• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1995.10a
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• pp.221-226
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• 1995

터빈 익렬, 펌프 익차, 원형 냉각탑, 치차 등과 같이 동일한 형상이 원주 방향으로 반복되어 있는 순환 대칭 구조물의 진동특성을 유한 요소법을 사용하여 해석하는 경우에 전체구조를 모델링하는 대신에 구조물을 동일한 형상의 부분구조로 분할하여 부분구조 한개만을 모델링하고 분할된 경계에서 적절한 경계조건을 부과하여 진동해석을 수행함으로서 컴퓨터 기억용량을 절감시키고 계산시간을 단축할 수 있는 방법이 널리 사용되고 있다. Orris and Petyt[1]는 부분구조의 양쪽 분할 경계면, 즉 연결 경계상에 있는 절점변위의 상관관계를 복소파동전파식을 이용해서 구하여 부분구조의 감소된 복소강성행렬 및 질량행렬을 만들고 실수부와 허수부를 분리하여 유한요소해석을 수행하는 방법을 제안하였다. 유한요소 프로그램 ANSYS[2]에서는 이와 같은 방법을 사용하고 있다. Thomas[3]는 순회 정규모드를 이용하였고, 참고문헌[4]에서는 순회행렬을 이용하였다. 또한 유한요소 프로그램 MSC/NASTRAN[5]에서는 푸리에 급수를 이용하고 유한요소 절점의 위치 및 변위를 원통 좌표계를 표현하여 순환대칭구조물의 유한요소해석을 수행할 수 있도록 되어있다. 본 논문에서는 순환 대칭구조물의 형상의 주기성과 순환성을 고려하여 이산퓨리에 변환을 이용함으로써 순환대칭구조물의 유한요소진동해석을 체계적으로 저용량의 컴퓨터에서 신속하고 정확하게 수행할 수 있는 방법을 제안하고자 한다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.12
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• pp.8-16
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• 2010

In this paper, we present a structure of computationally efficient MIMO-OFDM transmitters, using STBC. Straightforward implementation of these systems requires separate WFT processing blocks for each of the transmit antennas. In our proposed scheme, we use symmetry properties of Fourier transform, and thus use a frequency domain encoding strategy. This greatly reduces the computational burden. The proposed scheme uses just a single IFFT block at each OFDM symbol period, and thus resulting in the same complexity as a single antenna OFDM system. As specific examples of the proposed schemes, we present frequency domain encoding matrices for QO-STBC-OFDM and QO-SFBC-OFDM transmitters.

• Structural Engineering and Mechanics
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• v.54 no.4
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• pp.607-622
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• 2015

This paper presents a comparative study of analytical method and finite element method (FEM) for analysis of a continuous contact problem. The problem consists of two elastic layers loaded by means of a rigid circular punch and resting on semi-infinite plane. It is assumed that all surfaces are frictionless and only compressive normal tractions can be transmitted through the contact areas. Firstly, analytical solution of the problem is obtained by using theory of elasticity and integral transform techniques. Then, finite element model of the problem is constituted using ANSYS software and the two dimensional analysis of the problem is carried out. The contact stresses under rigid circular punch, the contact areas, normal stresses along the axis of symmetry are obtained for both solutions. The results show that contact stresses and the normal stresses obtained from finite element method (FEM) provide boundary conditions of the problem as well as analytical results. Also, the contact areas obtained from finite element method are very close to results obtained from analytical method; disagree by 0.03-1.61%. Finally, it can be said that there is a good agreement between two methods.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.6
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• pp.949-958
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• 2001

A semi-infinite interfacial crack propagated with constant velocity in two bonded anisotropic strips under out-of-plane clamped displacements is analyzed. Using Fourier integral transform the problem is formulated and the Wiener-Hopf equation is derived. By solving this equation the asymptotic stress and displacement fields near the crack tip are obtained, where the results get more general expressions applicable not only to isotropic/orthotropic materials but also to the extent of the anisotropic material having one plane of elastic symmetry for the interfacial crack. The dynamic stress intensity factor is obtained as a closed form, which is decreased as the velocity of crack propagation increases. The critical velocity where the stress intensity factor comes to zero is obtained, which agrees with the lower value between the critical values of parallel crack merged in the material 1 and 2 adjacent to the interface. Using the near tip fields of stresses and displacements, the dynamic energy release rate is also obtained as a form of the stress intensiy factor.

• Journal of Korea Multimedia Society
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• v.11 no.6
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• pp.764-776
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• 2008

Image identification is the process of checking whether the query image is the transformed version of the specific original image or not. In this paper, image identification method based on feature composition is proposed. Used features include color distance, texture information and average pixel intensity. We extract color characteristics using color distance and texture information by Modified Generalized Symmetry Transform as well as average intensity of each pixel as features. Individual feature is quantized adaptively to be used as bins of histogram. The histogram is normalized according to data type and it is used as the signature in comparing the query image with database images. In matching part, Manhattan distance is used for measuring distance between two signatures. To evaluate the performance of the proposed method, independent test and accuracy test are achieved. In independent test, 60,433 images are used to evaluate the ability of discrimination between different images. And 4,002 original images and its 29 transformed versions are used in accuracy test, which evaluate the ability that the proposed algorithm can find the original image correctly when some transforms was applied in original image. Experiment results show that the proposed identification method has good performance in accuracy test. And the proposed method is very useful in real environment because of its high accuracy and fast matching capacity.

• Journal of Industrial and Engineering Chemistry
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• v.68
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• pp.109-116
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• 2018

$Eu_2(SO_4)_3$ was synthesized by chemical precipitation method and the crystal structure was determined by Rietveld analysis. The compound crystallizes in monoclinic space group C2/c. In the air environment, $Eu_2(SO_4)_3$ is stable up to $670^{\circ}C$. The sample of $Eu_2(SO_4)_3$ was examined by Raman, Fourier-transform infrared absorption and luminescence spectroscopy methods. The low site symmetry of $SO_4$ tetrahedra results in the appearance of the IR inactive ${\nu}_1$ mode around $1000cm^{-1}$ and ${\nu}_2$ modes below $500cm^{-1}$. The band intensities redistribution in the luminescent spectra of $Eu^{3+}$ ions is analyzed in terms of the peculiarities of its local environment.

• Journal of the Korean Chemical Society
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• v.9 no.3
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• pp.128-133
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• 1965

Hydrazonium diphosphate crystallizes with the space-group symmetry $P2_1/C.$ There are two formular units of $N_2H_6H_4(PO_4)_2$ in the unit cell, for which $a = 4.52{\pm}0.02, b = 8.06{\pm}0.03, c = 10.74{\pm}0.03{\AA}\;and\; {\beta} = 100{\pm}0.5^{\circ}.$ The determination of the crystal structure was carried out by means of Patterson, Fourier and difference syntheses. The phosphate group has configuration of nearly regular tetrahedron with the mean P-O distance of $1.55{\AA}.$ The N-N distance found is $1.40{\AA},$ which corresponds to previously reported values for the $N_2H_6^{++} \;ion \;in\; N_2H_6SO_4.$ A molecule has a transform with a center of symmetry in it. Each nitrogen atom forms three hydrogen bonds with the N…O distances 2.62, 2.79 and $2.89{\AA}.$ And a O…O hydrogen bond between different phosphate groups is found with the distance $2.63{\AA}.$ The structure is held together by three-dimensional network of the strong hydrogen bonds.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.41 no.6
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• pp.121-126
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• 2004

An efficient multi face detection technique is proposed based on hierarchical context-free attention operators in which multiple faces are efficiently detected from a noisy and complex background. A noise-tolerant generalized symmetry transform (NTSGT) is applied hierarchically, as a context free attention operator, to the input pyramidal image for the high speed global location of the regions of face candidates (ROFCs) with a single mask. For the face verification, local NTGST is applied within each ROFC to confirm the existence of the detailed facial features. First, by globally applying NTGST which introduces the average pyramid method and focusing to the input image with complex background, ROFCs with recognizable resolution are detected robustly. Morphological operations are applied only to the each detected ROFCs to emphasize the facial features like eyes and lips. Then, eyes are detected by locally appling NTGST to the ROFCs and only faces are detected by verifying the existence of the geometrical features of the faces relatively to the location of eyes. The experimental results show that the proposed method can efficiently detect multiple faces from a noisy or complex background with 93.5% detection rate.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.41 no.6
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• pp.19-24
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• 2004

A novel fast parallel NTGST is proposed for high resolution computer vision inspection of the BLUs in a LCD production line. The conventional computation- intensive NTGST algorithm is modified and its C codes are optimized into fast NTGST to be adapted to the SIMD parallel architecture. And then, the input inspection image is partitioned and allocated to each of the P processors in multi-threaded implementation, and the NTGST is executed on SIMD architecture of N data items simultaneously in each thread. Thus, the proposed inspection system can achieve the speedup of O(NP). Experiments using Dual-Pentium III processor with its MMX and extended MMX SIMD technology show that the proposed parallel NTGST is about Sp=8 times faster than the conventional NTGST, which shows the scalability of the proposed system implementation for the fast, high resolution computer vision inspection of the various sized BLUs in LCD production lines.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.7
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• pp.29-38
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• 2009

In this paper, a high performance pipelined computing design of parallel multiplier-temporal buffer-parallel accumulator is present for the convolution-based non-cascaded architecture aiming at the real time Discrete Wavelet Transform(DWT) processing. The convolved multiplication of DWT would be reduced upto 1/4 by utilizing the filter coefficients symmetry and the up/down sampling; and it could be dealt with 3-5 times faster computation by LUT-based DA multiplication of multiple filter coefficients parallelized for product terms with an image data. Further, the reutilization of computed product terms could be achieved by storing in the temporal buffer, which yields the saving of computation as well as dynamic power by 50%. The convolved product terms of image data and filter coefficients are realigned and stored in the temporal buffer for the accumulated addition. Then, the buffer management of parallel aligned storage is carried out for the high speed sequential retrieval of parallel accumulations. The convolved computation is pipelined with parallel multiplier-temporal buffer-parallel accumulation in which the parallelization of temporal buffer and accumulator is optimize, with respect to the performance of parallel DA multiplier, to improve the pipelining performance. The proposed architecture is back-end designed with 0.18um library, which verifies the 30fps throughput of SVGA(800$\times$600) images at 90MHz.