• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.109.1-109
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• 2001

This paper deals with the path following problem of car-like intelligent mobile robot. A robust sliding mode control law based on time-varying state feedback is performed via Lyapunov method for path tracking of nonholonomic mobile robot with uncertainties. At first, A sliding control law is designed by combing the natural algebraic structure of the chained form system with ideas from sliding mode theory. Then, a robust control law is proposed to impose robustness against bounded uncertainties in path tracking. The problem of estimating the asymptotic stability region and the sliding domain of uncertain sliding mode system with bounded control input is also discussed. The proposed sliding mode control law can ensure the global reaching condition of the uncertain control system.

• Structural Engineering and Mechanics
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• 제76권1호
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• pp.129-139
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• 2020

In this piece of work, carbon nanotubes motion equations are framed by Kelvin's method. Employment of the Kelvin's method procedure gives birth to the tube frequency equation. It is also exhibited that the effect of frequencies is investigated by varying the different index of polynomial function. By using volume fraction for power law index, the fundamental natural frequency spectra for two forms of single-walled carbon nanotubes are calculated. The influence of frequencies against length-to-diameter ratios with varying power law index are investigated in detail for these tubes. Throughout the computation, it is observed that the frequency behavior for the boundary conditions follow as; clamped-clamped, simply supported-simply supported and these frequency curves are higher than that of clamped-free curves. Computer software MATLAB is utilized for the frequencies of single-walled carbon nanotubes.

• Steel and Composite Structures
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• 제37권5호
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• pp.621-632
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• 2020

This research deals with the study of vibrational behavior of armchair and zigzag single-walled carbon nanotubes invoking extended Love shell theory. The effects of different physical and material parameters on the fundamental frequencies are investigated. By using volume fraction for power law index, the fundamental natural frequency spectra for two forms of single-walled carbon nanotubes are calculated. The influence of frequencies against length-to-diameter ratios with varying power law index are investigated in detail for these tubes. To discretize the governing equation in eigen-value form, wave propagation approach is developed. Complex exponential functions have been used and the axial model depends on boundary condition that has been described at the edges of carbon nanotubes to calculate the axial modal dependence. Computer software MATLAB is utilized for the frequencies of single-walled carbon nanotubes and current results shows a good stability with comparison of other studies.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2015년도 학술발표회
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• pp.246-246
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• 2015

Runoff at any given location along a stream can be expressed as a function of its upstream area. The runoff-drainage area relationship can be well expressed as power-law (Brush, 1961) with its exponent, ranging as high as unity (e.g., Stall and Fok, 1968) and as low as 0.5 in natural rivers. Here, we study the runoff-drainage area relationships for Han River and Nakdong River, Korea. We find that the relationships follow power-law and their exponents are highly related with occurrence frequency of flow. To support this, we analyze flow frequency with historical data measured over decades. Findings in this study can broaden our understanding on mechanisms behind the catchment response to runoff.

• 노동경제논집
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• 제35권1호
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• pp.89-109
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• 2012

본 연구는 실업률 변화와 성장률 간의 경험적 관계를 나타내는 오쿤의 법칙을 우리나라의 자료를 이용하여 추정하고 그 결과를 새롭게 해석하는 것을 목표로 하고 있다. 분석 결과는 다음과 같다. 첫째, 벤치마크 오쿤의 추정계수 ${\beta}$는 방법론에 따라 대략 2~4의 계수 값을 보여주어 선진국의 경우보다 다소 높은 값을 보여주었다. 둘째, 경기변동에 따른 비대칭적인 반응이 관측되기는 하지만 추정방법에 따라 혼재된 결과를 보여주고 있다. 마지막으로 1979~80년, 1997~98년 등의 구조변화를 반영한 오쿤의 추정계수는 벤치마크와 비슷한 값으로 추정되었다.

• 대한수학회논문집
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• 제18권1호
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• pp.117-126
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• 2003

Let {$X_{nk}$\mid$1\;{\leq}\;k\;{\leq}\;n,\;n\;{\geq}\;1$} be an array of row negatively associated (NA) random variables which satisfy $P($\mid$X_{nk}$\mid$\;>\;x)\;{\leq}\;P($\mid$X$\mid$\;>\;x)$. For weighed sums ${{\Sigma}_{k=1}}^{Tn}\;a_kX_{nk}$ indexed by random variables {$T_n$\mid$n\;{\geq}$1$}, we establish a general weak law of large numbers (WLLN) of the form $({{\Sigma}_{k=1}}^{Tn}\;a_kX_{nk}\;-\;v_{[nk]})\;/b_{[an]}$ under some suitable conditions, where $\{a_n$\mid$n\;\geq\;1\},\; \{b_n$\mid$n\;\geq\;1\}$ are sequences of constants with $a_n\;>\;0,\;0\;<\;b_n\;\rightarrow \;\infty,\;n\;{\geq}\;1$, and {$v_{an}$\mid$n\;{\geq}\;1$} is an array of random variables, and the symbol [x] denotes the greatest integer in x.

• Structural Engineering and Mechanics
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• 제52권5호
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• pp.903-918
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• 2014

Large space structures may have resonant low eigenvalues and often these appear with closely-spaced natural frequencies. Owing to the coupling among modes with closely-spaced natural frequencies, each eigenvector corresponding to closely-spaced eigenvalues is ill-conditioned that may cause structural instability. The subspace to an invariant subspace corresponding to closely-spaced eigenvalues is well-conditioned, so a method is presented to design the feedback control law of intelligent structures with closely-spaced eigenvalues in this paper. The main steps are as follows: firstly, the system with closely-spaced eigenvalues is transformed into that with repeated eigenvalues by the spectral decomposition method; secondly, the computation for the linear combination of eigenvectors corresponding to repeated eigenvalues is obtained; thirdly, the feedback control law is designed on the basis of the system with repeated eigenvalues; fourthly, the system with closely-spaced eigenvalues is regarded as perturbed system on the basis of the system with repeated eigenvalues; finally, the feedback control law is applied to the original system, the first order perturbations of eigenvalues are discussed when the parameter modifications of the system are introduced. Numerical examples are given to demonstrate the application of the present method.

• Computers and Concrete
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• 제29권2호
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• pp.117-126
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• 2022

The vibrational characteristic of three-layered cylindrical shell (CS) submerged in fluid with the ring support has been studied. The inner and outer layer is supposed to construct by isotropic layer. The composition of central layer is of functionally graded material type. Acoustic Wave condition has been utilized to present the impact of fluid. The central layer of cylindrical shell (CS) varies by volume fraction law that has been expressed in terms of polynomial. The main shell frequency equation has been obtained by theory of Love's shell and Rayleigh-Ritz technique. The oscillation of natural frequency has been examined under a variety of end conditions. The dependence of axial model has been executed with the help of characteristic beam function. The natural frequencies (NFs) of functionally graded material (FGM) shell have been observed of cylindrical shell along the shell axial direction. Different physical parameters has been used to examine the vibration characteristics due to the effect of volume fraction law. MATLAB software has been used to get result.

• Journal of the Korean Statistical Society
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• 제31권3호
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• pp.369-378
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• 2002

Strong laws of large numbers for weighted sums of asymptotically almost negatively associated(AANA) sequence are proved by our generalized maximal inequality for AANA random variables at a crucial step.

• 한국전통조경학회지
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• 제37권3호
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• pp.127-133
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• 2019

본 연구는 지속적으로 변화하는 문화재 보호제도의 체계 속에서 문화재 조경의 제도 개선을 논의하고자 하였으며, 도출된 결과는 다음과 같다. 첫째, 천연기념물 및 명승을 포함하는 문화재 조경으로서의 위상을 정립하여야 한다. 가능하다면 조경에 관련된 천연기념물 및 명승법을 분법하여 제정하는 것에 대한 면밀한 검토가 요구된다. 둘째, 자연유산은 '개체' 중심의 보호에서 누락될 수 있는 문화적 산물과 주변 경관을 포함하기 위해 '공간' 중심의 보존이 이루어져야 한다. 제도적으로 관계 법령의 중복성과 상호 관계를 검토하여 업무 범위를 명확하게 분담하여야 한다. 셋째, 자연유산의 보호·관리를 위해 문화재청에 문화재 조경을 독립적이거나 주도적으로 전담할 부서를 신설하여야 한다. 넷째, 문화재보호법에 문화재위원의 위촉 자격에 조경 분야를 명시하고, 현행 '문화재 수리 등에 관한 법률'에서 '조경수리기술자'와 '식물보호기술자'의 역할을 확대하는 등의 제도 개선을 추진해야 한다.