통합 필터 변별도와 그래프 컬러링을 이용한 전술통신망 백본 무선 링크의 주파수 지정 방법

함재현,박휘성,이은형,최증원,Ham, Jae-Hyun,Park, Hwi-Sung,Lee, Eun-Hyoung,Choi, Jeung-Won 한국군사과학기술학회 2015 한국군사과학기술학회지 Vol.18 No.4

The tactical communications network has to be deployed rapidly at military operation area and support the communications between the military command systems and the weapon systems. For that, the frequency assignment is required for backbone wireless links of tactical communications network without frequency interferences. In this paper, we propose a frequency assignment method using net filter discrimination (NFD) and graph coloring to avoid frequency interferences. The proposed method presents frequency assignment problem of tactical communications network as vertex graph coloring problem of a weighted graph. And it makes frequency assignment sequences and assigns center frequencies to communication links according to the priority of communication links and graph coloring. The evaluation shows that this method can assign center frequencies to backbone communication links without frequency interferences. It also shows that the method can improve the frequency utilization in comparison with HTZ-warfare that is currently used by Korean Army.

RCD success criteria estimation based on allowable coping time

함재현,조재현,김재환,강현국 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.2

When a loss of coolant accident (LOCA) occurs in a nuclear power plant, accident scenarios which canprevent core damage are defined based on break size. Current probabilistic safety assessment evaluatesthat core damage can be prevented under small-break LOCA (SBLOCA) and steam generator tube rupture(SGTR) with rapid cool down (RCD) strategy when all safety injection systems are unavailable. However,previous research has pointed out a limitation of RCD in terms of initiation time. Therefore, RCD successcriteria estimation based on allowable coping time under a SBLOCA or SGTR when all safety injectionsystems are unavailable was performed based on time-line and thermal-hydraulic analyses. The time lineanalysis assumed a single emergency operating procedure flow, and the thermal hydraulic analysisutilized MARS-KS code with variables of break size, cooling rate, and operator allowable time. Resultsshow while RCD is possible under SGTR, it is impossible under SBLOCA at the APR1400’s current coolingrate limitation of 55 K/hr. A success criteria map for RCD under SBLOCA is suggested without cooling ratelimitation.

기계 학습을 활용한 노심용융물과 콘크리트 반응 현상의 민감도 분석

함재현(Jaehyun Ham),김상호(Sang Ho Kim),정재훈(Jaehoon Jung),박래준(Rae-Joon Park) 한국유체기계학회 2021 한국유체기계학회 학술대회 논문집 Vol.2021 No.12

모바일 애드 혹 네트워크를 위한 TDMA 스케쥴링 프로토콜 조사

강민석, 김태준, 김태홍, 이재생, 함재현 충북대학교 컴퓨터 정보통신 연구소 2019 컴퓨터정보통신연구 Vol.27 No.1

본문참고 본문참고

Analysis on the discharge characteristics and spreading behavior of an ex-vessel core melt in the SMART

김상호,함재현,이병희,김성일,김환열,박래준,정재훈 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.12

The aim of this research is to analyze the characteristics of a core melt discharged from the reactor vessel and the spreading behavior the core melt in the reactor cavity of the SMART. First, a severe accident sequence under conservative conditions is simulated by the MELCOR code to obtain the conditions for an analysis of the spreading behavior and coolability of the ex-vessel melt. Second, the spreading behavior and coolability of the ex-vessel melt are analyzed by the MELTSPREAD code. The level, temperature, and pressure of the water in the cavity as well as the temperature, mass, composition, and discharge velocity of the melt were utilized to construct the ex-vessel analysis. The melt spread only to part of the cavity, and that the height of the corium in a static state was less than 25 cm. The characteristics of a small modular reactor on the spreading behavior and coolability of melt were analyzed. In the SMART, the amount of melt discharged into the cavity is relatively small and the area of the cavity is sufficiently large when compared to a high-power pressurized water reactor. It was found that the coolability of an exvessel core melt can be sufficiently secured.

통계 정보 기반 트래픽 분석 방법론의 성능 향상

안현민,함재현,김명섭,An, Hyun Min,Ham, Jae Hyun,Kim, Myung Sup 한국정보처리학회 2013 정보처리학회논문지. 컴퓨터 및 통신시스템 Vol.2 No.8

네트워크의 고속화와 다양한 서비스의 등장으로 오늘날의 네트워크 트래픽은 복잡 다양해지고 있다. 효율적인 네트워크 관리를 위해서 QoS, SLA와 같은 정책을 적용하기 위해서는 트래픽 분석 중에서도 응용 트래픽 분류의 중요성이 크다. 현재까지 트래픽 분류에 관한 연구가 활발히 진행되어 왔는데 최근에는 플로우의 통계 정보를 이용한 트래픽 분류 방법론이 많이 연구되고 있다. 하지만 플로우의 통계 정보를 이용한 트래픽 분류 방법론에는 필히 고려해야 할 여러 문제점이 있다. 본 논문에서는 정답지 트래픽 분석을 통해 통계 정보 기반 트래픽 분석 방법론의 해결해야 하는 문제점들을 분석하고 그 해결방안에 대해 제안한다. 통계 정보 기반 트래픽 분석 방법론에서 필히 해결해야 할 문제점은 총 네 가지로 Feature들의 거리 측정 방법과 대표값 추출 방법, TCP 세션의 이상동작, 그리고 패킷 별 가중치이다. 제안하는 방법은 선정한 통계 시그니쳐 기반 트래픽 분석 시스템을 이용한 학내 망에서의 실험을 통해 그 성능을 검증한다. Nowadays, the traffic type and behavior are extremely diverse due to the growth of network speed and the appearance of various services on Internet. For efficient network operation and management, the importance of application-level traffic identification is more and more increasing in the area of traffic analysis. In recent years traffic identification methodology using statistical features of traffic flow has been broadly studied. However, there are several problems to be considered in the identification methodology base on statistical features of flow to improve the analysis accuracy. In this paper, we recognize these problems by analyzing the ground-truth traffic and propose the solution of these problems. The four problems considered in this paper are the distance measurement of features, the selection of the representative value of features, the abnormal behavior of TCP sessions, and the weight assignment to the feature. The proposed solutions were verified by showing the performance improvement through experiments in campus network.

이동 로봇의 상대위치 추정을 위한 기준노드 선택 기법

하태진,김선용,박선영,권대훈,함재현,임혁,Ha, Taejin,Kim, Sunyong,Park, Sun Young,Kwon, Daehoon,Ham, Jaehyun,Lim, Hyuk 한국군사과학기술학회 2016 한국군사과학기술학회지 Vol.19 No.4

When GPS signals are not available, a relative localization can be alternatively used to represent the topological relationship between mobile nodes. A relative location map of a network can be constructed by using the distance information between all the pairs of nodes in the network. If a network is large, a number of small local maps are individually constructed and are merged to obtain the whole map. However, this approach may result in a high computation and communication overhead. In this paper, we propose a reference-node selection scheme for relative localization map construction, which chooses a subset of nodes as a reference node that is supposed to construct local maps. The scheme is a greedy algorithm that iteratively chooses nodes with high degree as a reference node until the chosen local maps are successfully merged with a sufficient number of common nodes between nearby local maps. The simulation results indicate that the proposed scheme achieves higher localization accuracy with a reduced computational overhead.

무인 지상 차량 네트워크에서 GPS 재밍에 강인한 위치기반 라우팅

이진우,정우성,김용주,고영배,함재현,최증원,Lee, Jinwoo,Jung, Woo-Sung,Kim, Yong-joo,Ko, Young-Bae,Ham, Jae-Hyun,Choi, Jeung-Won 한국군사과학기술학회 2015 한국군사과학기술학회지 Vol.18 No.4

UGVs(Unmanned Ground Vehicles) are robots that can substitute humans in reconnaissance operations of potentially dangerous and contaminated sites. Currently, there have been active research on utilizing UGVs in military environments. Much resrach has been focused on exploiting the weakness of topology-based routing and instead utilize location-based routing for the networking of UGVs. It is generally assumed that location-based routing methods can fully utilize the location information gained from GPS. However, this may not be possible in tactical environments due to enemy GPS jamming and LOS(Line of Sight) limitations. To solve this problem, we propose a location-based routing scheme utilizing low control message that can calibrate the location information using GPS information as well as location of neighboring UGV, movement direct and speed information. Also utilizing topology-based routing scheme to solve incorrect location information in GPS jamming region.

위치정보기반 무인로봇체계 네트워크 구축 방안

권대훈,이재생,한명훈,함재현,최형석 한국통신학회 2017 정보와 통신 Vol.34 No.11

본고에서는 무인로봇 체계용 네트워크 구축방안으로 위치 정보를 활용하는 기법에 대해 다룬다. 현재까지 개발된 주요 위치정보 기반 기술에 대해 살펴보고 미래 무인로봇 체계를 위한 위치기반 네트워크 구축 방안에 대해 소개한다.

전술 에드혹 환경에서 이종망 게이트웨이 구조 및 시뮬레이션 연구

노봉수,한명훈,권대훈,함재현,윤선희,하재경,김기일,Roh, Bong Soo,Han, Myoung Hun,Kwon, Dae Hoon,Ham, Jae Hyun,Yun, Seon Hui,Ha, Jae Kyoung,Kim, Ki Il 한국시뮬레이션학회 2019 한국시뮬레이션학회 논문지 Vol.28 No.2

전술 에드혹 환경은 개별 지상 노드 간 분산적인 형태의 자율망으로 구성되므로 네트워크의 생존 가능성 및 유연성 측면에서 효과적이나 기동 간 통신 시 제한된 출력, 지형특성, 이동성 등의 제약으로 인하여 잦은 링크 단절 및 음영지역이 발생할 수 있다. 반면 위성 통신망은 지상 기동 망에 비해 지형특성과 이동성을 극복한 광역 무선 링크를 제공할 수 있는 장점이 있으나 상대적으로 한정된 대역폭 및 고지연 특성의 망이다. 미래 전장 환경에서 기존의 단독망 형태의 제약사항을 극복하고 지휘 통제 통신의 신뢰성 및 효율성을 높이기 위해서는 이종망 게이트웨이(Heterogeneous network gateway, HNG)를 중심으로 위성 통신망을 포함한 다계층 통합 네트워크 구조가 요구된다. 본 논문에서는 전술 에드혹 환경에서 위성-전술 에드혹 망을 통합적으로 고려하고 유통되는 임무 트래픽의 플로우 특성에 기반하여 신뢰성 있는 데이터 전달이 가능한 이종망 게이트웨이 구조 및 세부 알고리즘을 제시한다. 시뮬레이션은 네트워크 수준의 시뮬레이터인 Riverbed Modeler를 활용하여 제시하는 구조의 유효성을 확인하였다. The tactical mobile ad-hoc network(MANET) consists of distributed autonomous networks between individual ground nodes, which is effective in terms of network survivability and flexibility. However, due to constraints such as limited power, terrain, and mobility, frequent link disconnection and shadow area may occur in communication. On the other hand, the satellite network has the advantage of providing a wide-area wireless link overcoming terrain and mobility, but has limited bandwidth and high-latency characteristic. In the future battlefield, an integrated network architecture for interworking multi-layer networks through a heterogeneous network gateway (HNG) is required to overcome the limitations of the existing individual networks and increase reliability and efficiency of communication. In this paper, we propose a new HNG architecture and detailed algorithm that integrates satellite network and the tactical MANET and enables reliable data transfer based on flow characteristics of traffic. The simulations validated the proposed architecture using Riverbed Modeler, a network-level simulator.