• Current Optics and Photonics
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• 제5권5호
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• pp.514-523
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• 2021

Methods for absolute depth estimation have received lots of interest, and most algorithms are concerned about how to minimize the difference between an input defocused image and an estimated defocused image. These approaches may increase the complexity of the algorithms to calculate the defocused image from the estimation of the focused image. In this paper, we present a new method to recover depth of scene based on a sharpness-assessment algorithm. The proposed algorithm estimates the depth of scene by calculating the sharpness of deconvolved images with a specific point-spread function (PSF). While most depth estimation studies evaluate depth of the scene only behind a focal plane, the proposed method evaluates a broad depth range both nearer and farther than the focal plane. This is accomplished using an asymmetric aperture, so the PSF at a position nearer than the focal plane is different from that at a position farther than the focal plane. From the image taken with a focal plane of 160 cm, the depth of object over the broad range from 60 to 350 cm is estimated at 10 cm resolution. With an asymmetric aperture, we demonstrate the feasibility of the sharpness-assessment algorithm to recover absolute depth of scene from a single defocused image.

• 대한신경과학회지
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• 제36권4호
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• pp.314-317
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• 2018

Focal subarachnoid hemorrhage occasionally presents as transient focal neurologic episodes mimicking transient ischemic attack (TIA). Unless properly diagnosed, it may aggravate cerebral hemorrhage by administering antithrombotic agents. Therefore, clinicians need to be aware that such focal subarachnoid hemorrhage sometimes cannot be detected on noncontrast computed tomography and blood-sensitive magnetic resonance imaging can detect even a small amount of hemorrhage. We describe an 85-year-old woman with focal subarachnoid hemorrhage and possible cerebral amyloid angiopathy who presented transient left arm weakness recurrently, which mimicked TIA.

• ETRI Journal
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• 제45권2호
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• pp.291-303
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• 2023

Selfies are a popular form of photography. However, due to physical constraints, the compositions of selfies are limited. We present algorithms for creating virtual portraits with interesting compositions from a set of selfies. The selfies are taken at the same location while the user spins around. The scene is analyzed using multiple selfies to determine the locations of the camera, subject, and background. Then, a view from a virtual camera is synthesized. We present two use cases. After rearranging the distances between the camera, subject, and background, we render a virtual view from a camera with a longer focal length. Following that, changes in perspective and lens characteristics caused by new compositions and focal lengths are simulated. Second, a virtual panoramic view with a larger field of view is rendered, with the user's image placed in a preferred location. In our experiments, virtual portraits with a wide range of focal lengths were obtained using a device equipped with a lens that has only one focal length. The rendered portraits included compositions that would be photographed with actual lenses. Our proposed algorithms can provide new use cases in which selfie compositions are not limited by a camera's focal length or distance from the camera.

• 대한수학회지
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• 제40권6호
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• pp.951-962
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• 2003

In this paper we address focal points and treat manifolds (M, g) whose Lorentzian metric tensors g have a spacelike $C^{0}$-hypersurface $\Sigma$ [10]. We apply Jacobi fields for such manifolds, and check the local length maximizing properties of $C^1$-geodesics. The condition of maximality of timelike curves(geodesics) passing $C^{0}$-hypersurface is studied.ied.

• 대한수학회보
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• 제38권2호
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• pp.273-284
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• 2001

Let P be a spacelike (n-2)-dimensional submanifold of an n-dimensional Lorentz manifold M and let$\sigma$ be a P-normal null geodesic with Ric($\sigma',\sigma'$)$\geq$m, for the any given nonpositive constant m. We establish a sufficient condition such that there is a focal point of P along $\sigma$.

• 대한수학회보
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• 제38권2호
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• pp.285-292
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• 2001

The authors compute the Ricci curvature of the GRW space-time to obtain two conditions for the conjugate points which appear as the Timelike Convergence Condition(TCG) and the Jacobi inequality. Moreover, under such two conditions, we obtain a lower bound of the length of a unit timelike geodesic for focal points emanating form the immersed spacelike hypersurface, the graph over the fiber in the GRW space-time.

• 음성과학
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• 제8권2호
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• pp.165-180
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• 2001

In this paper prosodic characteristics of French language are analysed with a corpus of radio interview. Intonation patterns are interpreted in terms of raising pattern, focal raising pattern and falling pattern. Accentual prominence is classified in two types, rhythmic accent and focal accent. Focal accent permit to explain the cohesion in a utterance or between two utterances. As a prosodic variable of discourse pauses are described by their form of realization (filled pause, silent pause, hesitation etc), their distribution and their function in utterance.

• 전자공학회논문지A
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• 제32A권12호
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• pp.36-47
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• 1995

The main purpose of this paper is to determine a new focal point and field distribution due to the shape deformation of reflector antenna by numerical method such as geometrical optics and the aperture field method. It is shown the 4 types deformations to be added into original shape of parabola antenna and offset antenna: linear, quadratic, cubic and hybrid distortion. These results can be applied to deformed reflector antenna in order to fit a focal point and radiation pattern.

• 한국수학교육학회지시리즈B:순수및응용수학
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• 제24권4호
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• pp.191-200
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• 2017

The theory of $u_0-positive$ operators is applied to obtain smallest eigenvalue comparison results for right focal boundary value problems of Atici-Eloe fractional difference equations.

• Journal of Korean Neurosurgical Society
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• 제62권3호
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• pp.288-295
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• 2019

In 2011, the International League against Epilepsy (ILAE) proposed a first international consensus of the classification of focal cortical dysplasia (FCD). This FCD classification had been widely used in worldwide. In this review paper, the authors would like to give helpful comments for better understanding of the current FCD classification. Especially, the basic concepts of FCD type I, such as "radial", "tangential" and "microcolumn" will be discussed with figures. In addition, the limitations, genetic progress and prospect of FCD will be suggested.