• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1111-1117
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• 2003

NURBS (Non Uniform Rational B-Spline) is widely used in CAD system and NC data for high speed machining. Conventional CAM system changes NURBS surface to tessellated meshes or Z-map model, and produces linear tool path. The linear tool path is not good for precise machining and high speed machining. In this paper, an algorithm to change linear tool path to NURBS one was studied, and the machining result of NURBS tool path was compared with that of linear tool path. The N-post, post-processing and virtual machining software was developed. The N-Post post-processes linear tool path to NURBS tool path and quickly shades machined product on OpenGL view and compares a machined product with original CAD surface. A virtual machined model of original tool path and post-processed tool path was compared to original CAD model. The machining error of post-processed NURBS tool path was reduced to 43%. The original tool path and NURBS tool path was used to machine general model using same machine tool and machining condition. The machining time of post-processed NURBS tool path was reduced up to 38%.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 추계학술대회 초록집
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• pp.40.1-40.1
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• 2011

This paper presents a pitch controller which can hold output power constant at the rated value. Although wind turbine contains complicated nonlinearities, its behaviour within a certain operating range of a point can be approximated by that of a linear model. By doing so, we can apply rather simple and systematic linear control techniques such as PID and LQR(Linear Quadratic Regulator) to design a linear pitch controller. Because these linear controllers are valid only in a sufficiently small range around an operating point, linearized wind turbine model under the condition of varying wind speed needs a linear pitch controller can achieve the aims of tracking the rated rotor rotational speed. We propose an improved linear pitch controller taking each merit of LQR and PI controller under the condition of varying operating points in this paper.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 춘계 학술발표회
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• pp.1043-1052
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• 2009

To derive easily the coefficient of permeability from several other soil properties, the estimation model of coefficient of permeability was proposed using linear regression analysis. The coefficient of permeability is one of the major factors to evaluate the soil characteristics. The study area is located in Kangwon-do Pyeongchang-gun Jinbu-Myeon. Soil samples of 45 spots were taken from the study area and various soil tests were carried out in laboratory. After selecting the soil factor influenced by the coefficient of permeability through the correlation analysis, the estimation model of coefficient of permeability was developed using the linear regression analysis between the selected soil factor and the coefficient of permeability from permeability test. Also, the estimation model of coefficient of permeability was compared with the results from permeability test and empirical equation, and the suitability of proposed model was proved. As the result of correlation analysis between various soil factors and the coefficient of permeability using SPSS(statistical package for the social sciences), the largest influence factor of coefficient of permeability were the effective grain size, porosity and dry unit weight. The coefficient of permeability calculated from the proposed model was similar to that resulted from permeability test. Therefore, the proposed model can be used in case of estimating the coefficient of permeability at the same soil condition like study area.

• 한국환경보건학회지
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• 제50권4호
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• pp.229-236
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• 2024

The linear no-threshold (LNT) model is an assumption that explains the dose-response relationship for health risks, allowing for linear extrapolation from high doses to low doses without a threshold. The selection of an appropriate model for low-dose risk evaluation is a critical component in the risk assessment process for hazardous agents. This paper reviews the LNT model in light of epidemiological evidence from major international consortia studying ionizing radiation. From a scientific perspective, substantial evidence supporting the LNT model has been observed in epidemiological studies of low-dose ionizing radiation exposure, although some findings suggest non-linear dose relationships for certain cancer sites and variations across populations. From a practical standpoint, the LNT remains the most useful model for radiation protection purposes, with no alternative dose-response relationship proving more appropriate. It is important to note that the LNT model does not directly reflect the magnitude of risk at the population level, and this distinction should be clearly communicated to the public. While applying the LNT model as the principal basis for radiation protection, continuous research into various dose-response relationships is crucial for advancing our understanding.

• Journal of Electrical Engineering and Technology
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• 제10권5호
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• pp.2162-2169
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• 2015

Cruise control is a technology for automatically maintaining a steady speed of vehicle as set by the driver via controlling throttle valve and brake of vehicle. In this paper we investigate cruise controller design method with consideration for distance to vehicle ahead. We employ linear time varying (LTV) model to describe longitudinal vehicle dynamic motion. With this LTV system we approximately model the nonlinear dynamics of vehicle speed by frequent update of the system parameters. In addition we reformulate the LTV system by transforming distance to leading vehicle into variation of system parameters of the model. Note that in conventional control problem formulation this distance is considered as disturbance which should be rejected. Consequently a controller can be designed by pole placement at each instance of parameter update, based on the linear model with the present system parameters. The validity of this design method is examined by simulation study.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1994년도 Proceedings of the Korea Automatic Control Conference, 9th (KACC) ; Taejeon, Korea; 17-20 Oct. 1994
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• pp.628-633
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• 1994

A new Riemannian geometric model for the controlled plant is proposed by imbedding the control vector space in the state space, so as to reduce the dimension of the model. This geometric model is derived by replacing the orthogonal straight coordinate axes on the state space of a linear system with the curvilinear coordinate axes. Therefore the integral manifold of the geometric model becomes homeomorphic to that of fictitious linear system. For the lower dimensional Riemannian geometric model, a nonlinear optimal regulator with a quadratic form performance index which contains the Riemannian metric tensor is designed. Since the integral manifold of the nonlinear regulator is determined to be homeomorphic to that of the linear regulator, it is expected that the basic properties of the linear regulator such as feedback structure, stability and robustness are to be reflected in those of the nonlinear regulator. To apply the above regulator theory to a real nonlinear plant, it is discussed how to distort the curvilinear coordinate axes on which a nonlinear plant behaves as a linear system. Consequently, a partial differential equation with respect to the homeomorphism is derived. Finally, the computational algorithm for the nonlinear optimal regulator is discussed and a numerical example is shown.

• Macromolecular Research
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• 제10권5호
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• pp.266-272
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• 2002

Although the reptational model of Doi and Edwards gives a successful description of viscoelasticity of flexible linear polymers, the success is restricted to the terminal region./sup 1/ There have been several attempts to modify the Doi-Edwards model to describe wider range of time or frequency./sup 2-6/ This paper suggests a simple phenomenological model which can describe wider range of molecular weight than such molecular models can. Although our model is a phenomenological one, it is practical and convenient to predict the effect of molecular weight distribution on linear viscoelastic data because of its simple mathematical form.

• Journal of Electrical Engineering and Technology
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• 제11권2호
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• pp.265-273
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• 2016

A water wall system is one of the most important components of a boiler in a thermal power plant, and it is a nonlinear Multi-Input and Multi-Output (MIMO) system, with 6 inputs and 3 outputs. Three models are developed and comp for the controller design, including a linear model, a multilayer feed-forward neural network (MFNN) model and an Echo State Network (ESN) model. First, the linear model is developed by linearizing a given nonlinear model and is analyzed as a function of the operating point. Second, the MFNN and the ESN are developed by using training data from the nonlinear model. The three models are validated using Matlab with nonlinear input-output data that was not used during training.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 심포지엄 논문집 정보 및 제어부문
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• pp.213-215
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• 2007

This paper introduces an emotional behavior decision model for intelligent service robots. An emotional model should make different behavior decisions according to the purpose of the robots. We propose an emotional behavior decision model which can change the character of emotional model and make different behavior decisions although the situation and environment remain the same. We defined each emotional element such as reactive dynamics, internal dynamics, emotional dynamics, and behavior dynamics by state dynamic equations. The proposed system model is a linear system. If you want to add one external stimulus or behavior, you need to add just one dimensional vector to the matrix of external stimulus or behavior dynamics. The case of removing is same. The change of reactive dynamics, internal dynamics, emotional dynamics, and behavior dynamics also follows the same procedure. We implemented the proposed emotional behavior decision model and verified its performance.

• 상하수도학회지
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• 제16권6호
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• pp.710-716
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• 2002

A General Pipe Break Prediction Model that incorporates linear and exponential models in its form is developed. The model is capable of fitting pipe break trends that have linear, exponential or in between of linear and exponential trend by using a weighting factor. The weighting factor is adjusted to obtain a best model that minimizes the sum of squared errors of the model. The model essentially plots a best curve (or a line) passing through "cumulative number of pipe breaks" versus "break times since installation of a pipe" data points. Therefore, it prevents over-predicting future number of pipe breaks compared to the conventional exponential model. The optimal replacement time equation is derived by using the Threshold Break Rate equation by Loganathan et al. (2002).