• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.9
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• pp.1710-1718
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• 1994

In this paper, a broadband tunable YIG(Yittrium Iron Garnet) oscillator is designed and fabricated. To design an YTO(YIG Tuned Oscillator), a suitable YIG resonator is selected according to the design oscillation range and its equivalent R, L, C resonant circuit parameters are obtained through the measurement of its resonance characteristic. Using the equivalent circuit, the wideband topology which suppresses the parasitic oscillation is selected and implemented. The designed circuit is simulated by HBT(Harmoic Balance Technique) using EEsof's jOMEGA. The YTO thus fabricated has the wide oscillation range from 1.4 GHz to 4 GHz, and its linearity is 0.5% in the oscillation range. The phase noise is below 105dBc at 100kHz offset.

• Journal of Korean Academy of Nursing
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• v.21 no.3
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• pp.295-306
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• 1991

Han-Thought is a philosophy unique to the native to Korean culture. From the point view of etymological analysis the word “Han” means “Large”, “High” means “Whole” Ancient Korean people planted their philosophical roots deep in what has come to be known an Han-Thought. The goal of this study was to explore “Han-Thought” for concepts and principles which may contribute to the building of a Korean nursing philosophy, ethic, paradigm, theory and eventully practice. Ontologlly, our ancient people attempted to learn what was most essential and meaningful in life Han-Thought embraces the thought of complete harmony with in wholeness. Han encompasses everything in the universe. A chracteristic of Han-Thought is that all things relate to each other in harmonic balance, not in conflict. The harmonious balance of all things excludes both disruption and confrontation, making all things into a large oneness. Thus Han-Thought applied to Holism traditionally embraced by nursing philosophy. The principles of Han-Thought emphasize the love of peace. Extreme individualism and egoism are not allowed in Han-Thought. Thus Han-Thought provide a humanistic and ethical foundation for nursing philosophy. Han-Thought is a valuable philosophy for Korean nurse to explore toward the development of the discipline in Korea.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.376-378
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• 1996

This paper presents a new PFC control method which replaces a fast line current measurement with a filtered load current measurement. Using the power balance relation between the input and the output of the boost converter. the input current can be described as the function of load current. Thus the PWM signal which effects the switching control of the boost converter is generated using the PFC input voltage, the PFC output voltage and the load current as input variables. By using a filter between the bridge rectifier and a dc-to-dc converter, the input voltage of the dc-to-dc converter is forced to always maintain above zero volt. Then the input current traces a sinewave in phase. The proposed scheme accomplishes a very high power factor and a low harmonic distortion of the line current. The validity of this scheme is demonstrated through simulation.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2005.11a
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• pp.87-90
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• 2005

High-efficiency switched-mode circuits such as the class-E amplifier are well-known in the MHz frequency range. The class-E amplifier is a type of switching mode amplifier offering very high efficiency approaching 100%. In this paper of the class-E amplifier by using pHEMT device, the design has been done theoretically and experimentally, with simulation by using the harmonic balance method using circuit simulator. The amplifier using microstrip circuit and the pHEMT demonstrate 66% power-added- efficiency (PAE) at 2.4GHz with 17.6dBm of output power.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.853-861
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• 2007

To understand the concept of dynamic motion in two degree nonlinear coupled system, free vibration not including damping and excitation is investigated with the concept of nonlinear normal mode. Stability analysis of a coupled system is conducted, and the theoretical analysis performed for the bifurcation phenomenon in the system. Bifurcation point is estimated using harmonic balance method. When the bifurcation occurs, the saddle point is always found on Poincare's map. Nonlinear phenomenon result in amplitude modulation near the saddle point and the internal resonance in the system making continuous interchange of energy. If the bifurcation in the normal mode is local, the motion remains stable for a long time even when the total energy is increased in the system. On the other hand, if the bifurcation is global, the motion in the normal mode disappears into the chaos range as the range becomes gradually large.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1995.11a
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• pp.85-88
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• 1995

In this report the large-signal RF performance of GaN MESFETs at different operating temperatures is investigated using a harmonic balance modeling technique. The predicted device performance calculated by the large-si anal model of a GaN FET is shown to be in good agreement with experimen tar data. It is demonstrated that the optimal RF performance of a GaN MESFET amplifier is achieved by balancing the input impedence for a optimized de sign. A GaN MESFET with the optimized design is predicted to produce maximum RF output power of about 4W/mm and 1W/mm at room temperature and 773 K, respectively. The device produces a peak Power-Added Efficiency (PAE) of 52% and 32% at the two temperatures.

• Smart Structures and Systems
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• v.13 no.1
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• pp.25-39
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• 2014

The axisymmetric dynamic instability of polar orthotropic sandwich annular plate combined with electrorheological (ER) fluid core layer and constraining layer are studied in this paper. And, the ER core layer and constraining layer are used to improve the stability of the annular plate system. The boundaries of instability regions for the polar orthotropic sandwich annular plate system are obtained by discrete layer annular finite element and the harmonic balance method. The rheological property of an electrorheological material, such as viscosity, plasticity, and elasticity can be controlled by applying different electric field strength. Thus, the damping characteristics of the sandwich system are more effective when the electric field is applied on the sandwich structure. Additionally, variations of the instability regions for the polar orthotropic sandwich annular plate with different applying electric field strength, thickness of ER layer and some designed parameters are investigated and discussed in this study.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.289-294
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• 2001

Three kinds of viscoelastic damper model, which has a non-linear spring as an element is studied analytically and numerically. The behavior of the damper model shows non-linear hysteresis curves which is qualitatively similar to those of real viscoelastic materials. The motion is governed by a non-linear constitutive equation and an additional equation of motion. Harmonic balance method is applied to get analytic solutions of the system. The frequency-response curves show that multiple solutions co-exist and that the jump phenomena can occur. In addition, it is shown that separate solution branch exists and that it can merge with the primary response curve. Saddle-node bifurcation sets explain the occurrences of such non-linear phenomena.

• Structural Engineering and Mechanics
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• v.6 no.8
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• pp.939-953
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• 1998

Vibration, buckling and dynamic stability of a cantilever rectangular plate subjected to an in-plane sinusoidally varying load applied along the free end are analyzed. The thin plate small deflection theory is used. The Rayleigh-Ritz method is employed to solve vibration and buckling of the plate. The dynamic stability problem is solved by using the Hamilton principle to drive time variables. The resulting time variables are solved by the harmonic balance method. Buckling properties and natural frequencies of the plate are shown at first. Unstable regions are presented for various loading conditions. Simple parametric resonances and combination resonances with sum type are obtained for various loading conditions, static load and damping.

• Smart Structures and Systems
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• v.8 no.5
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• pp.487-499
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• 2011

The parametric resonance problems of axisymmetric sandwich annular plate with an electrorheological (ER) fluid core and constraining layer are investigated. The annular plate is covered an electrorheological fluid core layer and a constraining layer to improve the stability of the system. The discrete layer annular finite element and the harmonic balance method are adopted to calculate the boundary of instability regions for the sandwich annular plate system. Besides, the rheological property of an electrorheological material, such as viscosity, plasticity, and elasticity can be changed when applying an electric field. When the electric field is applied on the sandwich structure, the damping of the sandwich system is more effective. Thus, variations of the instability regions for the sandwich annular plate with different applying electric fields, thickness of ER layer, and some designed parameters are presented and discussed in this study. The ER fluid core is found to have a significant effect on the location of the boundaries of the instability regions.