• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.14 no.4
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• pp.201-210
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• 2010

We propose a new robust and accurate method for the numerical solution of medical image segmentation. The modified Allen-Cahn equation is used to model the boundaries of the image regions. Its numerical algorithm is based on operator splitting techniques. In the first step of the splitting scheme, we implicitly solve the heat equation with the variable diffusive coefficient and a source term. Then, in the second step, using a closed-form solution for the nonlinear equation, we get an analytic solution. We overcome the time step constraint associated with most numerical implementations of geometric active contours. We demonstrate performance of the proposed image segmentation algorithm on several artificial as well as real image examples.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.2
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• pp.35-42
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• 2004

The control systems with friction cause the steady state error and slow response, because friction is a sensitive to the change of system condition and has highly nonlinear characteristics. To overcome these problems and do precise position control for a ball-screw system, we use Coulomb friction estimator and the sliding mode control(SMC) to compensate its negative effect. The applied SMC for tracking position has a characteristics of robust stability and reducing chattering, and is derived from the Lyapunov stability theorem and reaching condition. Compensating the estimated friction torque to the bounded disturbance term of the SMC's equivalent control input, it has a tracking performance better than the PID from the experimental results.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2005.05a
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• pp.798-805
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• 2005

Estimating the effects of price increase on a company's sales is important task faced by managers. If consumer has prior information on price increase or expect it, there would be stockpiling and subsequent drops in sales. In addition, consumer can suppress demand in the short run. Above factors make the sales dynamic and unstable. We develop a time series model to evaluate the sales patterns with stockpiling and short term suppression of demand and also propose a forecasting procedure. For estimation, we use panel data and extend the model to Bayesian hierarchical structure. By borrowing strength across cross-sectional units, this estimation scheme gives more robust and reasonable result than one from the individual estimation. Furthermore, the proposed scheme yields improved predictive power in the forecasting of hold-out sample periods.

• Proceedings of the KIEE Conference
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• 2007.11b
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• pp.176-179
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• 2007

This paper proposes a fuzzy linear programming based solution approach fur the long-term generation mix with multi-stages (years) considering air pollution constraints on $CO_2$ emissions, under uncertain circumstances as like as ambiguities of budget and reliability criterion level. This paper approaches to generation mix problem for 2030 year in Korea eventually. The proposed approach may give more flexible solution rather than too robust plan. The effectiveness of the proposed approach is demonstrated by applying it to solve the multi-years best generation mix problem on the Korea power system which contains nuclear, coal, LNG, oil and pumped-storage hydro plants.

• Journal of information and communication convergence engineering
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• v.6 no.3
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• pp.249-254
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• 2008

Moored ocean buoys are technically feasible approach for making sustained time series observation in the oceans and will be an important component of any long-term ocean observing system. The 3M disc buoy carried Zeno 3200, MCCB, Orbcomm, Global Star and Bluetooth module. The deployments have relied on Orbcomm and Global Star as the primary satellite communications system. In addition to detailing our practical experience in the use of Orbcomm and Global Star as high latitudes, we will present some of scientific sensor results regarding real-time oceanographic and meteorological parameters such as wind speed, wave height and etc. In this paper we present the design and implementation of a small-scale buoy sensor network. One of the major challenges is that the network is hard to access after its deployment and hence both hardware and software must be robust and reliable.

• Information and Communications Magazine
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• v.32 no.4
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• pp.16-22
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• 2015

유비쿼터스 정보 기술을 기반으로 다양한 업무 지원 기기간 네트워크를 형성하여 업무 처리를 지원하는 u-Office와, 지능화된 다양한 사물에 인터넷 연결성을 제공하여 지능적 서비스를 제공하는 Internet of Things(IoT)는 기하급수적으로 증가하는 다수의 객체간 통신을 수행하므로 네트워킹 자원의 최적화 기술이 필수로 뒷받침되어야 한다. 데이터 패킷의 오버헤드를 줄이고 통신 자원을 절약하기 위한 기술 연구는 다방면으로 진행되고 있으며, 특히 패킷의 오버헤드를 줄이고 통신 자원을 절약하는 패킷 헤더 압축 기술은 다양한 국제 표준이 개발되어 모바일 와이맥스(Mobile WiMAX), Long Term Evolution(LTE), IPv6 over Low power Wireless Personal Area Network(6LoWPAN) 등의 네트워크에 활용되고 있다. 본 고에서는 모바일 와이맥스, LTE, 6LoWPAN에서 각각 사용되는 패킷 헤더 압축 기술인 Payload Header Suppression(PHS), Robust Header Compression(ROHC), Header Compression(HC), Improved Header Compression(IPHC)의 개발 동향을 제시하고 각 기술의 특징을 비교 분석한다.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.2275-2278
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• 2005

In this paper, a control algorithm for a servo manipulator is focused on. A servo manipulator system has been developed for remotely handling radioactive materials in a hot cell. It is driven by servo motors. The torque from a servo motor is transferred through a reducer to the corresponding axis. The PID control algorithm is a simple and effective algorithm for such application. However, since friction degrades the algorithm's performance, friction has to be considered and compensated. The major aberrations are the positional tracking errors and the limit cycle. The authors have considered a switching term to a conventional PID algorithm to reduce the friction's effect. It has been tested by a hardware test.

• 제어로봇시스템학회:학술대회논문집
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• 1989.10a
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• pp.931-933
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• 1989

If the nonlinear term in a nonlinear control system equation can be deleted by state feedback control, the original system becomes a linear system. For this linear control system, many well known methods may be used to handle it, and then reverse it back to nonlinear form. Many problems of nonlinear control systems can be solved in this way. In this paper, this method will be used to transfer the identification problem of nonlinear systems into a linear control problem. The nonlinear observer is established by constructing linear observer. Then the state control of nonlinear systems is realized. Finally, the technique of the PID controller obtained by using bang-bang tracker as a differentiator provides a stronger robust controller. Even though the method in this paper may not theoretically perfect, many numerical simulations show that it is applicable.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.893-898
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• 2003

Coulomb friction is an important factor for precise position tracking control systems. The control systems with friction causes the steady state error because of being sensitive to the change of system condition and highly nonlinear characteristics. To overcome these problems, we use an estimation scheme of Coulomb friction to experiment for it's compensating. The estimated factor for Coulomb friction is used as a feed-forward compensator to improve the tracking performance of ball-screw systems. The tracking performance was improved by compensating the estimated friction torque in the feed-forward term. And, the sliding mode control which is derived from the Lyapunov stability theorem is applied for robust stability and reducing chattering. The experimental results show that the sliding mode controller with adaptive friction compensator has a good tracking performance compared with the friction uncompensated controller.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.9
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• pp.1322-1331
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• 1989

This paper proposes a new adaptation algorithm with which a model reference adaptive control can give a local boundedness of the tracking error applied to a continuous-time linear time-invariant single-input single-output plant whose reduced-order model is of relative degree 1 and whose unmodeled dynamics may be represented in a sigular perturbation form. With the addition of an offset term and an extra adaptation structure, this algorithm is shown to have a robustness property in the sense that this gives zero residual tracking errors when the unmodeled dynamics are disappeared.