• 한국전산유체공학회:학술대회논문집
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• 2008.10a
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• pp.14-17
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• 2008

Recently, several advanced flow visualization techniques such as Particle Image Velocimetry (PIV) including stereo PIV, holographic PIV, and dynamic PIV have been developed. These advanced techniques have strong potential as the experimental technology which can be used for verifying numerical simulation. In addition, there would be indispensable in solving complicated thermo-fluid flow problems not only in the industrial fields such as automotive, space, electronics, aero- and hydro-dynamics, steel, and information engineering, but also in the basic research fields of medical science, bio-medical engineering, environmental and energy engineering etc. Especially, NT (Nano Technology) and BT (Bio Technology) strongly demand these advanced measurement techniques, because it is difficult for conventional methods to observe most complicated nano- and bio-fluidic phenomena. In this paper, the basic principle of these advanced visualization techniques and their practical applications which cannot be resolved by conventional methods, such as flow in automotive HVAC system, ship and propeller wake, three-dimensional flow measurement in micro-conduits, and flow around a circulating cylinder will be introduced.

• JSTS:Journal of Semiconductor Technology and Science
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• v.13 no.6
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• pp.589-593
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• 2013

An efficient measurement methodology is proposed to construct the scattering parameters of a multi-port device using a four-port vector network analyzer (VNA) without the external un-terminated ports. By using the four-port VNA, the reflected waves from the un-terminated ports could be minimized. The proposed method significantly enhances the accuracy of the S-parameters with less number of measurements compared to the results of classical renormalization technique which uses two-port VNA. The proposed method is validated from the measured data with the coupled 8-port micro-strip lines.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.187-190
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• 1999

We have developed fabrication processes that form a wide-head T-gate with a 0.2 ${\mu}{\textrm}{m}$ gate length using the combination of thickness of each PMMA layer, line doses and development times for applications in millimeter- and micro-waves monolithic integrated circuits. The three-layer resist structure (PMMA/P(MMA-MAA)/PMMA = 1800 $\AA$/5800 A/1900$\AA$), 4nC/cm and over development were used for fabrication of a wide-head T-gate by the conventional double E-beam exposure technology. The experimented results show that the cross sectional area of T-gate fabricated by the proposed method is easily enlarged without additional processes.

• JSTS:Journal of Semiconductor Technology and Science
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• v.3 no.4
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• pp.194-198
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• 2003

A 16-bit adiabatic low-power Micro-processor core is designed. The processor consists of control block, multi-port register file and ALU. A simplified four-phase clock generator is designed to provide supply clocks for adiabatic processor. All the clock line charge on the capacitive interconnections is recovered to recycle the energy. Adiabatic circuits are designed based on ECRL(efficient charge recovery logic) and $0.35\mu\textrm$ CMOS technology is used. Simulation results show that the power consumption of the adiabatic Microprocessor core is reduced by a factor of 2.9~3.1 compared to that of conventional CMOS Microprocessor

• ETRI Journal
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• v.20 no.2
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• pp.241-249
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• 1998

The structure and electrical characteristics of metal-ferroelectric-semiconductor FET(MFSFET) for a single transistor memory are presented. The MFSFET was comprised of polysilicon islands as source/drain electrodes and $BaMgF_4$ film as a gate dielectric. The polysilicon source and drain were built-up prior to the formation of the ferroelectric film to suppress a degradation of the film due to high thermal cycles. From the MFS capacitor, the remnant polarization and coercive field were measured to be about $0.6{\mu}C/cm^2$ and 100 kV/cm, respectively. The fabricated MFSFETs also showed good hysteretic I-V curves, while the current levels disperse probably due to film cracking or bad adhesion between the film and the Al electrode.

• Current Optics and Photonics
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• v.1 no.6
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• pp.567-572
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• 2017

A novel slotted-core hexagonal photonic crystal fiber (PCF) for terahertz (THz) wave guiding is proposed in this paper. A trade-off managed between effective material loss (EML) and birefringence for efficient guidance of THz waves is illustrated in this article. The rectangular slot shaped air-holes break the symmetry of the porous-core which offers ultra-high birefringence of $8.8{\times}10^{-2}$. The proposed structure offers low bending loss of $1.07{\times}10^{-34}cm^{-1}$ and extremely low effective material loss (EML) of $0.035cm^{-1}$ at an operating frequency of 1.0 THz. In addition other guiding properties such as power fraction, dispersion and confinement loss are also discussed. The proposed THz waveguide can be effectively used for convenient transmission of THz waves.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.3
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• pp.115-121
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• 2001

In micro automation technology, the concurrent realization of a high resolution and a large operating rage has been achieved by a dual actuator, usually called by piggy-back system, conventionally. But, because of its manufacturing cost, the complexity of control, and the limit of overall bandwidth, the contract-free and single servo actuators have been suggested with specific applications. In this paper, we suggest a novel non-contact surface actuator suing combination of the Lorentz force and the magnetized force, and discuss the actuating principles including an analytical approach. Differently from the existing planar system, an operating range of the suggested system can be expanded by an additional attachment of active elements. Therefore, it is estimated to be suitable for the next-generation moving system.

• Proceedings of the IEEK Conference
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• 2002.06e
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• pp.59-62
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• 2002

BLDC motor is widely used in automation areas for its good maintenance and controllability. In this paper it is designed for a speed control servo system of sinusoidal typo BLDC motor that can be easily adapted to automation systems with lower cost. Also, control parameters & periods are made adjustable according to the sensors of the motor, electric and mechanical time constant, and PI and PD control are used. The processor for the proposed system is a low cost 16bit One-Chip microprocessor. By experimental results from application to the industrial sewing machine, one of the application of BLDC motor, it can be verified that under the given reference, the system is enough as a speed and position servo without overshoots.

• Proceedings of the IEEK Conference
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• 2003.11b
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• pp.45-48
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• 2003

We can easily buy network system for high performance micro-processor, progress computer architecture is caused of high bandwidth and low delay time. Coupling PC-based commodity technology with distributed computing methodologies provides an important advance in the development of single-user dedicated systems. Lately Network is joined PC or workstation by computers of high performance and low cost. Than it make intensive that Cluster system is resembled supercomputer. Unix, Linux, BSD, NT(Windows series) can use Cluster system OS(operating system). I'm chosen linux gain low cost, high performance and open technical documentation. This paper is benchmark performance of Beowulf clustering by UltraSPARC-1K(64bit-RISC processor). Benchmark tools use MPI(Message Passing Interface) and NetPIPE. Beowulf is a class of experimental parallel workstations developed to evaluate and characterize the design space of this new operating point in price-performance.

• JSTS:Journal of Semiconductor Technology and Science
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• v.6 no.4
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• pp.275-280
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• 2006

We propose Doherty power amplifier structure which can be integrated in Silicon RF ICs. Doherty power amplifiers are widely used in RF transmitters, because of their high Power Added Efficiency (PAE) and good linearity. In this paper, it is proposed that a method to replace the quarter wavelength coupler with IQ up-conversion mixers to achieve 90 degree phase shift, which allows on-chip Doherty amplifier. This idea is implemented and manufactured in CMOS 5 GHz band direct-conversion RF transmitter. We measured a 3dB improvement output RF power and linearity.