• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.115-118
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• 2002

This paper presents the design method and performance characteristics of a chip-type quadrature hybrid using LTCC-MLC technology. The design method for a chip-type quadrature hybrid is based on lumped element equivalent circuit of quarter-wave transformer. The chip-type quadrature hybrid was miniaturized to a greater extent using multilayer structure and lumped element. The proposed design method can also reduce the undesirable parasitic effects of the chip-type quadrature hybrid. The proposed chip-type quadrature hybrid was designed and fabricated using the proposed design method and the equivalent circuit model of a quarter-wave transformer. Fabrication and measurement of designed chip-type quadrature hybrid show much smaller size than a conventional distributed quadrature hybrid and a good agreement with simulated results.

• Nuclear Engineering and Technology
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• v.52 no.6
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• pp.1137-1147
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• 2020

The discrete ordinates method (S_N) is one of the major shielding calculation method, which is suitable for solving deep-penetration transport problems. Our objective is to explore the available quadrature sets and to improve the accuracy in shielding problems involving strong anisotropy. The linear discontinuous finite-element (LDFE) quadrature sets based on the icosahedron (in short, ICLDFE quadrature sets) are developed by defining projected points on the surfaces of the icosahedron. Weights are then introduced in the integration of the discontinuous finite-element basis functions in the relevant angular regions. The multivariate secant method is used to optimize the discrete directions and their corresponding weights. The numerical integration of polynomials in the direction cosines and the Kobayashi benchmark are used to analyze and verify the properties of these new quadrature sets. Results show that the ICLDFE quadrature sets can exactly integrate the zero-order and first-order of the spherical harmonic functions over one-twentieth of the spherical surface. As for the Kobayashi benchmark problem, the maximum relative error between the fifth-order ICLDFE quadrature sets and references is only -0.55%. The ICLDFE quadrature sets provide better integration precision of the spherical harmonic functions in local discrete angle domains and higher accuracy for simple shielding problems.

• Journal of applied mathematics & informatics
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• v.5 no.3
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• pp.735-748
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• 1998

We analyze the error in the p version of the of the finite element method when the effect of the quadrature error is taken in the load vector. We briefly study some results on the $H^{1}$ norm error and present some new results for the error in the $L^{2}$ norm. We inves-tigate the quadrature error due to the numerical integration of the right hand side We present theoretical and computational examples showing the sharpness of our results.

• Structural Engineering and Mechanics
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• v.41 no.1
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• pp.67-81
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• 2012

Differential Quadrature Method (DQM) is a powerful method which can be used to solve numerical problems in the analysis of structural and dynamical systems. In this study the governing equation which represents the free vibration of coupled shear walls is solved using the DQM method. A one-dimensional model has been used in this study. At the end of study various examples are presented to verify the accuracy of the method.

• Proceedings of the KIEE Conference
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• 1988.07a
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• pp.297-300
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• 1988

The ultrasound Doppler effect is used for measuring the velocity of the bloodflow in an artry. Because of the range information, the pulsed doppler system is most commonly used. In this paper, we propose a new pulsed doppler system which uses a quadrature sampling method in R.F. range in order to detect the bloodflow direction and to simplify the compexity of hardware. The pulsed doppler system using quadrature sampling method in R.F. range eliminates In-phase, Quadrature phase channel balancing problem at demodulator. In addition, the improved pulsed Doppler system shows the possibility of serial processing.

• Journal of Biomedical Engineering Research
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• v.19 no.2
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• pp.105-112
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• 1998

In this paper, several bandwidth sampling methods were compared using experimental result in which contains "multi-order sampling", which was proposed for envelope detections in RF ultrasonic signals. A "Quadrature sampling method" and "Second-order sampling method" were compared with it. The resultant image of second-order sampling method introduces too much error as compared with the result of quadrature sampling. But Multi-order sampling method, specialy 5-th sampling method showed quite good envelope detection property. This means that more economical and quite good performance digital beamforming system can be built by adopting this multi-order sampling method.s multi-order sampling method.

• Current Optics and Photonics
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• v.3 no.3
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• pp.204-209
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• 2019

In an optical interferometer that uses sinusoidal modulation and quadrature detection, the amplitude and offset of the interference signal vary with time, even without considering system noise. As a result, the circular Lissajous figure becomes elliptical, with wide lines. We propose and experimentally demonstrate a method for compensating quadrature detection error, based on digital signal processing to deal with scaling and fitting. In scaling, fluctuations in the amplitudes of in-phase and quadrature signals are compensated, and the scaled signals are fitted to a Lissajous unit circle. To do so, we scale the average fluctuation, remove the offset, and fit the ellipse to a unit circle. Our measurements of a target moving with uniform velocity show that we reduce quadrature detection error from 5 to 2 nanometers.

• Journal of Biomedical Engineering Research
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• v.30 no.1
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• pp.79-88
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• 2009

A harmonic quadrature demodulation method to extract the second harmonic component from focused ultrasound signals after a single transmit-receive event is proposed. In the proposed method, the focused ultrasound signal is converted into baseband inphase and quadrature components by multiplying with sine and cosine signals both having twice the center frequency of the transmitted signal and filtering the two modulated signals. The quadrature component is then passed through a Hilbert filter to be added to the inphase component, which leaves only the envelope of the second harmonic component. A novel phase estimation technique is employed in the proposed method to avoid the phase mismatch between the focused signal and the two modulating signals. The proposed method is verified through both theoretical analysis and computer simulations. It is shown that compared to the pulse inversion scheme the proposed method provides almost the same results for stationary targets and significantly improved harmonic to fundamental ratio for moving targets.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.957-962
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• 2004

This paper deals with the free vibration analysis of beam-columns resting on Pasternak foundation by the Differential Quadrature Method. Based on the differential equation subjected to the boundary conditions, adopted from the open literature, which governs the free vibrations of such member, this equation is applied to the Differential Quadrature Method. For computing natural frequencies, the numerical procedures are developed by QR Algorithm, in which the Chebyshev-Gauss-Lobatto method is used for choosing the grid points. The numerical methods developed herein for computing natural frequencies are programmed in FORTRAN code, and all solutions obtained in this study are quite agreed with those in the open literature.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.1188-1200
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• 2015

A unified numerical method for computing the quadrature weights, integration matrix, and differentiation matrix is newly developed in this study. For this purpose, a spline-like interpolation using piecewise continuous polynomials is converted into a global spline interpolation formula, with which the quadrature formulas can be derived from integration and differentiation of the transformed function in an exact manner. To prove the usefulness of the suggested approach, both the Lagrange and tension spline interpolations are represented in exactly the same form as global spline interpolation. The applicability of the proposed method on arbitrary nodes is illustrated using two different sets of nodes. A series of validations using three test functions is conducted to show the flexibility in selecting computational nodes with the present method.