• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.7
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• pp.1217-1233
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• 2015

The paper studies characteristics of the minimum mean-square error symmetric scalar quantizers for the generalized gamma, Bucklew-Gallagher and Hui-Neuhoff probability density functions. Toward this goal, asymptotic formulas for the inner- and outermost thresholds, and distortion are derived herein for nonuniform quantizers for the Bucklew-Gallagher and Hui-Neuhoff densities, parallelling the previous studies for the generalized gamma density, and optimal uniform and nonuniform quantizers are designed numerically and their characteristics tabulated for integer rates up to 20 and 16 bits, respectively, except for the Hui-Neuhoff density. The assessed asymptotic formulas are found consistently more accurate as the rate increases, essentially making their asymptotic convergence to true values numerically acceptable at the studied bit range, except for the Hui-Neuhoff density, in which case they are still consistent and suggestive of convergence. Also investigated is the uniqueness problem of the differentiation method for finding optimal step sizes of uniform quantizers: it is observed that, for the commonly studied densities, the distortion has a unique local minimizer, hence showing that the differentiation method yields the optimal step size, but also observed that it leads to multiple solutions to numerous generalized gamma densities.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.1
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• pp.117-121
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• 2009

The fisheye image acquired with a fisheye camera has wider field of view than a general use camera. But large distortion of the object in the image requires conversion of the fisheye image to the perspective image because of user's difficult perception. The existing Ishii's method[1] has the problem that the object can has sire and geometrical distortion in the transformed image because it uses equidistance projection. This paper presented a conversion technique of the fisheye image to the perspective image using sealing function. In the experiments, it was shown that our method reduced size and geometrical distortion by applying the scaling function.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.2
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• pp.192-197
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• 2008

The value of this paper is to use reduced size apparatuses to perform field measurement in order to identify and validate that the harmonic-current effects are due to the presence of self-excitation capacitance connected at stator's terminals of the studied SEIG. This paper has presented the measured electrical quantities of a three-phase $\Delta$-connected wind induction generator (WIG) under sudden connection and disconnection of resistive loads. An intelligent power-system recorder/monitor has been employed to measure three-phase voltages and currents of the studied system at the terminals of the studied WIG and the load. The measured electrical quantities have been analyzed. Total harmonic distortion (THD) of current using cumulative probability density function has been employed to determine the penetration of harmonic distortion at load side. The results show that the harmonic currents generated by the studied WIG can be severely amplified by the connected self-excited capacitance at the stator's terminals.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.13 no.4
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• pp.134-141
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• 1999

Ths paper describes on the stability improvement of output voltage control on the power suwJy for railway. On the transient states such as input voltage sudden change, the inpJt and output voltage beccxre unstable by L-C resonance occurred due to constant output voltage control. In this paper, the new clamping circuit for system stability is proposed, and control method using band attenuated filter and feed-forward terms is introduced. The propoesd damping circuit is composed with sma1l size R-L. Also, the 3 level PWM method is adopted to decrease distortion of output voltage. The output voltage is controlledl with variation under 10% without oscillation at transient states and have total hanmnic distortion under 3%.der 3%.

• Journal of the Semiconductor & Display Technology
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• v.21 no.1
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• pp.22-26
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• 2022

This paper proposes a new method for the recognition of road surface marks and numbers. The proposed method designates a region of interest on the road surface without first detecting a lane. The road surface markings are extracted by location and size using a connection component analysis. Distortion due to the perspective effect is minimized by normalizing the size of the road markings. The road surface marking of the connected component is recognized by matching it with the stored road marking templates. The proposed method is implemented using C language in Raspberry Pi 4 system with a camera module for a real-time image processing. The system was fixedly installed in a moving vehicle, and it recorded a video like a vehicle black box. Each frame of the recorded video was extracted, and then the proposed method was tested. The results show that the proposed method is successful for the recognition of road surface marks and numbers.

• Journal of the Korean Association of Geographic Information Studies
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• v.20 no.1
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• pp.137-151
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• 2017

The space between urban buildings becomes a waterway during rain events and requires a boundary condition in numerical calculations on grids to separate overland storm flows from building areas. Minimization of the building data distortion as a boundary condition is a necessary step for generating accurate calculation results. A building generalization is used to reduce the distortion of building shapes and areas during a raster conversion. The objective of this study was to provide the appropriate threshold value for building generalization and grid size in a numerical calculation. The impact of building generation on the connectivity of urban storm waterways were analyzed for a general residential area. The building generalization threshold value and the grid size for numerical analysis were selected as the independent variables for analysis, and the number and area of sinks were used as the dependent variables. The values for the building generalization threshold and grid size were taken as the optimal values to maximize the building area and minimize the sink area. With a 3 m generalization threshold, sets of $5{\times}5m$ to $10{\times}10m$ caused 5% less building area and 94.4% more sink area compared to the original values. Two sites representing general residential area types 2 and 3 were used to verify building generalization thresholds for improving the connectivity of storm waterways. It is clear that the recommended values are effective for reducing the distortion in both building and sink areas.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.8
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• pp.2010-2024
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• 1998

In video coding, it is important to improve the average picture quality as well as to maintain cosistent picture quality between consecutive pictures. In this paper, we propose a distortion-rate estimation method for MPEG-2 video and a forward rate control method, using the proposed estimation result, to be able to obtain the improved and consistent picture quality of CBR (Constant Bit Rate) encoded MPEG-2 video. The proposed distortion-rate estimation enable us to predict the distortion and the bits generated from an encoded picture at a given quantization step size and vice versa. The most attactive features of proposed distortion-rate estimation are its accuracy and low computational complexity enough to be applied to the practical video coding. In addition, the proposed rate control first determined a quantization parameter per frame by following procedure: distortion-rate estimation, target bit allocation, distortion constraint and VBV(Video Buffer Verification) constraint. And then this quantization parameter is applied to the encoding so that improved and consisten picture quality can be obtained. Furthermore the proposed rate control method can solve the error propagation problem caused by scene change or anchor picture degradation by using the B-picture skipping and the guarantee of the minimum bit allocation for the anchor picture. Experimental results, comparing the proposed forward rate control method with TM5 method, show that the proposed method makes more improed and consistent picture quality than TM5.

• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.522-524
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• 1994

This paper presents power factor and distortion improvement methods via active boost converter and mode select. This method not only reduces the current and voltage distortion but also the physical size and expected low cost. Optimum parameter values arc derived to minimize the harmonise in the input current. A theoretical analysis, simulation and experimental results arc presented.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.45-48
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• 2002

This paper proposes a grid-connected inverter using the negative conductance of PV power system, which has four IGBTs and simple controller. Most of modern electric loads generate the current harmonics and the line voltage distortion. The new solar-to-ac converter(STAC) provides by emulating a negative conductance load to the line voltage, so the current harmonics from STAC is canceled the effect of the harmonics from other loads. As a result, the line voltage distortion is decreased. The proposed system have low cost, small size, and light weight compared to conventional photovoltaic converter

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.1232-1235
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• 2009

Image compression techniques such as JPEG and MPEG induce losses of image quality. These losses are usually investigated on the spatial distortions from reconstructed images. Representative specifications are blocking artifacts, color bleeding and smearing. However, the compression techniques also influence the color information. The distortion of color information means distortion of gamut characteristics such as gamut size and unique color from the CIELAB values for each pixel in the reconstructed images. Accordingly, this paper introduces the investigation of the relationship between image compression and the gamut characteristics for reconstructed images using MPEG compression. The results show the consist variation of gamut, hue, and chroma due to MPEG compression.