• Journal of Power System Engineering
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• v.22 no.1
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• pp.41-47
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• 2018

This paper analyzes the output characteristics of a self excited induction generator with isolated mode according to change of its speeds and loads for building a hybrid electric propulsion system in special purpose ships by using power take off. The induction generators are being considered as an alternative choice to the well-developed generators because of their lower unit cost, inherent ruggedness, operational and maintenance simplicity. However, the generator working by stand alone has a few problems that the reactive power is required to establish the air gap magnetic flux, and the induced voltage and magnetizing current fluctuate when the load is varied. In spite of its advantages, basic design data of the capacitor bank and behaviors of the output characteristics of the generator are not sufficient for the system. Based on the operating condition(speed range of main engine) of the target boat, a reduced experimental equipment system was constructed to analyze the output characteristics of the SEIG. And a suitable capacitor bank of a stand-alone generator and its output characteristics under various loads was investigated in detail through these experiments. According to the experimental result, it was confirmed that the capacitor bank should be $70{\mu}F{\sim}100{\mu}F$, and the proper SEIG induced voltage should be DC 80 V ~ 250 V in order to storage electrical energy into a battery.

• The KIPS Transactions:PartD
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• v.16D no.2
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• pp.191-200
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• 2009

Location based services (LBSs) have drawn huge attention as the growing number mobile devices and wireless technology demand more pervasive information access. In LBSs, Constraint nearest neighbor queries are one of the important queries of human to fulfill his desired quickly through wireless technology. We propose new query processing of constrained nearest neighbor query on the air to support mobile clients which demand optimal uses of wireless broadcast channel and using minimum battery power of client. First we proposed NN query processing with constrained region and then explain the novel NN query processing with various types of constraints. We have proposed novel algorithms to support Constrained Nearest Neighbor queries on the air based on Distributed Spatial Index and Bitmap-based Spatial Index.

• Safety and Health at Work
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• v.12 no.4
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• pp.462-470
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• 2021

Background: Fatigue is pervasive, under-reported, and potentially deadly where flight operations are concerned. The aviation industry appears to lack a standardized, practical, and easily replicable protocol for fatigue risk assessment which can be consistently applied across operators. Aim: Our paper sought to present a framework, supported by real-world data with subjective and objective parameters, to monitor aircrew fatigue and performance, and to determine the safe crew configuration for commercial airline operations. Methods: Our protocol identified risk factors for fatigue-induced performance degradation as triggers for fatigue risk and performance assessment. Using both subjective and objective measurements of sleep, fatigue, and performance in the form of instruments such as the Karolinska Sleepiness Scale, Samn-Perelli Crew Status Check, Psychomotor Vigilance Task, sleep logs, and a wearable actigraph for sleep log correlation and sleep duration and quality charting, a workflow flagging fatigue-prone flight operations for risk mitigation was developed and trialed. Results: In an operational study aimed at occupational assessment of fatigue and performance in airline pilots on a three-men crew versus a four-men crew for a long-haul flight, we affirmed the technical feasibility of our proposed framework and approach, the validity of the battery of assessment instruments, and the meaningful interpretation of fatigue and work performance indicators to enable the formulation of safe work recommendations. Conclusion: A standardized occupational assessment protocol like ours is useful to achieve consistency and objectivity in the occupational assessment of fatigue and work performance.

• Journal of Advanced Navigation Technology
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• v.25 no.1
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• pp.29-39
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• 2021

As a means of solving traffic congestion in the downtown of large city, the interest in urban air mobility (UAM) using electric vertical take-off landing personal aerial vehicle (eVTOL PAV) is increasing. eVTOL configurations that will be used for UAM are classified by lift-and-cruise, tilt rotors, tilt-wings, tilted-ducted fans, multicopters, depending on propulsion types. This study tries to perform preliminary conceptual design for a given mission profile using reverse engineering techniques by taking the multicopter type Airbus's CityAirbus as a basic model. Wetted area, lift to drag ratio, drag coefficients were calculated using the OpenVSP which is an aerodynamic analysis software. The power required for each mission section of CityAirbus were calculated, and the corresponding battery and motor were selected. Also, total weight was predicted by estimating component weights of eVTOL.

• Journal of Advanced Navigation Technology
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• v.26 no.3
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• pp.144-160
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• 2022

Research on urban air mobility (UAM) is being actively conducted as a method of next-generation transportation. eVTOL, an airplane to be used for urban air mobility, is classified into a complex type, a tilt rotor type, a tilt wing type, a tilt duct fan type, and a multicopter type according to the propulsion method. In this study, conceptual design was performed for the next generation eVTOL of the new tilt rotor type in accordance with the existing design requirements. The aerodynamic analysis programs of OpenVSP and XFLR5 were used to perform aerodynamic analysis. The power required for each flight mission stage was calculated, the battery and motor were selected accordingly, and MTOW (Maximum Take-Off Weight) was predicted by estimating the weight of each component.

• Journal of Advanced Navigation Technology
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• v.27 no.1
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• pp.77-95
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• 2023

In this study, the conceptual design of a tilt + stopped rotor type electric vertical take-off and landing (eVTOL) aircraft was performed using design iteration. Based on Hyundai Motor's S-A1, the mission profile was defined using the concept of urban air mobility (UAM), and configuration design and aerodynamic analysis were performed using OpenVSP and XFLR5 software. After estimating the required power for the designed eVTOL, the required performance of the battery and the maximum take-off weight (MTOW) were calculated. . It was iteratively calculated using Microsoft Excel and Visual Basic Application, and a new electric motor weight estimation formula was derived. Also, the sensitivity analyses of each design variables of an eVTOL was performed using the automated program.

• Journal of Audiology & Otology
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• v.23 no.2
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• pp.96-102
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• 2019

Background and Objectives: Temporal bone fracture (TBF) is a common occurrence in cases of head trauma. Although the incidence of temporal bone concussion (TBC) has increased in cases of head trauma, it has not been extensively studied. We assessed the characteristics of TBF and TBC in patients with head trauma. Subjects and Methods: We conducted a retrospective review of 432 patients with head injury who visited our hospital between January 2011 and April 2016. Of these patients, 211 who met the inclusion criteria were included in the study. Their clinical characteristics, causes of injury, and hearing function were analyzed. Results: Among the 211 patients, 157 had TBFs and 54 had TBCs. Ear symptoms were more common among patients with TBF than among those with TBC. Car accidents were the most common cause of both TBF and TBC, but assault and sports injuries were more common among patients with TBC than among those with TBF. The occurrence of facial palsy in both cases of TBF and TBC. Hearing loss was observed among 35 patients with TBF and 11 patients with TBC. However, patients with TBF showed conductive hearing loss with an air-bone gap. Hearing function of these patients with TBF recovered with a reduced air-bone gap, but the patients with TBC showed little recovery. Conclusions: Emergency physicians should focus more on temporal bone injury in patients with head trauma. Therefore, an early complete diagnostic battery, which includes high-resolution computed tomography, audiometric tests, neurologic examination, and vestibular tests, be performed in patients with head trauma.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.2
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• pp.207-214
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• 2023

Ships emit significant amounts of air pollution. To reduce ship emissions, the government has implemented the Eco-Friendly Ship Act to improve the marine air environment, under which the use of eco-friendly ships that use eco-friendly energy as a power source encouraged and technologies to reduce marine pollution are developed. Therefore, the revision of relevant laws and systems such as inspection and facility standards for the safe operation of eco-friendly ships is urgently needed, especially those for fishing vessels, which account for the majority of domestic coastal vessels. This study defines the core equipment for the application of electric complex propulsion systems to fishing boats and presents a minimum safety standard plan for the adoption and dissemination of eco-friendly fishing boats.

• Korean Journal of Audiology
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• v.23 no.2
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• pp.96-102
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• 2019

Background and Objectives: Temporal bone fracture (TBF) is a common occurrence in cases of head trauma. Although the incidence of temporal bone concussion (TBC) has increased in cases of head trauma, it has not been extensively studied. We assessed the characteristics of TBF and TBC in patients with head trauma. Subjects and Methods: We conducted a retrospective review of 432 patients with head injury who visited our hospital between January 2011 and April 2016. Of these patients, 211 who met the inclusion criteria were included in the study. Their clinical characteristics, causes of injury, and hearing function were analyzed. Results: Among the 211 patients, 157 had TBFs and 54 had TBCs. Ear symptoms were more common among patients with TBF than among those with TBC. Car accidents were the most common cause of both TBF and TBC, but assault and sports injuries were more common among patients with TBC than among those with TBF. The occurrence of facial palsy in both cases of TBF and TBC. Hearing loss was observed among 35 patients with TBF and 11 patients with TBC. However, patients with TBF showed conductive hearing loss with an air-bone gap. Hearing function of these patients with TBF recovered with a reduced air-bone gap, but the patients with TBC showed little recovery. Conclusions: Emergency physicians should focus more on temporal bone injury in patients with head trauma. Therefore, an early complete diagnostic battery, which includes high-resolution computed tomography, audiometric tests, neurologic examination, and vestibular tests, be performed in patients with head trauma.

• The Journal of the Convergence on Culture Technology
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• v.9 no.3
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• pp.701-706
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• 2023

The Korean government and industry have presented a roadmap for the commercialization of UAM services and are promoting it in earnest. In order to introduce full-scale UAM services, there are various issues to be solved, such as the development of high-performance aircraft, the design of network bases and corridors, the optimization of operation management, and the establishment of related laws and systems. In this study, in terms of optimizing operation management, we will examine research trends by field, focusing on Korea, and derive research topics that need to be solved in the future. Korean researchers have suggested that research is centered on UAM service usage fees, usage intentions and acceptance models, and vertiport location selection, but operational optimization studies such as service order acceptance, aircraft repositioning, and battery charging and maintenance scheduling are needed in the future.