• Title, Summary, Keyword: focal point

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Numerical study on the relation between flow parameters and the focal point of fluidic lens (유체 렌즈의 초점과 유동 인자의 상관관계에 대한 수치해석)

  • Lahooti, Mohsen;Kim, Daegyoum
    • Journal of the Korean Society of Visualization
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    • v.17 no.2
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    • pp.90-95
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    • 2019
  • In the present work, the effect of flow parameters such as volume flow rate on focal point of fluidic micro lens is investigated numerically. ANSYS Fluent is used for simulations, and the flow parameters and number of simulations are determined using the space filling method of design of experiment (DOE). Having determined the location of interfaces between fluids inside the micro lens which acts as the lens curvature, a ray tracking simulation on each case is performed using COMSOL Multiphysics to determine the focal point for each lens. These data are then used to provide a relation between flow parameters and the focal point of the lens.

APPLICATION OF HISTOGRAM OUTLIER ANALYSIS ON THE IMAGE DEGRADATION MODEL FOR BEST FOCAL POINT SELECTION

  • Shin, Hyun-Kyung
    • Journal of applied mathematics & informatics
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    • v.27 no.1_2
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    • pp.175-182
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    • 2009
  • Microscopic imaging system often requires the algorithm to adjust location of camera lenses automatically in machine level. An effort to detect the best focal point is naturally interpreted as a mathematical inverse problem [1]. Following Wiener's point of view [2], we interpret the focus level of images as the quantified factor appeared in image degradation model: g = $f{\ast}H+{\eta}$, a standard mathematical model for understanding signal or image degradation process [3]. In this paper we propose a simple, very fast and robust method to compare the degradation parameters among the multiple images given by introducing outlier analysis of histogram.

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A NULL FOCAL THEOREM ON LORENTZ MANIFOLDS

  • So, Jae-Up
    • Bulletin of the Korean Mathematical Society
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    • v.38 no.2
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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 $\sigma$.

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Shock Wave Generation and its Applications by Pulsed Power (펄스파워를 이용한 수중 충격파 발생 및 응용)

  • Cho, Chu-Hyun;Lee, Hong-Sik;Choi, Young-Wook;Jo, Sung-Chan;Jung, Woo-Geun
    • Proceedings of the KIEE Conference
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    • pp.190-191
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    • 2007
  • Focused shock wave generation was tested under the water by the method of wire explosion. The wire was installed a focal point of the half ellipsoid, and the shock wave was focused on the other focal point. A numerous cavitations were observed in the path of the traveling shock wave and focal point by using high speed camera.

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Parameter Estimation for Range Finding Algorithm of Equidistance Stereo Catadioptric Mirrors (등거리 스테레오 전방위 렌즈의 위치 측정 알고리듬을 위한 파라미터 측정에 관한 연구)

  • Choi, Young-Ho;Kang, Min-Goo;Zo, Moon-Shin
    • Journal of Internet Computing and Services
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    • v.8 no.5
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    • pp.117-123
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    • 2007
  • Catadioptric mirrors are widely used in automatic surveillance system. The major drawback of catadioptric mirror is its unequal image resolution. Equidistance catadioptric mirrir can be the solution to this problem. The exact axial alignment and the exact mount of mirror are the sources that can be avoided but the focal length variation is inevitable. In this paper, the effects of focal length variation on the computation of depth and height of object' point are explained and the effective and simple focal length finding algorithm is presented. First two object's points are selected, and the counterparts on the other stereo image are to be found using MSE criterion. Using four pixel distance from the image center, the assumed focal length is calculated. If the obtained focal length is different from the exact focal length, 24mm, the focal length value is modified by the proposed method. The method is very simple and gives the comparable results with the earlier sophisticated method.

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FOCAL POINT IN THE C0-LORENTZIAN METRIC

  • Choi, Jae-Dong
    • Journal of the Korean Mathematical Society
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    • v.40 no.6
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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.

RICCI CURVATURE FOR CONJUGATE AND FOCAL POINTS ON GRW SPACE-TIMES

  • Kim, Jeong-Sik;Kim, Seon-Bu
    • Bulletin of the Korean Mathematical Society
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    • v.38 no.2
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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.

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A Study of the field distribution in focal plane for the shape deformations of Satellite antenna (위성 반사경 안테나 변형으로 인한 초점영역의 전자장 분포에 관한 연구)

  • Yi Sang-Hoi
    • Journal of the Korean Institute of Telematics and Electronics A
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    • v.32A no.12
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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.

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Maximizing the Workspace of Optical Tweezers

  • Hwang, Sun-Uk;Lee, Yong-Gu
    • Journal of the Optical Society of Korea
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    • v.11 no.4
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    • pp.162-172
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    • 2007
  • Scanning Laser Optical Tweezers(SLOT) is an optical instrument frequently employed on a microscope with laser being delivered through its various ports. In most SLOT systems, a mechanical tilt stage with a mirror on top is used to dynamically move the laser focal point in two-dimensions. The focal point acts as a tweezing spot, trapping nearby microscopic objects. By adding a mechanical translational stage with a lens, SLOT can be expanded to work in three-dimensions. When two mechanical stages operate together, the focal point can address a closed three-dimensional volume that we call a workspace. It would be advantageous to have a large workspace since it means one can trap and work on multiple objects without interruptions, such as translating the microscope stage. However, previous studies have paid less consideration of the volumetric size of the workspace. In this paper, we propose a new method for designing a SLOT such that its workspace is maximized through optimization. The proposed method utilizes a matrix based ray tracing method and genetic algorithm(GA). To demonstrate the performance of the proposed method, experimental results are shown.

On the Beam Focusing Behavior of Time Reversed Ultrasonic Arrays Using a Multi-Gaussian Beam Model

  • Jeong, Hyun-Jo;Lee, Jeong-Sik;Jeong, Yon-Ho;Bae, Sung-Min
    • Journal of the Korean Society for Nondestructive Testing
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    • v.28 no.6
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    • pp.531-537
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    • 2008
  • One of the fundamental features of time reversal acoustic (TRA) techniques is the ability to focus the propagating ultrasonic beam to a specific point within the test material. Therefore, it is important to understand the focusing properties of a TR device in many applications including nondestructive testing. In this paper, we employ an analytical scheme for the analysis of TR beam focusing in a homogeneous medium. More specifically, a nonparaxial multi-Gaussian beam (NMGB) model is used to simulate the focusing behavior of array transducers composed of multiple rectangular elements. The NMGB model is found to generate accurate beam fields beyond the nonparaxial region. Two different simulation cases are considered here for the focal points specified on and off from the central axis of the array transducer. The simulation results show that the focal spot size increases with increasing focal length and focal angle. Furthermore, the maximum velocity amplitude does not always coincide with the specified focal point. Simulation results for the off-axis focusing cases do demonstrate the accurate steering capability of the TR focusing.