• Structural Engineering and Mechanics
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• v.5 no.4
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• pp.471-490
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• 1997

In this paper, the classical Irons' patch tests which have been generally accepted for the convergence proof of a finite element are performed for Mindlin plate bending elements with a special emphasis on the nonconforming elements. The elements considered are 4-node and 8-node quadrilateral isoparametric elements which have been dominantly used for the analyses of plate bending problems. It was recognized from the patch tests that some nonconforming Mindlin plate elements pass all the cases of patch tests even though nonconforming elements do not preserve conformity. Then, the clues for the Mindlin plate element to pass the Irons' patch tests are investigated. Also, the convergent characteristics of some nonconforming Mindlin plate elements that do not pass the Irons' patch tests are examined by weak patch tests. The convergence tests are performed on the benchmark numerical problems for both nonconforming elements which pass the patch tests and which do not. Some conclusions on the relationship between the patch test and convergence of nonconforming Mindlin plate elements are drawn.

• Korean Journal of Optics and Photonics
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• v.33 no.3
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• pp.106-112
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• 2022

A two-dimensional optical code division multiple access (OCDMA) encoder/decoder, which is composed of add/drop filters and all-pass filters for delay operation, is proposed. An example design is presented, and its feasibility is illustrated through numerical simulations. The chip area of the proposed OCDMA encoder/decoder could be about one-third that of a previous OCDMA device employing delay waveguides. Its performance is numerically investigated using the transfer-matrix method combined with the fast Fourier transform. The autocorrelation peak level over the maximum cross-correlation level for incorrect wavelength hopping and spectral phase code combinations is greater than 3 at the center of the correctly decoded pulse, which assures a bit error rate lower than 10^-3, corresponding to the forward error-correction limit.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.588-590
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• 1996

An AC induction motor or constant speed characteristics has been widely used as power source because of simple structure and low maintenance cost in industrial field. The variable frequency AC source with a conventional inverter which is composed or power semi-conductors and drive systems contains much noises in sine wave current due to high speed switching or direct current. In this paper, the low pass LC filter for a variable speed induction motor driven by a full bridge inverter is introduced to solve EMI problem originated by much noise current. The modified LC filter based on the 3rd order Butterworth LC filter is used for the computer simulations and real experiments. The characteristics or proposed LC filter are investigated through FET analysis.

• Proceedings of the Korea Information Processing Society Conference
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• 2010.11a
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• pp.603-604
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• 2010

본 연구는 이미지 필터링 효과를 적용한 이미지들을 3D tomogram으로 만들었을 때 어느 정도의 효과적인 복원이 가능하고 또 어떤 해상도의 필터를 사용했을 때 더 나은 결과를 얻어 낼 수 있는 지 확인하기 위해 진행하였다. 전자현미경으로 2D tilted image들을 찍는 과정에는 고전압의 사용으로 인한 다소의 오류들이 발생한다. 따라서 이러한 오류를 상쇄시키고 3D tomogram의 질적 향상을 위하여 Gaussian low-pass filtering을 사용하였다. 또한 Gaussian low-pass filtering 내에서도 어떤 해상도 값의 필터링을 사용해야 더 나은 결과를 얻을 수 있는 지 확인하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.12
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• pp.3546-3552
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• 2009

In this study, an analysis code was created for a 190*650*25-mm (W*H*D) parallel-flow evaporator, and research was done on how to increase the heat transfer rate of aluminum PF heat exchanger for application in IDU. After varying the R410A refrigerant up-down flow to two and three passes and the distribution ratio to 1:1:1 and 1:2:2, it was determined that the two-pass flow has a 30% higher partial heat transfer rate and a 25% lower heat transfer coefficient compared to the three-pass flow. As for the distribution ratios of the three-pass flow, 1:1:1 was found to have a lower refrigerant pressure loss than 1:2:2 distribution. It was assumed, though, that the refrigerant distribution had a uniform flow and that its value was thus overestimated in the actual case of maldistribution in each pass.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.9
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• pp.2189-2194
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• 2009

The automatic hot gas by-pass technique is applied to control the capacity of refrigeration and air-conditioning system when operating at part load. In the scheme, the hot gas from the compressor is extracted and injected into the outlet of an evaporator through a hot gas by-pass valve. Thus, In this paper, the hot gas by-pass scheme for CO2 is discussed and analyzed on the basis of mass and energy conservation law. A comparative study of the schemes is performed in terms of the coefficiency of performance (COP) and cooling capacity. The operating parameters considered in this study include compressor efficiency, superheating degree, outlet temperature of gas cooler and evaporating temperature in the R744 vapor compression cycle. The main results were summarized as follows : the superheating degree, outlet temperature and evaporating temperature of R744 vapor compression refrigeration system have an effect on the cooling capacity and COP of this system. With a thorough grasp of these effect, it is necessary to design the compression refrigeration cycle using R744.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.2
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• pp.178-182
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• 2004

In this paper, a 90$^{\circ}$ hybrid coupler with both power division and harmonic rejection characteristics is presented by applying a LPF characteristic to a conventional 90$^{\circ}$ hybrid. Since a conventional 90$^{\circ}$ hybrid coupler operates as a power divider/combiner using phase difference, it does not suppress higher order harmonics when it is incorporated with nonlinear amplifier. This requires an additional filter to take into account of the harmonics. The proposed 90$^{\circ}$hybrid coupler power provides the division capability and proper phase difference, as well as harmonic suppression characteristic by integrating LPF characteristic.

• Journal of electromagnetic engineering and science
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• v.16 no.1
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• pp.7-12
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• 2016

This paper presents the design of a negative group delay circuit (NGDC) using the filter synthesis approach. The proposed design method is based on a frequency transformation from a low-pass filter (LPF) to a bandstop filter (BSF). The predefined negative group delay (NGD) can be obtained by inserting resistors into resonators. To implement a circuit with a distributed transmission line, a circuit conversion technique is employed. Both theoretical and experimental results are provided for validating of the proposed approach. For NGD bandwidth and magnitude flatness enhancements, two second-order NGDCs with slightly different center frequencies are cascaded. In the experiment, group delay of $5.9{\pm}0.5ns$ and insertion loss of $39.95{\pm}0.5dB$ are obtained in the frequency range of 1.935-2.001 GHz.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.864-867
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• 2005

In this paper we introduce a design of parallel architecture for wavelet transformation on FPGA. We implement wavelet transforms though lifting scheme and apply Daubechies4 transform equations. This technique has an advantage that we can obtain perfect reconstruction of the data. We divide our process to high pass filter and low pass filter. With this division, we can find coefficients from low and high pass filters simultaneously using parallel processing properties of FPGA to reduce processing time. From the equations, we have to design real number computation module, referred to IEEE754 standard. We choose 32 bit computation that is fine enough to reconstruct data. After that we arrange the real number module according to Daubechies4 transform though lifting scheme.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.3
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• pp.575-591
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• 2011

We present a novel active contour-based two-pass approach to extract smooth feature regions from a triangular mesh. In the first pass, an active contour formulated in level-set surfaces is devised to extract feature regions with rough boundaries. In the second pass, the rough boundary curve is smoothed by minimizing internal energy, which is derived from its curvature. The separation of the extraction and smoothing process enables us to extract feature regions with smooth boundaries from a triangular mesh without user's initial model. Furthermore, smooth feature curves can also be obtained by skeletonizing the smooth feature regions. We tested our algorithm on facial models and proved its excellence.