• Smart Structures and Systems
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• v.25 no.6
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• pp.719-732
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• 2020

Real-time hybrid simulation (RTHS) which combines physical experiment with numerical simulation is an advanced method to investigate dynamic responses of structures subjected to earthquake excitation. The desired displacement computed from the numerical substructure is applied to the experimental substructure by a servo-hydraulic actuator in real time. However, the magnitude decay and phase delay resulted from the dynamics of the servo-hydraulic system affect the accuracy and stability of a RTHS. In this study, a robust stability analysis procedure for a general single-degree-of-freedom structure is proposed which considers the uncertainty of servo-hydraulic system dynamics. For discussion purposes, the experimental substructure is a portion of the entire structure in terms of a ratio of stiffness, mass, and damping, respectively. The dynamics of the servo-hydraulic system is represented by a multiplicative uncertainty model which is based on a nominal system and a weight function. The nominal system can be obtained by conducting system identification prior to the RTHS. A first-order weight function formulation is proposed which needs to cover the worst possible uncertainty envelope over the frequency range of interest. Then, the Nyquist plot of the perturbed system is adopted to determine the robust stability margin of the RTHS. In addition, three common delay compensation methods are applied to the RTHS loop to investigate the effect of delay compensation on the robust stability. Numerical simulation and experimental validation results indicate that the proposed procedure is able to obtain a robust stability margin in terms of mass, damping, and stiffness ratio which provides a simple and conservative approach to assess the stability of a RTHS before it is conducted.

• Journal of Service Research and Studies
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• v.6 no.2
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• pp.99-116
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• 2016

The purpose of this paper is to see what the problem is and what the direction of the strategy of asset management after this study has analyzed asset management status of domestic life insurance companies according to interest rate trends, analyzing in time series management asset lists, asset distribution state, and securities list of life insurance companies during 2000~2014. It has carried correlation analysis and regression analysis between yield and bond interest KOSPI index. As the study result, life insurance companies have managed assets in stability than profitability. The correlation coefficient between interest rate and performance rates of total asset, management asset and securities is highly plus, correlation of management asset performance rate is higher than that of total asset performance rate, and the correlation of securities performance rate is higher than that of management asset performance rate. The correlation coefficient of KOSPI and performance rate shows minus. The suggestion is that the change of asset management is required as the interest decline rises up a reverse margin risk because of the asset management of stability.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.9
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• pp.64-72
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• 2012

The interest in wind power generation area such as developing and operating wind-diesel pilot complex in remote and island regions that have difficulty in having power plant and connecting to power system is growing rapidly in the world. We have installed and researched the hybrid system in Sekgok Pilot Complex to meet the new generation system. From the monitored data of the system, the performance of each diesel power plant is outstanding. However, step out problem was detected with respect to load sharing and synchronization with decentralized power supply. An advanced controller design having better response time and stability is needed to solve such problem. In this paper, we proposed the algorithm, through digital controller of Governor, which is applied to hybrid system. As a result, we obtained the stable frequency value in variable loading conditions. Also, we proved the advanced response time and stability through the simulation and experiment by applying additional current signal to the control algorithm.

• IEIE Transactions on Smart Processing and Computing
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• v.2 no.3
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• pp.148-159
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• 2013

An analysis of the throughput and stability region of random access systems is currently of interest in research and industry. This study evaluated the performance of a multiuser random access channel with a retransmission gain. The channel was composed of a media access control (MAC) determined by the transmission probabilities and a multiuser communication channel characterized by the packet reception probabilities as functions of the number of packet transmissions and the collision status. The analysis began with an illustrative two-user channel, and was extended to a general multiuser channel. For the two-user channel, a sufficient condition was derived, under which the maximum throughput was achieved with a control-free MAC. For the channel with retransmission gain, the maximum steady throughput was obtained in a closed form. The condition under which the random access channel can acquire retransmission gain was also obtained. The stability region of the general random access channel was derived. These results include those of the well-known orthogonal channel, collision channel and slotted Aloha channel with packet reception as a special instance. The analytical and numerical results showed that exploiting the retransmission gain can increase the throughput significantly and expand the stability region of the random access channel. The analytical results predicted the performance in the simulations quite well.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1244-1250
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• 2008

The site of interest is a residence redevelopment area which has excavation construction with cut-off walls. The site is located over Dong-Mang-Bong tunnel and Seoul No. 6 subway tunnel. This study analyzed numerically the influence of vibrations from No. 6 subway tunnel to the basement of the redeveloped apartment away from the distance about 11m. Kyoung-bu highspeed railway's time history model with linearly reduced maximum acceleration is applied to take into the subway maximum speed of 75km/h. The maximum velocity of vibration for the cross section of the interest was estimated as 0.28cm/sec which satisfied the allowable standard of 0.5cm/sec for apartment and residence of Seoul.

• Journal of Aerospace System Engineering
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• v.15 no.6
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• pp.33-41
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• 2021

As interest in drones controlled by remote technology rapidly increases worldwide, drones are used in many fields such as military, rescue, and transportation as future innovations in many countries. In particular, as the drone has been spotlighted as a new future strategic industry, it is also used for public purposes such as disaster relief and crime investigation. However, security concerns such as the penetration of major national facilities, collisions with aircraft, and the possibility of privacy infringement due to aerial photography are also being raised. Unlike the increased interest in drones, there have been few studies on drone use, drone safety, and public attitudes toward drone use. This paper analyzed the perceptions of drone attitudes, drone stability and policy support for drones for Korean and United Kingdom.

• Journal of Environmental Science International
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• v.30 no.9
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• pp.741-752
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• 2021

Gardens are known to provide relaxation, including psychological stability and mental rest. Recently, social interest in gardens has been growing in various ways, including the increase of groups sensitive to environmental pollution and a rising interest in the overall management of natural resources. In reality, however, the owners of housing gardens lack fundamental knowledge for creating and maintaining the gardens, directly and indirectly. This limitation presents a number of problems and challenges. Therefore, this study conducted an analysis of various aspects relating to the creation and maintenance of housing gardens, reflecting the sense of ownership. The study aimed to examine the current status, and based on this, it was intended to present improvement measures for practical and efficient creation of housing gardens and their maintenance in the future.

• Asia Marketing Journal
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• v.12 no.3
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• pp.43-62
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• 2010

The notion of customer orientation is now importantly considered in the context of banking industries. Despite customer-oriented organizational cultures, there are few studies addressing the relationship between customer orientation and its outcomes. In particular, this study aims at testing the effect of customer orientation as a key marketing effort designed by a bank. This is because interest rate sensitivity is critical for evaluating banking services after raising the base rate. In so doing, first, this study investigates the relationships among customer orientation, interest rate sensitivity, and customer loyalty. Second, this paper examines how the moderating effects of both deposit interest and loan interest rates influence the linkages of customer orientation-interest rate sensitivity and customer orientation-customer loyalty. To test the proposed model, research data are collected from 304 subjects who use banking services(e.g., Shin-Han, Kookmin, the First Bank, Hana, and Woori banks). Each construct was measured by published items and the psychometric properties of the three constructs, excluding two constructs of the moderators, were evaluated by employing the method of confirmatory factor analysis via the use of AMOS. The model fit was also evaluated using the CFI, TLI, and RMSEA fit indices that are recommended based on their relative stability and insensitivity to sample size. The findings show that the relationship between customer orientation and customer loyalty is significant, whereas the relationships between customer orientation and interest rate sensitivity and between interest rate sensitivity and customer loyalty are not supported. Although customer orientation is highly evaluated, customers' interest rate sensitivity that results in the comparison of interest rates plays an important role in reducing the effect of customer orientation. As a consequence, interest rate sensitivity does not influence customer loyalty. First of all, one of interesting results in this study is that the moderating effect of loan interest rate is quite different from deposit interest rate. In the case of deposit interest rate, the linkages both customer orientation-interest rate sensitivity and customer orientation-customer loyalty are insignificant. In the case of loan interest rate, however, the two proposed linkages are supported. As our proposed relationships are still in its infancy in the context of banking industry, our study contributes to enhance scholars' knowledge of bank services and provides insights for practitioners when their marketing strategies, particularly both deposit and interest rates, have to be established. Finally, this research also illuminates the need for further research that considers the influence of customer orientation on consumer's decision-making and bank profits. More specifically, the results are encouraging and will lead us to further investigate this key outcome of the banking deposit/interest rates.

• Tunnel and Underground Space
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• v.3 no.1
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• pp.96-107
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• 1993

This paper deals with the analysis of rock slope stability using the distinct element method. This method consists in analysis of the interaction of discrete block assemblage delimited by elementary joints, which permits to consider the heterogeneous, anisotropic and discontinuous features of the rock mass. In particular, we were able to show that this method, and especially the BRIG3D software, is an outstanding tool which gives informations of greatest interest in order to analyze the toppling mechanisms. We have confirmed the fundamental role of the rock mass structure with different simulations. In the case of toppling phenomena, the essential parameter is the dip of major discontinuities. It has an influence on the intensity and volume of deformations. The anisotropic and heterogeneous features of the rock mass play also an important role. It is proved by insertion of thick rock bars in the structure or varying rock block sizes in the mass. These models modified considerably the stress distribution and the deformation distribution. Finally, we have analyzed the influence of mechanical parameters such as friction angle and tangential stiffness.

• Journal of the Korean Society of Safety
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• v.7 no.4
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• pp.101-104
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• 1992

It is shown that for a characteristic equation of continuous linear system, stability can be determined by conditions srggested in this paper. And also It Is of interest to Know how much coefficients of the low-order characteristic equation(N$\leq$5) can be perturbed while simutanously preserving the stable condition of the equation. This result is analogous to result by Anderson et al. based on the Kharitonov's conditions and Hermite - Biehler theorem.