• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2003년도 춘계학술대회
• /
• pp.678-683
• /
• 2003

Ultrasonic method using SH(shear horizontal) wave has been developed to determine the surface damage in fatigued material. Fatigue damages based on propagation energy were analyzed by multiregression analysis and phase measurement in interrupted fatigue test specimen including CrMoV and 12Cr alloy steel. From the test results, as the fatigue damage increased the propagation time of the launched waves increased and amplitude of wavelet decreased. Also, analysis for the waveform modulation showed a reliable estimation, with confidence limit of 97% for 12Cr steel and 95% for CrMoV steel, respectively. Therefore, It is thought that SH ultrasonic wave technique can be applied to determine fatigue damage of in-service component nondestructively.

• 한국정밀공학회지
• /
• 제26권6호
• /
• pp.90-96
• /
• 2009

Ultrasonic method using SH(shear horizontal) wave has been developed to determine the surface damage in fatigued material. Fatigue damages based on propagation energy were analyzed by multi-regression analysis in interrupted fatigue test specimen including CrMoV and 12Cr alloy steel. From the test results, as the fatigue damage increased the propagation time of the launched waves increased and amplitude of wavelet decreased. Also, analysis for the waveform modulation showed a reliable estimation, with confidence limit of 97% for 12Cr steel and 95% for CrMoV steel, respectively. Therefore, It is thought that SH ultrasonic wave technique can be applied to determine fatigue damage of in-service component nondestructively.

• 대한기계학회논문집A
• /
• 제20권1호
• /
• pp.24-34
• /
• 1996

In ordaer to hold an underwater vehicle at a certain depth, buoyancy that acts on the underwater vehicle can be modulated. In this research, buoyancy that could control depth of underwater vehicle is generated by a buoyancy bag. Solenoid valves are operated by pulse with modulation(PWM) method. State equation, in consideration of the volume of buoyancy bag, pressure inside bag, and dynamic of the underwater vehicle, is derived. This system is very unstable, inculdes modelling error and nonlinearity. In depth control system, maintanance of performance is required., anainst vatiation of systerm parameter and operating depth, and designed. Through the computer simulation, performance is comparerd for each controllers.

• 유공압시스템학회논문집
• /
• 제6권4호
• /
• pp.16-23
• /
• 2009

The major system of an agricultural shuttle power-shift tractor is the transmission, using power-shift. Because the shifting performance depends on the hydraulic control system, the most important aspect of the optimization is the design of the hydraulic control system. This study was conducted to develop the simulation model of hydraulic control system for the shuttle power-shift transmission by using Easy5 software. Bench test was conducted to verify the simulation. Also, the design parameters which influence the pressure modulation characteristics were investigated.

• Journal of Advanced Marine Engineering and Technology
• /
• 제23권2호
• /
• pp.236-243
• /
• 1999

This study deals with the application of high speed on-off valves to an electro-hydraulic servo indexing system incorporated electro-hydraulic servo valces. Comparing with the electro-hydraulic servo valve the high speed on-off valve has some merits. Which included low price robustness to the oil contamination and dircect control without D/A converter. The considered sys-tem of this study is controlled by pulse width modulation(PWM) of the control law which is pro-duced by a PID controller which is used broadly in industrial equipments. The dynamic character-istics corresponding to variations of system parameters such as inertia moment system gain and supply pressure are investigated by computer simulation and experiment. Consequently the availability of the application of high speed on-off valve to servo indexing system instead of electro-hydraulic servo valve is confirmed.

• 대한조선학회논문집
• /
• 제40권2호
• /
• pp.21-27
• /
• 2003

The phenomena of vortex shedding around a cylinder oscillating harmonically in a fluid at rest are investigated by a two-dimensional numerical simulation of the Navier-Stokes equations. The simulation is based on a vorticity-velocity integro-differential formulation dealing with vorticity, velocity and pressure variables. Three combinations of Reynolds number(Re) and Keulegan-Carpenter number(KC) were taken to investigate the associated vortex development around the cylinder in the different flow regimes. Drag and lift forces are computed to describe their dominant frequency modulation which is related to the vortex shedding and to the harmonic motion of the cylinder.

• 한국응용약물학회:학술대회논문집
• /
• 한국응용약물학회 1994년도 춘계학술대회 and 제3회 신약개발 연구발표회
• /
• pp.287-287
• /
• 1994

In the present study, it was aimed to asses the possibility that calcitonin gene-related peptide (CGRP) released in response to transient hypotension may contribute to the reflex autoregulation of cerebral blood flow as a putative modulator. Changes in pial arterial diameter (mean, 33.0 ${\pm}$ 1.1 $\mu\textrm{m}$) with changes in systemic arterial blood pressure (mean, 101.9 ${\pm}$ 2.7 mmHg) were observed directly through a closed cranial window in anesthetized normotensive rats. Image of the pial vessels was captured with a stereoscope connected to a CCD video camera and the diameter was measured with a microscaler. In the capsaicin-treated rats (one day prior to experiment, 50 nmol capsaicin injected intracisternally), both vasodilater and vasoconstrictor responses evoked by a transient hypotension and the reverse of blood pressure were markedly attenuated or almost abolished. When changes in pial arterial diameter were plotted as a function of changes in blood pressure, the slopes of both regression lines (for vasodilators and vasoconstrictors ) were markedly reduced. Similar reductions were evidenced under treatment wi th the CGRP antibody serum (1:1,000) and following CGRP receptor desensitization. However, the autoregulatory mechanics were neither affected by treatment wi th spantide (1 ${\mu}$M), substance P antagonist, nor by substance P receptor desensitization. Suffusion wi th mock cerebrospinal fluid containing CGRP and cromakalim caused a vasodilatation in a concentration-dependent manner, respectively and their effects were antagonized by glibenclamide. Substance P produced a vasodilatation, which was, however, little affected by glibenclamide. These observations indicate that the CGRP released from the perivascular sensory fibers in response to a hypotension is implicated in the modulation of the autoregulation of cerebral blood flow.

• 대한약리학회지
• /
• 제24권2호
• /
• pp.153-164
• /
• 1988

The potential role of endogenous opioid peptides (EOPS) in cardiovascular regulation has only recently been entertained. EOPS have been localized in brain, spinal cord, autonomic ganglia, particularly the adrenal gland, and many other peripheral tissues. There are at least five major types of opioid receptors; namely ${\mu},\;{\delta},\;k,\;{\sigma},\;and\;{\varepsilon}$ and Experimental evidence indicates that cardiovascular actions of the peptide are mediated primarily by ${\mu},\;{\delta}$ and k receptors, and that these receptor types may be allosterically coupled. In anesthetized rabbits met-enkephalin decreased blood pressure and heart rate, which closely paralleled a reduction in sympathetic discharge. Naloxone, but not naloxone methobromide, antagonized these effects, which suggests a central site of action of met-enkephalin. A number of autonomic agents, particularly adrenergic ${\alpha}$-and, ${\beta}-agonists$ and antagonists modify the cardiovascular actions of met-enkephalin. Experiments in reserpine-treated and adrenalectomized rats provide no evidence of sympathetic nervous system involvement in the pressor responses to intravenous injection of opioid peptides, but rather suggest a direct peripheral action. Finally, activation of a beta-endorphinergic pathway projecting from the arcuate nucleus to the nucleus tractos solitarii in rats can cause naloxone reversible hypotension and bradycardia. There is evidence to implicate this pathway in antihypertensive drug action and in the modulation of baroreflex activity.

• 한국운동역학회지
• /
• 제26권3호
• /
• pp.249-255
• /
• 2016

Objective: This purpose of this study was to analyze the relationship between dimensionless leg stiffness and kinetic variables during gait performance, and its modulation with body weight. Method: The study sample consisted of 10 young women divided into 2 groups (Control, n=5 and Obese, n=5). Four camcorders (HDR-HC7/HDV 1080i, Sony Corp, Japan) and one force plate (AMTI., USA) were used to analyze the vertical ground reaction force (GRF) variables, center of pressure (COP), low limb joint angle, position of pelvis center and leg lengths during the stance phase of the gait cycle. Results: Our results revealed that the center of mass (COM) displacement velocity along the y-axis was significantly higher in the obese group than that in control subjects. Displacement in the position of the center of the pelvis center (Z-axis) was also significantly higher in the obese group than that in control subjects. In addition, the peak vertical force (PVF) and dimensionless leg stiffness were also significantly higher in the obese group. However, when normalized to the body weight, the PVF did not show a significant between-group difference. When normalized to the leg length, the PVF and stiffness were both lower in the obese group than in control subjects. Conclusion: In the context of performance, we concluded that increased dimensionless leg stiffness during the gait cycle is associated with increased velocity of COM, PVF, and the change in leg lengths (%).

• 한국재료학회지
• /
• 제5권8호
• /
• pp.936-944
• /
• 1995

본 논문에서는 저압 유기금속 기상성장(low pressure metal organic vapor phase epitaxy) 장치에 의해 성장된 InGaAsP/InP 구조의 상(phase) 분리현상(Spinodal 분해)이 photoluminescence (PL)의 강도와 반치폭(full-width at half maximum, FWHM)에 미치는 영향에 대해 연구하였다. 시료의 격자부정합은 double crystal x-ray diffractometer를 사용하여 측정하였고, InGaAsP에피막의 Spinodal분해조직은 투과전자현미경 (transmission electron microscopy, TEM)을 사용하여 관측하였다. 격자부정합에서 도출된 부정합응력과 Spinodal 모듈레이션의 주기(periodicity)와 밀접한 관계가 있음이 밝혀졌다. 또한 이러한 InGaAsP에피막의 미세조직 구조와 시료의 광전 특성이 어떤 관계가 있는지 알기 위해 PL 실험을 수행했으며, PL강도와 FWHM이 조성 모듈레이션의 주기에 강하게 의존한다는 것을 알 수 있었다. 이 현상을 심층적으로 연구하기 위해 부정합응력이 야기할 수 있는 interaction 탄성변형 에너지라는 새로운 함수를 유도하였으며 이에 의하여 실험결과를 설명할 수 있었다.