• The Transactions of the Korean Institute of Electrical Engineers P
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• v.66 no.4
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• pp.206-212
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• 2017

In this paper, using the power system information obtained from real-time monitoring device, to analyze the voltage stability margin index and described the voltage stability control scheme for voltage stability enhancement. Based on the utilization of the voltage stability monitoring index based on local information provided by the PMU(Phasor Measurement Unit), the purpose of the plan is to control the system stably in real time. In order to apply the load control scheme, the voltage stability margin is calculated using the data acquired through the PMU installed in each load bus. If the voltage drops below a certain level, load control is performed for each. The effectiveness of the voltage stability control measures is applied to the actual KEPCO system to analyze the effectiveness.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.49 no.2
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• pp.43-49
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• 2000

It is a complex process to analyze power system voltage stability problems with all of the dynamics of a system, because a large power network system sophisticatedly consists of generators, lines, loads and so forth. So we considered the dynamics of loads so as to analyze voltage stability method- by carrying out an analysis of steady state voltage stability and dynamic voltage stability simultaneously. To perform a steady state voltage stability program in advance makes it possible to cut down on laborious calculations so that an analysis of dynamic voltage stability becomes concise. The validity and efficiency of the method presented in this paper were verified by applying the IEEE 14 bus system.

• Journal of applied mathematics & informatics
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• v.8 no.2
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• pp.581-590
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• 2001

In this paper we prove a local stability of Gavruta’s theorem for the generalized Hyers-Ulam-Rassias Stability of Cauchy functional equation.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.6
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• pp.227-233
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• 2002

A vehicle longitudinal control strategy with guaranteed string stability for vehicle stop-and-go(SG) cruise control is presented in this paper. The SG cruise control systems should be designed such that string stability can be guaranteed in addition to that every vehicle in a string of SG cruise control vehicles must track any bounded acceleration and velocity profile of its preceding vehicle with a bounded spacing and velocity error. An optimal vehicle following control law based on the information of the 1311owing distance (clearance) and its velocity relative to the vehicle ahead (relative velocity) has been used and string stability analysis has been done based on the control law and constant time gap spacing policy, A validated multi-vehicle simulation package has been shown that the string stability analysis using the approximate model of the vehicle servo-loop which includes vehicle powertrain and brake control system dynamics is valid in the design of the SG cruise control law with guaranteed string stability.

• Computers and Concrete
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• v.21 no.2
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• pp.111-116
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• 2018

Establishment of test methods to assess the fresh properties of self-compacting concrete (SCC) are required to ensure the homogeneity in fresh and hardened states. This paper discusses the suitability of a simple test method for assessing the slump flow and stability of SCC by testing on self-compacting mortar (SCM) fraction. The proposed test method aims at investigating slump flow diameter test and sieve stability test of SCC by testing SCM fraction with a plunger penetration apparatus. A central composite modeling design was performed to evaluate the effects of water/cement ratio (W/C), superplasticizer dosage (SP) and powder marble content (MP) on slump flow diameter, stability and plunger penetration test of fresh SCC. The responses of the derived statistical models are slump flow (Sf), sieve stability (S) and plunger penetration (P). Relationships obtained in this study show acceptable correlations between plunger penetration test value and slump flow diameter test results and stability. It should note that the developed relationships are very useful to predict slump flow diameter and stability of studied SCC mixtures by carrying out a simple plunger penetration test on its mortar, which can save labour and time in laboratory experiments.

• Safety and Health at Work
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• v.3 no.3
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• pp.192-198
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• 2012

Objectives: Slip and fall accidents in the workplace are one of the top causes of work related fatalities and injuries. Previous studies have indicated that fall risk was related to postural and dynamic stability. However, the usage of this theoretical relationship was limited by laboratory based measuring instruments. The current study proposed a new method for stability assessment by use of inertial measurement units (IMUs). Methods: Accelerations at different body parts were recorded by the IMUs. Postural and local dynamic stability was assessed from these measures and compared with that computed from the traditional method. Results: The results demonstrated: 1) significant differences between fall prone and healthy groups in IMU assessed dynamic stability; and 2) better power of discrimination with multi stability index assessed by IMUs. Conclusion: The findings can be utilized in the design of a portable screening or monitoring tool for fall risk assessment in various industrial settings.

• Korean Journal of Mathematics
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• v.24 no.1
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• pp.1-13
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• 2016

This paper shows that the solutions to the perturbed functional dierential system $$y^{\prime}=f(t,y)+{\int_{t_0}^{t}}g(s,y(s),Ty(s))ds$$ have uniformly Lipschitz stability and asymptotic property. To sRhow these properties, we impose conditions on the perturbed part ${\int_{t_0}^{t}}g(s,y(s),Ty(s))ds$ and the fundamental matrix of the unperturbed system $y^{\prime}=f(t,y)$.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.41-45
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• 1997

To design a control system, it is a elementary point that the stability of the system should be guaranteed. Also, the phase of the system plays an important role for its frequence performance. In this paper, we present two stability criterion of repetitive control system with phase-lead and lag compensator. First, the stability criterion for the servo control system with phase-lead and lag compensator is shown by using small-gain theorem. Second, for the repetitive control system with the compensator, the stability criterion, also, is determined by using small-gain theorem. Two stability criterions show the same results that the stability depends on a coefficient of the phase-lead and lag compensator under some condition in servo control system and repetitive control system.

• Journal of the Korean Mathematical Society
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• v.49 no.3
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• pp.515-536
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• 2012

This work focuses on the general decay stability of nonlinear stochastic differential equations with unbounded delay. A Razumikhin-type theorem is first established to obtain the moment stability but without almost sure stability. Then an improved edition is presented to derive not only the moment stability but also the almost sure stability, while existing Razumikhin-type theorems aim at only the moment stability. By virtue of the $M$-matrix techniques, we further develop the aforementioned Razumikhin-type theorems to be easily implementable. Two examples are given for illustration.

• Microbiology and Biotechnology Letters
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• v.19 no.1
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• pp.100-108
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• 1991

Molecular characteristics and improving methods for thermal stability of enzyme have been considered. Intrinsic and extrinsic stabilizing mechanisms are two governing principles for enhanced thermal stability of enzyme in molecular basis. Factors contributing to the former and the latter mechanisms may be involved in the enhanced thermal stability of enzyme complementarily. Also, the methods for improving thermal stability of enzyme which comprise reaction in organic solvent system, chemical modification, immobilization, sequential unfolding and refolding, gene manipulation techniques and enzyme-antibody complexing are reviewed.