• 대한의용생체공학회:학술대회논문집
• /
• 대한의용생체공학회 1997년도 춘계학술대회
• /
• pp.127-130
• /
• 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
• /
• 한국초전도학회 1999년도 High Temperature Superconductivity Vol.IX
• /
• pp.171-174
• /
• 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.

• 제어로봇시스템학회논문지
• /
• 제11권11호
• /
• pp.895-900
• /
• 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.

• 전자공학회논문지A
• /
• 제32A권10호
• /
• pp.51-63
• /
• 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
• /
• 제12권3호
• /
• pp.136-146
• /
• 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.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
• /
• 제49권8호
• /
• pp.529-535
• /
• 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
• /
• 제10권1호
• /
• pp.21-38
• /
• 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
• /
• 제19권2호
• /
• pp.193-203
• /
• 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.

• 한국결정성장학회지
• /
• 제19권1호
• /
• pp.6-10
• /
• 2009

본 논문에서는 혼합소스(mixed-source) HVPE(hydride vapor phase epitaxy)방법으로 선택성장(SAC: selective area growth) GaN/AlGaN 이종접합구조의 발광다이오드를 r-plane 사파이어 기판 위에 제작하였다. SAG-GaN/AlGaN DH(double heterostructure)는 고온 GaN 버퍼층, Te 도핑된 AlGaN n-클래딩층. Gan 활성층. Mg 도핑된 AlGaN p-클래딩층. Mg 도핑된 GaN p-캡층으로 구성되어있다. GaN/AlGaN 이종접합구조의 발광다이오드의 특성을 알아보기 위해 SEM을 통한 구조적 분석과 전류-전압 측정(I-V: current-voltage measurement), 전류-광출력(EL: electroluminescence) 측정을 통하여 전기적, 광학적 특성을 평가하였다.

• Journal of the Optical Society of Korea
• /
• 제18권5호
• /
• pp.500-506
• /
• 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.