• Journal of the Korean Society of Mechanical Technology
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• v.20 no.6
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• pp.836-843
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• 2018

In this paper, dynamic model of 120mm self-propelled mortar is developed, and multi flexible body dynamics analysis is performed to analyze stresses occurring in the mount during mortar fire. For this, vehicle dynamic system, mortar dynamic system, and finite element mount model are proposed. The commercial program Recurdyn is used in the analysis. As a result of the analysis, the maximum stress(146.9MPa) occurred at the mount side plate. In order to analyze the validity of the analysis results, we performed strain measurement tests by selecting three major points, and the errors of results were 7.91%, 11.15%, and 18.23%, respectively. It is confirmed that the tendency of analysis and test is similar.

• Korean Journal of Metals and Materials
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• v.49 no.2
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• pp.137-144
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• 2011

Strengthening mechanisms in an ordered intermetallic compound containing coherent precipitates of lower antiphase boundary energy than the matrix were investigated on the basis of the interaction between the deformation induced dislocations and the disordered precipitates in an $Ll_2$ ordered $Ni_3Al$-based alloy. Extra work was needed to pull out the dislocations from the precipitate, which was dependent on the difference in the antiphase boundary energy between the matrix and the precipitate, as well as the size and volume fraction of the precipitate. The strength of the $Ll_2$ ordered ${\gamma}^{\prime}$ phase containing fine precipitates of the disordered ${\gamma}$ phase was examined using the proposed model. The model can explain almost quantitatively the age hardening behavior of the $Ll_2$ ordered ${\gamma}^{\prime}$ phase.

• International Journal of Computer Science & Network Security
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• v.22 no.6
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• pp.67-74
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• 2022

One type of network security breach is the availability breach, which deprives legitimate users of their right to access services. The Denial of Service (DoS) attack is one way to have this breach, whereas using the Intrusion Detection System (IDS) is the trending way to detect a DoS attack. However, building IDS has two challenges: reducing the false alert and picking up the right dataset to train the IDS model. The survey concluded, in the end, that using a real dataset such as MAWILab or some tools like ID2T that give the researcher the ability to create a custom dataset may enhance the IDS model to handle the network threats, including DoS attacks. In addition to minimizing the rate of the false alert.

• Journal of Positioning, Navigation, and Timing
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• v.10 no.4
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• pp.271-278
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• 2021

In this paper, a tropospheric delay error was calculated by using meteorological data collect from weather station and Saastamoinen model, and an empirical variogram of the tropospheric delay in the Korean peninsula was estimated. In order to estimate the empirical variogram of the tropospheric delay according to weather condition, sunny day, rainy day, and typhoon day were selected as analysis days. Analysis results show that a maximum correlation range of the empirical variogram on sunny day was about 560 km because there is overall trend of the tropospheric delay. On the other hand, the maximum correlation range of the empirical variogram on rainy was about 150 km because the regional variation was large. Although there is regional variation when the typhoon exists, there is a trend of the tropospheric delay due to a movement of the typhoon. Therefore, the maximum correlation range of the empirical variogram on typhoon day was about 280 km which is between sunny and rainy day.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2021.05a
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• pp.547-549
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• 2021

In Artificial Intelligence analysis, the process of creating a model and verifying it is a task that requires computational processing time because it is Batch Processing performed with already generated data. We need to model, validate, and predict real-time data, such as stocks and defense information, with data generated directly in front of us. As a solution to this, we solve it by applying techniques to segment the data required for artificial intelligence modeling tasks in order of time processing and distribute the data across multiple processes.

• Journal of Aerospace System Engineering
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• v.17 no.5
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• pp.11-18
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• 2023

The architecture of the Fuel Thermal Management System (FTMS) in a commercial aircraft engine was built to model and simulate the fuel system. The study shows the thermal interactions between the fuel and engine lubrication oil through the mission profile of a high bypass ratio, two-spool turbofan engine. Fuel temperature was monitored as it flowed through each sub-component of the fuel system during the mission. The heat load in the fuel system strongly depended on the fuel flow rate, and was significantly increased for the periods of cruise and descent with decrease of fuel flow rate, rather than for the periods of take-off. Due to the thermal interaction in the pump housing, the fuel temperature at the outlet of the low-pressure pump was increased (4.0, 9.2, and 30.0) % over the case without thermal interaction for take-off, cruise, and descent, respectively.

• Annual Conference of KIPS
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• 2024.10a
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• pp.98-99
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• 2024

본 연구는 딥러닝 기반 추천 모델 중 하나인 DLRM(Deep Learning Recommendation Model)의 학습 시간을 CPU 단일 환경과 GPU-가속 환경에서 비교한다. GPU를 사용하는 경우 일반적으로 더 빠른 학습이 기대되나, 배치 크기가 작아 GPU의 병렬 연산을 효율적으로 활용하지 못하는 경우 CPU만 사용하는 학습이 오히려 빠를 수도 있음을 실험을 통해 확인하였다. 학습 시간 외에 배치 크기는 자원 활용률에도 영향을 미치며, 이는 딥러닝 기반 모델의 학습과 추론에 도입 환경과 워크로드를 고려하여 실행 하드웨어를 선택할 필요가 있음을 시사한다.

• Journal of the Korea Institute of Military Science and Technology
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• v.20 no.1
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• pp.137-147
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• 2017

Wartime warship damage rate indicates how much damage of friend warships shall have occurred during naval battles accomplished under specific war operational plans. The wartime damage rate analysis provides the baseline of wartime resources requirements. If wartime damage rate is overestimated, the national finance will get to negative effects because of exceeding the budget for inventory, operation, and maintenance of resources. Otherwise, if wartime damage rate is underestimated, the national defense will lose in the war because of lack of critical resources. In this respect, it is important to estimate the wartime damage rate accurately and reasonably. This paper proposes a systematic procedure to estimate the wartime warship damage rate. The procedure consists of five steps; force analysis, operation plan analysis, input variable definition, simulation modeling, and output analysis. Since the combat simulation model is regarded as the main tool to estimate damage rate, the procedure is focused on the development of model and experiments using the model. A case study with virtual data is performed to demonstrate the effectiveness of the developed procedure.

• Journal of Power Electronics
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• v.17 no.2
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• pp.442-452
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• 2017

This paper deals with the input-output modeling of a vector controlled PMSM drive system and design of a simple multiple model adaptive control (MMAC) scheme with desired transient responses. We present a discrete-time modeling technique using closed-loop identification that can experimentally identify the equivalent models in the d-q coordinates. A bank of linear models for the equivalent plant of the current loop is first obtained by identifying them at several operating points of the current to account for nonlinearity. Based on these models, we suggest a simple q-axis MMAC combined with a fixed d-axis controller. After the current controller is designed, another equivalent model including the current controller in the speed control loop shall be similarly obtained, and then a fixed speed controller is synthesized. The proposed approach is demonstrated by experiments. The experimental set up consists of a surface mounted PMSM (5 KW, 220V, 8 poles) equipped with a flywheel load of 220kg and a digital controller using DSP (TMS320F28335).

• Journal of the Korea Institute of Military Science and Technology
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• v.19 no.6
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• pp.698-702
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• 2016

Thermal imager is now regarded as one of the key observation devices for ISR activities and getting important more and more. As other detectors, however, the thermal detectors also have maximum input and therefore they will be saturated if the input IR energy exceeds the allowed range. The saturation in the thermal detector makes it impossible to distinguish the target from background, as a result, the thermal imager does not perform its own mission anymore. In order to get an insight related with the image saturation, this paper develops a saturation model for a thermal imaging system, not a thermal detector. The proposed modeling starts from analyzing the specification of a thermal imager. Coupled with the characteristic parameters of the object, the saturation model can be used to predict the distance on which the detector is saturated. The proposed saturation model prove its validity by applying it for the case of observing a flash-bang.