• Journal of Digital Convergence
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• v.10 no.10
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• pp.539-544
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• 2012

Most of the man-made systems can be modeled as a hybrid system which consists of both the high-level and the low-level component model. High level model is responsible for decision-making and the low-level one takes control of the mechanical component parts. Since the two models requires different interpretation method according to their type, analysis of a hybrid system becomes a difficult job. For the Analysis of the high-level model, methods for discrete event system models such as FSM can be used. On the contrary, numerical analysis techniques are required for the low-level continuous-time system model. Since it becomes a difficult thing for a modeller specifies and develops both the two-level models altogether, we propose an efficient hybrid simulation method which employs a game physics engine that has been widely and successfully used in the area of game industry.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.4
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• pp.100-108
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• 2006

Experimental study has been a general way to evaluate inlet and exhaust duct performances, but this is not only costly but also time consuming. Computational simulation is hence replacing experimental study and consequently time and cost saving. This paper therefore aims to investigate typical component performance of the intake and exhaust ducts using 3D representation. In this study a specific inlet and exhaust was modeled and analyzed to estimate its losses and flow field using computational fluid dynamic program with flow visualization capabilities. A process that requires geometry data to be modeled. That allowed for possibility of design trade off in designing phase. Installed performance of a specific turbo shaft engine was finally evaluated with the estimated inlet, exhaust and other accessories losses.

• Journal of KIISE:Computing Practices and Letters
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• v.11 no.3
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• pp.246-256
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• 2005

Rule-based paradigm is one of the principal types of software process modeling and enaction approaches, as they provide formality and flexibility sufficient to handle complex processes. However, the systems adopting rule-based paradigms are hard to define and understand process models, and their inference engine should be modified or redeveloped at worst according to the change of process language. In this paper, we describe a rule-based PSEE(Process-Centered Software Engineering Environment) PRAiSE that solves the above limitations of existing rule-based PSEEs as well as maintains the merits of rule-based paradigm such as the ability to incorporate the nature of software processes flexibly in which dynamic changes and parallelism are pervasive and prevalent. PRAiSE provides RAiSE, a graphical Process modeling language, and defined process models are interpreted and enacted by process engine implemented using CLiPS, a rule based expert system tool.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.11
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• pp.1105-1111
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• 2015

The exhaust system is one of the major sources of vibrations, along with the suspension system and engine. When the exhaust system is connected directly to the engine, it transfers vibrations to the vehicle body through the body mounts. Therefore, in order to reduce the vibrations transmitted from the exhaust system, the vibration characteristics of the exhaust system should be predicted. Thus, the dynamic characteristics of the bellows, which form a key component of the exhaust system, must be modeled accurately. However, it is difficult to model the bellows because of the complicated geometry. Though the equivalent beam modeling technique has been applied in the design stage, it is not sufficiently accurate in the case of the bellows which have complicated geometries. In this paper, we present an improved technique for modeling the bellows in a vehicle. The accuracy of the modeling method is verified by comparison with the experimental results.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.1
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• pp.12-18
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• 2021

In this study, the performance modeling of MT30 gas turbine engine is performed. The design point is determined, and the component performance maps to which the scaling technique is applied are generated using standard maps provided by the commercial program. Off-design point performance analysis is performed with the generated performance model, and this is compared with the performance deck data of the engine. It is confirmed that the data of the performance maps generated by the one-point scaling method had some errors from the performance deck data, and it is determined that correction is necessary to increase the accuracy of the performance model. Therefore, the off-design point analysis is performed by creating the correction performance model in a manner that obtains the scaling factors for each operating point(off-design point) according to the high pressure spool speed.

• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.6
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• pp.53-59
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• 2010

This research aims in finding a more optimal ejector size for evacuating engine exhaust gasses and 20% of the cell cooling air. The remaining 80% of cell cooling air pumped into the test chamber is separately exhausted from the test chamber via a discharge port fitted with flow control valves and vacuum pump. Unlike its predecessor this configuration utilizes a smaller capture area to improve pressure recovery. The modified ejector size has a diameter of 1100mm enough to evacuate 66kg/s jet engine exhaust in addition to about 20%, 24kg/s of the cell cooling air tapped from the sterling chamber. This configurations has an area ratio of the engine exit and ejector inlet of about 1.2. Simulation results of the proposed ejector configuration, indicates improved pressure recovery.

• Journal of the Korea Society for Simulation
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• v.20 no.3
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• pp.111-117
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• 2011

This paper suggests the passenger model considered evacuation behavioral characteristics on the passenger ship fire using a rules-based agent technique. The existing evacuation simulation system was modeled only passenger speed. The speed-based model considered passenger's physical characteristics, so it couldn't consider evacuation behavioral characteristics. For solving this problem, we modeled the passenger model using a rule-based agent applied evacuation behavioral characteristics. The rule-based agent consists of knowledge base and inference engine. In knowledge base, we represented evacuation behavioral characteristics, and chose the examples of the evacuation behavioral characteristics to show various patterns of behavior. And we simulated in the IMO MSC/Circ.1238 example 8 and we proved the simulation results could represent variety patterns of human behavior.

• Journal of Internet Computing and Services
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• v.10 no.3
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• pp.1-8
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• 2009

The primary tasks of a workflow management system specify workflow models with respect to resource, control-flow, data-flow, functional, and operational perspectives, and to enact their workcases (workflow instances). In terms of enacting workflow models, the essential criterion grading the quality of the system is "how much is the system able to guarantee the correctness of workflow models' enactment?". Particularly, the workflow determinacy problem, which may be caused by the interference of the control-flow and the data-flow specifications, is the most challenging issue in guaranteeing the correctness of the system. We are able to solve the problem by either of the following two approaches-analysis of workflow model and verification of workflow enactment. In the paper, we propose a technique that guarantee the system's correctness through verifying workflow enactment. In other words, the technique is able to detect the conflicts of control-flow and data-flow enactments existing on a workflow model, which causes the system to be non-determinant in enacting workflow models. Finally, by applying the technique to the e-Chautauque workflow management system developed by the authors' research group, we prove that the technique is a feasible solution for the workflow determinacy problem.

• Journal of the Korea Society for Simulation
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• v.22 no.4
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• pp.57-66
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• 2013

The needs for reusable 3D visualization tool has been being raised in various industries. Especially in the defense modeling and simulation (M&S) domain, there are abundant researches about reusable and interoperable visualization system, since it has a critical role to the efficient decision making by offering diverse validation and analyzing processes. To facilitate the effectiveness, states-of-the-arts M&S systems are applying VR (Virtual Reality) or AR (Augmented Reality) technologies. To reduce the work burden authors design a collaborative visualization environment based on a commercial game engine Unity3D. We define the requirements of the warfare simulation by analyzing pros and cons of existing tools and engines such as SIMDIS or Vega, and apply functionalities of the commercial game engine to satisfy the requirements. A prototype has been implemented as the collaborative visualization environment of iCAVE at KAIST, which is a facility for immersive virtual environment. The facility is intraoperative with smart devices.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.3
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• pp.237-242
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• 2014

Surge phenomenon can be occurred in a compressor when the performance of turbofan engine for an aircraft is changed considerably such as take-off phase. This study is aimed to avoid surge phenomenon. This paper propose the PID and Fuzzy control System for the turbofan engine with control inputs, the VIGV(Variable Inlet Guide Vane) in closed loop, and the fuel mass flow in open loop. We design the Dynamic modeling, NPSS S-function, which is connection block of simulink between NPSS(Engine analysis program) and Simulink. Finally, we certify the performance to prevent a serge phenomenon in the VIGV control system using the both methods, PID and fuzzy.