• Proceedings of the KOSOMBE Conference
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• v.1997 no.05
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• pp.127-130
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• 1997

Phase-contrast(PC) methods have been used for quantitative measurements of velocity and volume flow rate. In addition, phase contrast cine magnetic resonance imaging (MRI) combines the flow dependent contrast of PC MRI with the ability of cardiac cine imaging to produce images throughout the cardiac cycle. In this method, the through-plane velocity has been encoded generally. However, the accuracy of the flow data can be reduced by the effect of flow direction, finite slice thickness, resolution, pulsatile flow pattern, and so on. In this study we calculated the error caused by misalignment of tomographic plane and flow directon. To reduce this error and encode the velocity for more complex flow, we suggested 3 directional velocity encoding method.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.171-174
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• 1999

We have characterized solid solution Y$_{l-x}Ca_xBa_2Cu_3O_y$ (0${\le}$x${\le}$0.3) materials by measuring the XRD pattern, resistivity and hole concentrations, etc. As Ca concentration increases, T$_c$, is decreased monotonically because the hole concentration on the superconducting plane increases beyond the optimum region in the electronic phase diagram due to the hole transfer from the Cu-O chain to the CuO$_2$ plane. A very small amount of secondary phase have large effects on the analysis of oxygen content and hole concentration etc. The results before the correction of impurity phase are compared with those after the correction.

• Journal of Institute of Control, Robotics and Systems
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• v.11 no.11
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• pp.895-900
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• 2005

We derive a linear matrix inequality(LMI) condition guaranteeing that any invariant zeros of a triple (A, B, C) lie in the open left half plane of the complex plane, i.e. $C(sI-A)^{-1}B$ is minimum phase. The LMI condition is equivalent to a certain constrained Lyapunov matrix equation which can be found in many results relating to stability analysis or control design. We show that the LMI condition can be used to simplify various control engineering problems such as a dynamic output feedback control problem, a variable structure static output feedback control problem, and a nonlinear system observer design problem. Finally, we give some numerical examples.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.10
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• pp.51-63
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• 1995

In this paper, a new real-time optical image switching system based on the phase-typed BPEJTC is suggested. The phase filter mask which has the arbitrary position mapping function between input and output planes is constructed by using the modified JTPS of the BPEJTC. Then, the input image is convolved with this phase filter mask in the spatial frequency domain and through further Fourier transform the input image is switched to the new positions in the output correlation plane where the correlation peaks are occurred. And, based on the computer simulation results, the practical optical switched to the new positions in the output correlation plane where the correlation peaks are occurred. And, based on the computer simulation results, the practical optical switching system is opto-digitally constructed and through some experiments on image switching the possiblity of real-time implementation of the multiple optical image switching system by using the BPEJTC is suggeste.

• Journal of the Optical Society of Korea
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• v.12 no.3
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• pp.136-146
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• 2008

We proposed an adaptive steganography of an optical image using bit-planes and multichannel characteristics. The experiment's purpose was to compare the most popular methods used in optical steganography and to examine their advantages and disadvantages. In this paper we describe two digital methods: the first uses less significant bits(LSB) to encode hidden data, and in the other all blocks of $n{\times}n$ pixels are coded by using DCT(Digital Cosine Transformation), and two optical methods: double phase encoding and digital hologram watermarking with double binary phase encoding by using IFTA(Iterative Fourier Transform Algorithm) with phase quantization. Therefore, we investigated the complexity on bit plane and data, similarity insert information into bit planes. As a result, the proposed method increased the insertion capacity and improved the optical image quality as compared to fixing threshold and variable length method.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.8
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• pp.529-535
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• 2000

In this paper, a current control system of a single phase PWM AC/DC converter using a reduced-order Luenberger observer without source voltage sensors is proposed. The sinusoidal input current and unity input power factor are realised based on the estimated source voltage performed by the reduced-order Luenberger observer using actual currents and DC link voltage. The poles of the reduced-order Luenberger observer are placed in the left half plane of s-plane by the pole-placement method in order to acquire the stability of the observer. The magnitude and the phase of the estimated source voltage are used to accomplish the unity power factor. The proposed method is implemented by DSP(Digital Signal Processor). Experimental Results verify that the reduced-order observer estimates the source voltage without the estimation error and the control system accomplishes the unity power factor, and constant DC link voltage.

• Coupled systems mechanics
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• v.10 no.1
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• pp.21-38
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• 2021

This work is an attempt to design a dynamic model for a non local bio-thermoelastic medium with diffusion. The system of governing equations are formulated in terms of displacement vector field, chemical potential and the tissue temperature in the context of non local dual phase lag (NL DPL) theories of heat conduction and mass diffusion. Based on this considered model, we study the fundamental solution and propagation of plane harmonic waves in tissues. In order to analyze the behavior of the NL DPL model, we construct basic theorem in the terms of elementary function which determine the existence of three longitudinal and one transverse wave. The effects of various parameters on the characteristics of waves i.e., phase velocity and attenuation coefficients are elaborated by plotting various figures of physical quantities in the later part of the paper.

• Journal of Oral Medicine and Pain
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• v.19 no.2
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• pp.193-203
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• 1994

The author performed this study for investigation of the magnitude of mandibular positional change caused by joint sound during mandibular opening and closing movement. There have been many studies stated mandibular border movement or other functional movement, and there also have been many studies reported clicking sound related to mandibular movement speed, trajectory and clinicl course of temporomandibular disorders(TMDs), but there have not been so many studies stated spatial mandibular position accompanied by joint sound. For this study 46 TM joint from the patients with TMDs were used and they were compared by character and occuring phase of the joint sound. Synchronized data which were amplitude and frequency of joint sound and amount of mandibular positional change were collected through sonopak and BioEGN rotate of Biopak system, respectively. Mandibular position was analyzed for translational and rotational movement change between before and after joint sound. The obtained data were processed with SAS program and summary of this paper were as follows : 1. Mean value of the amount of translational movement in whole joints were 6.0mm in vertical direction, 3.3mm in anteroposterior direction and 0.8mm in lateral direction between before and after joint sound. 2. Mean value of the amount of translational movement in clicking joinnts showed slightly increased tendency than in popping joints. 3. The amount of mandibular change in translational movement during closing phase were more than during opening phase. 4. The amount of mandibular rotational change in whole joints were $1.1^{\circ}$, 1.0mm in frontal plane and $0.9^{\circ}$, and 0.8mm in horizontal plane. 5. The amount of rotational movement were more in clicking joints than in popping joints and were more during closing phase than during opening phase, but statistically significance were showed only in frontal plane.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.1
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• pp.6-10
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• 2009

In this paper, a selective area growth (SAG) of a GaN/AlGaN double heterostructure (DH) has been performed on r-plane sapphire substrate by using the mixed-source hydride vapor phase epitaxy (HVPE) with multi-sliding boat system. The SAG-GaN/AlGaN DH consists of GaN buffer layer, Te-doped AlGaN n-cladding layer, GaN active layer, Mg-doped AlGaN p-cladding layer, and Mg-doped GaN p-capping layer. The electroluminescence (EL) characteristics show an emission peak of wavelength, 439 nm with a full width at half maximum (FWHM) of approximately 0.64 eV at 20 mA. The I-V measurements show that the turn-on voltage of the SAG-GaN/AlGaN DH is 3.4 V at room temperature. We found that the mixed-source HVPE method with a multi-sliding boat system was one of promising growth methods for III-Nitride LEDs.

• Journal of the Optical Society of Korea
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• v.18 no.5
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• pp.500-506
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• 2014

A new 3-D reconstruction algorithm for the human face is proposed using the derivative Moir$\acute{e}$ topography which ensures fast and robust reconstruction even for rough surfaces. The Moir$\acute{e}$ interference fringe pattern is initially obtained through the projection Moir$\acute{e}$ topography based on phase shifting, and then differentiated to provide a full unwrapped phase map for a human face. $2{\pi}$ ambiguity, which has been a chronically unsolved problem with Moir$\acute{e}$ topography, is successfully surmounted by differentiating the Moir$\acute{e}$ fringe patterns both in x- and y-directions when the object is located in the x-y plane. A real human face is used for verifying the proposed derivative Moir$\acute{e}$ topography. A human face of 4 different phase-shifted images taken in the fixed plane is almost fully reconstructed in 3-D format in 0.1 mm lateral resolution.