Earticle

본 논문은 분산 시스템에서의 표준합성환경 기반 수중 교전 시뮬레이션을 위한 방법론이다. 수 중 교전 시뮬레이션의 경우 염분과 수온 등의 수중 환경 데이터를 시뮬레이션에 반영하는 것이 중요 하다. 분산 시뮬레이션 시스템에서 이러한 환경 데이터의 재사용성과 상호운용성 향상을 위해 합성 환 경 표현 및 교환 표준(Synthetic Environmental Data Representation and Interchange Specification, SEDRIS(ISO standard for environmental data))이 개발되었고, 본 논문에서는 SEDRIS 를 활용하여 수중 합성환경을 구축한다. 본 논문을 통해 SEDRIS가 합성환경 데이터의 국제 표준이 지만 그 방대함과 복잡함으로 인하여 사용이 저해된 문제점을 대기/해양 환경에 대해 효율적인 SEDRIS 기술 활용 방법을 제시하여 해결한다. 본 논문의 최종 목적은 대기/해양 환경 표현을 위한 다차원 격자 기반의 SEDRIS 구조를 구축하고, High Level Architecture (HLA)/Run-Time Infrastructure (RTI) 기반의 분산 시스템에서 대기/해양 합성전장환경 구축에 SEDRIS 적용 방법을 제시한다.

Presented in the paper is a methodology for the distributed simulation of underwater warfare based on standard synthetic environment. In the case of underwater warfare simulation, it is very important to reflect environmental data, such as salinity and temperature. For the reusability and interoperability of environmental data, this paper adopts Synthetic Environmental Data Representation and Interchange Specification (SEDRIS(ISO standard for environmental data)). Although SEDRIS provides various merits as an international standard, applying of SEDRIS has been hindered by its broadness and heaviness. To relieve the difficulties, this paper proposes an efficient procedure to utilize SEDRIS technology for the atmosphere and underwater environment. This paper identifies SEDRIS structure for the atmosphere/underwater structured dimensional grid-based and implements the proposed procedure on the High Level Architecture (HLA) / Run-Time Infrastructure (RTI) to explain the generation of the battlefield in a distributed simulation system.

일반적으로 초고속 네트워크에서 실행되는 분산 시스템의 데이터 전달처리 효율은 시스템 구조 및 데이터의 전달처리 시스템에 의존한다. 분산 환경을 이용한 실시간 분산 시뮬레이션 시스템은 데이터전달처리의 실시간성과 시스템의 신뢰성 보장을 위하여 데이터 전달처리 시스템에 의하여 요구된 성능을 만족하고자 하였다. 그러나 실시간 시뮬레이션 시스템에 적용된 클라이언트/서버 기반의 데이터 전달처리 시스템은 시스템의 안정성 및 시스템의 변경에 따른 확장성과 유지보수성 확보가 어려웠다. 따라서 기존의 데이터 전달처리 시스템의 문제점을 해결하기 위하여 새로운 데이터 전달처리 시스템이 필요하다. 본 논문에서는 기존의 실시간 시뮬레이션 시스템을 분석하여 시스템 개선방향을 제시하고, 시스템 확장성, 상호운용성, 재사용성 및 유지보수성을 위하여 소프트웨어 디자인 패턴을 적용한 새로운 실시간 데이터 전달처리 시스템을 제안한다.

Usually, The data transmission processing efficiency of the distributed system running on high speed networks depends on the system architecture and the data transmission processing system. In order to secure the real-time rate and the system reliability, the real-time distributed simulation system on the distributed environment has tried to satisfy the performance required by the data transmission processing system. However, the client/server-based data transmission processing system in the real-time simulation system has been difficult to satisfy the system stability, extensibility and maintenability, especially when system changes. So, it is natural to study another improved data transmission processing system to solve the problems at the existing real-time simulation system. After analyzing the existing real-time simulation system, this paper will propose the improved real-time data transmission system by using Software Design Pattern, which enhances extensibility, interoperability, reusability and maintenability of the system.

Promising the developers with the facility of distributed collaborative development for complex simulation applications, HLA (High Level Architecture) provides a baseline supporting the reuse of capabilities available in different simulations with a significant reduction in cost and time. Along with improved execution process and reusability, the induction of object oriented model in the implementation design of HLA also enable to take the advantage of latest object oriented features making design, implementation and maintainability easier and at each level of federate development and execution. The important areas to be addressed for design reconsideration consists of data exchange model and HLA communication layer. The data exchange model comprises of federates in federation and between runtime infrastructure and federation. The Federate Object Model (FOM) architecture is not completely object oriented, the induction of Object Service Tier (OST) middleware may offer a degree of FOM agility which is the ability of an application to adjust according to different FOMs (behaviors for Federates). Whereas, in HLA communication layer, customary HLA systems are based upon bidirectional call/callback interactions between federate. Several enhancements and changes anticipated in object oriented communication layer (OOP-COMM) introduced in Object Service Tier (OST) as compared to native procedures, such as communication mechanisms, data encoding, session handling, distributed environment and performance analysis. The motivation behind the use of core object oriented modeling features and proposed Object Service Tier (OST) middleware is the reuse of legacy systems, features which may further enhance the integration of distributed simulation systems and extension types. So, this paper provides a multidimensional analysis of important design aspects of Object Service Tier (OST) middleware in HLA framework and devises some design constructs of Object Service Tier (OST) using object oriented model. This paper is intended to propose object-oriented model providing generalization through the Object Service Tier (OST) middleware in HLA framework for the distributed simulation system environment.

In order to achieve iterative design in early R&D period, a Distributed and Real-time Integrated Simulation System for avionics based on a Model-Based Systems Engineering (MBSE) method is proposed. The proposed simulation system includes driver, simulation model, monitor, flight visual model and aircraft external model.The effect of this simulation system in iterative design and system verification is testified by several use cases. The result shows that the simulation system, which can play an important role in iterative design and system verification, can reduce project costs and shorten the entire R&D period.

This paper describes a fast circuit simulation technique using the latency insertion method (LIM) with a parallel and distributed leapfrog algorithm. The numerical simulation results on the PC cluster system that uses the cloud computing system are shown. As a result, it is confirmed that our method is very useful and practical.

Microturbines system (MTS) are currently being deployed as small scale on-site distributed generators for microgrids and smart grids. In order to fully exploit DG potentialities, advanced integrated controls that include power electronics facilities, communication technologies and advanced modeling are required. Significant expectations are posed on gas microturbines that can be easily installed in large commercial and public buildings. Modeling, control, simulation of microturbine generator based distributed generation system in smart grid application of buildings for both grid-connected and islanding conditions are presented. It also incorporates modeling and simulation of MT with a speed control system of the MT-permanent magnet synchronous generator to keep the speed constant with load variation. Model and simulations are performed using MATLAB, Simulink and SimPowerSystem software package. The model is built from the dynamics of each part with their interconnections. This simplified model is a useful tool for studying the various operational aspects of MT and is also applicable with building cooling, heating and power (BCHP) systems

최근에 시뮬레이션 범위의 확대, 고수준의 사용자 요구사항 증가, 시스템 간의 연동 요구로 시뮬레이션 시스템의 구조가 복잡해지고 있다. 따라서 기존의 통신 미들웨어 구조로는 다양한 요구사항의 수용이 어렵다. 본 논문의 선행연구에서는 기존의 분산 시뮬레이션 시스템에서 실시간 데이터 전달기능을 가진 통신 미들웨어의 문제점을 분석하고, 3계층 클라이언트/서버 구조에 대한 개선된 통신 미들웨어를 디자인 패턴을 사용하여 제안하였다. 그러므로 본 논문에서는 제안한 통신 미들웨어를 개선 및 구현하고 실험을 통하여 기존 시스템과의 성능을 비교하였다.

Recently, the structure of the simulated system is becoming more complex due to the expanded range of simulations,increase in high-level requirements from users and integration requirement between different systems. Unfortunately, the existing structure of the communication middleware can hardly accommodate recent various requirements. In this paper,previous studies analyzed the problems of communication middleware of the existing distributed simulation system with real-time data transfer capability, and proposed an advanced communication middleware for the three-tier client/server architecture using design patterns. In this paper, the proposed communication middleware has been improvement and implemented, and verified through the tested with existing systems.

본 논문에서는 CEMTool환경에서 수행된는 일반적 형태 분산 시뮬레이터의 구조를 제안한다. 먼저, 분산시뮬레이션을 할 수 있도록 SIMTool에서 전체 시스템을 패럴랠블록의 형식으로 여러개의 서브시스템으로 분할한다. 그런후에 CEMTool환경에서 분할된 시스템에 대하여 초기화, one step ahead 시뮬레이션, distribute와 ordering의 과정을 진행한 후 각각의 서브시스템에 대하여 독립적인 C code과 실행파일을 생성한다. 여러 대의 PC에서는 분할된 각각의 서브시스템을 독자적으로 실행시키는 동시에 서로간에 reflective memory를 통해 데이터를 주고반는다. 본 논문의 실험대상인 냉간압연 시스템은 각각의 서브시스템 내부의 계산량이 통신량보다 훨씬 많기 때문에 분산처리를 하기에 아주 적합하며, 본 논문에서는 냉간압연 시스템에 대한 분산시뮬레이션의 결과를 분석하고 제시된 방법으로 확실한 속도향상의 결과를 보여준다는 것을 설명하고자 한다.

4차 산업혁명에 대한 관심도가 높아지면서, 현실에 존재하는 요소들과 가상에 존재하는 요소들이 상호작용 하는 CPS 라는 개념이 중요한 기술로 주목받고 있다. 전기자동차, 자율주행, 스마트 팩토리나 스마트 그리드 시스템과 같은 복잡한 구조를 가진 시스템들은 4차 산업혁명의 핵심 기술 분야로 간주되고 있으며, 이를 개발하기 위해 많은 연구가 이루어지고 있다. 하지만 시스템 구성요소들의 복잡한 연결은 개발을 어렵게 하고, 개발의 신뢰성을 보장하기 쉽지 않다. 시스템의 신뢰성은 자율주행자동차 경우 사람의 안전 직결되며 실제 자동차의 하드웨어와 ADAS의 소프트웨어의 연결된 검증이 필수적이다. 본 논문에서는 복잡한 하이브리드 시스템의 신뢰성 있는 검증을 위해 HILS를 지원하는 분산 시뮬레이션 미들웨어를 제안한다.

As interest in the 4th Industrial Revolution increases, the CPS, in which things existing in the reality and things existing in the virtual interact with each other, is attracting attention as an important technology. Complex systems such as electric vehicles, autonomous driving, smart factories, and smart grid system are considered as core technology fields of the 4th Industrial Revolution, and many types of research have been conducted to develop it. The reliability of the system is directly related to the safety of people in case of the autonomous driving, and verification of the actual vehicle's hardware and software of ADAS is essential. In this paper, we proposed distributed simulation middleware supporting HILS for reliable verification of the complex hybrid systems.

현대사회의 다양한 분야에서는 복잡한 사회현상에 대하여 문제를 정의하고 문제해결책의 결과를 분석하는 과정으로 모델링 및 시뮬레이션을 활용하고 있다. 나날이 사회현상의 문제가 복잡해짐에 따라 요구되는 모델링 및 시뮬레이션 환경의 계산자원의 요구사항도 높아지고 있다. 이러한 요구사항을 수용하기 위해서 클라우드 서비스 등과 같이 컴퓨팅 자원을 유동적으로 사용할 수 있는 환경이 대두되었다. 본 연구에서는 이러한 컴퓨팅 자원 활용 시스템을 보다 효율적으로 활용할 수 있는 웹 기반 재구성이 가능한 시뮬레이션 실험 틀을 제안한다. 제안하는 시뮬레이션 실험 틀은 다양한 분산 컴퓨팅 환경을 지원할 수 있도록 프론트엔드(Front-end)에서 웹을 활용하여 시뮬레이션 모델의 재구성 시스템을 구축하고 백엔드(Back-end) 이산 사건 시뮬레이션의 실행을 담당하는 이산사건 시뮬레이션 실행단으로 구성된다. 본 연구는 사례연구를 통해 분산형 시뮬레이션 환경이 단일 시뮬레이션 환경보다 시간적 효율이 더 높음을 확인하였다.

The problem of social phenomenon is getting more complicated than past decades, and the simulation engineers need more computation power to solve the problem. Therefore, the needs of the computational resources of the modeling and simulation environment are increasing. In the perspective of the simulation, it is necessary to allocate computational resources flexibly so that the simulation can be performed per the available budget range. As an alternative to the simulation environment to accommodate these requirements, cloud service has emerged as an environment in which computing resources can be used flexibly. This paper proposes a web-based simulation framework which consists of a front-end that reconstructs the simulation model using the web, and a back-end that executes the discrete event simulation. This paper also carried out a case study which shows web-based simulation framework has better overall runtime than standalone simulation framework.

본 논문에서는 지진하중하의 대형구조물의 시뮬레이션을 위해 실험과 해석을 병합한 분산공유 하이브리드 해석 및 실험소프트웨어 framework를 개발하였다. 제안된 소프트웨어 framework은 별도의 동적 그리고 정적 해석을 위한 프로그램의 개발이 필요 없기 때문에 일반 범용 유한요소해석 프로그램을 개발된 해석 및 실험 제어 프로그램과 interface API를 이용하여 사용할 수 있는 장점이 있다. 본 논문에서 개발된 소프트웨어 framework은 독자적 기능을 가진 module로 구성이 되어 있을 뿐만 아니라 개체지향형 프로그램 개념을 바탕으로 개발되었다. 예제를 통하여 개발된 시스템의 기능과 분산공유하이브리드 해석 및 실험에서의 유용성을 증명하였다.

In this paper, a software framework that integrates computational and experimental simulation has been developed to simulate and test a large-scale structural system under earthquake loading. The proposed software framework does not need development of the computer codes for both dynamic and static simulations. Any general-purpose software can be utilized with a main control module and interface APIs. This opens up a new opportunity to facilitate use of sophisticated finite elements into hybrid simulation regime to enhance accuracy and efficiency of simulations. The software framework described in the paper is modular and uses object oriented programming concepts. A series of illustrative examples demonstrate that the system is fully-functional and is capable of running any number of experimental and/or analytical components.

Electrical transmission and distribution networks must withstand an occasionally abnormal condition such as a fault, with prejudicial consequences for the line, transformers or generators. And the improvement of reliability and quality of the delivered power from an electric utility motivates the development of new technologies in power applications. As a part of these studies, the usefulness and utility of a superconduction fault current limiter(SFCL) are shown. The SFCL is applied to 22.9KV three-phase power system and performed short circuit studies. The verified quench characteristic of SFCL is adopted for fault simulation and the results are compared with those of system which have not SFCL.

This paper presents the concepts developed to propose Distributed Control System(DCS). To achieve adequate satisfaction under various conditions, the DCS should be designed from two points of view of functions distributions and performance planning. Performance evaluation criteria can be specified by the response time between units and the utilization of each unit. One has to also consider the ease and the cost of installation, maintenance, repair. Based on these characteristics, different system configuration can be evaluated and compared through results about evaluation criteria in order lo select the best DCS for particular process. The results, in abbreviated form, of the simulation DCS controlling a CAL(Continuos Annealing Line) plant of iron process ate presented.

One of the components that constitute the simulation models is the state variables whose values are determined by the time related simulation process. Embedding rule-based expert systems into the simulation models should provide a systematic way of handling these time-dependent variables without distracting the essential problem solving capabilities of the expert systems which are well suited for expressing the decision making function of complex cases. The expert system, however, is inefficient in dealing with the time elapsing characteristics of target system compare to the simulation models. To solve the problem, this paper provides an interruptible inference engine whose inferencing process can be interrupted when the variables' value, which are used as the parameters of the rules, are not yet determined due to the time dependent nature of the state variables. The process is resumed when the variables are ready. The elapse of time is calculated by time-advance function of the simulation model to which the expert system has been embedded. The example modeling shown exploits the embedded interruptible inferencing capability for the controlling and monitoring of metal grating process.

A distributed sewer cluster system is a cost-effective system to provide a service application for clients with reliable, scalable, available, and fault-tolerant features. In order to provide high quality services, it is necessary to evaluate service performances, tune the server system, and analyze performances. In this paper, we propose a simulator to generate workloads based on statistic configuration according to estimated application traffics, apply workload scheduling algorithms, and evaluate the simulation results. We introduce the simulator design modelling and architecture. By using flexible parameters, the simulator is able to generate various patterns of workloads with different statistics, and configure system environments such as the number of server nodes, system resources considered, and their capacities. With this simulator, we introduce two scenarios: one is to find appropriate thresholds for the best performance of cluster system, and the other is to find the suitable scheduling algorithm for workload characteristics of service applications.

A distributed server cluster system is a cost-effective system to provide a service application for clients with reliable, scalable, available, and fault-tolerant features. In order to provide high quality services, it is necessary to evaluate service performances, tune the server system, and analyze performances. In this paper, we propose a simulator to generate workloads based on statistic configuration according to estimated application traffics, apply workload scheduling algorithms, and evaluate the simulation results. We introduce the simulator design modelling and architecture. By using flexible parameters, the simulator is able to generate various patterns of workloads with different statistics, and configure system environments such as the number of server nodes, system resources considered, and their capacities. With this simulator, we introduce two scenarios: one is to find appropriate thresholds for the best performance of cluster system, and the other is to find the suitable scheduling algorithm for workload characteristics of service applications.

본 연구에서는 분산인공지능의 한 영역인 블랙보드구조를 통한 침입탐지 에이전트간의 연동 방법에 대해서 소개한다. 연동을 위해서 블랙보드를 사용한 시스템은 쉽게 확장이 가능하여 새로운 에이전트를 추가하기 용이하고, 블랙보드의 레벨을 수정하기 용이하다. 대상시스템에 시뮬레이션을 수행한다. 본 연구에서는 정책기반 네트워크를 사용하여 침입 탐지의 성능을 높이고자 하는데, 이를 적용함으로써 false positive를 줄일 수 있다. 정책기반네트워크를 통해 침입탐지 에이전트들이 서로 연동함으로써 성능의 향상을 이룬다는 것을 기존의 시스템과 비교함으로써 증명한다. 본 연구의 결과는 다양한 보안 정책을 적용하는데 사용될 수 있다.

We introduce the coordination among the intrusion detection agents by BBA(BlackBoard Architecture) that belongs to the field of distributed artificial intelligence. The system which uses BBA for the coordination can be easily expanded by adding new agents and increasing the number of BB(BlackBoard) levels. Several simulation tests performed on the targer network will illustrate our techniques. And this paper applies PBN(Policy-Based Network) to reduce the false positives that is one of the main problems of IDS. The performance obtained from the coordination of intrusion detection agent with PBN is compared against the corresponding non PBN type intrusion detection agent. The application of the research results lies in the experimentation of the various security policies according to the network types in selecting the best security policy that is most suitable for a given network.

복잡하고 특수한 기능을 수행하고 기존의 여러 다른 시스템과 연동해야 하는 내장형 시스템을 저비용 고효율적으로 개발하고 시험 및 평가하기 위해서는 분산 실시간 시뮬레이션 환경이 효과적이다. 또한, 특정한 목적으로 개발된 기존의 이질적인 시뮬레이션 모델들간의 상호호환과 재사용이 요구된다. 이러한 요구 사항을 만족시키고, 내장형 시스템과 시뮬레이션 환경의 연동 및 상호운용의 문제점을 해결하기 위해 HLA(High Level Architecture)기반으로 새로운 시뮬레이션 환경구조, 동작과정 및 운영절차를 제안하고 고찰한다.

In this paper load redistribution algorithm to allow fault-tolerance by redistributing the workload of n failure nodes to the remaining good nodes in distributed systems are investigated. To evaluate the efficiency of the algorithms a simulation model of algorithms is developed using SLAM II simulation language. The job arrival rate service rate failure and repair rate of nodes and communication delay time due to load migraion are used as parameters. The result of the simulation shows that the job arrival rate failure and repair rate of nodes do not affected on the relative efficiency of algorithms. If the communication delay time is greater than average job processing time algorithm B is better. Otherwise algorithm C is superior to the others.