• 전기의세계
• /
• 제16권5호
• /
• pp.6-14
• /
• 1967

The relaxation oscillations which occur independently by increasing the

• 대한기계학회논문집B
• /
• 제24권6호
• /
• pp.792-801
• /
• 2000

The problem of phase change from liquid to solid in the inviscid plane-stagnation flow is theoretically investigated. The solution at the initial stage of freezing is obtained by expanding it in powers of time, and the final equilibrium state is determined from the steady-state governing equations. The transient solution is dependent on the three dimensionless parameters, but the equilibrium state is determined by one parameter of (temperature ratio/conductivity ratio). The effect of the fluid flow on the growth rate of the solid in the pure conduction problem can be clearly seen from the solution of the initial stage and the final equilibrium state. The characteristics of the transient heat transfer at the surface of the solid and the liquid side of the solid-liquid interface for all the dimensionless parameters are elucidated.

• 대한치과보철학회지
• /
• 제32권4호
• /
• pp.565-572
• /
• 1994

According to the classification of dental arch form and the analysis of patterns of chewing movement, the patterns of chewing movement in each group were evaluated and compared with those of the normal group. Results were summarized as follows ; 1. Opening phase in chewing movement In the group which the maxillary second molar positionsbuccal side, the chewing patterns which have the Vertical Guide Openings in frontal plane, the Posterior Guide Openings in hjorizontal plane were observed. In the group which the maxillary premolars position lingual side, the chewing paterns which have the Protrusive Shift Openings in horizontal plane and sagittal plane were observed. 2. Closing phase in chewing movement. In each group except for the normal group, the chewing patterns which have the Concave Closure in frontal plane and in Horizontal plane were observed. In the group which the maxillary premolars position buccal side, the chewing patterns which have the Lateral Guide Closure in frontal plane and in horizontal plane, the Vertical Guide Closre in sagittal plane were observed: From the results, as the characteristics of the dental arch form have appeared in chewing movement, the close relationships were found between dental arch form and chewing movement. It is suggested that the evaluation of dental arch form is effective in the diagnosis of function of stomatognathic system.

• 한국정밀공학회지
• /
• 제15권12호
• /
• pp.113-119
• /
• 1998

Recently Electronic Speckle Pattern Interferometry(ESPI) has been studied because it has the advantages to be able to measure the whole-field surface deformations of engineering components and materials in industrial areas with noncontact. The speckle patterns to be formed with interference phenomena of scattering light from rough surfaces illuminated by laser light have phase informations of surface deformations. In this study we used this interference phenomena and the phase shifting method to measure the inplane deformations, together with the use of digital image equipment to process the informations contained in the speckle pattern and to display consequent interferograms on TV monitor. FEA was performed before experiments and we obtained good agreement between the experimental results and FEA.

• 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.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2002년도 추계학술대회논문집
• /
• pp.255-261
• /
• 2002

A four-degree of freedom model is suggested to understand the basic dynamical behaviors of the normal interaction between two masses of the friction induced normal vibration system. The two masses may be considered as the pad and the disk of the brake. The phase space analysis is performed to understand complicated in-plane dynamics of the non-linear model. Attractors in the phase space are examined for various conditions of the parameters. In certain conditions, the attractor becomes a limit cycle showing the stick-slip phenomena. In this paper, on the basis of the in-plane motion not only the existence of the limit cycle but also the size of the limit cycle is examined o demonstrate the non-linear dynamics that leads the unstable state and then the normal vibration is investigated as the state of the in-plane motion For only one case of the system frequency(two masses with same natural frequencies), the propensity of the normal vibration is discussed in detail. The results show an important fact that it may be not effective when too much damping is present in the only one part of the masses.

• Journal of Electrical Engineering and Technology
• /
• 제13권1호
• /
• pp.20-29
• /
• 2018

The dynamic characteristics of power systems become more and more complex because of the integration of large-scale wind power, which needs appropriate control strategy to guarantee stable operation. With wide area measurement system(WAMS) creating conditions for realizing realt-ime transient stability analysis, a new coordinated control strategy for power system transient stability control based on phase-plane trajectory was proposed. When the outputs of the wind farms change, the proposed control method is capable of selecting optimal generators to balance the deviation of wind power and prevent transient instability. With small disturbance on the base operating point, the coordinated sensitivity of each synchronous generator is obtained. Then the priority matrix can be formed by sorting the coordinated sensitivity in ascending order. Based on the real-time output change of wind farm, coordinated generators can be selected to accomplish the coordinated control with wind farms. The results in New England 10-genrator 39-bus system validate the effectiveness and superiority of the proposed coordinated control strategy.

• 대한기계학회논문집B
• /
• 제26권2호
• /
• pp.362-373
• /
• 2002

A stereoscopic PIV (SPIV) measurement system based on the translation configuration was developed and applied to the flow behind a forward-swept axial-fan. Measurement of three orthogonal velocity components is essential for flow analysis of three-dimensional flows such as flow around a fan or propeller. In this study, the translation configuration was adopted to calculate the out-of-plane velocity component from 2-D PIV data obtained from two CCD cameras. The error caused by the out-of-plane motion was estimated by direct comparison of the 2-D PIV and 3-D SPIV results that measured from the particle images captured simultaneously. The comparison shows that the error ratio is relatively high in the region of higher out-of-plane motion near the axial fan blade. The turbulence intensity measured by the 2-D PIV method is bigger by about 5.8% in maximum compared with that of the 3-D SPIV method. The phase-averaged velocity field results show that the wake behind an axial fan has a periodic flow structure with respect to the blade phase and the characteristic flow structure is shifted downstream in the next phase.

• International Journal of Automotive Technology
• /
• 제7권7호
• /
• pp.821-826
• /
• 2006

This paper describes a rollover index (RI)-based rollover mitigation control (RMC) system. A rollover index which indicates an impending rollover has been developed by a roll dynamics phase plane analysis. The rollover index is calculated using the roll angle, the roll rate, the lateral acceleration and time to wheel lift (TTWL). A differential braking control law based on a 2-D bicycle model has been designed using the direct yaw control (DYC) method. An RMC threshold has been determined from the rollover index. The performance of the RMC scheme and the effectiveness of the proposed rollover index are illustrated using a vehicle simulator.

• 항공우주기술
• /
• 제11권1호
• /
• pp.145-157
• /
• 2012

상평면상에서 추력기를 사용하는 자세제어 시스템의 리밋 사이클을 해석하는 새로운 기법이 논문에 의해서 제안되었다. 그러나 이것은 소프트 시뮬레이션상에서 Haloulakos 방식보다 제안 방식이 정확함을 보였지만, 실제 시스템으로 검증하지는 못하였다. 그래서 저자의 제안 방식을 KSLV-I 추력기 자세제어 시스템에 대한 실시간 모의시험으로 검증하고, 리밋 사이클 해석에 대하여 실시간 모의시험 결과와 이론적으로 구한 값을 비교/분석하였다.