• 전기학회논문지
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• 제58권4호
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• pp.700-707
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• 2009

The application of renewable energy in electric power systems is growing rapidly in order to make provision for the inequality of the climate, the dwindling supplies of coal, oil and natural gas and a further rise in oil prices. Solar cell generators(SCG) is one of the fastest growing renewable energy. This paper presents a methodology on probabilistic production cost simulation of a power system including SCGs. The generated power by SCGs is variable due to the random variation of solar radiation. In order to solve this problem, the SCGs is modeled as multi-state operational model in this paper. Probabilistic production cost of a power system can be calculated by proposed method considering SCGs with multi-state. The results show that the impacts of SCGs added to a power system can be analyzed in view point of production cost using the proposed method.

• 한국농촌건축학회논문집
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• 제13권4호
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• pp.59-66
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• 2011

This study aims to understand the degree of inequality of surveyed rural amenity resources according to resources and region in basic self governing body by estimating the Gini Coefficient and Lorenz Curve. Case Study was performed in Sunchang basic self governing body which full survey of rural amenity resources was completed. The Gini Coefficient was applied to measure the concentration of amenity resources in 11 Eup-Myun regions, Sunchang county of Jeonbuk province. The results demonstrate significantly different variation according to Eup-Myun regions and amenity variables. This result would be used as a basic data for rational rural planning based on amenity resources through identifying distributional concentration of rural amenity resources in basic self governing body.

• 대한전기학회논문지:시스템및제어부문D
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• 제53권11호
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• pp.741-746
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• 2004

When investigating a control problem for network based control systems, the main issue is network-induced delay. This delay can degrade the performance of control systems designed without considering the delay and even destabilize the system. In this paper, we consider the stabilization of network based control systems, where there is bounded time-varying delay. This delay is treated like parameter variation of a discrete time system. The state feedback controller design is formulated as linear matrix inequality. Finally, we show that the stability of control systems designed with considering the delay is superior to that is not so.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.427-431
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• 1996

The MRAS proposed by Schauder [8] is modified to improve robustness to the change of load torque and/or the variation of the stator resistance. The difference between the voltage and the current model is fed into the current model via proportional and integral gains. In order to generalize the MRAS, supposing that the rotor speed is time varying, we add a compensating term to the current model. It does not alter the Popov's integral inequality condition. Also, the asymptotic stability of the modified MRAS (MMRAS) is shown with the stability proof technique as in the original paper. By the simulation works, it is verified that the MMRAS obtains improved performance than the original MRAS.

• 충청수학회지
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• 제19권2호
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• pp.141-151
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• 2006

We investigate the multiplicity of $2{\pi}$-periodic solutions of the nonlinear Hamiltonian system with almost polynomial and exponential potentials, $\dot{z}=J(G^{\prime}(z)+h(t))$, where $z:R{\rightarrow}R^{2n}$, $\dot{z}=\frac{dz}{dt}$, $J=\(\array{0&-I\\I&o}\)$, I is the identity matrix on $R^n$, $H:R^{2n}{\rightarrow}R$, and $H_z$ is the gradient of H. We look for the weak solutions $z=(p,q){\in}E$ of the nonlinear Hamiltonian system.

• Journal of Power Electronics
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• 제13권4호
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• pp.712-718
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• 2013

This paper proposes a control method for reducing the total harmonic distortion (THD) of the grid current of three-phase grid-connected inverter systems when the grid voltage is distorted. The THD of the grid current caused by grid voltage harmonics is derived by considering the phase delay and magnitude attenuation due to the hardware low-pass filter (LPF). The Cauchy-Schwarz inequality theory is used in order to search more easily for the minimum point of the THD. Both the gain and angle of the compensation voltage at the minimum point of the THD of the grid current are derived with the variation of cut-off frequencies of the hardware LPF. Simulation and experimental results show the validity of the proposed control methods.

• Smart Structures and Systems
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• 제26권6호
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• pp.797-807
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• 2020

Due to the influence of nonlinearity and time-variation, it is difficult to establish an accurate model of concrete frame structures that adopt active controllers. Fuzzy theory is a relatively appropriate method but susceptible to human subjective experience to decrease the performance. This paper proposes a novel artificial intelligence based EBA (Evolved Bat Algorithm) controller with machine learning matched membership functions in the complex nonlinear system. The proposed affine transformed membership functions are adopted and stabilization and performance criterion of the closed-loop fuzzy systems are obtained through a new parametrized linear matrix inequality which is rearranged by machine learning affine matched membership functions. The trajectory of the closed-loop dithered system and that of the closed-loop fuzzy relaxed system can be made as close as desired. This enables us to get a rigorous prediction of stability of the closed-loop dithered system by establishing that of the closed-loop fuzzy relaxed system.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.1060-1065
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• 2005

An Independent Administrative Corporation Japan Agency for Marine-Earth Science and Technology (JAMSTEC) is developing light-and-small Autonomous Underwater Vehicles (AUV)$^{1)}$, named 'MR-X1' (Marine Robot Experimental 1), which can cruise, investigate and observe by itself without human's help. In this paper, we consider the motion control problem of 'MR-X1' and derive a controller. Since the dynamic property of 'MR-X1' is changed by the influence of the speed, the mathematical model of 'MR-X1' becomes the nonlinear model. In order to design a controller for 'MR-X1', we generally apply nonlinear control theories or linear control theories with some constant speed situation. If we design a controller by applying Linear Quadratic (LQ) optimal control theory, the obtained controller only compensates t e optimality at the designed speed situation, and does not compensate the stability at another speed situations. This paper proposes a controller design method using Linear Matrix Inequalities (LMIs)$^{2),3),4)}$, which can adapt the speed variation of 'MR-X1'. And examples of numerical analysis using our designed controller are shown.

• 한국해양학회지
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• 제15권2호
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• pp.123-128
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• 1980

인천을 포함한 경기만 일대는 우리나라에서 조차가 가장 큰 곳으로 오래전부터 조력발전의 가능성에 대하여 논의되고 있는 곳이다. 조력발전의 타당성을 논하거나 오염물질을 바다에 버릴 때 그 확산문제를 풀기 위해서는 해수의 유출입량을 정확하게 결정해야 하는데 이때 조차는 가장 중요한 요소가 되며 나아가서 평균유속을 구할 수 있게 된다. 그러므로 조차의 변동범위를 가능한대로 정확하게 파악하고 있으면 좀 더 슬기롭게 자연환경을 이용할 수 있게 된다. 인천에서 조차를 정량적으로 조사하기 시작한 것은 1876년 7월∼8월 일본해군에 의하여 부근 해역의 원점측량시부터이며 1882년 영국인 Hoskyn이 이곳의 해도를 작성할 때 좀 더 자세히 조사된 것으로 믿어진다. 인천항 해도는 그후 각국에서 다투어 가면서 작성하게되는데 1884년에는 독일이, 1887년에는 러시아가, 1891년에는 일본이, 1893년에는 미국이 해도를 작성하였다. 영국인 Eldridge와 Allen은 각기 1893년과 1896년에 1해리를 12인치와 5.5인치로 하는 대축척 해도를 작성하기에 이르렀으며 한국수산지(농상공부 수산국, 1908)에 기재된 인천의 대조승 31척 1/4 및 소조승 21척 1/2은 해도작성시에 조사된 조석자료를 종합하여 정리한 것이다.

• 대한치과의사협회지
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• 제54권12호
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• pp.971-984
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• 2016

The increase rate of dentists' competition is very fast at metropolitan areas in South Korea. We compare metropolitan and rural parameters to investigate the relation between competition and revenue variation. The competition and revenue variables of 73 metropolitan and 75 rural areas were calculated from 2010 Census of Service Industry microdata which include non-insurance revenues of dental clinics. Independent sample t-test results showed that the level of competition among dental clinics in metropolitan areas is higher. The lowest and the low ranked revenues are higher in rural areas. The highest and the average revenues are higher in metropolitan areas. But, 25 percentile and median revenues has no significant difference between two areas. Simple log linear regression results showed that the number of clinics could explain the distribution of revenues in both areas better than the density of active dentists and Herfindahl-Hirschman index. In the areas with many clinics have high maximum and average revenues and low minimum revenues. The increasing rate of maximum revenues is higher in metropolitan areas though the decreasing rate of minimum revenues is higher in rural areas. Metropolitan areas have higher Gini coefficients than rural areas, but the increasing rate of Gini coefficients is lower than rural areas. Findings from this study are useful reference when the dentists select the opening areas. One is that the median revenues between metropolitan and rural areas have no significant difference. The other is that the rural areas ensure the more stable and uniform revenues. The results would help to relieve the consumptive competition among dentists and to achieve the distributional efficiency of dental human resources.