• 한국군사과학기술학회지
• /
• 제18권2호
• /
• pp.167-172
• /
• 2015

In this paper, we have compared some radio propagation models in order to verify the performance of W.C.Y LEE propagation model in mountain area. The four propagation models, which are Okumura-Hata, ITU-R P.525, Egli and W.C.Y. LEE, are analyzed by comparing the differences between measured values and propagation loss estimation values. And a correction method for W.C.Y LEE model is suggested to improve the performance of W.C.Y. LEE model with measured data in mountain area. Simulation results show that the estimation error using W.C.Y LEE model is the lowest among four propagation models. Also, the results show that the corrected W.C.Y LEE model with suggested method improves the performance of propagation loss estimation.

• 한국군사과학기술학회지
• /
• 제21권3호
• /
• pp.396-402
• /
• 2018

Earned Value Management(EVM) has been used to manage and forecast defense project schedule and cost over the last two decades in the world. However to support the lacking ability of schedule analysis in traditional EVM, earned schedule(ES) has been introduced as a tool to more accurately estimate schedule performance. This paper compares which method EVM or ES, provides more accurate schedule predictors in 32 Korean defense research and development projects. As a result of comparison, the ES method can predict the future schedule more reliably than the EVM method. We also analyze early warning function of schedule performance index considering project duration extension point. Through the analysis results, we confirm that both the EVM and the ES method lack the ability of the early warning in terms of the current schedule management criterion.

• 한국항공우주학회지
• /
• 제49권3호
• /
• pp.175-183
• /
• 2021

초음속 비행체에서 발생하는 소닉붐은 일반적인 환경소음과 달리 초저주파 영역을 포함한 충격음으로 전파된다. 본 논문에서는 배열 음향센서를 이용하여 소닉붐의 특징을 왜곡 없이 측정하기 위한 계측방법과 소닉붐의 전파방향을 추정하기 위한 도래각 추정 방법에 대해 연구하였다. 음향센서의 배치에 따른 도래각 추정성능을 이론적인 방법으로 제시하였고 모의실험에서 얻은 통계값을 이용하여 본 연구에서 제안하는 도래각 추정 방법의 성능을 검증하였다. 또한 실제 초음속 비행체에서 발생한 소닉붐을 제안한 방법으로 측정하였고 그 결과를 분석하였다. 본 연구에서 얻은 결과로 소닉붐 측정을 위한 시스템 구성, 도래각 추정 방법과 그 성능에 대한 직관적인 개념을 제공하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제17권9호
• /
• pp.2399-2418
• /
• 2023

The paper focuses on investigating secure transmission in wireless powered communication networks (WPCN) that involve multiple energy-constrained relays and one energy-constrained source. The energy is harvested from a power beacon (PB) while operating in the presence of a passive eavesdropper. The study primarily aims to achieve energy-efficient secure communications by examining the impact of channel estimation on the secrecy performance of WPCN under both perfect and imperfect CSI scenarios. To obtain practical insights on improving security and energy efficiency, we propose closed-form expressions for secrecy outage probability (SOP) under the linear energy harvesting (LEH) model of WPCN. Furthermore, we suggest a search method to optimize the secure energy efficiency (SEE) with limited power from PB. The research emphasizes the significance of channel estimation in maintaining the desired performance levels in WPCN in real-world applications. The theoretical results are validated through simulations to ensure their accuracy and reliability.

• 한국군사과학기술학회지
• /
• 제27권3호
• /
• pp.387-394
• /
• 2024

This paper describes a progressive test and evaluation strategy for verification of Korean Fighter eXperimental (KF-X) AESA(Active Electronically Scanned Array) radar development. Three progressive stages of development test and evaluation were officially performed from simulated test conditions to actual operating conditions according to standards: radar function/performance and avionics integration. KF-X AESA radar development is repeatedly verified by progressive stages consisting of five tests: Roof-lab ground test, System Integration Laboratory(SIL) ground test, Flying Test Bed(FTB) test, KF-X ground test, and KF-X flight test. As a result, the risk factor decreases as stages and tests progress. Therefore, development test and evaluation of KF-X AESA radar are successfully performed at low development risk.

• 한국항공우주학회지
• /
• 제45권7호
• /
• pp.610-617
• /
• 2017

최근의 무기체계에서는 효율적으로 적진을 탐색, 타격할 수 있는 저가의 소형 유도무기 개발이 많이 요구되고 있다. 이처럼 저가의 소형 드론형 무기의 제어를 위해서는 무선 인터페이스, 자세제어 위치탐색 타깃 탐색들을 위한 다양한 센서들과 고성능 카메라, 그리고 이를 실시간으로 통합하여 처리할 수 있는 고성능의 프로세싱 능력들을 갖춘 통합 전자장치가 필수적이다. 본 논문에서는 이를 위한 솔루션으로 안드로이드 스마트폰을 통합 전자 제어장치로 제안하고, 유도조종 알고리듬을 수행할 어플리케이션을 구현한다. 제안된 어플리케이션을 실제 스마트폰에 올려 비행모의 시뮬레이션을 통해 성능을 분석한다.

• 품질경영학회지
• /
• 제48권1호
• /
• pp.149-169
• /
• 2020

Purpose: This study analyzes the characteristics of the Quality Management performed by SMEs in the Defense Industry in supply chains and analyzes the effect of the continuous improvement activities based on cooperation. Especially, for Military Supplies, the suitability of products is usually decided by judging their conformity to the specification, and from this structural characteristic, this study would analyze the structural relationship of systematic improvement activities with Supply Chain Quality Management(SCQM) and Business Performance(BP). Methods: Continuous improvement activities(CI) have significance as the driver force for the promotion of Quality Management. Thus, this study analyzed the causal relationships from the perspective of the process among CI, SCQM and BP. For an analysis of the structural characteristics and causal relationships among the constituents, AMOS was used, and 297 companies in the Defense Industry were utilized as samples. Results: It turned out that CI had significant impacts on Management Infra(MGT_Infra), Process Management(PM), Human Resources Management(HRM) and Communication(COMU) and had an indirect impact on the enterprises' financial performance through the parameters of HRM and Communication. Meanwhile, it turned out that between CI and non-financial performance, there was a direct effect, and there was also an indirect effect through the variables of the Management Infra and Communication. Conclusion: It turned out that CI had a positive effect on SCQM as a proactive driver and that they had significant relationships with BP(financial, Non-financial), both financial performance and non-financial performance. However, PM did not have a significant relationship of effect with BP because of the character appearing by the evaluation method of military supplies for the conformity to the specifications.

• 한국군사과학기술학회지
• /
• 제21권5호
• /
• pp.623-629
• /
• 2018

The acceleration and the angular velocity that include natural frequencies of a missile detected by Inertial Measurement Unit(IMU) are transmitted to the control loop of a missile. The control loop command that is calculated using above signals can cause the resonance of the missile while it flies. Hence it is common to adapt the filter and the control loop for attenuating or eliminating the undesired signals such as natural frequencies. This paper introduces the new test technique using a floating system for performance evaluation of the designed filter and the control loop prior to a flight test. The proposed scheme can check out the degradation property of vibration in the filter and the control loop, while the conventional hardware-in-the-loop simulation(HILS) scheme cannot.

• 한국기계가공학회지
• /
• 제17권3호
• /
• pp.59-64
• /
• 2018

In general, tracked combat vehicles require excellent output performance of a power unit system to drive on special terrains and in extreme environmental conditions. However, high temperature and pressure are readily applied to the coolant hose in the power unit of the vehicles during high-speed driving under extreme road and weather conditions. These driving conditions can cause the separation phenomenon of the coolant hose in the power unit and consequentially engine overheating during driving. Therefore, a newly designed decompression device for the coolant hose has been proposed and manufactured to solve these problems in the present study. To validate of the newly proposed decompression device, the input and output pressures were measured under the before- and after-improvement conditions using experimental methods for different engine RPMs. In addition, the pre-heater temperature was measured under both conditions. From the experimental results, we expect that the current investigation can help to improve the driving performance of tracked combat vehicles.

• 한국자동차공학회논문집
• /
• 제20권4호
• /
• pp.1-9
• /
• 2012

The NCF control algorithm for an active suspension system was proposed and investigated. The NCF algorithm using spring dynamic variation force and suspension relative velocity was applied to the 1/4 vehicle model and numerical analysis was performed. Vehicle's performances such as vehicle displacement, vehicle acceleration, suspension deflection, tire deflection and absorbed power were calculated and compared with those of the passive, semi-active and LQR active suspension system that use full state feedback. Numerical results show that the proposed NCF active suspension system has superior performance compared with the passive and semi-active suspension system and has very similar performance compared with the LQR active suspension system. So the proposed NCF algorithm is considered as a highly practical algorithm because it requires only one displacement sensor in a 1/4 vehicle model.