• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.1
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• pp.203-209
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• 2019

In this work, a new land-specific resistance measuring device (GM) and a measuring probe (Grounding Rod) are connected to the WENNER quadrant as power-line communication (PLC). In groups of two (P1,P2) probes, five to ten probes are installed in series on the ground at intervals of 1m, 2m, 4m, 8m, and 16m, respectively. If the PLC signal from the GMD is detected by the receiver of the Probe 1 (P1) for measurement, the minute voltage and current for measurement flow from the PSD (power supply) attached to the probe to the ground, and then, through the soil between P1 and P2, enters the Probe 1 (P2). The resistance value is then measured by the principle of voltage drop due to ground resistance. Measure the earth resistance every T seconds up to 1 trillion and store the measured data on the Arduino Server mounted on the main equipment. Stored measurement data can be derived from formulas by Ohm's Law and from inherent resistance (here,). Data obtained in real time will be linked to CDGES programs installed on Main PC, enabling data analysis and real-time monitoring of the ground environment on land. In addition, a three-dimensional display is possible with 3D graph support by identifying seasonal characteristics such as temperature and humidity of land (soils). The limitations of the study will require specific application measures of Test Bed for commercial access to a model that has been developed and operated experimentally.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.5
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• pp.468-476
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• 2019

This paper presents the means of improving the strength of LTV's FRP structure for resolve and prevent quality problems. LTV secures enough kerb weight by applying FRP materials at hood and rear van assembly. However, because of FRP's inherent limitations, many initial quality problems such as crack at connections have occurred. Moreover, hood assy' is concerned about fall of endurance, because hood assy' have operated in abnormal condition. Therefore, this study executes lamination structure optimizations of FRP structure for improving bending strength. As a results, hood and rear van's bending strength at connections is improved 8.1 times and 1.5 times, respectively. Also hood assy's plate secures endurance life and improve 1.7 times of critical load about abnormal operating conditions through 1.4 times improvement of bending strength.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.7
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• pp.291-298
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• 2019

We describe the improvement of insulation performance and the prevention of electrolyte leakage in a single cell in order to prevent the fuming phenomenon caused by leakage of electrolyte in a lithium secondary battery in a submerged weapon (torpedo) operated in Korea. A torpedo using lithium secondary battery as a main power source (propulsion battery) can induce the heat and fuming phenomenon, which makes it inconvenient for naval equipment operation in Korea. In the simulation test, the electrolyte of some battery cells leaked in the battery pack unit, leading to a short circuit between the main power circuit and the terminal tab of the high voltage part. We analyzed the characteristics and mechanism of the lithium secondary battery during this heat generation and fuming phenomenon. In order to prevent leakage of the electrolyte in the lithium secondary battery, the design was improved via fundamental (terminal tap enhancement) and complementary (insulation block selection and installation) measures. Comparison of the performance test before and after the improvement showed that the tensile strength of the tap terminal was improved about 2 times and the withstand voltage characteristic was improved. The application of quality improvement measures resulted in no fuming even after more than 3 years of field operation. This result is expected to improve the operation and storage stability of the torpedo propulsion cell.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.1
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• pp.1-8
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• 2021

This study developed low-cost and high-efficiency pavement condition monitoring technology to produce the key information required for pavement management. A noise and artificial intelligence-based monitoring system was devised to compensate for the shortcomings of existing high-end equipment that relies on visual information and high-end sensors. From idea establishment to system development, functional definition, information flow, architecture design, and finally, on-site field evaluations were carried out. As a result, confidence in the high level of artificial intelligence evaluation was secured. In addition, hardware and software elements and well-organized guidelines on system utilization were developed. The on-site evaluation process confirmed that non-experts could easily and quickly investigate and visualized the data. The evaluation results could support the management works of road managers. Furthermore, it could improve the completeness of the technologies, such as prior discriminating techniques for external conditions that are not considered in AI learning, system simplification, and variable speed response techniques. This paper presents a new paradigm for pavement monitoring technology that has lasted since the 1960s.

• Korean Journal of Construction Engineering and Management
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• v.22 no.1
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• pp.36-46
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• 2021

With an increasing trend toward high-rise modular construction, the simultaneous use of tower cranes at a modular construction site has recently been observed. Tower crane layout planning (TCLP) has a significant effect on cost, duration, safety and productivity of a project. In a modular construction project, particularly, poor decision about the layout of tower cranes is likely to have negative effects like additional employment of cranes and redesign, which will lead to additional costs and possible delays. It is, therefore, crucial to conduct thorough inspection of field conditions, lifting materials, tower crane capacity to make decisions on the layout of tower cranes. However, several challenges exist in planning for a multi-crane construction site in terms of safety and collaboration, which makes planning with experience and intuition complicated. This paper suggests a multi-objective optimization model for selection of the number of tower cranes, their models and locations, which minimizes cost and conflict. The proposed model contributes to the body of knowledge by showing the feasibility of using multi-objective optimization for TCLP decision-making process with consideration of trade-offs between cost and conflict.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.6
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• pp.188-196
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• 2021

For the tactical vehicles operated by the Korean army, the hub-reduction portal axle was applied considering Korea's topographical characteristics. Hub-reduction was applied to a Korean military vehicle to increase the vehicle body to secure ground clearance and improve the driving capability on rough roads, such as unpaved and field land by increasing the torque. The Korean military is operating tactical vehicles after various performance tests, including durability driving, but wheel damage occurred in one of the vehicles operating in the front units. Failure analysis revealed many damaged parts, including the hub, making it difficult to determine the cause. Therefore, an analysis of the failure occurrence mechanism for each damaged part was conducted, which confirmed that the cause of wheel breakage was a hub. Furthermore, the root cause of the hub breakage was a crack due to internal pores and foreign matters. In addition, a realistic improvement plan that can be applied throughout the design, manufacture, and shipping stages was presented using the fishbone diagram analysis. The derived improvement plan was verified through unit performance tests, including CAE and actual vehicle tests, and by reflecting this, the driving safety of Korean tactical vehicles was improved. Finally, it is expected that the proposed method for analyzing the failure occurrence mechanism will be used as reference material when analyzing the quality problems of similar military vehicles in the future.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.2
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• pp.1-10
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• 2021

In this study, a circular pipe can be installed by suction pressure for construction on soft ground with a low-water level. A series of laboratory-scale model tests were conducted in sandy ground to comprehend the suction pressure of the circular pipe in low-water levels. For repeated tests on saturated sandy soil, a container was mounted with three vibration generators on the floor. A repetitive vibration was applied using the vibration system for ground compaction. In the model tests, different diameters and thicknesses on saturated sandy soil with a water depth were considered. The result showed that the suction pressure increased with increasing penetration depth of the circular pipe. Moreover, the suction pressure required to penetrate the pipe decreased with increasing diameter. In the low-water level, the total suction pressure measured at the top lid increased because additional suction pressure is required to lift the water column. On the other hand, this led to a decrease in suction pressure to penetrate the circular pipe because the weight of the water column is applied as a dead load. Therefore, it is necessary to consider the water level to design the required suction pressure accurately.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.1
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• pp.134-145
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• 2021

It is common to optimize the propulsion control system through a so-called tuning process that modifies the parameter values of the propulsion control software during a ship commissioning. However, during this process, if the error of the initial setting value is large, the tuning time may take too long, or the propulsion equipment can be seriously damaged. Therefore, we conducted research on the design of a propulsion controller that applied a Processor lever controller even for inexperienced people with relatively little experience in tuning propulsion control software to be able to reduce the tuning time while protecting the propulsion system. Through simulation, by comparing the execution result of propulsion control lever commands through the PI controller without applying the Processor lever controller. We analyzed the improvement of the Overshoot and propulsion performance. The simulation results showed that the safety of the propulsion system increased because Overshoot of approximately 9.74%, which occurred when the Processor lever function was not applied.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.4
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• pp.498-505
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• 2020

Aggregate occupies about 70-85% of the concrete volume and is an important factor in reducing the drying shrinkage of concrete. However, when constructing high-rise buildings, it acts as a problem due to the high load of natural aggregates. If the load becomes large during the construction of a high-rise building, creep may occur and the ground may be eroded. Material costs increase and there are financial problems. In order to reduce the load on concrete, we are working to reduce the weight of aggregates. However, artificial lightweight aggregates affect the interface between the aggregate and the paste due to its higher absorption rate and lower adhesion strength than natural aggregates, affecting the overall strength of concrete. Therefore, in this study, in order to grasp the interface between natural aggregate and lightweight aggregate by type, we adopted a method of measuring electrical resistance using an EIS measuring device, which is a non-destructive test, and lightweight bone. The change in the state of the interface was tested on the outside of the material through a blast furnace slag coating. As a result of the experiment, it was confirmed that the electric resistance was about 90% lower than that in the air-dried state through the electrolyte immersion, and the electric resistance differs depending on the type of aggregate and the presence or absence of coating. As a result of the experiment, the difference in compressive strength depending on the type of aggregate and the presence or absence of coating was shown, and the difference in impedance value and phase angle for each type of lightweight aggregate was shown.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.2
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• pp.193-201
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• 2021

The welding has a high proportion of the production and drying of ships or offshore plants. Non-destructive testing is carried out to verify the quality of welds in Korea, radiography test (RT) is mainly used. Currently, most shipyards adopt analog-type techniques to print the films through the shoot of welding parts. Therefore, the time required from radiography test to pass or fail judgment is long and complex, and is being manually carried out by qualified inspectors. To improve this problem, this paper covers a platform for scanning and digitalizing RT films occurring in shipyards with high resolution, accumulating them in management servers, and applying artificial intelligence (AI) technology to detect welding defects. To do this, we describe the process of designing and developing RT film scanning equipment, welding inspection information integrated management platform, fault reading algorithms, visualization software, and testing and verification of each developed element in conjunction.