• Proceedings of the KSME Conference
• /
• 2000.04a
• /
• pp.499-504
• /
• 2000

Since large space structures(LSS) such as a space station, a solar power station satellite, etc., are theoretically distributed parameter and infinite-dimensional system, they have to be modeled into large finite-dimensional systems for control system design. Besides, there are fundamental problems in active vibration control of the large flexible structures. For example, a modeled large finite-dimensional system must be controlled with a much smaller dimensional controller. This causes the spillover phenomenon which degrades the control performances and reduces the stability margin. Furthermore, it may destabilize the entire feedback control system. In this paper, we proposed a novel control method for spillover suppression in the control of large flexible structures by using eigenstructure assignment. Its effectiveness in spillover suppression is investigated and verified by the numerical experiments using an example of the simply supported flexible beam which is modeled to have four controlled modes and eight uncontrolled modes.

• Journal of Technology Innovation
• /
• v.17 no.1
• /
• pp.69-95
• /
• 2009

This paper examines the motives for location decisions of startups and dynamics of cluster growth. Because the location decision is intrinsically strategic choice by entrepreneurs, it is an interplay of three critical forces; cost-benefit of the choice, R&D ability of new entrants, and R&D capability of incumbents in clusters. The effect of knowledge spillovers influences the cluster growth like a double-edge sword; both a positive effect of technology learning and a negative effect of knowledge de-learning. Using data on 710 bio-tech venture firms in Korea, this paper tests the hypotheses about the factors influencing the growth of the cluster. The empirical analyses suggested that early entrepreneurial activity in the clustered regions were important, however other factors such as the organizational legacy, internal dynamics inside a cluster, and the existence of cooperation norm in the cluster, affected long term viability of the cluster.

• 제어로봇시스템학회:학술대회논문집
• /
• 1997.10a
• /
• pp.1700-1703
• /
• 1997

The flexibility of the manipulator inevitably inducess the vibration at the end effector. For the increase in speed and accuracy at the end tip, in this work, position and vibration control of a flexible manipuator with a separate voice coil type actrator for vibration suppression, is studied. The flexible manipulator with a tip mass is modeled an Euler-Bernoulli beam. An H.inf. controller is designed in order to make the controlled system robust against unmodeled higher-order mode vibration of the manipulator, output sensor noise, and etc. Simulations and experiments show that the modeling of the system is valid and that robust vibration control of the flexible manipulator is efficiently achieved.

• Journal of KSNVE
• /
• v.7 no.6
• /
• pp.967-974
• /
• 1997

Distributed piezoeletric sensor and actuator have been designed for efficient vibration control of a cantilevered beam. Both PZT and PVDF have been used in this study, the former as an actuator and the latter as a sensor for the integrated structure. We have optimized the position and the size of the PZT actuator and the electrode shape of the PVDF sensor. Finite element method is used to model the structure and the optimized actuators, we have designed the active electrode width of the PVDF sensor along the span of the beam. Actuator design is based on the criterion of minimizing the system energy in the control modes under a given initial condition. Model control forces for the residual (uncontrolled) modes have been minimized during the sensor design to minimize the observation spill-over. Genetic algorithm and sequential quadratic programming technique have been utilized as an optimization scheme. Discrete LQG control law has been applied to the integrated structure for real time vibration control. Performance of the sensor, the actuator, and the integrated smart structure has been demonstrated by experiments.

• Journal of Korea Game Society
• /
• v.10 no.5
• /
• pp.87-94
• /
• 2010

This research investigated the relationship between MMORPG players' leadership-related game experience and offline leadership using online survey samples(N=664). According to the correlation results, MMORPG players' leadership-related game experience, age, game usage time and offline leadership exhibited a significantly positive relationship. When players had more leadership-related game experience, they reported higher offline leadership scores. In terms of "spillover effect", more valuable implications of using MMORPGs are discussed in conclusion.

• Journal of the Korean Society for Precision Engineering
• /
• v.17 no.3
• /
• pp.68-75
• /
• 2000

The flexibility of a manipulator inevitably yields vibration at the end effector. In this work, position and vibration control for a flexible robot arm was studied using a separate voice coil type actuator to raise the accuracy and speed of end tip. A flexible robot arm with a tip mass is modeled as an Euler-Bernoulli beam. An $H_$\infty$$ controller is adapted to get a robust control against unmodeled higher-order mode vibration, output sensor noise, and etc. Simulations and experiments show that the modeling of the system is acceptable and robust vibration control is also achieved.

• 한국신재생에너지학회:학술대회논문집
• /
• 2011.05a
• /
• pp.160-160
• /
• 2011

In this work, magnesium (Mg) nanoparticles were plated onto the surfaces of multi-walled carbon nanotubes (MWNTs) in order to investigate the effects of their presence on the high pressure hydrogen storage behaviors of the resultant Mg/MWNTs. The structure of Mg/MWNTs was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The pore structure and total pore volumes of Mg/MWNTs were analyzed by $N_2$/77 K adsorption isotherms. The hydrogen storage behaviors of the Mg/MWNTs were investigated by BEL-HP at 298K and 100 bar. From the results, it was found that Mg particles were homogeneously distributed on the MWNT surfaces. The hydrogen storage capacity increased in proportion to the Mg content. It can be concluded that Mg paricles play an important role in hydrogen storage characteristics due to the hydrogen spillover effect.

• Journal of Institute of Control, Robotics and Systems
• /
• v.6 no.11
• /
• pp.955-962
• /
• 2000

Although large space structures(LSS) such as a space station, a solar power station satellite, etc., are theoretically distributed parameter and infinite-dimensional systems, they have to be modeled into a lumped parameter and large finite-dimensional system for control system design. Besides, there remains the fundamental problem that the modeled large finite-dimensional system must be controled with a much smaller dimensional controller due to the limitation of computing resources. This causes the spillover phenomenon which degrades control performances and reduces the stability margin. Furthermore, it may destabilize the entire feedback control system. In this paper, we propose a novel spillover suppression method in the active vibration control of large flexible structures by using eigenstructure assignment. Its validity and effectiveness are investigated and verified by the numerical experiments using a simply supported flexible beam, which is modeled to have four controlled modes and eight uncontrolled modes.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
• /
• v.9 no.6
• /
• pp.47-64
• /
• 2014

Considering the network externality and spill-over effects, this paper constructs the theoretical model for analyzing the financial policies focusing on the credit guarantee system for Creative Economy, which has been set as the new policy paradigm for the Korean Economy. The analytical results show that it is as much as important to improve the efficiency of the financial markets and construct the infrastructure for reducing the information asymmetry problem which would be more serious in the creative finance. Although it is important to fill the gap due to the market failure it is also crucial to construct the appropriate financial schemes for the various stages of the innovative firms growth. Without these, the impacts of current public funding policies may crowd out the amount of private market funds for the innovative firms or reduce the possibility of commercialization of new technologies in these firms. Based on the evaluation of current related public policies from the perspectives of creative finance, we imply that the current financial policies appear to be quantity oriented not the quality based. Although the policy goals would be appropriately set for vitalizing the Creative Economy in Korea, they appear to be still unsuccessful to address the information asymmetry issue which is the major concern in vitalizing the creative economy. Thus we emphasize the market friendly policies, risk-sharing between the various market participants, revitalizing the relationship banking and efficient management of credit guarantee system in Korea based on the analytical model as well as the evaluation of related policies regarding the creative economy.

• Journal of KSNVE
• /
• v.8 no.4
• /
• pp.632-642
• /
• 1998

A method based on finite element discretization is developed for optimizing the polarization profile of PVDF film to create the modal transducer for specific modes. Using this concept, one can design the modal transducer in two-dimensional structure having arbitrary geometry and boundary conditions. As a practical means for implementing this polarization profile without repoling the PVDF film the polarization profile is approximated by optimizing electrode patterns, lamination angles, and poling directions of the multi-layered PVDF transducer. This corresponds to the approximation of a continuous function using discrete values. The electrode pattern of each PVDF layer is optimized by deciding the electrode of each finite element to be used or not. Genetic algorithm, suitable for discrete problems, is used as an optimization scheme. For the optimization of each layers lamination angle, the continuous lamination angle is encoded into discrete value using binary 5 bit string. For the experimental demonstration, a modal sensor for first and second modes of cantilevered composite plate is designed using two layers of PVDF films. The actuator is designed based on the criterion of minimizing the system energy in the control modes under a given initial condition. Experimental results show that the signals from residual modes are successfully reduced using the optimized multi-layered PVDF sensor. Using discrete LQG control law, the modal peaks of first and second modes are reduced in the amount of 12 dB and 4 dB, resepctively.