• 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.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.2
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• pp.235-243
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• 2022

A total of 97,623 ships were registered in Korea in 2019. Among these, 65,835 vessels, accounting for approximately 67 % of the total number of ships, were registered as fishing vessels. As with the proportion of fishing vessels, the frequency of marine accidents is also high. In 2020, 2,331 of 3,535 accidents occurred on fishing vessels. Hence, various institutional arrangements are required for improving the safety of domestic fishing vessels. In this study, we examined domestic and international regulations on domestic and foreign control performance related to fishing boats for improving the safety of fishing boats. Additionally, the ratio of the rudder area of 153 fishing boats operating in Korea was investigated to examine the current status of the rudder area design of fishing boats whose design standards have not been clearly established compared to fishing boats. Resultantly, we statistically confirmed that most fishing boats were designing rudder areas because they did not meet international standards. In the future, these analysis results can be used as basic data to prepare rudder area design standards for improving the maneuvering performance of domestic fishing boats.

• Journal of Platform Technology
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• v.9 no.4
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• pp.71-78
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• 2021

Self-driving vehicles are increasing as new alternatives to solving problems such as human safety, environment and aging. And such technology development has a great ripple effect on other industries. However, various problems are occurring. The number of casualties caused by self-driving is increasing. Although the collision of fixed obstacles is somewhat decreasing, on the contrary, the technology by active obstacles is still insignificant. Therefore, in this study, in order to solve the core problem of self-driving vehicles, we propose a method of extracting active obstacles on the road. First, a center scene is extracted from a continuous image. In addition, it was proposed to extract activity obstacles using activity size and activity repeatability information from objects included in the center scene. The center scene is calculated using region segmentation and merging. Based on these results, the size of the frequency for each pixel in the region was calculated and the size of the activity of the obstacle was calculated using information that frequently appears in activity. Compared to the results extracted directly by humans, the extraction accuracy was somewhat lower, but satisfactory results were obtained. Therefore, it is believed that the proposed method will contribute to solving the problems of self-driving and reducing human accidents.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.7
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• pp.1026-1031
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• 2022

Cognitive Radio Ad-Hoc Networks (CRAHNs) enable to overcome the shortage of frequency resources due to the increase of radio services. In order to avoid interference with the primary user in CRANH, channel sensing to check the idle channel is required, and when the primary user appears, the time delay due to handover should be minimized through fast idle channel selection. In this paper, throughput was improved by reducing the number of channel sensing and preferentially sensing a channel with a high probability of being idle, using reinforcement learning. In addition, we proposed a multi-channel MAC (Medium Access Control) protocol that can minimize the possibility of collision with the primary user by sensing the channel at the time of data transmission without performing periodic sensing. The performance was compared and analyzed through computer simulation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.2
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• pp.239-250
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• 2022

LoRa is a physical layer technology designed to secure highly reliable long-range communication with introducing loco parentis tree network and chirp spreading spectrum. Since since a leaf can send message to more than one parents simultaneously with a single transmission in a region, packet delivery ratio increases logarithmically as the number of gateways increases. The delivery ratio, however, dramatically collapses even under loco parentis tree topology due to the limitations of ALOHA-like primitive MAC, . The proposed method is intended to exploit SDMA approach to reuse frequency in an area. With the view, TxPower of each sender for each message in a concurrent transmission is elaborately controlled to survive the collision at different gateway. Thus, the gain from the capture effect improves the capacity of resource-hungry Low Power and Wide Area Networks.

• Fisheries and Aquatic Sciences
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• v.27 no.1
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• pp.7-16
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• 2024

Fishing is considered one of the most dangerous industries alongside mining that needs further efforts to improve safety. In this study, we have investigated safety management of the gillnet fishing industry in South Korea through identifying safety level and classifying common accident types from the statements of accident com-pensation insurance payments for the last 5 years (2016-2020). There were in total 3,895 accidents and 159 fatalities with an average accident frequency of 5.34 × 10^-2 per year per fisher and an average fatality of 2.18 × 10^-3 fishers per year. We have also identified that 62.4% of the accidents occurred during Fishing (FS), and the most common and the most severe accident type is Slips and Trips (ST) and Other (OT) marine accidents such as collision and capsizing, respectively. The hand was most frequently injured. Finally, the risk assessment indicated that most of the accident types of gillnet fishing in South Korea have unacceptable levels of risks, and it is urgent to implement improved safety measures to reduce accidents during gillnet fishing operation. The findings of this study are expected to provide valuable data to create a safer working environment for fishers working on gillnet fishing vessels.

• Journal of Trauma and Injury
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• v.37 no.1
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• pp.67-73
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• 2024

Purpose: Posttraumatic stress disorder (PTSD) is prevalent and is associated with protracted recovery and worse outcomes after injury. This study compared PTSD prevalence using the PTSD Checklist for DSM-5 (PCL-5) with the prevalence of PTSD risk using the Injured Trauma Survivor Screen (ITSS). Methods: Adult trauma patients at a level I trauma center were screened with the PCL-5 (sample 1) at follow-up visits or using the ITSS as inpatients (sample 2). Results: Sample 1 (n=285) had significantly fewer patients with gunshot wounds than sample 2 (n=45) (8.1% vs. 22.2%, P=0.003), nonsignificantly fewer patients with a fall from a height (17.2% vs. 28.9%, P=0.06), and similar numbers of patients with motor vehicle collision (40.7% vs. 37.8%, P=0.07). Screening was performed at a mean of 154 days following injury for sample 1 versus 7.1 days in sample 2. The mean age of the patients in sample 1 was 45.4 years, and the mean age of those in sample 2 was 46.1 years. The two samples had similar proportions of female patients (38.2% vs. 40.0%, P=0.80). The positive screening rate was 18.9% in sample 1 and 40.0% in sample 2 (P=0.001). For specific mechanisms, the positive rates were as follows: motor vehicle collisions, 17.2% in sample 1 and 17.6% in sample 2 (P>0.999); fall from height, 12.2% in sample 1 and 30.8% in sample 2 (P=0.20); and gunshot wounds, 39.1% in sample 1 and 80.0% in sample 2 (P=0.06). Conclusions: The ITSS was obtained earlier than PCL-5 and may identify PTSD in more orthopedic trauma patients. Differences in the frequency of PTSD may also be related to the screening tool itself, or underlying patient risk factors, such as mechanism of injury, or mental or social health.

• Journal of the Korean Society of Combustion
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• v.21 no.3
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• pp.1-6
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• 2016

The effect of applied electric fields on jet flow instability was investigated experimentally by varying the direct current (DC) voltage and the alternating current (AC) frequency and voltage applied to a jet nozzle. We aimed to elucidate the origin of the occurrence of twin-lifted jet flames in laminar jet flow configuration, which occur when AC electric fields are applied. The results indicate that a twin-lifted jet flames originates from cold jet instability, caused by interactions between negative ions in the jet flow via electron attachment as $O_2+e{\rightarrow}O_2{^-}$ when AC electric fields are applied. This was confirmed by experiments in which a variety of gaseous jets were ejected from a nozzle to which DC voltages and AC frequencies and voltages were applied, with ambient air between two deflection plates connected to a DC power source. Experiments in which jet flows of several gases were ejected from a nozzle and AC electric fields were applied in coflow-nitrogen provided further evidence. The flow instability occurred only for oxygen and air jets. Additionally, jet instability occurred when the applied frequency was less than 80 Hz, corresponding to the characteristic collision response time. The effect of AC electric fields on the overall structure of the jet flows is also reported. Based on these results, we propose a mechanism to reduce jet flow instability when AC electric fields are applied to the nozzle.

• Journal of Korean Society for Geospatial Information Science
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• v.23 no.2
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• pp.3-9
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• 2015

Since changes in land use in urban space cause traffic volume and it is closely related to traffic accidents. Therefore, an analysis on the causes of traffic accidents is judged to be an essential factor to establish the measure to reduce traffic accidents. In this regard, the analysis was conducted on the clustering by using the nearest neighbor indexes with regard to the occurrence frequencies of commercial and residential zone based on traffic accident data of the past five years (2009-2013) with the target of local small-medium sized city, Jinju-si. The analysis results, obtained in this study, are as follows: the occurrence frequency of traffic accidents was the highest in spring and the lowest in winter respectively. The clustering of traffic accident occurrence at nighttime was stronger than at daytime. In addition, terms of the analysis on the clustering of traffic accident according to land use, changes according to the seasons was not significant in commercial areas, while clustering density in winter tended to become significantly lower in residential areas. The analysis results of traffic accident types showed that the side-right angle collision of cars was the highest in frequency occurrence, and widespread in both commercial areas and residential areas. These results can provide us with important information to identify the occurrence pattern of traffic accidents in the structure of urban space, and it is expected that they will be appropriately utilized to establish measures to reduce traffic accidents.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.5
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• pp.800-808
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• 2022

The International Maritime Organization adopted the interim standards for ship maneuverability in November 1993 for preventing collision of ships at sea and for protecting the marine environment, and based on the accumulated data, in December 2002, the established standards for ship maneuverability were adopted. However, the standards adopted are those at full load, even keel, and at least 90 % of the ship speed at 85 % of the ship's maximum power. Moreover, these standards have limitations in providing information on maneuverability under actual navigational conditions. Therefore, in this study, frequency analysis AHP analysis techniques were studied by consulting navigational officers, captains, and experts, who have significant knowledge on ship maneuverability, utilization of the current standards, and the information necessary for the operation of the actual ship. The results of this study confirmed that the necessary information on maneuverability for the navigational officer operating the vessel is information about the turning circle at a small angle of 5°-10° and z-test information at maneuvering speed, not sea speed. Additionally, in relation to speed control, additional information on deceleration inertia and acceleration inertia is needed than the information on the stopping ability at sea speed and full loaded condition. The derived results are considered to be useful as basic data for preparing guidelines for ship maneuverability necessary for navigational of icers who operate ships.