• Transactions of the KSME C: Technology and Education
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• v.1 no.1
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• pp.39-47
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• 2013

Top Drive Machine is drilling equipment which transfers motor torque to the drill bit. Kelly Rotary Table of the Derrick Drilling Machine (DDM) is firstly developed at 1983, and the first commercial model DDM 650DC was released at 1984. Offshore drilling business is high value-added industries. "N" Company of U.S.A and "A" company of Norway hold more than 90 percent of the global offshore drill system market, so it is hard to take away market share and develop offshore drilling equipment. Consequently, this paper introduce method for concept design of new reliability machine by limited information. To achieve this, design & analysis tools as CATIA, DELMIA, Pro Engineering, ANSYS were used to evaluate design error and strength/flow analysis at new concept design in Top Drive Machine.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.6
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• pp.2465-2471
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• 2012

For the steel structures those are used in harsh sea environments, corrosion fatigue is a challenging issue in connection with design life. In this research, in order to investigate the influence of cathodic overprotection on the corrosion fatigue crack propagation behavior, corrosion fatigue crack propagation test under the condition of -950mV vs SCE was conducted by using of high tensile TMCP steel plate and the relationships between da/dN-${\Delta}K$ were obtained. At this test, when ${\Delta}K$ is low, the crack propagation rates were accelerated compared to those of seawater condition, however, when ${\Delta}K$ is high, the crack propagation rates were lower than those of seawater condition. As the cause for the acceleration and deceleration of corrosion fatigue crack propagation rates under the condition of cathodic overprotection, the role of hydrogen and calcareous deposits are discussed.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.5
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• pp.484-492
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• 2013

With the industrial acceleration in a lot of countries of the world, the demand for anti-corrosion and anti-abrasion material increases continuously. Particularly, stainless steel with the fine surface and excellent corrosion resistance is widely used in various industrial fields including ship, offshore structures tidal power plant, and etc. In marine environment, however, it is easy to generate by the corrosion damage by $Cl^-$ ion and cavitation damage due to high rotation speed on stainless steel. Therefore, in this research, the cavitation erosion-corrosion test (Hybrid test) was performed for 304 stainless steel specimen used in the high flow rate seawater environment. And the cavitation damage behavior in the corrosive environment was analyzed overall. The high hardness was shown due to the formation of compressive residual stress by the water cavitation peening effect in cavitation condition. However, high current density in the potentiodynamic polarization experiment presented with the breakdown of the passive film caused by physical impact. Therefore, both electrochemical characteristics and mechanical properties must be taken into account to improve the cavitation resistance in seawater.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.25 no.1
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• pp.18-23
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• 1989

An approach for robustness recovery of the observer-based control system is presented. The approach is developed by adding a loop with appropriate constant matrix to the observer-based closed-loop system. It will be shown that if there exists an added-loop matrix M satisfying F=MC for a feedback gain F and output matrix C, then the observer-based control systems have the same loop transfer functions as full-state feedback implementations, in other words, the former has the same relative stability and robustness as the latter.

• Journal of the Korean Society of Marine Environment & Safety
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• v.12 no.2 s.25
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• pp.151-155
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• 2006

In these days, welding is the most commonly used metallic connection technology and also is the fundamental production technology of the modem industrial, which is used in various areas of the industrial fields, such as shipbuilding, automobiles, airplanes and plant facilities. However welding process produces strong light, electric currents, and fume gases etc., and the welding automation is not so easy compared to the other works of manufacturing industries which produce the standardized products in large quantities. So it is difficult to weld and detect the all kinds of seams automatically by a specific sensor. In this paper the sensor applying strain gauges is used to detect the seams of triangular wave form. With the auto carriage having the sensor we proposed the experiment to weld and track the seam automatically.

• Journal of the Korean Geotechnical Society
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• v.34 no.12
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• pp.43-58
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• 2018

In this study, the load-transfer behavior along the shaft of the prebored and precast piles was investigated by pile loading tests. Special attention was given to quantifying the skin frictions developed between the pile-soil interfaces of the 14 instrumented test piles. Based on this detailed field tests, the load - settlement curves and axial load distributions of piles were obtained and the load-transfer curves (t-z curves) for the test piles were proposed. As such, it is found that the test results show two different load transfer behaviors; ductile and brittle behavior curves. The corresponding t-z curves are proposed based on the hyperbolic- and sawtooth-shape, respectively. By validating the accuracy of the proposed curves, it is also found that the prediction results based on the proposed load-transfer curve are in good agreement with the general trends observed by the field loading tests.

• Journal of the Institute of Convergence Signal Processing
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• v.22 no.2
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• pp.57-63
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• 2021

The purpose of this study is to develop a Smart Helmet to safeguard forest firefighting crews and provide on-site information in real time. The Smart Helmet for forest firefingting crews is equipped with a camera, video/voice communication module, GPS, Bluetooth, and LTE module to promote the safety of them, and through the Smart Helmet, the site situation is is transmitted in real time, and full duplex communication is possible. As a result of testing using the Smart Helmet, the control center was able to receive on-site information and communication with on-site forest firefighting crews. Through site evaluation and user evaluation, it was confirmed that the Smart Helmet needs to be improved. The developed Smart Helmet can be used in various ways in forest disasters and forest industry.

• Journal of the Institute of Convergence Signal Processing
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• v.21 no.2
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• pp.92-100
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• 2020

Currently, the demand for underwater or underwater photography is growing very fast. Its coverage of underwater shooting for broadcasting, leisure and sports, and military and operational use is also growing rapidly. Among them, we specifically select the best camera to be used in underwater drones to photograph and inspect marine life attached to the ship's hull. To compare three cameras performance, they are compared and evaluated using objective and subjective criteria in special circumstances such as underwater shooting. This study checks whether performance criteria, such as resolution of a camera, meet objective and subjective standards in the unusual situation of underwater shooting. And it shows that in addition to the filter that calibrates the image, proper camera selection is important for providing good picture quality. Even after this study, research using more diverse cameras could provide an appropriate standard for comparison of underwater camera quality.

• Journal of the Institute of Convergence Signal Processing
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• v.22 no.3
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• pp.134-140
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• 2021

This study relates to the development of a wearable device that can identify a personal location using low-power GPS and IMU based on energy harvesting. The energy harvesting technology using a piezoelectric device was applied for the development of personal location identification, and made it possible to acquire precise personal location data using GPS and IMU. As a result of the experiment, it was confirmed that GPS and IMU data were normally received. The personal location identification device can be prepared for an accident by identifying a personal location in a disaster area, etc., and the user will be able to use it easily regardless of time, place, and environment. It is expected that it can be used in various fields such as leisure and health care.

• Journal of the Society of Naval Architects of Korea
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• v.59 no.2
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• pp.64-71
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• 2022

In this paper, we simulate the collision of a solitary wave on a vertical wall in a uniform water channel and investigate the effect of damping on the amplitude attenuation. In order to take into account the damping effect, we introduce the Stokes damping whose dissipation is dependent on the velocity of wave motion on the surface of a thin layer of oil. That is, we use the improved Boussinesq equation with Stokes damping to describe the damped wave motion. Our work mainly focuses on the amplitude attenuation of a propagating solitary wave, which may depend on the Stokes damping together with the initial position and initial amplitude of the wave. We utilize the method of images and a powerful numerical tool (functional iteration method) for solving the improved Boussinesq equation, yielding an effective numerical simulation. This enables us to find the amplitudes of the incident wave and reflected one, whose ratio is a measure of the (wave) amplitude attenuation. Accordingly, we have shown that the reflection of a solitary wave by a vertical wall is dependent on not only the initial amplitude and position of a solitary but the Stokes damping.