• 대한수학회보
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• 제39권4호
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• pp.589-606
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• 2002

We introduce and analyze a frequency-domain method for parabolic partial differential equations. The method is naturally parallelizable. After taking the Fourier transformation of given equations in the space-time domain into the space-frequency domain, we propose to solve an indefinite, complex elliptic problem for each frequency. Fourier inversion will then recover the solution in the space-time domain. Existence and uniqueness as well as error estimates are given. Fourier invertibility is also examined. Numerical experiments are presented.

• Kyungpook Mathematical Journal
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• 제47권2호
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• pp.175-190
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• 2007

By employing the Riccati transformation technique some new oscillation criteria for the second-order neutral delay dynamic equation $$(y(t)+r(t)y({\tau}(t)))^{{\Delta}{\Delta}}+p(t)y(\delta(t))=0$$, on a time scale $\mathbb{T}$ are established. Our results as a special case when $\mathbb{T}=\mathbb{R}$ and $\mathbb{T}=\mathbb{N}$ improve some well known oscillation criteria for second order neutral delay differential and difference equations, and when $\mathbb{T}=q^{\mathbb{N}}$, i.e., for second-order $q$-neutral difference equations our results are essentially new and can be applied on different types of time scales. Some examples are considered to illustrate the main results.

• 대한지리학회지
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• 제35권4호
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• pp.599-619
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• 2000

본 연구는 지난 30여 년 동안 두 번의 신도시개발 정책으로 인하여 이원적 도시구조를 지니게 된 성남시의 차별적 생성과 변화를 행위주체자로서 여성을 선택하여 그들의 생활세계-생활사, 사회.경제적 배경, 지역정체성, 지역사회의 관계, 일상과 생활공간-를 통하여 공간과 사회와의 관계에서 경험적으로 입증하고자 하였다. 그 결과 성남시는 차별성을 지닌 두 지역사회를 생성하게 되었으며, 각 장소의 행위주체자(여성)의 생활세계에 있어서도 차별적 특성을 나타내어 기존시가지 주부들은 신시가지에 <가까이 하려는> 경향을, 신시간지 주부들는 <구별짓기>의 경향을 나타내고 있었다. 또한 전업주부의 일상생활을 통해서 볼 때 기존시가지의 경우에는 오전에는 주로 부업활동에, 오후에는 주변 이웃과의 교제활동을 주로 함으로써 자신의 거주지를 생산현장으로서의 공간으로 형성해 가고 있는 반면 신시가지 주부들은 오전에는 사적인 생활 즉 여가활동에, 오후에는 자녀교육활동에 참여하는 등 자신의 거주지를 소비현장으로서의 공간으로 형성해 가고 있었다.

• 대한치과의사협회지
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• 제50권12호
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• pp.732-742
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• 2012

White lesions of the oral mucosa are a common clinical finding that often present first to general dentist. Some white lesion may have possibility of malignancy. Leukoplakia is the most common "potentially malignant disorder" of the oral mucosa. Leukoplakia is at present defined as "A white plaque of questionable risk having excluded (other) known disease or disorders that carry no increased risk for cancer.". Therefore, it is important for general dentist to be familiar to clinical differential diagnosis of leukoplakia from the known white lesions such as candidiasis, lichen planus, leukoedema, frictional keratosis, and so on. It is also important to decide whether such lesions require further investigation through the biopsy. As a result of biopsy, the presence of epithelial dysplasia in the leukoplakia is still the strongest predictor of future malignant transformation. In this article, oral white lesions that must be differentiated from potentially malignant disorders or early invasive squamous cell carcinoma will be reviewed together with presenting clinical cases.

• Journal of applied mathematics & informatics
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• 제30권1_2호
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• pp.219-234
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• 2012

By using the generalized Riccati transformation and the inequality technique, we establish some new oscillation criterion for the second-order nonlinear delay dynamic equations $$(a(t)(x^{\Delta}(t))^{\gamma})^{\Delta}+q(t)f(x({\tau}(t)))=0$$ on a time scale $\mathbb{T}$, here ${\gamma}{\geq}1$ is the ratio of two positive odd integers with $a$ and $q$ real-valued positive right-dense continuous functions defined on $\mathbb{T}$. Our results not only extend and improve some known results, but also unify the oscillation of the second-order nonlinear delay differential equation and the second-order nonlinear delay difference equation.

• Journal of Mechanical Science and Technology
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• 제14권2호
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• pp.159-167
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• 2000

A computational method for the dynamic analysis of a constrained mechanical system is presented in this paper. The partial velocity matrix, which is the null space of the Jacobian of the constraint equations, is used as the key ingredient for the derivation of reduced equations of motion. The acceleration constraint equations are solved simultaneously with the equations of motion. Thus, the total number of equations to be integrated is equivalent to that of the pseudo generalized coordinates, which denote all the variables employed to describe the configuration of the system of concern. Two well-known conventional methods are briefly introduced and compared with the present method. Three numerical examples are solved to demonstrate the solution accuracy, the computational efficiency, and the numerical stability of the present method.

• Interaction and multiscale mechanics
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• 제2권4호
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• pp.431-454
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• 2009

This paper presents a simple model for studying the dynamic response of multi-span bridges resting on piers with different heights and subjected to earthquake forces acting transversely to the bridge, but varying spatially along its length. The analysis is carried out using the modal superposition technique, while the solution of the resulting integral-differential equations is obtained via the Laplace transformation. It has been found that the piers' height and the quality of the foundation soil can affect significantly the dynamic behavior of such bridges. Typical examples showing the effectiveness of the method are presented with useful results listed.

• Structural Engineering and Mechanics
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• 제60권1호
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• pp.21-30
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• 2016

In this paper two procedures for determination of the elastic curve of the simply and multiple supported beams are developed. Determination of the elastic curve is complex as it requires to solve a strong nonlinear differential equation with given boundary conditions. For numerical solution the initial guess of the slope at the end of the beam is necessary. Two procedures for obtaining of the initial guess are developed: one, based on transformation of the supported beam into a clamped-free one, and second, on the linearization of the problem. Procedures are applied for calculating of elastic curve of a simply supported beam and a beam with three supports. Obtained results are compared. Advantages and disadvantages of both methods are discussed. It is proved that both suggested procedures give us technically accurate results.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1986년도 한국자동제어학술회의논문집; 한국과학기술대학, 충남; 17-18 Oct. 1986
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• pp.304-309
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• 1986

This paper is about the Inverse Jacobian for the TOP-1 robot. The robot Jacobian is used for the movement in accordance with differental changes. A Matrix and Homogeneous Transformation Matrix, Differential Motion Vector D are applied to Jacobian equation for the movement of the robot in accordance with the minut changes. The solution of Jacobian equation is acquired and applied for the subtle movement of each arms of the robot. The interface with APPLE-II Micro-computer is searched out too. The Software and the interface resulted from this paper are considered to be higly useful in the accurate control on the robot when they are linked with dynamics of robot.

• 대한전자공학회논문지
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• 제27권6호
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• pp.937-943
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• 1990

In this paper, a subband coding scheme using the human visual system(HVS) model for encoding monochrome images is proposed to produce perceptually higher quality images compared with the regular subband coding scheme. The proposed approach first transforms the intensity image to the density image by a point nonlinear transformation. A frequency band dexomposition of the density image is carried out by means of 2-D seaprable quadrature mirror filters, which split the density image spectrum into 16 equall rate subbands. Bits are allocated among the subbands to minimize the weighted mean squar error (WMSE) for differential pulse code modulation(DPCM) coding of the subbands. The weight for each subband is calculated from the modulation transfer function (MTF) of the HVS model at corresponding frequencies. The performances of the proposed approach are evaluated for 256 * 256 monochrome images at the bit rates of 0.5, 0.75 and 1.0 bita per pixel. Computer simulation results indicate that using the HVS model yields more pleasing reconstructed images than regular subband coding approach which does not use HVS model.