• International Journal of Naval Architecture and Ocean Engineering
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• v.3 no.3
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• pp.208-215
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• 2011

A full-scale field trial in ice-covered sea is one of the most important tasks in the design of icebreaking ships. The first Korean icebreaking research vessel 'ARAON', after her delivery in late 2009, had a sea ice field trial in the Arctic Sea during July-August, 2010. This paper describes the test procedures and data analysis on the icebreaking performance of the IBRV ARAON. The data gathered from the icebreaking performance test in the Chukchi Sea and the Beaufort Sea during the Arctic voyage of ARAON includes the speed and engine power of the ship as well as sea ice thickness and strength data. The air temperature, wind speed and heading of the ship were also measured during each sea ice trial. The ARAON was designed to break 1 m thick level ice with a flexural strength of 630kPa at a continuous speed of 3knots. She is registered as a KR POLAR 10 class ship. The principal dimensions of ARAON are 110 m, 19 m and 6.8 m in length, breadth and draft respectively. She is equipped with four 3,500kW diesel-electric main engines and two Azipod type propulsion motors. Four sea ice trials were carried out to understand the relationship between the engine power and the ship speed, given the Arctic ice condition. The analysis shows that the ARAON was able to operate at 1.5knots in a 2.5m thick medium ice floe condition with the engine power of 5MW, and the speed reached 3.1 knots at the same ice floe condition when the power increased to 6.6MW. She showed a good performance of speed in medium ice floe compared to the speed performance in level ice. More detailed analysis is summarized in this paper.

• Journal of the Korean Society of Safety
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• v.34 no.5
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• pp.55-62
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• 2019

In this paper, we introduce a case of a fire accident during parking of a large truck that is repeatedly occurring. The shape and location of the combustion and electrical singularity commonly found in other vehicle fire accidents could limit the starter motor as the ignition section. In addition, it was possible to confirm the electrical melting singularity that could act as a cause of ignition between the start motor B terminal and the start motor enclosure. By combining the above investigations and investigations, it was possible to estimate the electric fire expressed from insulation breaking of the starter motor B terminal, and by using the renewable starter motor comparison product mounted on the fire vehicle, an experiment was performed to reproduce the ignition process from the starter motor under specific conditions. So. It is hoped that this will raise awareness about vehicle fires, which can lead to large fires or casualties, share the risks of using starter motors for regeneration, and help in the rapid and accurate investigation of similar vehicle fires in the future.

• Journal of Aerospace System Engineering
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• v.15 no.5
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• pp.43-49
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• 2021

This research shows how is designed, and its performance is evaluated on the ground for the VTOL drone before the flight test initiates. The targeted drone weight is approximately 45 kg including battery packs, and 4 motors are utilized to produce thrust and control directions. 30 min flight schedules were simulated to estimate the total power consumptions which result in 2.4 kWh. Then, two packs of 13-cells lithium-polymer battery with operating voltage ranging between 54 V and 44 V with up to 4 C-rate were fabricated to safely operate a VTOL drone. Moreover, the battery management system was installed to prevent over and under-voltage and over-current while running a battery system. To finally verify battery's performance, we conducted a ground evaluation for discharging battery tests at -10 ℃, 25 ℃ and 40 ℃, resulting in satisfying simulated power consumption conditions for flight schedules.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.12
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• pp.44-53
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• 2021

As environmental issues have emerged worldwide, emission gas regulations have been strengthened. In the construction machinery sector, studies have been actively conducted to utilize the power source of electric motors owing to the increasing demand for zero emissions. In this study, the gear specifications of an electric axle for construction machinery were selected by considering the specifications of the motor, gear tooth contact pattern, and face load factor. The gear strength evaluation was performed at the system level using the simulation model. The bending and contact strength of the spiral bevel gears and the bending strength of the planetary gear set showed a safety factor of 1 or more. However, the contact strength of the planetary gear set showed a safety factor of 0.92. Conservative results were derived by performing the analysis under the rated load condition of the motor. However, the ratio of the equivalent torque to the rated torque of the motor was 45% or less, hence, it was determined that no difficulties should arise regarding the durability of the axle.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.6
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• pp.856-866
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• 2021

The increasing international awareness regarding air pollutant reduction has resulted in increasing demand for eco-friendly ships; hence, electric ships are being actively developed by various countries. Presently, studies on electric ships are mainly focused on electric propulsion systems and electric motors. However, from the ship perspective, there are no studies on conceptual designs for coastal car ferries powered by removable power supply systems. In the present study, the main research consideration is regarding the conceptual design of a fully electrified car ferry using a battery-based removable system as the main power source. By analyzing the dimensions of more than 100 domestic coastal car ferries, the main criteria satisfying the requirements for developing a suitable vessel were derived, and a study on intact/damage stability was conducted considering the application of a removable battery truck. Further analyses of the problems concerning the conceptual design were also performed to derive solutions.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.10
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• pp.19-26
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• 2021

In fine-particle injection processing, hard fine particles, such as silicon carbide or aluminum oxide, are injected - using high-pressure air, and a small amount of material is removed by applying an impact to the workpiece by spraying at high speeds. In this study, a two-axis stage device capable of sequence control was developed to spray various shapes, such as circles and squares, on the surface during the micro-particle jetting process to understand the surface-shape micro-particle-processing characteristics. In the experimental device, two stepper motors were used for the linear movement of the two degree-of-freedom mechanism. The signal output from the microcontroller is - converted into a signal with a current sufficient to drive the stepper motor. The stepper motor rotates precisely in synchronization with the pulse-signal input from the outside, eliminating the need for a separate rotation-angle sensor. The major factors of the processing conditions are fine particles (silicon carbide, aluminum oxide), injection pressure, nozzle diameter, feed rate, and number of injection cycles. They were identified using the ANOVA technique on the design of the experimental method. Based on this, the surface roughness of the spraying surface, surface depth of the spraying surface, and radius of the corner of the spraying surface were measured, and depending on the characteristics, the required spraying conditions were studied.

• Journal of IKEEE
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• v.25 no.3
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• pp.556-564
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• 2021

This paper presents trends of safety improvement technologies for an electric propulsion system of eco-friendly ships. As an effort to reduce a green house effect, demands for eco-friendly ships have been increased. An energy storage system (ESS) is one of key systems in an eco-friendly ship and a lithium-ion battery generally used in an ESS system due to its high power density and efficiency. However, a lithium-ion battery is considered as one of reasons for ESS fire hazard. Since a fire extinguishing facility is especially limited in the ocean, safety issue in an eco-friendly ship is important. In this paper, recent safety improvement technologies for traction motors, ESS batteries and structures for eco-friendly ships are presented.

• Journal of Technology Innovation
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• v.29 no.2
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• pp.1-30
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• 2021

Recent years have witnessed various attempts of firms to acquire new knowledge. Purchasing intellectual property or merger and acquisition (M&A) can be such attempts, but joint venture can also be an effective way internalizing new complementary assets from external partners. However, due to difficulties in the formation and implementation of learning strategies, many joint ventures have failed to acquire necessary knowledge. In this respect, based on contingency theory and dynamic capability, the current research aims to investigate the failure case of knowledge transfer in an international joint venture - KEFICO established by Hyundai motors and BOSCH. Case firm optimized for hardware technology but did not establish a differentiated learning strategy and organizational structure to acquire software skills, which are intellectuals of different natures. Due to this inconsistency, it was not able for KEFICO to absorb new type of knowledge (skills related to engine control system). This study suggests the theoretical framework illustrating the case and provides some important implications for organizational learning.

• Journal of Powder Materials
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• v.26 no.2
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• pp.146-155
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• 2019

Rare earth magnets are the strongest type of permanent magnets and are integral to the high tech industry, particularly in clean energies, such as electric vehicle motors and wind turbine generators. However, the cost of rare earth materials and the imbalance in supply and demand still remain big problems to solve for permanent magnet related industries. Thus, a magnet with abundant elements and moderate magnetic performance is required to replace rare-earth magnets. Recently, $a^{{\prime}{\prime}}-Fe_{16}N_2$ has attracted considerable attention as a promising candidate for next-generation non-rare-earth permanent magnets due to its gigantic magnetization (3.23 T). Also, metastable $a^{{\prime}{\prime}}-Fe_{16}N_2$ exhibits high tetragonality (c/a = 1.1) by interstitial introduction of N atoms, leading to a high magnetocrystalline anisotropy constant ($K_1=1.0MJ/m^3$). In addition, Fe has a large amount of reserves on the Earth compared to other magnetic materials, leading to low cost of raw materials and manufacturing for industrial production. In this paper, we review the synthetic methods of metastable $a^{{\prime}{\prime}}-Fe_{16}N_2$ with film, powder and bulk form and discuss the approaches to enhance magnetocrystalline anisotropy of $a^{{\prime}{\prime}}-Fe_{16}N_2$. Future research prospects are also offered with patent trends observed thus far.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.3
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• pp.465-469
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• 2019

In this paper, the design of BLDC (brushless direct current) motors based on torque and back-EMF equations was carried out to assess the application of the motor in concrete vibrators. The air gap flux density of the motor is an important parameter because the length of the motor and the size of the diameter are given. The air gap magnetic flux density was calculated through a simplified magnetic circuit, and basic design of the shape and dimensions of the motor were then determined by carrying out experiments based on torque, back-EMF, and air magnetic flux density equations. After setting the outer and inner diameters, stack lengths, and rated speed of the motor, a detailed design was performed by simulations using the finite element method by designating the diameter and thickness of the motor as the key parameters. The final design to satisfy the target torque and the lowest THD (Total Harmonic Distortion) was carried out along with a simulation.