• Journal of Internet Computing and Services
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• v.23 no.1
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• pp.77-86
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• 2022

The Republic of Korea is a country in which coastal surveillance is an imperative national task as it is surrounded by seas on three sides under the confrontation between South and North Korea. However, due to Defense Reform 2.0, the number of R/D (Radar) operating personnel has decreased, and the period of service has also been shortened. Moreover, there is always a possibility that a human error will occur. This paper presents specific guidelines for developing an AI learning model for the intelligent coastal surveillance system. We present a three-step strategy to realize the guidelines. The first stage is a typical stage of building an AI learning model, including data collection, storage, filtering, purification, and data transformation. In the second stage, R/D signal analysis is first performed. Subsequently, AI learning model development for classifying real and false images, coastal area analysis, and vulnerable area/time analysis are performed. In the final stage, validation, visualization, and demonstration of the AI learning model are performed. Through this research, the first achievement of making the existing weapon system intelligent by applying the application of AI technology was achieved.

• The Journal of the Acoustical Society of Korea
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• v.41 no.4
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• pp.446-460
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• 2022

In this paper, we propose an algorithm to improve target detection rate degradation due to direct blast in a bi-static sonar systems with high duty cycle using an adaptive filters. It is very important to suppress the direct blast in the aforementioned sonar systems because it has a fatal effect on the actual system operation. In this paper, the performance was evaluated by applying the Normalized Least Mean Square (NLMS) and Recursive Least Square (RLS) algorithms to the simulation and sea experimental data. The beam signals of the target and direct blast bearings were used as the input and desired signals, respectively. By optimizing the difference between the two signals, the direct blast is removed and only the target signal is remained. As a result of evaluating the results of the matched filter in the simulation, it was confirmed that the direct blast was removed to the noise level in both Linear Frequency Modultated (LFM) and Generalized Sinusoidal Frequency Modulated (GSFM), and in the case of GSFM, the target sidelobe decreased by more than 20 dB, thereby improving performance. In the sea experiment, it was confirmed that the LFM reduced the level of the transmitted direct wave by 10 dB, the GSFM reduced the level of the transmitted direct wave by about 4 dB, and the side lobe of the target decreased by about 4 dB, thereby improving the performance.

• Journal of Aerospace System Engineering
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• v.15 no.3
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• pp.1-10
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• 2021

The electro-hydrostatic actuators (EHA) are widely used in various industrial fields since they can independently execute the function of the hydraulic power source and have high efficiency. Particularly, in the aviation field, the EHA is mainly designed as dual redundant asymmetric tandem actuator to mitigate failure and minimize installation space. However, aviation EHAs designed in the form of dual redundant asymmetric tandem actuator have the disadvantage of decreased durability performance due to the occurrence of force fighting. In this paper, the controller is designed based on backstepping technique to improve control performance and reduce force fighting for aviation EHA. The augmented state observer is proposed to estimate the states required for control. Through simulation, it was verified that the proposed controller had superior control performance and significantly reduces the force fighting compared to the general PI controller.

• The Journal of the Acoustical Society of Korea
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• v.40 no.4
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• pp.297-303
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• 2021

When sound waves propagate over long distances in shallow water, measured transmission loss is greater than predicted one using underwater acoustic model with the Rayleigh reflection model due to inhomogeneity of the bottom. Accordingly, the US Navy predicts sound wave propagation by applying the empirical formula-based High Frequency Bottom Loss (HFBL) model. In this study, the measurement and analysis of transmission loss was conducted using mid-frequency (2.3 kHz, 3 kHz) in the shallow water of the East Sea in summer. BELLHOP eigenray tracing output shows that only sound waves with lower grazing angle than the critical angle propagate long distances for several kilometers or more, and the difference between the predicted transmission loss based on the Rayleigh reflection model and the measured transmission loss tend to increase along the propagation range. By comparing the Rayleigh reflection model and the HFBL model at the high grazing angle region, the bottom province, the input value of the HFBL model, is estimated and BELLHOP transmission loss with HFBL model is compared to measured transmission loss. As a result, it agrees well with the measurements of transmission loss.

• Journal of Aerospace System Engineering
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• v.16 no.3
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• pp.84-92
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• 2022

The electro-hydrostatic actuator (EHA) recently has been used in flight control fields for aircraft because of its benefits of minimizing oil leakage and weight, improving safety, and etc. while independently operating the hydraulic power source and eliminating complex hydraulic piping. The aircraft of which EHA is installed inside, has the thermal management issue of EHA, because of its limited cooling source as compared with the aircraft which installs the traditional central hydraulic system. So, the thermal analysis model which predicts the thermal characteristics of EHA, is required to resolve this thermal management issue. In this study, an oil circulation circuit inside the hydraulic power module comprised of hydraulic pump and electrical motor for EHA was applied. This is for the purpose of developing the internal rotary group of hydraulic power module, which operates under the conditions of high rotation speed and hydraulic pressure. After formulating an appropriate thermal analysis model, the thermal analysis results with oil cooled or no oil cooled hydraulic control module were compared and reviewed, for the purpose of predicting the thermal characteristics of EHA.

• Journal of Aerospace System Engineering
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• v.16 no.5
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• pp.62-69
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• 2022

EHA (Electro-Hydrostatic Actuator) is more energy efficiency than a centralized hydraulic system. In particular, the EHA used for aircraft has a redundant design in preparation for failure scenario. Also, due to the aircraft's internal space limitation, the actuator's length must be optimized. Therefore, a series configuration of double rod and single rod cylinder is advantageous. However, due to the asymmetry of the cross-sectional area of the piston, the force fighting phenomenon between the two cylinder areas occurs during redundant operation with a general control system. In this paper, the force fighting phenomenon of redundant EHA was simulated. A controller with load compensation and a force control-based position controller as a method to suppress its stimulation

• Maritime Security
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• v.5 no.1
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• pp.55-83
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• 2022

For humankind, the ocean is a treasure trove of natural resources and an important area that provides major transportation routes. However, marine ecosystems are under threat amidst the global climate change crisis. This is partly due to various sources of pollution emitted from ships, shore facilities, and other sources. In response, the navies of advanced countries such as the United States, the United Kingdom, and Europe have assessed such a climate change crisis as a new maritime security threat. These countries have made early efforts to prevent marine pollution from warships. These efforts have been legally embodied. This was legislation for technical and organizational structures to be practically applied in the field. Among these navies of developed countries, France has established parliamentary and intergovernmental plans to become a leader in environmental protection at the defense level, not only in the European region but throughout the world. Within this framework, the French Navy, through its internal instruction, has inclined its legal efforts to prevent marine pollution from warships. Therefore, this study examines the legislation for the prevention of marine pollution from warships within the French Navy and compares it with the marine environmental legislation applicable to the ROK Navy. It then deduces the implications for the ROK navy, which is advancing toward a Blue-Water navy.

• Journal of Platform Technology
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• v.10 no.4
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• pp.25-38
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• 2022

Recently, it is reported that the Korean Unmanned Aerial Vehicle (UAV) interface protocol (K-4586) based on STANAG-4586 is being developed to secure interoperability between UAVs. The core elements of the K-4586-based Unmanned Aircraft System (UAS) are the Core UAV Control System (CUCS), Vehicle Specific Module (VSM), Data Link Interface (DLI), and C4I systems. In UAS based on K-4586, the DLI function for transmitting and receiving messages to link UAVs is included in VSM and CUCS respectively. The Generator/Analyzer (G/A) tool is an apparatus that is developed for protocol conformance verification for VSM and CUCS, and G/A tools with DLI message transmitting and receiving should be developed separately. Core applications (VSM, CUCS, DLI) and G/A tools based on K-4586 may be developed independently depending on the developers. If the DLI message modules are different for each developer, the scope and results of protocol conformance verification will be dissimilar, and some problems may happen during system integration. In this study, common DLI message module based on the API was designed to provide the DLI message transmitting and receiving function necessary to the development of core applications and the protocol conformance verification tool of based on K-4586. When applying the proposed common DLI message module, it can be expected to shorten the UAS system development period and reduce costs, and ensure conformance of protocol. In this paper, the design and implementation method for the common DLI message module based on API was proposed and the results of functional test was described.

• The Journal of Engineering Geology
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• v.32 no.1
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• pp.157-171
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• 2022

Electrical resistivity tomography (ERT) is a traditional and representative geophysical method for determining the resistivity distributions of surrounding soil and rock volumes. Depth resolution profiles and sensitivity distribution sections of the resistivities with respect to various electrode configurations are calculated and investigated using numerical model data. Shallow vertical resolution decreases in the order of Wenner, Schlumberger, and dipole-dipole arrays. A high investigable depth in homogeneous medium is calculated to be 0.11-0.19 times the active electrode spacing, but is counterbalanced by a low vertical resolution. For the application of ERT depth resolution profiles and sensitivity distributions, we provide subsurface structure models for two types of land-creping failure (planar and curved), subvertical fracture, and weathered layer over felsic and mafic igneous rocks. The dipole-dipole configuration appears to be most effective for mapping land-creeping failure planes (especially for curved planes), whereas the Wenner array gives the best resolution of soil horizons and shallow structures in the weathered zone.

• Journal of Public Diplomacy
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• v.3 no.1
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• pp.21-42
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• 2023

Objective: To understand the contents and effects of public diplomacy by leaders, this paper throws out two questions: "To draw cooperation and support of international society in the middle of national crises, with what content do leaders conduct public diplomacy?" and "Through what mechanism, does leaders' public diplomacy promote cooperation and support of other countries?" Methods: To answer the research questions, this paper conducts a single case study with Ukrainian President Volodymyr Zelensky's public diplomacy in the Russia-Ukraine war in 2022. More specifically, the author collects text from Zelesky's Twitter and analyzes it in a descriptive manner. Results: When Russia invaded Ukraine in 2022, President Zelensky proactively utilized his SNS to communicate with people in other countries and thereby achieved the desired effect of public diplomacy. He has been delivering messages of 'appreciation of cooperation and support', 'situation of Ukraine', and 'congratulations or condolences', which could augment support, credibility, and audience cost. Conclusion: The effects of public diplomacy led to enhanced cooperation by alleviating problems within international cooperation and support. However, in the case of Ukraine, the patron's dilemma and commitment problem lasted, from which conducting public diplomacy has not been proven to be enough. The result of this paper provides lessons for the public diplomacy of the Republic of Korea in times of national crises in the future. In this regard, leaders should make efforts to promote the effectiveness of public diplomacy even in times of peace.