• Journal of the Korean Mathematical Society
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• v.36 no.6
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• pp.1033-1046
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• 1999

This paper is devoted to the point wise error estimate up to boundary for the standard finite element solution of Poisson equation with Dirichlet boundary condition. Our new approach used the discrete maximum principle for the discrete harmonic solution. once the mesh in our domain satisfies the $\beta$-condition defined by us, the discrete harmonic solution with dirichlet boundary condition has the discrete maximum principle and the pointwise error should be bounded by L-errors newly obtained.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.156.4-156
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• 2001

The uncertainties of an atmospheric re-entry flight with respect to stability and controllability are aerodynamic error, measurement error of the angle of attack, variation of dynamic pressure, wind, and trim position of the control surfaces, etc. During hypersonic flight, a future angle of attack is biased from a nominal schedule. In order words, because the angle of attack is estimated from the navigation data, estimation error occurs due to wind, atmospheric density variation, etc. Error models used in this study, include a standard deviation of +-3 sigma, and are the normal distribution of statistics. This paper shows the appraisement of tracking performance onto the reference trajectory, satisfaction of the initial condition of TAEM about the re-entry system.

• Proceedings of the IEEK Conference
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• 2003.11a
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• pp.275-278
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• 2003

Terrestrial DMB(Digital Multimedia Broadcasting) system is the standard that offers multimedia broadcasting services at mobile environment and is based on Eureka-147 DAB(Digital Audio Broadcasting) for transmission method. Also DMB provides the error protection method of convolution coding. In this paper, we study on the effective error resilience coding of MPEG-4 video stream over DMB system. To accomplish error resilience, we first partition one data into several data using the data partitioning, and we control the coding rate of the convolution coding according to the importance of the partitioned data. In this algorithm, we suggest and analyze the efficient rate control algorithm considering convolution code rate.

• Proceedings of the IEEK Conference
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• 2003.11a
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• pp.279-282
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• 2003

Terrestrial DMB(Digital Multimedia Broadcasting) system is the standard that offers multimedia broadcasting services at mobile environment and is based on Eureka-147 DAB(Digital Audio Broadcasting) for transmission method. Also DMB provides the error protection method of convolution coding. In this paper, we study on the effective error resilience coding of MPEG-4 video stream over DMB system. To accomplish error resilience, we first partition one data into several data using the data partitioning, and we control the coding rate of the convolution coding according to the importance of the partitioned data. In this algorithm, we suggest and analyze the efficient rate control algorithm considering convolution code rate.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.597-601
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• 1996

Nowadays, the STL format, industrial standard data, which approximates three dimensional CAD model to triangular facets, is used for RP(Rapid Prototyping) system. Because most RP machine is accpted to only two dimensional line segments, but some STL translators are sometimes poorly implemented. The error verifying process is as follows. 1) Remove facets with two or more vertices equal to each other. 2) Fix overlapping error such as more than three facets adjacent to an edge. 3) Fill holes in the mesh by using Delaunay triangulation method. 4) Repair wrong direction and value of normal vectors. This paper is concerned with searching the mentioned errors in advance and modifying them.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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• pp.613-617
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• 2000

This paper descries the effect of the stylus tip size on the measuring error in surface topography measurement. To analyze the distortional effect of an actual surface geometry originating from the finite stylus size, the surface is modeled as a sinusoid and the stylus tip as a circle. the measuring error is defined as the ratio of the standard deviation of a tracing profile and an original profile. It is shown that this measuring error depends on the amplitude and wavelength of an original profile. In this paper, the spectrum analysis is applied to investigate the distortional effect due to the mechanical filtering of the stylus in the frequency domain. and, the cumulative power spectrum is applied to determinate the minimum wavelength limits to be measured with the various stylus tip radius from these results, a new method to select proper stylus tip radius is proposed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.11C
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• pp.1130-1139
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• 2003

In this work, we propose a multi-hypothesis error concealment algorithm, which replaces a lost block with a weighted superposition of more than two reference blocks in previous frames. Three methods are developed to find the set of reference blocks and determine the weighting coefficients. These methods are implemented based on H.26L standard, and their performances are evaluated. It is shown that the proposed multi-hypothesis algorithm provides up to 1.5㏈ better PSNR performance than the conventional single-hypothesis concealment algorithm.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.6
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• pp.317-322
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• 2006

A accurate potential transformer(PT) with the nominal ratio errors in the wide range of - 9 % to + 11 % has been developed. The developed wide ratio error PT can be used to evaluate the linearity of the PT comparator by comparing both the theoretical values as standard values and experimental values of the PT. The new method has been successfully applied for calibration and correction in the PT comparator including very low ratio error values from ${\pm}0.005%$ to ${\pm}0.3%$ belonging to industry.

• ETRI Journal
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• v.28 no.5
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• pp.574-582
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• 2006

In this paper, a new error concealment algorithm is proposed for the H.264 standard. The algorithm consists of two processes. The first process uses a fuzzy logic method to select the size type of lost blocks. The motion vector of a lost block is calculated from the current frame, if the motion vectors of the neighboring blocks surrounding the lost block are discontinuous. Otherwise, the size type of the lost block can be determined from the preceding frame. The second process is an error concealment algorithm via a proposed adapted multiple-reference-frames selection for finding the lost motion vector. The adapted multiple-reference-frames selection is based on the motion estimation analysis of H.264 coding so that the number of searched frames can be reduced. Therefore the most accurate mode of the lost block can be determined with much less computation time in the selection of the lost motion vector. Experimental results show that the proposed algorithm achieves from 0.5 to 4.52 dB improvement when compared to the method in VM 9.0.

• Proceedings of the IEEK Conference
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• 2003.11c
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• pp.216-219
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• 2003

In this paper, we present performance analysis of an IEEE P802.15.3a high rate wireless personal area network transceiver. This physical layer standard uses QOSK as its sub-channel modulation scheme and orthogonal frequency domain modulation (OFDM) for sub-bands. OFDM is used for each sub-band so that multi-path effects are absorbed by equalizer and guard, and fading can be approximately modeled as additive white Gaussian noise. In multi-band ultra-wideband system, DAC quantization error is important noise source since high resolution conversion cannot be used due to high power consumption. Simulation result shows that, to get 640-Mbps throughput, at least 5-bits precision is necessary to maintain bit-error rate under 10$\^$-2/, which can be lowered, with channel coding, to 10$\^$-6/ that is the bit-error rate required by IEEE 802.15 upper protocol layer, in 4-meter LOS fading channel.