• Journal of Power Electronics
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• v.15 no.1
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• pp.78-85
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• 2015

This paper presents a new structure of single-stage flyback power factor correction (PFC) converter with a controllable coupled negative magnetic feedback (NMF) winding. NMF winding is used to reduce the bulk capacitor voltage at high line voltages and light loads. However, it would cause line current distortion at zero crossing condition. In the proposed circuit, a series winding is used with NMF inductor to eliminate the NMF inductor at low line voltages. As a result, the dead angle of the input current, near zero voltage crossing, is eliminated and the power factor is increased. The presented experimental results of the proposed PFC converter confirm the integrity of the new idea and the theoretical analysis.

• Proceedings of the KIEE Conference
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• 2003.07d
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• pp.2690-2692
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• 2003

Amplifier linearity plays a major role in the design of mordern communication systems. An independently controllable AM/AM and AM/PM predistortion linearizers that consists of two bias feed resistance linearizers is proposed. This linearizer allows independent adjustment of the AM/AM and AM/PM curves by using two adjustable voltages to compensate the power amplifier non-linearities. The predistortion linearizer can improve the ACPR by SdB with cdma2000 multi carrier signals. By applying this linearizer to two-tone 880MHz power amplifier, an improvement of adjacent channel leakage power up to 5dBm has been achieved.

• Journal of Power Electronics
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• v.15 no.4
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• pp.876-885
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• 2015

High frequency alternating current (HFAC) has been widely used in a wide range of power distribution systems (PDS) due to its superior performance. A high frequency AC/DC converter plays the role of converting HFAC voltage to DC voltage. In this paper, a new LCL-T resonant AC/DC converter has been proposed, and an easier control method based on input voltage comparison is presented, without the complicated calculation of the zero-crossing point. Both a low distortion and near-to-unity power factor can be achieved by the proposed resonant converter and control strategy. The operational principle and steady-state analysis are given for the proposed resonant converter. A simulation model and experimental prototype are implemented with an operation frequency of 25kHz and a rated power of 20W. The simulation and experimental results verify the accuracy of the analysis and the excellent performance of the proposed topology.

• Proceedings of the KIEE Conference
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• 2002.11a
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• pp.153-155
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• 2002

Trench sate CB-BRT:TC-BRT의 최대 제어 가능 전류(Maximum Controllable Current)에 영향을 미치는 설계 변수들을 조사하였다. 최대 제어 가능 전류를 결정하는 중요 설계 변수들로 트렌치 깊이, 핑거 게이트 길이, 메인 게이트 길이, 트렌치 밀도를 고려하였다. TC-BRT의 실험적 결과를 기존의 BRT와 CB-BRT의 결과와 비교하였다. 최대 제어 가능 전류는 트렌치 깊이와 트렌치 밀도가 증가하고 메인 게이트 길이가 감소할수록 증가하였으며 핑거 게이트 길이에 대해서는 큰 영향을 받지 않았다. 핑거 게이트가 있는 TC-BRT가 없는 것에 비해 최대 제어 가능 전류가 약 15% 높게 나타났다. 트렌치 밀도가 작을 때는 핑거 게이트에 의한 영향이 두드러지고 트렌치 밀도가 높아질수록 트렌치 게이트의 역할이 증가하였다.

• Macromolecular Research
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• v.16 no.6
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• pp.544-548
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• 2008

An HPLC column with a self-contained temperature control device was constructed for preparative temperature programmed interaction chromatography. Two Peltier plates were attached to a large bore column ($120{\times}22\;mm$ i.d.) and the column temperature was controlled by PID mode feed back control. At a flow rate of 1.5 mL/min, the column temperature could be increased and decreased at a rate as high as $50^{\circ}C/min$ and $10^{\circ}C/min$, respectively, which is much faster than using a column jacket and bath/circulator. The rapid heating and cooling rates allows a high repetition rate of chromatographic fractionation. The performance of the temperature controllable column was demonstrated successfully by the fractionation of homo-polymer precursors from diblock copolymers.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.256-261
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• 2000

Electro-Rheological(ER) fluid is applied to a controllable squeeze film damper(SFD) for stabilizing a flexible rotor system. ER fluid is a class of functional fluid whose yield stress varies according to the applied electric field strength, which is observed as viscosity variation of the fluid. In applying ER fluid to a SFD, a pair of rings of the damper can be used as electrodes. When the electrodes are divided into a horizontal pair and a vertical one, the SFD can produce damping force in each direction independently. A prototype of the directionally controllable SFD was constructed and its performance was experimentally and numerically investigated in the present work.

• Smart Structures and Systems
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• v.24 no.1
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• pp.37-52
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• 2019

Despite its success and wide application, base isolation system has been challenged for its passive nature, i.e., incapable of working with versatile external loadings. This is particularly exaggerated during near-source earthquakes and earthquakes with dominate low-frequency components. To address this issue, many efforts have been explored, including active base isolation system and hybrid base isolation system (with added controllable damping). Active base isolation system requires extra energy input which is not economical and the power supply may not be available during earthquakes. Although with tunable energy dissipation ability, hybrid base isolation systems are not able to alter its fundamental natural frequency to cope with varying external loadings. This paper reports an overview of new adventure with aim to develop adaptive base isolation system with controllable stiffness (thus adaptive natural frequency). With assistance of the feedback control system and the use of smart material technology, the proposed smart base isolation system is able to realize real-time decoupling of external loading and hence provides effective seismic protection against different types of earthquakes.

• Journal of Information Processing Systems
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• v.20 no.1
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• pp.24-37
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• 2024

To address the requirement for high-speed encryption of large amounts of data, this study improves the widely adopted cipher block chaining (CBC) mode and proposes a controllable parallel cipher block chaining (CPCBC) block cipher mode of operation. The mode consists of two phases: extension and parallel encryption. In the extension phase, the degree of parallelism n is determined as needed. In the parallel encryption phase, n cipher blocks generated in the expansion phase are used as the initialization vectors to open n parallel encryption chains for parallel encryption. The security analysis demonstrates that CPCBC mode can enhance the resistance to byte-flipping attacks and padding oracle attacks if parallelism n is kept secret. Security has been improved when compared to the traditional CBC mode. Performance analysis reveals that this scheme has an almost linear acceleration ratio in the case of encrypting a large amount of data. Compared with the conventional CBC mode, the encryption speed is significantly faster.

• Proceedings of the Materials Research Society of Korea Conference
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• 2007.11a
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• pp.141.1-141.1
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• 2007

• Proceedings of the Materials Research Society of Korea Conference
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• 2001.11a
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• pp.53-53
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• 2001