• Journal of the Institute of Convergence Signal Processing
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• v.21 no.1
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• pp.38-48
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• 2020

In order to inspect the existing or newly constructed ship's hull, a professional diver directly inspects the ship's bottom of the water. However, since it is a work done by people, there are many dangers such as human casualties and crashes. To solve this problem, it is necessary to develop underwater drones for ship inspection for visual inspection. The technology applied to underwater drones, the use and manufacturing process of each component, and the method of manufacture such as firmware development were described, and the difference was compared by measuring the drone's own driving ability and driving ability using crawler under water, and the location tracking device test confirmed the error from the actual location. It is estimated that the use of underwater drones produced through this research will prevent human casualties and achieve economic effects and stability.

• Korean Journal of Optics and Photonics
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• v.31 no.6
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• pp.259-267
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• 2020

We evaluate the degradation of receiver sensitivity induced by direct and indirect exposure to solar irradiance in free-space optical communication systems. For this purpose, we calculate the variances of numerous noise components arising from solar irradiance, and then estimate the receiver sensitivity penalties for intensity-modulation/direct-detection and coherent systems. The results show that the penalties are less than 1.3 dB when indirect sunlight impinges on the detector, regardless of the system. However, the sensitivity penalties are estimated to be larger than 30 dB when the sunlight is directly incident upon the receiver. These penalties are barely reduced if we insert an optical polarizer, or if we adjust the bandwidth of an optical filter at the receiver to be as narrow as the signal's bandwidth.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.44 no.1
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• pp.9-16
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• 2021

Modern combat has been extended to the concept of real-time response to a variety of threats simultaneously occurring in vast areas. In order to quick command determination and accurate engagement in these threats, the combat system has emerged in frigate. Frigates conduct anti-surface, anti-submarine, and anti-aircraft as the core forces of the fleet. In this study, the combat effectiveness measures naval frigates using AHP (analytic hierarchy process) method. A hierarchical structure for measuring the combat effectiveness was developed, and weights of criteria were calculated by expert surveys and pair-wise comparisons. In addition, the combat effectiveness of frigates was synthesized and compared. The weights for each attribute were calculated, and the weights for the three main attributes were in the order of act (0.594), evaluate (0.277), and see (0.129). As a result of calculating the weight, anti surface warfare (0.203) was the highest. The combat effectiveness of FFG Batch-III, which has advanced hardware and software and improved combat system capabilities, see (1.73 to 2.56 times), evaluate (1.68 to 2.08 times), and act (1.31 to 3.80 times) better than the comparative frigate. In summarizing the combat effects of the frigate, FFG Batch-III was 1.41~2.95 times superior to the comparative frigate. In particular, a group of experts evaluated the act importantly, resulting in better combat effectiveness.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.3
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• pp.405-411
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• 2020

Recently, studies on underwater communication, related to the development of underwater resources, disaster monitoring and defense, have been actively carried out. In the design of wireless communication systems, path loss is the most important information to derive a link budget that is required to guarantee communication reliability by calculating received power level for the given communication link. The underwater acoustic channel have different characteristics according to geographical location and relevant environmental factors such as water temperature, depth, wave height, algae, and turbidity. Subsequently, many research institutes aiming to develop underwater acoustic communication systems are researching actively on the underwater acoustic channels in various sea areas. In Korea, however, studies on the path loss of the acoustic channel are still insufficient. Therefore, in this study, the path loss of the acoustic channel are studied based on measurement data of the at-sea experiment conducted at Geohae-do, southern sea of Korea.

• Journal of IKEEE
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• v.26 no.4
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• pp.537-544
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• 2022

This paper analyzes the occurrence and cause of bond wires fusing used in the manufacture of pulsed high power amplifiers. Recently GaN HEMT has been spotlight in the fields of electronic warfare, radar, base station and satellite communication. In order to produce the maximum output power, which is the main performance of the high-power amplifier, optimal impedance matching is required. And the material, diameter and number of bond wires must be determined in consideration of not only the rated current but also the heat generated by the transient current. In particular, it was confirmed that compound semiconductor with a wide energy band gap such as GaN trigger fusing of the bond wire due to an increase in thermal resistance when the design efficiency is low or the heat dissipation is insufficient. This data has been simulated for exothermic conditions, and it is expected to be used as a reference for applications using GaN devices as verified through IR microscope.

• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.5
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• pp.889-896
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• 2022

Data required in a wireless sensor network environment requires more accurate figures as technology advances and its complexity increases. However, in the case of operating a large number of sensor nodes in a large area, the balance between the power consumed and the data quality that can be acquired accordingly should be considered for that purpose. In particular, in complex, densely populated urban areas or military operations with specific goals, location data requires increasingly detailed and high accuracy over a wide range. In this paper, we propose a method of mounting a Global Positioning System(: GPS) only on some of the sensor nodes deployed in the wireless sensor network and improving the error of GPS location data measured on that sensor node through Angle of Arrival(: AoA) and Received Signal Strength Indicator(: RSSI).

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.11
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• pp.1457-1462
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• 2021

Untact order payment has become a new normal since the COVID-19. BLE beacon is a technology that supports low-power wireless communication within 70 meters without Bluetooth pairing and is specialized for indoor positioning. Therefore, it is suitable for building and providing O2O services beyond B2C and B2B services. However, beacons have a lower utilization rate because they have fewer platforms than wifi that support long-distance wireless communication. Therefore, this paper aims to provide more convenient non-face-to-face related services than before by designing and proposing an O2O service platform using BLE beacons. When scanning beacons, not only does it receive advertising data that beacons have, but it also ensures that the actual distance between the user's terminal and beacons is accurately calculated. Through accurate location, the O2O service platform will be able to provide users with store information, such as coupons and discounts, museum exhibits, and traffic information at the right time.

• The Journal of the Acoustical Society of Korea
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• v.42 no.1
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• pp.57-66
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• 2023

In this paper, it was investigated how the amount of energy harvesting will be varied from the FTEH which has inlet area is wider than outer area and attaching cantilever type MFC (Macro Fiber Composite) using by theoretical and experimental approaches. When MFC length increased 50 % vibration displacement also increased 3.5 times. When thickness decreased vibration displacement increased 30.9 times. In underwater tank experiments FTEH with spiral screw, flexible support, vertical direction fabrication cases showed maximum energy harvesting more 5 times than the case of MFC installed horizontally without spiral screws and on rigid supports. When the flow speed of 0.24 m/s FTEH's optimal resistance applied 4,10 kΩ, energy storage in the capacitor was measured 4 ㎼·s during 350 seconds. It was confirmed that the charging energy can be increased by lengthening the capacitor charging time of the large-area MFC installed vertically on the flexible support at high flow speed.

• Journal of Korea Society of Industrial Information Systems
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• v.14 no.3
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• pp.76-97
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• 2009

The strategic management process includes the establishment of competitive strategy, its implementation and the measurement of its performance. The sucess of strategic management largely depends on the integration of strategic management process into a managerial tool. This study is on the integration of strategic management process into a managerial tool based on the power process, so that it contributes to strategic success or sustainable competitive advantage of a ￡inn In order to do this, I discussed the principles of the power process, its characteristics, and then suggest their applications to the integration of the strategic management process. According to the results, the power process offers a theoretical and managerial tool which integrates the establishment of competitive strategy with managerial concepts, so that it increases the likelihood of strategic success. Furthermore I discussed the position of the power process approach to competitive advantage in a manner that displays similarities and differences with existing approaches such as industry organizational, resource-based and game theory approach.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.4
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• pp.617-624
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• 2023

Recently, miniaturization and low power consumption of electronic products and improved efficiency and power factor improvement have become a matter of great interest. In this paper, an AC-DC converter based on PWM control was designed and made. The AC-DC converter is designed with a structure in which one rectifier circuit and one output voltage control circuit are connected in series. The rectifier circuit is a diode-based single phase full-wave current circuit and the output voltage control circuit is a DC-DC conversion circuit based on PWM control. Arduino was used as the main control device for PWM control, and LCD was configured at the output stage so that the control result could be checked. The error between the output voltage displayed on the oscilloscope and LCD and the target output voltage was confirmed through repeated experiments with the test circuit, and the validity of the proposed design methodology was confirmed by showing an error rate of about 5% based on the oscilloscope measurement value.