• Structural Engineering and Mechanics
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• v.51 no.4
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• pp.643-650
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• 2014

A chaotic vibration isolation system is designed according to the chaotic vibration theory in this paper. The strong nonlinearity is generated by the system. Line spectra in the radiated noise maybe easily detected caused by marine vessels. It is Important to reduce the line spectra by improving the acoustic stealth of marine vessels. A multi-degree-freedom (MDF) nonlinear vibration isolation system (NVIS) system is setup by the experiment and finite element method. The model is established with finite element method. The results show that the behavior of the device gradually varies from period bifurcation into chaotic state and the line spectrum is changed from single spectral structure into broadband spectral structure. It is concluded that chaotic vibration isolation is preferable contrasted on line spectra isolation.

• Journal of Power Electronics
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• v.15 no.6
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• pp.1559-1566
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• 2015

The brushless DC motor (BLDCM) has many advantages. As a result, it is widely used in electric vehicle (EV) drive systems. To improve the reliability of the motor control system, a position sensorless control strategy based on a sliding mode observer (SMO) is proposed. The global fast terminal sliding mode observer (GFTSMO) is proposed to enhance the control performance of the SMO control system. The advantages of the linear sliding mode and the nonsingular terminal sliding mode (NTSM) are combined in the control strategy. The convergence speed of the system state is enhanced. The motor commutation point is obtained with the observation of the back EMF, and the instantaneous torque value of the motor is calculated. Therefore, the position sensorless control of the BLDCM is realized. Experimental results show that the proposed control strategy can improve the convergence speed, dynamic characteristics and robustness of the system.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.1000-1001
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• 2006

In this paper, an DC/DC converter system has been proposed, which is suitable for fuel cell based power generation systems. The proposed converter system has outstanding advantages over the conventional dc-dc converters with respect to high efficiency and high power density. The developed converter system has been experimentally tested with using DSP PWM controller so that the performance of the proposed converter could be effectively examined and the validity of the converter could be verified.

• International Journal of Aeronautical and Space Sciences
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• v.18 no.3
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• pp.522-534
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• 2017

According to the characteristics of salvo attack for the multiple flight vehicles (MFV), the design of cooperative guidance law can be converted into the consensus problem of multi-vehicle system through the concept of multi-agent cooperative control. The flight vehicles can be divided into leader and followers depending on different functions, and the flight conditions of leader are independent of the ones of followers. The consensus problem of leader-follower multi-vehicle system is researched by graph theory, and the consensus protocol is also presented. Meanwhile, the finite time guidance law is designed for the flight vehicles via the finite time control method, and the system stability is also analyzed. Whereby, the guidance law can guarantee the line of sight (LOS) angular rates converge to zero in finite time, and hence the cooperative attack of the MFV can be realized. The effectiveness of the designed cooperative guidance method is validated through the simulation with a stationary target and a moving target, respectively.

• Journal of the Korean Society of Radiology
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• v.6 no.6
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• pp.489-493
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• 2012

Positron Annihilation Lifetime Spectroscopy is a non-destructive technique to study voids and defects in solids by the measurement of gammas from electron-positron annihilation. In this study, we measured the lifetime of CR, EPDM, NBR, all of which are widely used polymer in various fields. A conventional fast-fast coincidence system in KAERI(Korea Atomic Energy Research Institute) has been used to measure the lifetime spectra, Three lifetime components were analyzed from each lifetime spectra. According to Tao-Eldrup model equation, the size and fraction of free-volume were calculated. Mean radius and free volume fraction of CR, EPDM NBR are $0.1217nm^3$(1.9103%), $0.14780nm^3$(5.3147%), $0.1216nm^3$(2.6381%), respectively. Through these measurements, we identified the feasibility of the PAL system for polymer analysis.

• Korean System Dynamics Review
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• v.13 no.1
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• pp.5-40
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• 2012

This study focus on oriental way for Win-win leadership of modern time using systems thinking approach. We constructed concept, 'Modesty Leadership' from oriental bible- Tao Te Ching, Change Ching, the Analects of Confucius. This work described in the paper based on case collected from 2011 Seoul city mayor election in the Korea. There are three initial aims : to confirm what feedback loop affected approval rating, to determine how these feedback interacted and to establish the significance of cognitive mapping. The use of system thinking to model cognitive mapping of political election untraditional approach in study of oriental bible. This approach is valuable in that it can be to understand management strategies and their effect on decision making.

• 한국경영정보학회:학술대회논문집
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• 2007.06a
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• pp.646-651
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• 2007

Secure digital payment is critical in the successful shaping of global digital business. Digital payments are increasingly being used as a substitute to traditional payments, contributing markedly to the efficiency of the economy. The focus of every digital business transaction is to minimize risks arising from transactions. It is essential to ensure the security of digital payment whether used in internal networks or over wireless Internet. This paper analyses secure digital payment methods from the viewpoint of systemic security and transaction security. According to comparative analysis of digital payment models, this paper proposes a comparative analysis framework to investigate and evaluate secure digital payment. In conclusion, the comparative analysis framework, comparison of digital payment models and mobile payment models proposes a useful academic and practical foundation to enhance the understanding of secure digital payment methods. It also provides academic background and practical guidelines for the development of secure digital payment systems.

• Journal of Korea Multimedia Society
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• v.9 no.12
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• pp.1628-1635
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• 2006

A new frequency-modulated m-sequence correlation technique was described. It has. been seen that the frequency modulation scheme leads to higher signal-to-noise ratio than direct sequencing and less hardware effort than PSK modulation scheme. The operating frequency of the correlation system was deduced. The optimal frequency for the frequency-modulated m-sequence correlation system should be 1.35 times of the center frequency of the transducer. The application of this correlation technique to electromagnetic ultrasonic system was computer-simulated.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.11
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• pp.3837-3859
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• 2014

Vehicular Ad hoc Networks (VANET) becomes more popular in industry, academia and government. However, Typical VANET is challenged by high speed mobility and insufficient spectrum resources over congested scenarios. To address those serious problems, some articles have introduced Cognitive Radio (CR) technology into VANET and formed CR-VANET. In this article, we propose an overview of CR-VANET by exploring different architectures and features. Moreover, we provide taxonomy of state-of-the-art papers in this emerging field and the key articles are well analyzed respectively. In addition, we illustrate both research and application frameworks of CR-VANET based on our works, and propose some open research issues for inspiring future work.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.52.4-52
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• 2001

In this paper we propose a framework of an open architectured manufacturing system base on CORBA middleware. The manufacturing system consists of four configurable software modules 9mchine control module, database module, monitoring module, and operation module). Each module is distributed through the network and integrated with CORBA middleware technology. CORBA Characteristics including independence from programming languages, computing platforms and networking protocols makes us to easily develop new applications and to effectively integrate new module into existing distributed systems. The CORBA program used in this study is The ACE ORB (TAO) developed by the laboratory in Washington University.