• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권2호
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• pp.234-252
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• 2013

Due to the uncertain of connections in Delay Tolerant Networks (DTNs), most routing algorithms in DTNs need nodes to forward the message to others based on the opportunistic contact. The contact is related with the beaconing rate. In particular, nodes have more chances to encounter with each other with bigger beaconing rate, but more energy will be used. On the other hand, if the nodes forward the message to every node all the time, the efficiency of the routing algorithm is better, but it needs more energy, too. This paper tries to exploit the optimal beaconing rate and forwarding rate when the total energy is constraint. First, a theoretical framework is proposed, which can be used to evaluate the performance with different forwarding rate and beaconing rate. Then, this paper formulates a joint optimization problem based on the framework. Through Pontryagin's Maximal Principle, this paper obtains the optimal policy and proves that both the optimal forwarding and beaconing rates conform to threshold form. Simulation results show the accuracy of the theoretical framework. Extensive numerical results show that the optimal policy obtained in this paper is the best.

• ETRI Journal
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• 제35권5호
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• pp.748-756
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• 2013

This paper addresses the problem of online hop timing detection and frequency estimation of multiple frequency-hopping (FH) signals with antenna arrays. The problem is deemed as a dynamic one, as no information about the hop timing, pattern, or rate is known in advance, and the hop rate may change during the observation time. The technique of particle filtering is introduced to solve this dynamic problem, and real-time frequency and direction of arrival estimates of the FH signals can be obtained directly, while the hop timing is detected online according to the temporal autoregressive moving average process. The problem of network sorting is also addressed in this paper. Numerical examples are carried out to show the performance of the proposed method.

• 전기학회논문지
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• 제68권4호
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• pp.566-572
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• 2019

This paper proposes a new composite guidance law that can intercept moving targets and satisfy look angle rate constraint. In order to obtain the composite guidance law, we first develop a new look angle rate control guidance law which can maintain the maximum look angle rate limitation. And then, we propose the composite guidance scheme on the basis of the look angle rate control guidance and the proportional navigation guidance. To investigate the capturablity and characteristics of the proposed guidance, we also derive closed-form solutions and perform various numerical simulations. The proposed composite guidance only requires the line-of-sight rate, closing velocity, and missile's speed, thereby easily implementing in practical homing missiles.

• 한국국방경영분석학회지
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• 제36권2호
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• pp.1-10
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• 2010

Learning rate is generally applied to estimate an appropriate production labor cost. Learning effect is obtained from repetitive work during the production period under 3 assumptions ; homogeneous production, same producer, quantity measure in continuous unit. However, production breaks occur frequently in Korean defense industry environment because of budget constraint and annual requirements. In this case previous learning effect can not be applied due to learning loss. This paper proposed the application of learning rate when a production break occurs in Korea defense industry. To obtain a learning loss, we surveyed various learning loss factors for different production breaks(6, 12, 18 months) from 4 defense industry companies. Then, we estimate the first unit labor hours in re-production phase after production break using Anderlohr method and Retrograde method with the result of the survey. This work is the first attempt to show a method which defines and evaluates the learning loss factors in Korean defense industry environment.

• 정보보호학회논문지
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• 제21권4호
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• pp.39-46
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• 2011

본 논문은 다양한 네트워크 보안장비들이 갖는 고유의 보안정책들을 하나의 시스템 내에 단일 알고리즘으로 구현함으로써 네트워크를 기반으로 하는 공격 발생 시 최적의 통합 보안정책에 대한 연구이다. 실험을 위한 정책들은 Firewall, VPN(Virtual Private Network), IDS(Intrusion Detection System), IPS(Intrusion Prevention System)가 갖는 고유의 방어정책을 상호 조합하는 과정을 통해 최적의 보안 시스템을 구현하기 위한 실험을 한다. 또한, 보안정책 설정에 따른 시스템 부하와 빠른 탐지, 신속하고 효율적인 방어를 위한 통합 메커니즘 설계 및 네트워크 인프라 구현 기반을 확보하는데 의의가 있다.

• 한국산학기술학회논문지
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• 제22권3호
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• pp.261-267
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• 2021

예비군훈련을 담당하는 부대의 임무는 예비군이 평시에 실전적인 훈련을 받을 수 있는 환경을 만들어주는 것이다. 하지만 예비군훈련 담당부대의 특성상 운용 할 수 있는 병력부족의 문제로 실전적인 훈련환경을 만들어주는 예비군 훈련 지원 인원편성에 어려움이 많이 있다. 이러한 이유로 현재 군에서는 전년도 월 평균 예비군 입소율 결과로 당해연도 일일단위 예비군 입소율을 예측하면서 인력편성과 부대운영에 대한 계획을 수립하고 있다. 그러나 기존 예측방법은 실제 입소율과 비교 시 오차가 크게 발생할 수 있다는 문제점을 가지고 있다. 이 문제점은 훈련을 지원하는 교관과 조교 선정에 어려움을 주어 훈련성과 달성에 부정적으로 작용할 수 있다. 그러므로 실제 입소율과 오차를 최소화 할 수 있는 더 정확한 예측모형이 필요하다. 따라서 본 연구에서는 데이터마이닝을 기반으로 일일단위 예비군훈련 입소율을 예측한 모형을 제시하였다. 데이터마이닝 기반 모형의 검증을 위해 예비군훈련 담당부대에서 수집한 실제 데이터로 현재 군에서 사용하는 기존 예측방법과 비교하였다. 그 결과 본 연구에서 제시한 데이터마이닝 기반 예측모형이 기존 예측방법보다 오차를 줄이는 우수한 성능을 보였다.

• 한국추진공학회지
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• 제26권4호
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• pp.44-53
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• 2022

추력조절이 가능한 고체추진기관에서 감압률은 추력중단 성능에 가장 큰 영향을 미치는 인자이다. 본 연구에서는 몇 종류의 추진기관에서 구현 가능한 감압률의 범위를 파악하였으며 이를 통하여 추진기관 감압률에 미치는 주요 인자를 도출하였다. 추진제에 대한 소화특성 파악뿐만 아니라 추진기관의 목표성능을 만족할 수 있는 감압률을 파악하는 것이 실제 추력조절 시스템 설계에 중요하며 본 연구에서와 같은 감압률 모델획득 방법론은 추력중단이 필요한 고체추진기관 설계에 적용 가능할 것으로 판단된다.

• 한국IT서비스학회지
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• 제9권4호
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• pp.187-206
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• 2010

Evolutionary acquisition is an alternative to the grand design acquisition approaches. It has activities to make it possible to develop quickly and respond flexibly to changing customer needs and technological opportunities. The Ministry of Defense adopted an evolutionary strategy to acquire defense information systems. but it does not work well always. We look at problems from aspects of acquisition system and project management. We benchmark successful cases for evolutionary acquisition strategy in the DoD, the pubic and the private sector. We suggest an evolutionary strategy for defense information systems. The evolutionary strategy in this study includes an evolutionary acquisition framework, an evolutionary acquisition process, and an evolutionary acquisition guideline for defense information systems. The evolutionary strategy can help to implement evolutionary acquisition process for defense information system, and the process can increase the success rate of projects.

• 한국전기전자재료학회논문지
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• 제35권4호
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• pp.377-385
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• 2022

Thermal batteries are specialized as primary reserve batteries that operate when the internal heat source is ignited and the produced heat (450~550℃) melts the initially insulating salt into highly conductive eutectic electrolyte. The heat source is composed of Fe powder and KClO₄ with different mass ratios and is inserted in-between the cells (stacks) to allow homogeneous heat transfer and ensure complete melting of the electrolyte. An ideal heat source has following criteria to satisfy: sufficient mechanical durability for stacking, appropriate heat calories, ease of combustion by an igniter, stable combustion rate, and modest peak temperature. To satisfy the aforementioned requirements, Fe powder must have high surface area and porosity to increase the reaction rate. Herein, the hydrothermal and spray drying synthesis techniques for Fe powder samples are employed to investigate the physicochemical properties of Fe powder samples and their applicability as a heat source constituent. The direct comparison with the state-of-the-art Fe powder is made to confirm the validity of synthesized products. Finally, the actual batteries were made with the synthesized iron powder samples to examine their performances during the battery operation.

• 한국산업융합학회 논문집
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• 제26권5호
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• pp.885-894
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• 2023

Setting RAM target value for a defense system plays a crucial role in the development and design phases and the production phase as well. It is apparent that the achieved RAM target value can help maximizing the combat capability of a defense system and improving its performance throughout the system's life cycle from acquisition phase to disposal. Usually a defense system operates according to its OMS/MP (Operational Mode Summary / Mission Profile) and it consists of several subsystems which are supposed to be operated at each utilization rate under its operating conditions and the mission profiles assigned. In this study, a method of setting RAM target value is proposed for a defense system that are composed of several independent subsystems considering their utilization rates and the mission profiles assigned. And the case study of applying the proposed method of setting RAM target value to system A is dealt with.