the means of taking real-time traffic information as state, and adjusting traffic light scheme as action. However, existing works behave inefficient in complex intersections and they are lack of feasibility because most of them adopt traffic light scheme whose phase sequence is flexible. To address these issues, a novel adaptive traffic signal timing scheme is proposed. It's based on actor-critic reinforcement learning algorithm, and advanced techniques proximal policy optimization and generalized advantage estimation are integrated. In particular, a new kind of reward function and a simplified form of state representation are carefully defined, and they facilitate to improve the learning efficiency and reduce the computational complexity, respectively. Meanwhile, a fixed phase sequence signal scheme is derived, and constraint on the variations of successive phase durations is introduced, which enhances its feasibility and robustness in field applications. The proposed scheme is verified through field-data-based experiments in both medium and high traffic density scenarios. Simulation results exhibit remarkable improvement in traffic performance as well as the learning efficiency comparing with the existing reinforcement learning-based methods such as 3DQN and DDQN.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.1
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• pp.52-68
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• 2019

Aiming at the optimal placement of communication relay nodes (OPCRN) problem in manned/unmanned aerial vehicle cooperative engagement system, this paper designed a kind of fully connected broadband backbone communication topology. Firstly, problem description of OPCRN was given. Secondly, based on problem analysis, the element attributes and decision variables were defined, and a bi-level programming model including physical layer and logical layer was established. Thirdly, a hierarchical artificial bee colony (HABC) algorithm was adopted to solve the model. Finally, multiple sets of simulation experiments were carried out to prove the effectiveness and superiority of the algorithm.

• Journal of Advanced Navigation Technology
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• v.12 no.6
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• pp.539-547
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• 2008

In this paper, preliminary results for design of prototype ADS-ADS-B/TIS-B Validation Testbed (AVT) are described. Automatic Dependent Surveillance (ADS-B) is a novel surveillance concept using the Global Navigation Satellite System (GNSS) and a digital datalink. Air traffic information from ADS-B non-equipped aircraft is not acquired since ADS-B is a dependent surveillance. Traffic Information Service-Broadcast (TIS-B) provides surveillance data from Secondary surveillance Radar (SSR) for ADS-B non-equipped aircraft. AVT is based on ADS-B and TIS-B as an integrated platform for air traffic surveillance system for CNS/ATM.

• Journal of the Korean Institute of Navigation
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• v.20 no.3
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• pp.43-63
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• 1996

The purpose of this study is to find out what is the functional role of VTS in order to get the people concerned with marine traffic/transportation understand about VTS. VTS could be described as the essential risk management system in both cost effective on cost-benefit analysis and the sea space or time management at port, coastal environment. The important role of the VTS are those functions such as the decision making infrastructure, the passive/active safety measures at sea. VTS could not control/regulate marine traffic as strong as ATC(Air Traffic Control) owing to the marine traffic characters. However, the right and responsibility of VTS finally are belong to the master, pilot and mariners. For the benefit of the electronic technology development, VTS system also cloud be upgraded to communication system from information system. In connection with these system upgrading, the right and responsibility of VTS/staff should be supported by domestic legal system. The followings are presented for VTS to be effective. First, the cooperation and understanding of VTS between the peoples concerned with marine traffic/transportation are essential. Because they are all data supplier and also information consumers. Second, VTS staff/regulator should be selected, educated, trained accordingly as per their career, ability, quality, qualification, certification and etc. Third, the port reliability from VTS users depends on the factors such as economic interests, safety and effectiveness/efficiency of VTS.

• Atmosphere
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• v.33 no.4
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• pp.343-354
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• 2023

Turbulence produced on roadways is one of the major factors determining the dilution rates at the initial stage of traffic emissions of air pollutants and, thus, the distribution of air pollutants near the roadways. Field experiments were conducted on Gyeongbu Highway, one of the busiest highways in Korea, for 4~7 days in winter, spring, and summer. Two three-dimensional ultrasonic anemometers were installed on both sides of the highway to estimate turbulence intensities (vertical wind fluctuation and kinetic turbulence energy) induced by the roadway. Roadway-induced turbulence consists of three components: structural road-induced turbulence (S-RIT), thermal road-induced turbulence (T-RIT), and vehicle-induced turbulence (VIT). The contribution of T-RIT to the total RIT was insignificant (less than 10%), and the majority of RIT was S-RIT (by the highway embankment) and VIT. In this study, we propose the empirical relationships of VIT as a function of traffic density and wind speed under free-flow traffic conditions. Although this empirical relationship appears to underestimate the VIT, it can be applied to the air quality models easily because the relationship is simple and only needs readily obtainable input variables (wind speed and traffic information).

• Journal of the Korean Society for Aviation and Aeronautics
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• v.16 no.4
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• pp.54-62
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• 2008

International organizations related to air transport such as ICAO, IATA, ACI are forecasting that the number of passenger will grow about 4.4% annually up to 2015. Therefore, the innovation of given system technology and operation procedure is required in global scale to cope with the increase of air traffic demand. CNS/ATM infrastructure based on satellite is considered to play key role in order to solve the problems due to the dramatic increase of air traffic demand over the world. Free flight concept in the air transport operation has been proved with CNS/ATM infrastructure especially in USA and Europe. Therefore, it is necessary to develop key technologies to overcome technology gap and to secure international competitiveness in Korea. ADS-B is an important issue, and new element technologies should be considered as essential items which were shown in Capstone project. Nowadays, the free flight concept is combined to Air Transport Road Map such as NextGen project in USA, SESAR in Europe. In this process, free flight is included in the concepts such as ATM(Air Traffic Management), aviation security and safety, environmental protection and economy development, wide area weather variable reduction service, information integration and application between the related authorities (civil/military) etc. The purpose of research is to establish mid-term and long-term infrastructure plan and strategy for free flight realization in Korea. The analysis of action target and equipment construction status, phase construction plan of infrastructure has been performed by considering mid-term and long-term free flight plans of USA and Europe.

• Environmental Analysis Health and Toxicology
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• v.30
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• pp.10.1-10.14
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• 2015

Recent cohort studies have relied on exposure prediction models to estimate individual-level air pollution concentrations because individual air pollution measurements are not available for cohort locations. For such prediction models, geographic variables related to pollution sources are important inputs. We demonstrated the computation process of geographic variables mostly recorded in 2010 at regulatory air pollution monitoring sites in South Korea. On the basis of previous studies, we finalized a list of 313 geographic variables related to air pollution sources in eight categories including traffic, demographic characteristics, land use, transportation facilities, physical geography, emissions, vegetation, and altitude. We then obtained data from different sources such as the Statistics Geographic Information Service and Korean Transport Database. After integrating all available data to a single database by matching coordinate systems and converting non-spatial data to spatial data, we computed geographic variables at 294 regulatory monitoring sites in South Korea. The data integration and variable computation were performed by using ArcGIS version 10.2 (ESRI Inc., Redlands, CA, USA). For traffic, we computed the distances to the nearest roads and the sums of road lengths within different sizes of circular buffers. In addition, we calculated the numbers of residents, households, housing buildings, companies, and employees within the buffers. The percentages of areas for different types of land use compared to total areas were calculated within the buffers. For transportation facilities and physical geography, we computed the distances to the closest public transportation depots and the boundary lines. The vegetation index and altitude were estimated at a given location by using satellite data. The summary statistics of geographic variables in Seoul across monitoring sites showed different patterns between urban background and urban roadside sites. This study provided practical knowledge on the computation process of geographic variables in South Korea, which will improve air pollution prediction models and contribute to subsequent health analyses.