• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.10
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• pp.2060-2066
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• 2002

The closed-loop state and input observer is a pole-placement type observer and estimates unknown state and input variables simultaneously. Pole-placement type observers may have poor transient performance with respect to ill-conditioning factors such as unknown initial estimates, round-off error, etc. For the robust transient performance, the effects of these ill-conditioning factors must be minimized in designing observers. In this paper, the transient performance of the closed-loop state and input observer is investigated quantitatively by considering the error bounds due to ill-conditioning factors. The performance indices are selected from these error bounds and are related to the observer robustness with respect to the ill -conditioning factors. The closed-loop state and input observer with small performance indices is considered as a well-conditioned observer from the transient perspective.

• Journal of the Korean Mathematical Society
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• v.49 no.4
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• pp.715-731
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• 2012

This paper considers the stability of positive steady-state solutions bifurcating from the trivial solution in a delayed Lotka-Volterra two-species predator-prey diffusion system with a discrete delay and subject to the homogeneous Dirichlet boundary conditions on a general bounded open spatial domain with smooth boundary. The existence, uniqueness and asymptotic expressions of small positive steady-sate solutions bifurcating from the trivial solution are given by using the implicit function theorem. By regarding the time delay as the bifurcation parameter and analyzing in detail the eigenvalue problems of system at the positive steady-state solutions, the asymptotic stability of bifurcating steady-state solutions is studied. It is demonstrated that the bifurcating steady-state solutions are asymptotically stable when the delay is less than a certain critical value and is unstable when the delay is greater than this critical value and the system under consideration can undergo a Hopf bifurcation at the bifurcating steady-state solutions when the delay crosses through a sequence of critical values.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.09a
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• pp.66-73
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• 2003

The technique for the seismic reliability evaluation of the electric power network is presented. In the previous study, the state of the substations was represented by the bi-state which is classified as failure or survival. However, the hi-state model can result in oversimplified analysis, because substations are worked by the parallel operating system. In this paper, Considering the characteristics of the parallel operating system, the damage of the substation is expressed by the multi-state for the more realistic seismic reliability evaluation. Using Monte-Carlo simulation method, the seismic reliability for Korean 345㎸ electric power network is evaluated. Analysis results show that reliability levels of the network by the multi-state analysis is higher than that by the hi-state analysis and the electric power network in southeastern area of the Korean Peninsular may be vulnerable to earthquakes.

• Proceedings of the KIPE Conference
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• 2019.07a
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• pp.307-308
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• 2019

The Pohang Light Source (PLS) - II is a 3 GeV third-generation synchrotron radiation facility. To inject electron beam from LINAC, a kicker modulator system and kicker magnets are installed in the PLS-II storage ring tunnel. The injected beam then falls into the storage ring beam dynamic aperture. This paper describes the design and implementation of the solid-state kicker modulator for PLS-II. The solid-state kicker modulator is consisted of high voltage solid state switch stacks. the technical considerations of the solid-state switch stacking for kicker modulator is discussed. The achieved capability of the solid-state kicker modulator demonstrates that is fulfills the design requirement of providing half-sine pulsed current of 10kA (peak), 6us (Base-width), with jitter < 2ns (Standard deviation). simulation and experimental results are presented to demonstrate the performance of the solid-state kicker modulator.

• International Journal of Computer Science & Network Security
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• v.22 no.11
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• pp.51-56
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• 2022

The main purpose of the study is to analyze the features of ensuring the financial and economic security of the state in an aggressive external environment. The concept of financial and economic security should contain the priority goals and objectives of ensuring security, ways and methods to achieve them, adequately reflecting the role of finance in the socioeconomic development of the state. Its content is designed to coordinate nationwide actions in the field of security at the level of individual citizens, business entities, industries, sectors of the economy, as well as at the regional, national and international levels. The methodology includes a number of scientific and theoretical methods of analysis. Based on the results of the study, the key aspects of the system for ensuring the financial and economic security of the state in an aggressive external environment were identified.

• Journal of the Korean Chemical Society
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• v.67 no.3
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• pp.165-174
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• 2023

The development of all-solid-state batteries (ASSBs) has been gaining attention in recent years due to their potential to offer higher energy densities, improved safety, and longer cycle life compared to conventional lithium-ion batteries. However, several challenges must be addressed to achieve the practical application of ASSBs, such as the development of high-performance solid-state electrolytes, stable electrode-electrolyte interfaces, and cost-effective manufacturing processes. In this review paper, we present an overview of the current state of ASSB research, including recent progress in solid-state electrolyte and cathode/anode materials, and cell architecture. We also summarize the recent advancements and highlight the remaining challenges in ASSB research, with an outlook on the future of this promising technology.

• Asian Journal of Innovation and Policy
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• v.12 no.3
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• pp.345-362
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• 2023

As the widespread adoption and proliferation of electric vehicles continue, the secondary battery market is experiencing rapid growth. However, lithium-ion batteries, which constitute a majority of secondary batteries, present high risks of fire and explosion. Solid-state batteries are thus garnering attention as the next-generation batteries since they eliminate fire hazards and significantly reduce the risk of explosions. Against this background, the study aimed to analyze research trends and provide insights by examining 2,927 domestic papers related to solid-state batteries over the past decade (2013-2022). Specifically, we used topic modeling to extract major keywords associated with solid-state batteries research and to explore the network characteristics across major topics. The changes in research on solid-state batteries were analyzed in-depth by calculating topic dominance by year. The findings provide an overview of the emerging trends in domestic solid-state battery research, and might serve as a valuable reference in shaping long-term research directions.

• International Journal of Computer Science & Network Security
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• v.23 no.12
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• pp.181-186
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• 2023

The main purpose of the study is to analyze the features of state regulation of the labor market in a crisis. Structural shifts in the labor market are due to the transformation of public and economic relations in today's globalized world. Increasing competition, the development of the knowledge economy, information technology, changes in the content and forms of labor require updating the labor market regulation system. The research methodology implies the use of modern methods of analysis. The analysis of the features of state regulation of the labor market in crisis conditions is carried out.

• Proceedings of the Korean Magnestics Society Conference
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• 2007.05a
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• pp.125.2-125.2
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• 2007

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.7
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• pp.613-616
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• 2012

This paper proposes the state observer design for nonlinear systems with delayed output. It is shown that by considering a nonlinear term of error dynamics as an additional state variable, the nonlinear error dynamics with time delay can be transformed into the linear one with time delay. Sufficient conditions for existence of a state observer are characterized by linear matrix inequalities. Finally, an illustrative example is given in order to show the effectiveness of our design method.