• International Journal of Control, Automation, and Systems
• /
• v.3 no.spc2
• /
• pp.341-345
• /
• 2005

Part-I of this two-part paper develops an optimal algorithm for transient stability control to coordinate the preventive actions and emergency actions for a subset of contingencies with an identical unstable mode. In this portion, several subsets of contingencies having dissimilar unstable modes are dealt with. Preventive actions benefiting a subset of contingencies may go against the stability of others, thus coordination among the optimal schemes for individual subsets is necessary. The coordination can be achieved by replacing some preventive actions with contingency-specified emergency actions. It is formulated as a classical model of economic dispatch with stability constraints and stability control costs. Such an optimal algorithm is proposed based on the algorithm in Part-I of the paper and is verified by simulations on a Chinese power system.

• 제어로봇시스템학회:학술대회논문집
• /
• 2005.06a
• /
• pp.2455-2458
• /
• 2005

In this paper, we analyzed the effect of a training system for improving equilibrium sense. This training system consists of an unstable platform, a force plate, a computer, and training programs. Using the system with training programs, we performed various experiments to train the equilibrium sense of fifteen subjects. To evaluate the effect of the training system, we measured the time a subject maintains a focus, the moving time to the target, and the absolute deviation of the trace. We analyzed these parameters obtained before and after the training using paired-samples T-test. The results showed that the subjects experienced a distinctive enhancement of their equilibrium senses through the training using our system.

• Journal of the Korean housing association
• /
• v.26 no.6
• /
• pp.9-16
• /
• 2015

The Japanese economy has been unstable since 1990. Economic instability and changes in working conditions have made the acquisition of housing and the improvement in housing standards difficult. Unstable working and habitation conditions have also spread, and the Nagoya Metropolitan Area is recognized as a traction community in the Japanese economy. This study employed existing statistics and helpline consultations in 2013 to clarify the state of housing poverty in the Nagoya Metropolitan Area. Moreover, it clarified the conditions for improvement in the housing standards for the low-income households, a regional gap, and reasons for the deteriorating housing levels of low-income households by investigating the "Housing and Land Survey." Furthermore, it clarified housing difficulties that do not appear in existing statistics by investigating the examples of "toll-free call consultations" in 2013.

• Journal of Ocean Engineering and Technology
• /
• v.22 no.4
• /
• pp.1-7
• /
• 2008

The primary aim of the paper is to solve an unstable axisymmetric initial value problem of wave propagation when given initial data that is deteriorated by noise such as measurement error. To overcome the instability of the problem, Tikhonov's regularization, known as a non-iterative numerical regularization method, is introduced to solve the problem. The L-curvecriterion is introduced to find the optimal regularization parameter for the solution. It is confirmed that fairly stable solutions are realized and that they are accurate when compared to the exact solution.

• Journal of Institute of Control, Robotics and Systems
• /
• v.18 no.5
• /
• pp.496-501
• /
• 2012

An equilibrium point of a WIP (Wheeled Inverted Pendulum) with changing its center of gravity is derived and validated by various numerical simulations. Generally, the WIP has two equilibrium points which are unstable and stable one. The unstable one is interested in this study. To keep the WIP over the unstable equilibrium point, the WIP is consistently being adjusted. A state feedback controller for the WIP needs a control reference for the equilibrium point. The control reference can be obtained by studying an equilibrium point of the WIP based on statics. By using Lagrange method, this study is deriving dynamic equations of the WIP both with and without changing its center of gravity. Various numerical simulations are carried out to show the validation of the equilibrium point.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.22 no.4
• /
• pp.452-458
• /
• 1998

The objective of this study is to obtain the unstable characteristics of the high-speed two-dimensional jet impinging normally onto a flat plate. The study is based on the feedback model and the experiment of the frequency characteristics of the impinging tones. Using the experimental data for the tonal frequencies of the impinging tones the convection speed of the unstable jet is obtained along with all the other features. Three kinds of unstable modes are clarified: asymmetric $A_{1}$ and $A_{2}$ and symmetric S. The condition for the excitation of each mode is found in terms of Strouhal number and Reynolds number. The convection speed is estimated and discussed in comparison with existing theoretical models. It is found that the convection speed increases with frequency when the mode is asymmetric, but decreases when it is symmetric. In addition, the characteristics of the high-speed impinging jet are compared with the low-speed impinging jet.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2003.05a
• /
• pp.253-257
• /
• 2003

Theoretical-numerical analysis of wave instability is conducted with parametric response function model. Fluctuating instantaneous mass evaporation rate functionally coupled with pressure perturbations with phase lag is assumed to examine the validity of the method. With sufficiently large amplitude and less phase lag to perturbation, combustion response is resonant to pressure waves, unstable waves are amplified, and the system is driven to instability. Magnitude of response is a crucial instability parameter in the determination of a stability margins and makes a critical change of balancing conditions between the amplifying and damping acoustic energies. In the phase regime the unstable waves are amplified, whereas, the acoustic waves are attenuated in the out-of-phase regime. In the intermediate regime, no distinct tendency of unstable waves was determined.

• Journal of KSNVE
• /
• v.9 no.3
• /
• pp.461-465
• /
• 1999

This paper presents theoretical analyses for unstable vibrations caused by the couple of bending and torsion in a rotating shaft driven through a universal joint. A driving shaft is assumed to be rigid and to rotate with a constant angular velocity. The driven shaft system consists of a flexible shaft with a circular section and a symmetrical rotor attached at a point between the shaft ends. Equations of motion derived hold with an accuracy of the second order of shaft deformations, and are analyzed by the asymptotic method. The vibrations become unstable when the driving shaft rotates with the angular velocity to be approximately equal to half of the sum of the natural frequencies for whirling and torsional vibrations.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.17 no.1
• /
• pp.35-40
• /
• 1981

This pape presents a study of stability of the two mass rotor with limited power similar to that employed by Kononenko and also presents a study on the digital computer to obtain the unstable region of the ;'ot::r oyer two critical speed ranges. The unstable region is identified by studying the Routh-Hurwitz criterion of the chc.rc.cteristic equation. The results are presented in two and three-dimensional diagrams to show how the various parameters affeCt the unstable region.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.20 no.2
• /
• pp.616-623
• /
• 1996

This paper investigates the linear stability of reacting mixing layers with special emphasis on the existence of multiple unstable modes. The governing equations for laminar flows are from two-dimensional compressible boundary-layer equations. The chemistry is a finite rate single step irreversible reaction with Arrhenius kinetics. For the incompressible reacintg mixing layer with variable density. A necessary condition for instability has been derived. The condition requires that the angular momentum, not the vorticity, to have a maximum in the flow domain. New inflectional modes of instability are found to exist in the outer part of the mixing layer. For the compressible reacting mixing layer, supersonic unstable modes may exist in the abscence of a generalized inflection point. The outer modes at high Mach numbers in the reacting mixing layer are continuations of the inflectional modes of low Mach number flows. However, the generalized inflection point is less important at supersonic flows.