• Proceedings of the Korean Operations and Management Science Society Conference
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• 2006.05a
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• pp.1342-1349
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• 2006

오늘날의 제품개발환경은 분산환경에 존재하는 다양한 역량을 가진 참여자들의 협업을 요구하고 있으며, 협업은 참여자들이 필요로 하는 제품개발관련 정보들의 실시간 교환을 지원할 수 있도록 제품정보 간 상호운용성 확보를 기반으로 한다. STEP으로 알려진 ISO 10303은 제품개발의 전체적인 라이프사이클에서 필요한 제품정보의 표현과 공유 및 교환을 위한 대표적인 표준이다. 하지만 STEP을 이용하기 위해서는 각 도메인이 표준인 STEP 모델에 기반하여 제품정보를 모델링 하여야 한다. 그러나 대부분의 도메인은 자신의 목적에 따라 특화된 모델을 정의하고 사용하기 때문에 도메인에 특화된 형태의 제품정보모델을 STEP 모델로 변환할 수 있는 추가적인 메커니즘이 필요하다. 즉, STEP은 참조모델보다는 모든 도메인에서 제품정보모델링을 위해 사용가능한 표준의 정의에 초점을 맞춘다. 그러므로 참조모델로서의 STEP을 기반으로 다양한 도메인 특화된 제품정보모델 간 상호운용성 확보를 지원하기 위하여 본 논문에서는 STEP 제품정보모델의 시맨틱스를 체계적으로 정의할 수 있도록 온톨로지 구축을 통한 컨셉추얼 모델링을 수행한다. 컨셉추얼 모델링은 STEP 모델에 정확하고 완전한 의미를 부여하여, 다양한 도메인 특화된 모델 사이의 상호운용성 확보를 지원하고 참조모델로서 STEP의 능력을 확장한다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.3
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• pp.147-155
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• 2022

The accumulated ice and snow during the operation of aircraft and railway vehicles can degrade aerodynamic performance or damage the major components of vehicles. Therefore, it is crucial to predict the temporal growth of ice for operational safety. Numerical simulation of ice is widely used owing to the fact that it is economically cheaper and free from similarity problems compared to experimental methods. However, numerical simulation of ice generally divides the analysis into multi-step and assumes the quasi-steady assumption that considers every time step as steady state. Although this method enables efficient analysis, it has a disadvantage in that it cannot track continuous ice evolution. The purpose of this study is to construct a surrogate model that can predict the temporal evolution of ice shape using reduced-order modeling. Reduced-order modeling technique was validated for various ice shape generated under 100 different icing conditions, and the effect of the number of training data and the icing conditions on the prediction error of model was analyzed.

• JSTS:Journal of Semiconductor Technology and Science
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• v.5 no.2
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• pp.89-101
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• 2005

Research on highly abstracted system modeling and simulation has received a great deal of attention as of the concept of platform based design is becoming ubiquitous. From a practical design point of view, such modeling and simulation must consider the following: (i) fast simulation speed and cycle accuracy, (ii) early availability for early stage software development, (iii) inter-operability with external tools for software development, and (iv) reusability of the models. Unfortunately, however, all of the previous works only partially addresses the requirements, due to the inherent conflicts among the requirements. The objective of this study is to develop a new system design methodology to effectively address the requirements mentioned above. We propose a new transaction-level system modeling methodology, called ViP (Virtual Platform). We propose a two-step approach in the ViP method. In phase 1, we create a ViP for early stage software development (before RTL freeze). The ViP created in this step provides high speed simulation, lower cycle accuracy with only minor modeling effort.(satisfying (ii)). In phase 2, we refine the ViP to increase the cycle accuracy for system performance analysis and software optimization (satisfying (i)). We also propose a systematic ViP modeling flow and unified interface scheme based on utilities developed for maximizing reusability and productivity (satisfying (ii) and (iv)) and finally, we demonstrate VChannel, a generic scheme to provide a connection between the ViP and the host-resident application software (satisfying (iii)). ViP had been applied to several System-on-a-chip (SoC) designs including mobile applications, enabling engineers to improve performance while reducing the software development time by 30% compared to traditional methods.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2010.04a
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• pp.217-219
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• 2010

Sensor modeling is the basic step to extract and to use the information from satellite images. Sensor modeling requires ground control points. If we use a single image, we have limitations on modeling about images captured from regions that we can not approach or take GCPs. In this research, we use strip images to do sensor modeling by two methods. At first, we apply sensor modeiling to single image and apply the results by extrapolation. Next, we consider strip images to single image. As a result, we find the second method is more accurate about whole image.

• Journal of the Society of Naval Architects of Korea
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• v.38 no.2
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• pp.71-78
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• 2001

In ship building industry, CNC and CAM are mostly applied to NC cutting and manufacturing of propeller and prototype ship model. Herein, prototype ship model is producted by CAD/CAM process. Hull form data is obtained from the ship drawing and used for 3D modeling by CAD software Pro/Engineer. CAD data is transferred into CAM s/w SPEEDplus to perform CNC process and the prototype small ship model is manufactured by CNC machine. To solve data transfer among different systems. IGES and STEP neutral formats are currently used. Herein IGES format is adopted for data transfer between CAD/CAM softwares.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.6
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• pp.71-78
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• 1989

The imput-output relations for nonlinear systems can be explicitly represented by the Volterra series and they can be characterized by the Volterra kernels. This study is concerned with modeling an elastomer force-displacement relation due to step inputs by utilizing the truncated Volterra series. Since it is practically impossible to apply step inputs that have infinite slope at zero time, the loads due to constant penetration(displacement) rate followed by constant penetration inputs are measured as an alternative approach and estimated for step inputs and then utilized for the truncated Volterra series models. One second order and one third order truncated Volterra series models have been employed to model the force-displacement relation which is one of the prominent properties to characterize the viscoelastic material. The third order truncated Volterra series model has better results, compared with those of the second order truncated Volterra series model.

• Journal of Institute of Control, Robotics and Systems
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• v.11 no.4
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• pp.385-391
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• 2005

As the Internet real-time multimedia applications increases, the bandwidth available to TCP connections is oppressed by the UDP traffic, result in the performance of overall system is extremely deteriorated. Therefore, developing a new transmission protocol is necessary. The TCP-friendly algorithm is an example satisfying this necessity. The TCP-Friendly Rate Control (TFRC) is an UDP-based protocol that controls the transmission rate that is based on the available round trip time (RTT) and the packet loss rate (PLR). In the data transmission processing, transmission rate is determined based on the conditions of the previous transmission period. If the one-step ahead predicted values of the control factors are available, the performance will be improved significantly. This paper proposes a prediction model of transmission rate control factors that will be used in the transmission rate control, which improves the performance of the networks. The model developed through this research is predicting one-step ahead variables of RTT and PLR. A multiplayer perceptron neural network is used as the prediction model and Levenberg-Marquardt algorithm is used for the training. The values of RTT and PLR were collected using TFRC protocol in the real system. The obtained prediction model is validated using new data set and the results show that the obtained model predicts the factors accurately.

• Advances in Computational Design
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• v.1 no.3
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• pp.235-251
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• 2016

We have performed a design optimization of a stiffened panel with curvilinear stiffeners using an artificial neural network (ANN) residual kriging based surrogate modeling approach. The ANN residual kriging based surrogate modeling involves two steps. In the first step, we approximate the objective function using ANN. In the next step we use kriging to model the residue. We optimize the panel in an iterative way. Each iteration involves two steps-shape optimization and size optimization. For both shape and size optimization, we use ANN residual kriging based surrogate model. At each optimization step, we do an initial sampling and fit an ANN residual kriging model for the objective function. Then we keep updating this surrogate model using an adaptive sampling algorithm until the minimum value of the objective function converges. The comparison of the design obtained using our optimization scheme with that obtained using a traditional genetic algorithm (GA) based optimization scheme shows satisfactory agreement. However, with this surrogate model based approach we reach optimum design with less computation effort as compared to the GA based approach which does not use any surrogate model.

• Journal of Sensor Science and Technology
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• v.28 no.3
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• pp.182-186
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• 2019

When a camera is employed for 3D sensing, accurate camera calibration is vital as it is a prerequisite for the subsequent steps of the sensing process. Camera calibration is usually performed by complex mathematical modeling and geometric analysis. On the other contrary, data learning using an artificial neural network can establish a transformation relation between the 3D space and the 2D camera image without explicit camera modeling. However, a neural network requires a large amount of accurate data for its learning. A significantly large amount of time and work using a precise system setup is needed to collect extensive data accurately in practice. In this study, we propose a two-step neural calibration method that is effective when only a small amount of learning data is available. In the first step, the camera projection transformation matrix is determined using the limited available data. In the second step, the transformation matrix is used for generating a large amount of synthetic data, and the neural network is trained using the generated data. Results of simulation study have shown that the proposed method as valid and effective.

• 한국연소학회:학술대회논문집
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• 2003.05a
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• pp.57-62
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• 2003

A general procedure of obtaining reliable one-step kinetics model for hydrocarbon mixture from the fully detailed chemistry is described iin this study. One-step theoretical formulation of the induction parameter model IPM uses a theoretical reconstruction of the induction time database obtained from a detailed kinetics library. Non-dimensional induction time calculations is compared with that of detailed kinetics. The IPM was latter implemented to fluid dynamics code and applied for the numerical simulation of detonation wave propagation. The numerical results including the numerical smoked-foil record show the all the details of the detonation wave propagation characteristics at the cost around 1/100 of the detailed kinetics calculation.