• International Journal of Aeronautical and Space Sciences
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• 제13권3호
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• pp.361-368
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• 2012

This paper presents an approach on the design of a nonlinear controller to track a reference velocity for an air-breathing supersonic vehicle. The nonlinear control scheme involves an adaptation of propulsive and aerodynamic characteristics in the equations of motion. In this paper, the coefficients of given thrust and drag functions are estimated and they are used to approximate the equations of motion under varying flight conditions. The form of the function of propulsive thrust is extracted from a thrust database which is given by preliminary engine input/output performance analysis. The aerodynamic drag is approximated as a function of angle of attack and fin deflection. The nonlinear controller, designed by using the approximated nonlinear control model equations, provides engine fuel supply command to follow the desired velocity varying with time. On the other hand, the stabilization of altitude, separated from the velocity control scheme, is done by a classical altitude hold autopilot design. Finally, several simulations are performed in order to demonstrate the relevance of the controller design regarding the vehicle.

• 수산해양기술연구
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• 제50권4호
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• pp.435-446
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• 2014

Tidal turbulence was examined using three-dimensional tidal velocity data observed at a trench offshore of Tongyoung, Korea. The kinetic energy and intensity, including the variation period of the flow velocity and direction, were used to investigate the relationships between tidal turbulence and fishing gear dynamics, including the effects of swimming fish during fishing operations. As the resultant velocity increased from 0.2 to 0.9 m/s, the kinetic energy also significantly increased, while the turbulence intensity decreased from 50 to 10%. Tidal flow in strong flow fields displayed shorter periods of between 4 and 10 s, as determined by fast Fourier transform, the global wavelet method, and peak event analysis, and the periods were compared with the period of response to swimming fish and to oscillation of fishing gear. As mean velocity increased, velocity amplitude also increased from 0.1 to 0.6 m/s, and its directional amplitude changed markedly from 20 and $90^{\circ}$. Our study suggests that tidal turbulence can influence fish behavior or fishing gear geometry during fishing operations, although our analysis considered only a limited area. In future work, observations should be carried out over a more extensive depth and area.

• 한국군사과학기술학회지
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• 제6권4호
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• pp.22-28
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• 2003

In the conventional weapon system, such as gun and small arms, it Is a general trend that for maximization of its performance and enhancement of its effectiveness, the firing control system(FCS) is developed and applied with the guns and small arms in the world. The FCS of the small arms for infantry man is composed of a few of sensors for acquisition of input data of FCS, such as range measurement, position sensing of weapon, temperature, etc., computer, displayer and power pack, and also the air burst munition is developed in parallel for the maximization of FCS's effectiveness. Since the flight time setting fuze for the air burst munition is adapted for next me, the measuring device of the muzzle velocity is needed to overcome the variation of muzzle velocity due to producing procedures and the differences of the using temperatures and so maintain the burst position accuracy This paper contained the technical information on the development of the measuring device of muzzle velocity, which designed in compact & light weight configuration with reliability and accuracy.

• 지질공학
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• 제4권3호
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• pp.333-341
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• 1994

Ray Method와 관측지진 자료에 의해서 지각구조 상부 Mantle을 연구하면서 저속도층이 탐지되었다. 우리는 한반도에서 부곡 온천 지역과 추가령 지구대를 통과하는 P파와 S의 도착 시간 지연을 관측했다. 현재 지열 탐사는 이 지역이 심부 저속도 물체는 "지연 암영"이라고 불리우는 높은 지열이상을 설명 해주고 있다. 우리는 하부지각의 부분 용융에 기인한 저속도 물체의 가설을 하부지각의 이차원 비등질 모델의 속도변화가 있음을 Ray Method(Cerveny and Psencik, 1983)에 의해서 분석 하였다.

• 제어로봇시스템학회논문지
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• 제21권9호
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• pp.801-806
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• 2015

In this paper, we propose cascade-form velocity controller for a permanent magnet synchronous motor (PMSM). The proposed controller consists of a sliding-mode controller (SMC) for the inner current control loop and a model-predictive controller (MPC) for the outer velocity control loop. With SMC, we can ensure that the current tracking error always converges to zero in finite time. The SMC is designed to track the desired currents. Additionally, with MPC, we can obtain the optimal velocity control input which minimizes the cost function. Constraint conditions for input and input variation are included in the MPC design. The simulation results are included to validate the performance of the proposed controller.

• 대한기계학회논문집A
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• 제27권11호
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• pp.1824-1830
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• 2003

The vibrational system of this study is consisted of a rotating cantilever pipe conveying fluid and the tip mass. The equation of motion is derived by using the Lagrange equation. The influences of the rotating angular velocity and the velocity of fluid flow in a cantilever pipe have been studied on the dynamic characteristics of a rotating cantilever pipe by the numerical method. The effects of a tip mass on the dynamic response of a cantilever pipe are also studied. The tip-amplitude and maximum tip-deflection of each direction are directly proportional to the tip mass of the cantilever pipe in steady state. It identifies that the influence of the fluid velocity and the rotating angular velocity of the cantilever pipe give much variation the bending tip-displacement of steady state and the bending tip-displacement of non-steady state, respectively. The influence of the rotating angular velocity gives much the deflection of axial direction.

• The Journal of Korean Physical Therapy
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• 제22권6호
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• pp.71-76
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• 2010

Purpose: The purpose of this study was to examine changes in autonomic nerve responses after low-frequency transcutaneous electrical nerve stimulation (TENS). Methods: Research subjects were 24 students who attend University. Subjects were divided into two groups: 1 = a low intensity group; 2 = a high intensity group. Electrodes were attached to the forearm of the dominant arm and electrical stimuli were administered for 15 minutes. Outcome measures were skin conduction velocity, skin temperature, blood flow, and pulse frequency, each of which was measured a total of 4 times. The data were analyzed using a repeated measures ANOVA. Results: In changes in conduction velocity, the main effect of time variation (in black) was statistically significant. The interaction between time and group main effects was not statistically significant; nor was the difference between the groups. Results showed that skin conduction velocity changed without any relation to group. Conclusions: Low frequency TENS selectively increases skin conduction velocity, which may be helpful for activating sudomotor function regardless of intensity.

• 한국재료학회지
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• 제17권8호
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• pp.425-432
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• 2007

The microstructural evolution of ferritic 9Cr-1Mo-V-Nb steel, subjected to creep-fatigue at $550^{\circ}C$, was evaluated nondestructively by measuring the ultrasonic velocity. The variation of the ultrasonic velocity with the fatigue life fraction exhibited three regions. In the first region ($N/N_f$<0.2), a significant increase in the velocity was observed, followed by a slight increase between the fatigue life fractions of $0.2N_f$ and $0.8N_f$, and then a decrease in the final region. The change of the ultrasonic velocity during creep-fatigue was interpreted in relation to the microstructural properties. This study proposes an ultrasonic nondestructive evaluation method of quantifying the level of damage and microstructural change during the creep-fatigue of ferritic 9Cr-1Mo-V-Nb steel.

• 물과 미래
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• 제23권4호
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• pp.435-444
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• 1990

만곡수로에서의 곡률반경에 대한 하폭비 변화에 따른 흐름특성을 단순화된 수치모형을 이용하여 분석하였다. 각 운동량 방정식과 힘의 평형원리로부터 각가 2차 흐름속도와 횡방향하상경사를 계산하였다. 깊이 방향으로 적분된 연속방정식과 흐름방향의 운동방정식을 양적 유한차분법으로부터 그 해를 구하였다. 곡률반경에 대한 하폭의 비를(Rc/B) 2.7, 5.4 및 8.1로 변화시키면 수치실험을 실행하여, 그 결과로부터 2차 흐름속도, 흐름방향유속, 최대유속의 이동경로, 편의각 및 질량이동유속에 관한 특성을 분석하였다.

• 반도체디스플레이기술학회지
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• 제12권2호
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• pp.19-25
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• 2013

Extrusion is one of the most important operations in the polymer-processing industry. Balancing the distribution of flow through a die to achieve a uniform velocity distribution is the primary objective and one of the most difficult tasks of extrusion die design. If the manifold in a coat-hanger die is not properly designed, the exit velocity distribution may be not uniform; this can affect the thickness across the width of the die. Yet, no procedure is known to optimize the coat hanger die with respect to an even velocity profile at the exit. While optimizing the exit velocity distribution, the constraint optimization used in this work with allowable pressure drop in the die; according to this constraint we can control the pressure in the die. The computational approach incorporates three-dimensional finite element simulations software STAR-CCM+. These simulations are used with numerical optimization to design polymer coat hanger dies with pressure drop, uniform velocity and temperature variation across the die exit.