• 한국정보과학회논문지:정보통신
• /
• 제30권3호
• /
• pp.397-406
• /
• 2003

정보통신기술이 발전함에 따라 내부자의 불법적인 시스템 사용이나 외부 침입자에 의한 중요 정보의 유출 및 조작을 알아내는 침입탐지시스템에 대한 연구가 활발히 이루어지고 있다. 이제까지는 네트워크 패킷, 시스템 호출 감사자료 등의 척도에 은닉 마르코프 모델, 인공 신경망, 통계적 방법 등의 모델링 방법을 적용하는 연구가 이루어졌다. 그러나 사용하는 척도와 모델링 방법에 따라 취약점이 있어 탐지하지 못하는 침입이 많은데 이는 침입의 형태에 따라 흔적을 남기는 척도가 다르기 때문이다. 본 논문에서는 이러한 단일척도 침입탐지시스템의 단점을 보완하기 위해 시스템 호출, 프로세스의 자원점유율, 파일 접근이벤트 등의 세 가지 척도에 대하여 은닉 마르코프 모델, 통계적 방법, 규칙기반 방법을 사용하여 모델링한 후, 그 결과를 규칙기반 방법으로 결합하는 침입탐지 방법을 제안한다. 실험결과 다양한 침입 패턴에 대하여 다중척도 결합방법이 매우 낮은 false-positive 오류율을 보여 그 가능성을 확인할 수 있었다.

• 인터넷정보학회논문지
• /
• 제10권6호
• /
• pp.7-17
• /
• 2009

무선통신 프로토콜의 구현에서 MAC 계층은 하드웨어와 소프트웨어를 결합한 시스템-온-칩으로 출시하는 것이 일반적이다. 하지만 이러한 시스템 개발에서 하드웨어의 개발에 많은 시간이 소요되므로 하드웨어의 개발 완료 이전에 소프트웨어의 개발 및 검증하기 위한 환경이 필요하다. 하드웨어와 소프트웨어의 통합 개발에서 하드웨어는 HDL(Hardware Description Level)을 이용한 RTL(Register Transfer Level) 로의 하드웨어 모델링을 통해서, 소프트웨어는 ISS를 통해 시뮬레이션 환경을 제공할 수 있다. 시스템의 개발 복잡도가 점차 증가함에 따라 기존 RTL(Register Transfer Level) 보다 높은 추상 레벨에서의 모델링을 이용하는 ESL(Electronic System Level) 설계가 이루어지고 있다. ESL 설계는 비시간 모델과 시간 모델로 나눌 수 있다. 본 논문에서는 시간 모델이 아닌 비시간 모델 시뮬레이션을 위한 MCU를 설계 및 구현한다. 제안하는 MCU는 비시간 모델에서 정확한 시간이 요구되는 부분 보다는 시스템의 동작을 쉽고 빠르게 검증함으로써 시스템 설계 초기 단계에 시스템의 최적화뿐만 아니라 설계 완료 시점을 앞당길 수 있다. 또한 운영체제를 구동할 수 있는 MCU 모듈을 설계함으로써 MAC 계층의 소프트웨어 부분을 실시간 운영체제 상에서 구현할 수 있는 환경을 제공할 수 있다. 따라서 본 논문에서는 SystemC 기반의 MCU 모듈과 실시간 운영체제 동작을 지원하는 UC/OS-II 모듈을 제안한다.

• Journal of Mechanical Science and Technology
• /
• 제20권1호
• /
• pp.85-93
• /
• 2006

The trend of miniaturization has been applied to the research of rockets to develop prototypes of micro rockets. In this paper, the development of a web-integrated prototyping system for three-dimensional micro rockets, and the results of combustion tests are discussed. The body of rocket was made of 6061 aluminum cylinder by lathe process. The three-dimensional micro nozzles were fabricated on the same aluminum by using micro endmills with ${\phi}100{\mu}m{sim}{\phi}500{\mu}m$ diameter. Two types of micro nozzle were fabricated and compared for performance. The total mass of the rockets was 7.32 g and that of propellant (gun powder) was 0.65 g. The thrust-to-weight ratio was between 1.58 and 1.74, and the flight test with 45 degree launch angle from the ground resulted in $46\;m{\sim}53\;m$ of horizontal flight distance. In addition, ABS housing for the micro machined rocket was fabricated using Fused Deposition Modeling (FDM). A web-based design, fabrication, and test system for micro nozzles was proposed to integrate the distributed hardware resources. Test data was sent to the designer via the same web server for the faster feedback to the rocket designer.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 2009년도 정기 학술대회
• /
• pp.344-347
• /
• 2009

건축, 토목 분야의 정보 교환을 위한 표준으로 주목받고 있는 BIM 모델의 국제 표준인 IFC 표준을 위해, 소프트웨어가 IFC 표준에 맞게 유효한 정보를 입출력 하도록 도와주고, IFC 파일이 표준에 맞는지 검증할 수 있는 모듈을 개발했다. 특히, 지역별 및 국가별 상황에 맞게 BIM 모델을 수정하거나 확장해 사용하도록 권고하고 있는 상황에서 다양한 확장 IFC 표준을 효과적으로 지원할 수 있도록 IFC 표준을 정의하는 EXPRESS 언어로부터, 객체 지향 언어를 위한 소프트웨어 개발 라이브러리를 자동으로 생성하고, 해당 SDK를 활용해 IFC 모델을 검증하는 라이브러리를 자동으로 생성하며, IFC 파일을 검증할 수 있는 독립적인 실행 파일도 자동으로 생성할 수 있도록 했다. 또한 객체 지향 라이브러리를 사용함으로써 주어진 IFC 모델을 효과적으로 문서화 할 수 있도록 HTML 생성 도구를 개발하거나 3차원 형상 확인이 가능하도록 VRML 생성 도구를 개발하는 등의 작업이 쉽게 이뤄짐을 확인했다. 이렇게 자동화된 BIM 소프트웨어 개발 도구는 IFC 모델의 수정이나 확장을 고려하는 BIM 소프트웨어 개발 프로젝트의 생산성을 향상시키고, 해당 시스템의 운영에 신뢰도를 높이는 것은 물론이며, 향후 국내 실정에 맞게 운영될 BIM 인증 제도에도 활용하면 기존의 수작업 방식 인증제도에 비해 인증에 걸리는 시간과 비용을 줄이는 것은 물론 인증 자체의 객관성과 정확성, 투명성과 신뢰성을 높일 수 있을 것으로 기대된다.

• 한국CDE학회논문집
• /
• 제9권2호
• /
• pp.167-174
• /
• 2004

As the networks connect the world, enterprises tend to move manufacturing activities into virtual spaces. Since different applications use different data terminology, it becomes a problem to interoperate, interchange, and manage electronic data among different systems. According to RTI, approximately one billion dollar has been being spent yearly for product data exchange and interoperability. As commercial CAD systems have brought in the concept of design feature for the sake of interoperability, terminologies of design feature need to be harmonized. In order to define design feature terminology for integration, knowledge about feature definitions of different CAD systems should be considered. STEP (Standard for the Exchange of Product model data) have attempted to solve this problem, but it defines only syntactic data representation so that semantic data integration is unattainable. In this paper, we utilize the ontology concept to build a data model of design feature which can be a semantic standard of feature definitions of CAD systems. Using feature ontology, we implement an integrated virtual database and a simple system which searches and edits design features in a semantic way. This paper proposes a methodology for integrating modeling features of CAD systems.

• Ocean Systems Engineering
• /
• 제5권4호
• /
• pp.261-277
• /
• 2015

Internal solitary waves occur due to density stratification and are nonlinear in nature. These waves have been observed in many parts of the world including the South China Sea, Andaman Sea and Sulu Sea. Their effect on floating systems has been an emerging field of interest and recent offshore developments in the South China Sea where several offshore oil and gas discoveries are located have confirmed adverse effects including large platform motions and riser system damage. A valid numerical model conforming to the physics of internal waves is implemented in this paper and the effect on a spar platform is studied. The physics of internal waves is modeled by the Korteweg-de Vries (KdV) equation, which has a general solution involving Jacobian elliptical functions. The effects of vertical density stratification are captured by solving the Taylor Goldstein equation. Fully coupled time domain analyses are conducted to estimate the effect of internal waves on a typical truss spar, which is configured to South China Sea development requirements and environmental conditions. The hull, moorings and risers are considered as an integrated system and the platform global motions are analyzed. The study could be useful for future guidance and development of offshore systems in the South China Sea and other areas where the internal wave phenomenon is prominent.

• 한국자동차공학회논문집
• /
• 제16권4호
• /
• pp.110-119
• /
• 2008

Computer methods with simplified mathematical models in conjunction with empirical model parameters can be efficiently practiced into an optimization of a diesel aftertreatment system. Components of prime interests are diesel particulate filter, diesel oxidation catalyst and de-$NO_x$ catalytic converter. de-$NO_x$, de-PM, and de-HC processes in each part are individually modeled, formulated and then combined into an integrated analysis procedure for a unified simulation of the diesel emission aftertreatment. The model is empirically tuned and validated with comprehensive engine and laboratory data. The effects of emission species and space velocity on the $NO_x$ and soot reductions are parametrically investigated. A lowered $NO_2/NO_x$ ratio due to PM oxidation in DPF contributes to promote the $NO_x$ reduction by SCR at intermediate gas temperatures. $NO_x$ reduction is inert to the PM oxidation at high temperatures. Rate of PM trapping strongly depends on temperature and $NO_x$ concentration.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제11권4호
• /
• pp.1972-1986
• /
• 2017

With the advent of the knowledge economy, science and technology resources have played an important role in economic competition, and their optimal allocation has been regarded as very important across the world. Thus, allocation optimization research for regional science and technology resources is significant for accelerating the reform of regional science and technology systems. Regional science and technology resource allocation optimization is modeled as a double-layer optimization model: the entire system is characterized by top-layer optimization, whereas the subsystems are characterized by bottom-layer optimization. To efficaciously solve this optimization problem, we propose a mixed search method based on the orthogonal genetic algorithm and sensitivity analysis. This novel method adopts the integrated modeling concept with a combination of the knowledge model and heuristic search model, on the basis of the heuristic search model, and simultaneously highlights the effect of the knowledge model. To compare the performance of different methods, five methods and two channels were used to address an application example. Both the optimized results and simulation time of the proposed method outperformed those of the other methods. The application of the proposed method to solve the problem of entire system optimization is feasible, correct, and effective.

• 제어로봇시스템학회논문지
• /
• 제16권4호
• /
• pp.319-328
• /
• 2010

This paper proposes a robust adaptive fuzzy tracking control scheme for a nonholonomic mobile robot with external disturbances as well as parameter uncertainties in the robot kinematics, the robot dynamics, and the actuator dynamics. In modeling a mobile robot, the actuator dynamics is integrated with the robot kinematics and dynamics so that the actuator input voltages are the control inputs. The presented controller is designed based on a FBFN (Fuzzy Basis Function Network) to approximate an unknown nonlinear dynamic function with the uncertainties, and a robust adaptive input to overcome the uncertainties. When the controller is designed, the different parameters for two actuator models in the actuator dynamics are taken into account. The proposed control scheme does not require the kinematic and dynamic parameters of the robot and actuators accurately. It can also alleviate the input chattering and overcome the unknown friction force. The stability of the closed-loop control system including the kinematic control system is guaranteed by using the Lyapunov stability theory and the presented adaptive laws. The validity and robustness of the proposed control scheme are shown through a computer simulation.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2004년도 춘계학술대회논문집
• /
• pp.607-612
• /
• 2004

Disc brake noise continues to be a major concern throughout the automotive industry despite efforts to reduce its occurrence. Eliminating vibrations during braking is an important task for both vehicle passenger comfort and reducing the overall environmental noise levels. There are several classes of disc brake noise, the major ones being squeal, judder, groan, and moan. In this study, analytical model for moan noise of rear disk brake is investigated. Modeling of the disc brake assembly to take account of the effect of different geometrical and contact parameters is studied through the use of multi-body model. The contact stiffness of the caliper and torque member plays an important role in controlling brake vibration. Therefore, a suitable material pair at the caliper/body contact has been made. An ADAMS model of a rear disc brake system was integrated with a flexible suspension trailng arm from MSC/NASTRAN. A fully non-linear dynamic simulatin of brake system behavior, containing rigid and flexible bodies, was performed for a Prescribed set of operating conditions. Simulation results were validated using data from vehicle experimental testing.