Dae-Kyu Choi

The Active Clamp Sepic- Flyback Converter

A high efficiency active clamp sepic-flyback converter is presented. The proposed converter is superposition of sepic converter mode and flyback converter mode. Not only sepic mode output but also flyback mode output can be fully regulated by constant frequency PWM control. Merging sepic and flyback topology can share the transformer, power MOSFET, and active clamp circuit. It has outstanding advantages over the conventional dc-dc converters with respect to high efficiency, high power density, and component utilization. The operation principle of the proposed converter is described and verified by simulation and experimental result

Cost effective location management scheme based on hierarchical mobile IPv6

Recently MIP becomes more important for the macro mobility support in the emergence of the global system such as IMT-2000. However this protocol suffers from many weaknesses on the location management. MIPv4 regional registration is presented for the local registration of MNs. MIPv6 can benefit from the reduced mobility signaling with external networks by employing a local MAP, that is called HMIPv6. The total signaling cost of HMIPv6 is rapidly increased by the number of CNs of an MN when the MN moves around between MAPs. In this paper, we propose a new location management scheme in MIPv6 that reduces the total signaling cost in the location update based on HMIPv6. Here the MN does not send the BU to CNs and HA when it moves around between MAPs. Instead it informs the current location by transferring the modified BU to the previous MAP. According to the results of the performance analysis, we determine the upper bound for the number of forwarding links allowed among adjacent MAPs without the BU information.

Partial dual unicasting based handoff for real-time traffic in MIPv6 networks

Recently QoS guaranteed real-time data support with user mobility in wireless Internet becomes more significant due to drastic increase of network users called netizens. Mobile IP(MIP) supporting user mobility evolves from versions v4 to v6 with comprehensive analysis of mobile users. However, Mobile IPv6 still has the buffering problem and problems occurred by the zigzag effect. In this paper, we propose a new MIPv6 handoff mechanism called partial dual unicasting(PDU) based on QoS supported RSVP signaling protocol. This scheme reduces the handoff failure rate up to about 24% and guarantees the time for the handoff completion. Furthermore, it resolves the ineffectiveness of path usage in dual unicasting(DU).

Plasma etching for the application to low-k dielectrics devices

We present a study of the photoresist (PR) etching and the low-k materials damage using a ferrite-core inductively coupled plasma (ICP) etcher, in order to develop an etching process for the low-k dielectric devices. We reveal that the N2/O2 flow ratio and bias power affected the PR etching rate. By Fourier transform infrared spectroscopy and HF dipping test, we investigated the effect of the gas flow ratio and bias power on the amount of etching damage to the low-k material.

Efficient Handover Scheme with Prior Process for Heterogeneous Networking Environment

Recently real-time and QoS guaranteed services for mobile terminals between two adjacent heterogeneous networks are investigated based on the cellular structure of small cells in the literature. An efficient handoff is a very important factor for those services and it is called inter-system handoff(ISHO). The time required to complete the handoff can vary and depends on the network structure. And also the transmission of additional signals can increase the probability of failure for ISHO. The proposed scheme significantly reduces the ISHO failure rate up to about 16% compared to the existing one. This can be done by alleviating workloads of boundary base stations and distributing them to predetermined neighboring cells. The overhead of the proposed scheme is considered as well.

RF Power Conversional System for Environment-friendly Ferrite Core Inductively Coupled Plasma Generator

This paper is a study about a proper method of plasma generation to cleaning method and a high frequency power equipment circuit to generation of plasma that used cleaning of chamber for TFT-LCD PECVD. The high density plasma required for cleaning causes a possibility of high density plasma more than . It apply a ferrite core of ferromagnetic body to a existing ICP form. In case of power transfer equipment on 400[kHz] high frequency to generation of plasma it makes certain a stable switching operation in condition of plasma through using a inverter form for general purpose HB. And it demonstrates the performance of power transfer equipment using methods of measurement which use a transformer of series combination the density of plasma and the rate of dissolution of in condition of .

Cost Effective Location Management Scheme in MIPv6

Recently MIP becomes more important for the macro mobility support in the emergence of the global system such as IMT-2000. However this Protocol suffers from many weaknesses on the location management. MIPv4 regional registration is presented for the local registration of MNs. MIPv6 can benefit from the reduced mobility signaling with external networks by employing a local MAP, that is called HMIPv6. The total signaling cost of HMIPv6 is rapidly increased by the number of CNs of an MN when the MN moves around between MAPs. In this paper, we propose a new location management scheme in MIPv6 that reduces the total signaling cost in the location update based on HMIPv6 Here the MN does not send the BU to CNs and HA when it moves around between MAPs. Instead it informs the current location by transferring the modified BU to the previous MAP. According to the results of the performance analysis, we determine the upper bound for the number of forwarding links allowed among adjacent MAPs without the BU information.

Performance Improvments of Inter-System Handoff for IMT-2000

For a successful inter-system handoff, several important issues must be handled and additional new features must be considered. This paper focuses on the cellular structure of small cells which are required for the high density of population and a handoff scheme designed between two heterogenous networks. Incase of inter-system handoff (ISHO), the time required to complete the handoff can vary and depends on the structure of networks. And also the transmission of additional signals can increase the probability of failure for ISHO. Here we propose the sub-boundary cell base station (Sub-BBS) to alleviate the role of the BBS. The Sub-BBS is adjacent to BBS in the same regional mobile network. 쪼en the mobile terminal enters Sub-BBS, the network starts finding a new route and after entering BBS, it initiates the transformation process. The proposed scheme significantly reduces the ISHO failure rate compared to the existing one which is the most recent and known as efficient.