• Journal of the Korean Society for Precision Engineering
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• v.24 no.10
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• pp.37-45
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• 2007

End-milling is intermittent cutting process performed by a tool with a number of teeth. Its cutting forces are commonly measured by the tool dynamometer which has rectangular coordinates. In this case, the pattern of cutting forces is different according to cutting conditions. At a certain cutting condition, the sign of cutting force changes from positive to negative during a revolution of one tooth. The change of force direction excites a cutting tool and severe vibration arises when radial depth of cut increases. In this study, cutting experiments and simulations were carried out in order to explain the cause of the change of the cutting force direction. In addition, the effect of the cutting force change was discussed in terms of chatter vibration in end milling.

• Journal of the Korean Society of Safety
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• v.11 no.1
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• pp.46-52
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• 1996

In this paper, an analytical method is proposed to find the dimensions of impact stresses with using the dimensions of impact loading parameter regardless of mass of impactor, velocity of impactor, and plate thickness. In analytical method of Impulsive stresses, the three-dimensional dynamic theory of elasticity using rectangular coordinates and the potential theory of displacement are utilized, and when the measurement of Impact loading is difficult especially for a steel ball colliding on an infinite plate, the impact loading can be obtained by using the classical plate theory and Hertz’s contact theory. And in the numerical analysis, the fast Fourier transform (F. F. T.) algorithm and the numerical inverse Laplace transformation are used because the analysis of impact loading Is difficult to obtain solutions by using the thress-dimensional dynamic theory of elasticity.

• Journal of Platform Technology
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• v.6 no.4
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• pp.18-25
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• 2018

This paper describes a real-time human and robot tracking method in Intelligent Space with multi-camera networks. The proposed method detects candidates for humans and robots by using the histogram of oriented gradients (HOG) feature in an image. To classify humans and robots from the candidates in real time, we apply cascaded structure to constructing a strong classifier which consists of many weak classifiers as follows: a linear support vector machine (SVM) and a radial-basis function (RBF) SVM. By using the multiple view geometry, the method estimates the 3D position of humans and robots from their 2D coordinates on image coordinate system, and tracks their positions by using stochastic approach. To test the performance of the method, humans and robots are asked to move according to given rectangular and circular paths. Experimental results show that the proposed method is able to reduce the localization error and be good for a practical application of human-centered services in the Intelligent Space.

• Progress in Superconductivity and Cryogenics
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• v.8 no.3
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• pp.63-69
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• 2006

This paper describes the effect of rotating frequency on the pulse tube of Stirling type pulse tube refrigerator. Various conditions were analyzed by two-dimensional analysis with several dominant non-dimensional parameters. With the additional pressure term influenced by centrifugal force in rotating condition, the linearized conservation equations of mass, momentum, energy of the gas were solved to obtain the first order variables and calculate the enthalpy flow in rectangular coordinates. The rotational effect in pulse tube for the refrigerator's performance were quantitatively evaluated. According to the first order analysis, the enthalpy flow decreases with the rotating speed.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.10
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• pp.77-82
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• 2004

This paper presents polar converting logic(PCL) of BTT missiles against slowly moving or stationary targets. A guidance commands expressed in rectangular coordinates must be converted in the form of polar coordinates for BTT control. Since conventional PCL has nonlinear and discontinuous function, the missiles may lose controllability when pitch acceleration command equals to zero. Further, roll coupling may have a serious unstabilizing influence on homing guidance with two gimbals seeker. In this paper, a linear homotopy equation is introduced to improve the controllability and a command following performance at midcourse phase. We also design a PCL which is less sensitive to pitch acceleration command so that it may improve the stability of the homing loop. To substantiate our conclusion, results of the computer simulation have been illustrated.

• Journal of Korea Multimedia Society
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• v.9 no.5
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• pp.624-634
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• 2006

This paper presents a new watermarking scheme that is robust against geometrical attacks such as translation and rotation. The proposed method is based on the conventional PSADT(Polar Coordinates Shape Adaptive Discrete Transform) method which is an robust watermarking scheme for an arbitrarily-shaped image such as character images. The PSADT method shows perfect robustness against geometrical attack if there is no change in the shape of the image object. However, it cannot be utilized to watermark general rectangular images because of the missing alignment between the watermarked signals in the embedding and extracting side. To overcome this problem we propose a new watermarking scheme that aligns the watermark signal using the image inherent feature, especially corner. Namely the proposed method decides a consistent target region whose shape and position isn't changed by any malicious attack and then embeds the watermark in it using the PSADT method. Experimental results show the robustness of the proposed method against geometrical attacks as well as image compression.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.4
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• pp.105-117
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• 2015

In this paper, we consider 19 cells with the two tiers for polar-rectangular coordinates (PRCs) and provide the cell edge performance of cellular networks based on distance from cell center i.e., BS (base station). When FFR is applied(or adopted) to cell edge, it is expected that BS cooperation, or a coordinated multipoint (CoMP) multiple access strategy will further improve the system performance. We proposed a new method to evaluate the sum rate capacity of the MIMO DC of multicell system. We improve the performance of cell edge users for intercell interference cancelation in cooperative downlink multicell systems. Simulation results show that the proposed scheme outperforms the reference schemes, in terms of cell edge SINR (signal-to-interference-noise ratio) with a minimal impact on the network path loss exponent. We show 13 dB improvements in cell-edge SINR by using reuse of three relative to reuse of one. BS cooperation has been proposed to mitigate the cell edge effect.

• Journal of IKEEE
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• v.7 no.1 s.12
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• pp.32-42
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• 2003

In this paper, radiation pattern of rectangular microstrip patch antenna with anisotropy substrates and superstrate is studied by using a rigorous full-wave approach and a moment method calculation. Dyadic Green's function is derived for selected anisotropy material by constitutive relation. From these results, integral equations of electric fields are formulated. The electric field integral equations are discretized into the matrix form by applying Galerkin's moment method and then the current coefficients are obtained.. After solving the current coefficients, the far-zone electric field in spherical coordinates can be obtained by using the stationary phase method. To verify the validity of numerical result, we compare our result with existing one and get a good agreement between them. From the numerical results, the radiation patterns for variation of uniaxial superstrate thickness, anisotropy ratio of substrate and superstrate layer are presented and analyzed.

• The Transactions of the Korea Information Processing Society
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• v.6 no.11
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• pp.3140-3149
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• 1999

Skew correction for document images can be using a rotational transformation of pixel coordinates. In this paper we propose a method which corrects the document skew, by an amount of $\theta$ degrees, using block information, where the block is defined as a rectangular area containing adjacent black pixels. Processing speed of the proposed method is faster than that of the method using pixel transformation, since the number of floating-point operations can be reduced significantly. In the proposed method, we rotate only the four corner points of each block, and then identify the pixels inside the block. Two methods for inside pixel identification are proposed; the first method finds two points intersecting the boundary of the rotated block in each row, and determines the pixels between the two intersection points as the inside pixel. The second method finds boundary points based on Bresenham's line drawing algorithm, using fixed-point operation, and fills the region surrounded by these boundaries as black pixels. We have measured the performance of the proposed method by experimenting it with 2,016 images of various English and Korean documents. We have also proven the superiority of our algorithm through performance comparison with respect to existing methods based on pixel transformation.

• The Journal of Korea Robotics Society
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• v.11 no.1
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• pp.9-18
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• 2016

A rectangle-based relative localization method is proposed for a mobile robot based on a novel geometric formulation. In an artificial environment where a mobile robot navigates, rectangular shapes are ubiquitous. When a scene rectangle is captured using a camera attached to a mobile robot, localization can be performed and described in the relative coordinates of the scene rectangle. Especially, our method works with a single image for a scene rectangle whose aspect ratio is not known. Moreover, a camera calibration is unnecessary with an assumption of the pinhole camera model. The proposed method is largely based on the theory of coupled line cameras (CLC), which provides a basis for efficient computation with analytic solutions and intuitive geometric interpretation. We introduce the fundamentals of CLC and describe the proposed method with some experimental results in simulation environment.