• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.1
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• pp.13-19
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• 1995

The objective of this study is do obtain the relationship between the acoustic mode and cavity tone induced in a perforated tube exhaust muffler. First, the modal frequency for the axisymmetric radial mode and the mode shape have been computed using the impedance model for the perforated tube. Then, experiment has been perfonned for the onset frequencies of the cavity tone for various design parameters and through-flow. The theoretically obtained modal frequencies are well consistent with the measured onset frequencies of the cavity tone, showing that the cavity tone is induced by the axisymmetric radial mode. And it is found that the modal frequency of a perforated tube muffler is much lower than that of a simple expansion chamber.

• Proceedings of the KIPE Conference
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• 2011.07a
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• pp.346-347
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• 2011

본 논문에서는 정전류 LED조명 구동을 위한 일차측 전류 제어의 새로운 기법을 제안한다. 일정한 온-타임으로 동작하는 경계 모드(Critical Mode) 플라이백 타입으로 우수한 역률을 달성하였고, 의사 공진(Quasi-resonant) 동작으로 스위칭 손실을 최소화 하였다. 본문에서 LED전류가 5% 이하로 정전류 제어되는 9W급 플라이백 타입의 일차 측 전류 제어 기법을 실험으로 검증한다.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.1121-1124
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• 2003

For high quality displays, analog responding liquid crystals with spontaneous polarization ($P_{s}$) need to be coupled with active matrix driving schemes. We have characterized the half-V-shaped switching ferroelectric liquid crystal mode (half-V FLC mode) in terms of dielectiric and voltage holding properties. Research on these switching properties provided us with the technology for switching half-V FLC mode FLCs by using amorphous silicon TFTs.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.10
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• pp.914-920
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• 2002

This study investigates the mechanism of a dual mode probe that generates both of the longitudinal and shear waves simultaneously with a single FZT element. Most of conventional ultrasonic probes are constructed to generate either longitudinal or shear waves. After poling, PZT has the hexagonal 6mm crystal symmetry. All possible crystal cuts are checked to determine appropriate Euler transformation angles for efficient excitation of dual modes. For the selected cut, performance of the dual mode element is analyzed through numerical simulation and experiments. Results of the analysis determine the optimal crystal cut for simultaneous generation of P and S waves of equal strength.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.367-370
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• 2004

This paper present a new disk-type piezoelectric transformer. The input side of the transformer has a crescent-shaped electrode and the output side has a focused poling direction. The piezoelectric transformers operated in each transformer's resonance vibration mode. The electrodes and poling directions on commercially available piezoelectric ceramic disks were designed so that the planar or shear mode coupling factor $(k_p,\;k_{15})$ becomes effective rather than the transverse meed coupling factor $(k_{31})$. A single layer prototype transformer, 26[m] in diameter and 2.0[mm] thickness, was fabricated, such as step-up ratio, power transformation efficiency and temperature were measured.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.1
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• pp.113-120
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• 2002

Experimental procedure to measure fracture toughness (J$_{c}$) under mixed mode loading using CTS(Compact Tension-Shear) specimens is described. It\`s loading angle ranges from 0$^{\circ}$ to 45$^{\circ}$ with interval of 157. The general outline of experimental procedure is similar to that of ASTM E8l3-89 fur mode I fracture. Equations fur determining J-integral is quoted from the authors' previous works. The relation between unloading compliance and physical crack size was calibrated. As an example, fracture toughness of aluminum alloy 2024p-7361 was measured and some reasonable results of J$_{c}$ with various loading angles were obtained.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.234-235
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• 2005

This paper present a new disk-type piezoelectric transformer. The input side of the transformer has a crescent-shaped electrode and the output side has a focused poling direction. The piezoelectric transformers operated in each transformer's resonance vibration mode. The electrodes and poling directions on commercially available piezoelectric ceramic disks were designed so that the planar or shear mode coupling factor ($k_p,\;k_{15}$) becomes effective rather than the transverse mode coupling factor ($k_{31}$).

• Proceedings of the KIEE Conference
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• 1988.07a
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• pp.328-331
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• 1988

Sealed Interface Local Oxidation (SILO) technology has been investigated using a nitride/oxide/nitride three-layered sandwich structure. P-type silicon substrate was either nitrided by rapid thermal processing, or silicon nitride was deposited by LPCVD method. A three-layered sandwich structure was patterned either by reactive ion etch (RIE) mode or by plasma mode. Sacrificial oxidation conditions were also varied. Physical characterization such as cross-section analysis of field oxide, and electrical characterization such as gate oxide integrity, junction leakage and transistor behavior were carried out. It was found that bird's beak was nearly zero or below 0.1um, and the junction leakages in plasma mode were low compared to devices of the same geometry patterned in RIE mode, and gate oxide integrity and transistor behavior were comparable. Conclusively, SILO process is compatible with conventional local oxidation process.

• The Journal of Pediatrics of Korean Medicine
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• v.14 no.2
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• pp.1-32
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• 2000

It has long been known that SOAT is effective for sudden palpitation occurring unexpectedly in Oriental Medicine. However, effect of SOAT on the isolated heart has not been studied yet. The purpose of this study is to investigate the effect of SOAT on hemodynamics and ECG of isolated rat hearts induced by electrical stimulation using Langendorff perfusion apparatus for nonworking heart. SOAT extract was manufactured by water-alcohol precipitated method. Sprague-Dawley rats weighting $120{\sim}150g$ were used for the experiments, Subject animals were divided into four groups, which are consisted of 1) control(Group orally administered by normal saline 1ml for 14days), 2) sample A(Group orally administered by SOAT extract 1ml for 14days), 3) sample C(Group injected by SOAT extract 0.5ml after stimulation, 4) sample C(Group injected by SOAT extract 1ml after stimulation. To evluate the effects of SOAT on hemodynamics and ECG of isolated rat heart induced by stimulation, heart rate, left ventricular pressure, systolic power, diastolic power, coronary artery perfusion volume and ECG were measured using Langendorff apparatus in both stimulation mode(5 volts, 450 beats/min) and arrythmic mode(5 volts, 420 beats/min including 60 beats/min) The results obtained are as follows : 1. After receiving stressful electrical stimuli, isolated heart showed the heart rate, left ventricular pressure, systolic power, diastolic power, coronary artery perfusion volume were all decreased temporarily, but perfusion continued longer recovery to the control state appeared. However, the coronary artery perfusion volume diminished continuously. 2. The heart rates did not change significantly with both stimulation mode and arrhythmic mode, among experimental groups. 3. The left ventricular pressure showed with both stimulation mode and arrhythmic mode, the significant changes(p<0.05) especially in the injection sample group. In case of stimulation mode, low concentration injection group(0.5ml) was more significantly increased rather than high concentration group(1ml) and in case of arrhythmic mode, high density group(1ml) was so increased than the other(0.5ml). 4. For the systolic power and diastolic power, no significant changes were noticed in the stimulation mode, but in the arrhythmic mode of injection sample groups, significant change(p<0.05) was noticed in both systolic power and diastolic power. Specially the high concentration group(1ml) showed more significant increase than the low concentration group. 5. For the coronary artery perfusion volume, no significant change difference among sample groups was observed in both the stimulation mode and the arrhythmic mode. 6. For the ECG recordings, arrhythmia was induced by electrical stimulus of arrythmia mode and after the stimulus was removed, irregular wave appeared temporarily, but as perpusion continued, recovery to the control state was abtained like the stimulation mode. According to the above results, SOAT significantly changed the hemodynamic data from the electrically stressed, isolated hearts of connected Langendorff perfusion apparatus and we propose SOAT has the direct effects on the muscular function of heart.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1115-1119
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• 2005

The paper proposes the elastic modulus evaluation technique of a cantilever beam by vibration analysis based on time-average electronic speckle pattern interferometry (TA-ESPI) with non-contact and nondestructive and Euler-Bernoulli equation. General approaches for the measurement of elastic modulus of thin film are Nano indentation test, Bulge test and Micro-tensile test and so on. They each have strength and weakness in the preparation of test specimen and the analysis of experimental result. ESPI has been developed as a common measurement method for vibration mode visualization and surface displacement. Whole-field vibration mode shape (surface displacement distribution) at a resonance frequency can be visualized by ESPI. And the maximum surface displacement distribution from ESPI is a clue to find the resonance frequency at each vibration mode shape. And the elastic modules of test material can be easily estimated from the measured resonance frequency and Euler-Bernoulli equation. The TA-ESPI vibration analysis technique is able to give the elastic modulus of materials through the simple processing of preparation and analysis.