• Journal of Korean Society of Industrial and Systems Engineering
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• v.45 no.3
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• pp.31-39
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• 2022

The Army, Navy, and Air Force are currently making various efforts to apply defense IoT technology by reflecting the characteristics of each military. However, there are concerns that comprehensive collection, management, and analysis may be limited because each military has no overlapping system or guaranteed interoperability of data, and there are inefficient aspects in terms of using and investing a limited defense budget. In this study, evaluation items and priorities for pilot projects were selected by applying Delphi technique and AHP method to determine which projects are preferentially effective when commonly applied in terms of Army, Navy, and Air force. As a result of the analysis, the project basis and driving force, project feasibility, performance and ripple effect, redundancy and connection were identified in the order of IoT-based small detachment units and unmanned base construction, intelligent smart unit, smart ground ammunition depot, and smart training management system. According to the comprehensive results reflecting the weights of each evaluation item, the fact that small detachment units and unmanned base construction project are recognized as the first project to be applied to the Army, Navy, and Air Force is a valid approach to be effective while each military is burdened with personnel management because of the reduction of manpower. Through the research results, it is expected that the direction of application to the policy of the defense IoT project can be confirmed in terms of efficient use of limited budgets.

• The Journal of the Acoustical Society of Korea
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• v.42 no.1
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• pp.32-41
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• 2023

Recently, studies on reverberation suppression using Non-negative Matrix Factorization (NMF) have been actively conducted. The NMF method uses a cost function based on the Kullback-Leibler divergence for optimization. And some constraints are added such as temporal continuity, pulse length, and energy ratio between reverberation and target. The tendency of constraints are controlled by hyperparameters. Therefore, in order to effectively suppress reverberation, hyperparameters need to be optimized. However, related studies are insufficient so far. In this paper, the reverberation suppression performance according to the three hyperparameters of the NMF was analyzed by using sea experimental data. As a result of analysis, when the value of hyperparameters for time continuity and pulse length were high, the energy ratio between the reverberation and the target showed better performance at less than 0.4, but it was confirmed that there was variability depending on the ocean environment. It is expected that the analysis results in this paper will be utilized as a useful guideline for planning precise experiments for optimizing hyperparameters of NMF in the future.

• Journal of the Korea Society for Simulation
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• v.19 no.4
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• pp.319-326
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• 2010

Effectiveness analysis of weapon system has been accomplished using engagement-level model alone. However, most previous works are prone to errors due to lack of behavioral information about the weapon systems. In order to overcome these limitations, this paper proposes an interoperation approach between the engagement- and engineering-level models. The proposed approach enables the engagement-level model to be supported by the engineering-level model representing the detailed behavior of weapon systems. Our methodology consider a limited combat situation including operational environments, dynamics and operational errors of weapons, and engagement orders. The paper describes a formalization of the system effectiveness analysis and defines an interface for interoperation between engagement- and engineering-level models. Then, we perform an anti-torpedo combat simulation as a case study.

• Transactions of the Korean hydrogen and new energy society
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• v.33 no.6
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• pp.733-742
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• 2022

Hydrogen fuel cell propulsion ships are emerging to respond to the recently strengthened carbon emission regulations in the international shipping sector. Methanol can be stored in a liquid state at normal pressure and temperature, and has the advantage of lower reforming temperature compared to other fuels. In this study, the optimal operating point of the methanol steam reforming system was derived by changing the Steam Carbon Ratio (SCR) from 0.10 to 3.00. Results showed that In terms of methanol conversion rate and hydrogen yield, the larger the SCR is the better, but in terms of system efficiency, it is most advantageous to operate at SCR 0.70 in Pressure Swing Adsorption (PSA) mode and SCR 0.80 in Pd membrane mode. Through this study, it was found that the optimal SCR in the reformer and the entire system including the reformer may be different, which indicates that the optimum operating point may be different depending on the change of the system configuration.

• The Journal of the Acoustical Society of Korea
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• v.41 no.2
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• pp.218-226
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• 2022

The main characteristics of the underwater acoustic channel have varying multipath and fast fading. Especially, Frequency Shift Keying (FSK) signals with multiple frequency bands caused loss of information bits allocated on the specific frequencies due to selective fading phenomenon. Therefore, this paper proposes frequency gain control algorithm based on preamble error rates. The proposed algorithm estimates optimal gain value in the range of preamble error rate with less than 10 % for specific faded frequency. By employing turbo equalized FSK signals with rate of 1/3, the experiment was conducted on a lake in Munkyeong city with distance of 300 m to 500 m. The result confirms that packets are decoded successfully by applying proposed algorithm as increasing number of iterations.

• The Journal of the Acoustical Society of Korea
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• v.41 no.2
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• pp.242-253
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• 2022

When the source waveform is unknown, the Green's function can be estimated by Ray-based Blind Deconvolution (RBD) based on the simple array signal processing. In previous papers, RBD was successfully demonstrated using simulation and experiments in shallow water environment. In this paper, we investigate the applicability of RBD for a long-range communication (e.g., 30 km, 60 km, and 90 km) in a deep water environment (1,000 m ~), using experimental data conducted in the east of Pohang, South Korea, in October 2018. Data results are presented to demonstrate Green's function estimation of a communication signal (2.2 kHz ~ 2.9 kHz) using a 16-element, 42-m long vertical array. The results show that the Green's function estimated from RBD is comparable to that of matched filter result. Additional communication performance at a maximum range of 90 km will be also presented.

• Convergence Security Journal
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• v.22 no.4
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• pp.53-63
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• 2022

The Ministry of National Defense reintroduced the non-commissioned officer corps (RNTC) system for colleges from 2015 and has been testing it for five years. The reason for this is that the acquisition of non-commissioned officers in the military is low and the level of manpower management is low. Through the implementation of the NCO(RNTC) system, the military expected that the colleges would stably acquire non-commissioned officers with excellent resources in various major fields, and the colleges expected positive results in entrance exams and employment. However, when analyzing the results of the pilot operation, it can be evaluated that the expected results have not been achieved. It was found that the system needs to be supplemented and improved to achieve the purpose of the system implementation in the promotion of recruitment of district candidates, selection evaluation, operation and the cooperative system between the military and colleges. Therefore, in this study, a development plan was presented to supplement the system and operation system so that the non-commissioned officer corps system can be smoothly established at universities and obtain the expected results from the military and colleges.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3D
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• pp.511-517
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• 2006

In this paper, we studied the techniques to analyze the flying safety area focused on the air base rules for military that has been the criteria of the altitude restrictions around the airfield for both civilian and military purposes in Korea. We wanted to present the effective method to analyze the restricted area and to help solving problems that could result recently from the altitude restrictions around the airfield at the beginning of the development projects. To do this we proposed the methods to effectively generate the model of the flying safety area in accordance with the air base rules using 3D GIS techniques and to automatically identify the obstructions caused by the natural and man-made features in those areas. To apply the proposed methods actually to the airfield chosen for the study area, we presented the approaches to generate geospatial informations based on the commercial digital maps and satellite imagery and by generating the flying safety area model, identifying the obstructions, and visualizing the integrated model for the flying safety area analysis we showed the practical usability of the proposed techniques.

• The Journal of the Convergence on Culture Technology
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• v.9 no.6
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• pp.789-793
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• 2023

Evalution of counter drone systems is conducted in order to designate plausible countermeasues against possible drone threats, assess the level of safety of national major facilities and derive complementary measures for detected weakness. Recently drone threats by North Korea have heavily impacted ROK(Republic of Korea) people and it has been stronly stressed to build efficient counter drone system for make the society protected and secured against drone threats. The researchers has conducted field investigations for some of national major facilites. There is, however, no standardized evaluation checklist, so we have proposed an evaluation checklist for counter drone systems though thinking process of RMA(Revolution in Military Affairs). This paper is to introduce the evaluation checklist for properly diagnosing each counter drone system.

• Journal of Aerospace System Engineering
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• v.18 no.2
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• pp.104-116
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• 2024

A satellite is ultimately verified by performing a coupled load analysis with the launch vehicle. To increase the accuracy of the coupled load analysis results, it is important to have good accuracy of the finite element model. Therefore, finite element model correlation is essential. In general, model correlation is performed by changing the material properties and thickness one by one, but this process takes a lot of time and cost. The current paper proposes an efficient model correlation method using optimization. Significant variables were selected through analysis of variance, and the time and cost required for analysis and optimization were reduced by using the Kriging surrogate model. The method proposed in this paper can be applied only with the vibration test results, and it has a great advantage in terms of efficiency in that it can significantly reduce the numerical calculation cost and time required.