• 한국가시화정보학회지
• /
• 제11권3호
• /
• pp.12-16
• /
• 2013

The impact and spreading behaviors of silicon dioxide nanoparticle colloidal suspension droplets were quantitatively visualized using a high-speed imaging system. Millimeter-scale droplets were generated by a syringe pump and a needle. Droplets of different velocity were impacted on a non-porous solid surface. Images were consecutively recorded using a CMOS high-speed camera at 5000 fps (frames per second) for millimeter-scale droplets. Temporal variations of droplet diameter, velocity and maximum spreading diameters were evaluated from the sequential images captured for each experimental condition. Effects of Reynolds number, Weber number, and particle concentration were investigated experimentally.

• 한국기계가공학회지
• /
• 제11권2호
• /
• pp.112-117
• /
• 2012

This paper presents a new stopper mechanism for precision stage by using the Piezoelectric element actuator. The new stage including a new stopper mechanism has the precision positioning mechanism that was been developed for generation displacements with nanometer accuracy and a millimeter dynamic range simulataneouly. The stage is composed not of the mechanical two stopper but of only one Piezoelectric element actuator. The characteristics for the new stage and the stopper have been evaluated experimentally. As the results, we can know that the linearity error characteristics of stage is 30nm in the $20{\mu}m$ measurement range. In addition, the experimental results are confirmed the possibility of the movement in millimeter range.

• Journal of Electrical Engineering and Technology
• /
• 제5권3호
• /
• pp.497-502
• /
• 2010

In this paper, the O-mode ultrashort-pulse reflectometry (USPR) millimeter-wave signals that propagate into the plasma and cover a frequency bandwidth of 33-158 GHz are examined numerically using MATLAB. Two important processes are involved in the computation: the propagation of the USPR impulse signal through a waveguide and the frequency up-conversion using millimeter-wave mixers. These mixers are limited to intermediate frequency signals that are less than 500 mV; thus, it is necessary to disperse the impulse signal into a chirped waveform using the waveguide. The stationary phase method is utilized to derive a closed-form formula for a chirped waveform under the assumption that the USPR impulse is Gaussian. In the process of frequency up-conversion, the chirped waveform is mixed with the mixer LO signal, and the lower frequency components of the RF signal are removed using high pass filters.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
• /
• pp.135-138
• /
• 2003

The circular cavity resonator which can measure the dielectric properties of dielectrics in the V-band($50GHz{\sim}75GHz$) frequency range was designed and fabricated. Exciting and detecting of the resonator is peformed by WR15 rectangular waveguides using Bethe's small hole coupling. The GaAs plate sample was used for the verification of the performance of the fabricated circular cavity resonator. In the measurement of GaAs single crystal using that resonator, the resonant frequency of the dominant $TE_{011}$ mode, the permittivity and $Q{\times}f_0$ were measured as 53.29GHz, 12.87 and 138,000, respectively.

• 한국정밀공학회지
• /
• 제13권6호
• /
• pp.128-135
• /
• 1996

This paper proposes a high precision measurement technique to obtain the height of gage block with a few millimeter height. The proposed technique is consisted of two steps : In the first step, laser position transducer and electric micrometer are adopted to obtain a coarse value of the height of gage block, and then, in the second step, heterodyne laser interferometry is adopted to acquire the precision value. A new kind of phase detector is constructed in the low cost for the heterodyne interferometer and its linearity with ${\pm}1%$ is confirmed by experiment. Also measurement error factors due to enviroments are discussed and methodology to reduce such errors is proposed. Preliminary experiments are carried out for the gage blocks of as high as a few millimeter.

• 대한기계학회논문집A
• /
• 제31권5호
• /
• pp.617-624
• /
• 2007

This paper presents a novel quadstable monolithic mechanism (QsMM) which provides four stable equilibrium positions within its operation range. The quadstable mechanism has been realized from the use of both X- and Y-directional bistable structures which use curved snapping beams. A millimeter-scale brass mechanism was fabricated by ultra-precision milling to test the quadstability and the displacement-load behavior, and the prototype clearly demonstrated four distinct stable positions in its millimeter-scale planar operation. We discuss the design concept, finite element simulation for static and transient responses, fabrication by ultra-precision milling, and experimental measurement of the proposed quadstable mechanism.

• 수산해양기술연구
• /
• 제33권3호
• /
• pp.248-258
• /
• 1997

The analytical solutions of the Fraunhofer Diffraction(FD) theory and the principle for measurement of the dispersion relation of plasma wave is presented. Especially, the method for measurement of low-frequency wave is discussed. The wavenumbers of the density fluctuations are obtained from the curve fitting between the expremental FD profile and theoretical one for each frequency component. In measurement of the wavenumber of the low -frequency region, the information of the wavenumber is easily obtained from the ratio of the intensity at = 0 to the intensity at =0.5. The millimeter wave FD apparatus was designed to measure low-frequency density fluctuations. The determined wavenumbers are in the range of =0.1~ 1.0cm. Thus, the millimeter wave FD method was shown to be useful for the measurement of low-frequency density fluctuations, which are impossible to be measured by using a convention. Thomson scattering. The obtained dispersion relations will be useful information for plasma waves.

• 한국전자파학회논문지
• /
• 제11권2호
• /
• pp.151-157
• /
• 2000

ITR-R의 강우에 의한 교차편파 모델은 35GHz까지만 적용 가능하다. 본 논문에서는 실제의 강우환경에서 충분한 정확도를 가지는 교차편파에 대한 단순한 이론 모델을 제안하였다. 이를 측정치 및 ITU-R모델과 비교함으로써 밀리미터파대역까지 적용할 수 있는 교차편파 추정모델을 도출하였다.

• 한국전자파학회논문지
• /
• 제14권12호
• /
• pp.1264-1268
• /
• 2003

본 논문에서는 밀리미터파 대역에서 NRD guide를 이용한 듀플렉서를 설계하였다. 설계된 듀플렉서는 두개의 stepped-impedance 필터와 한 개의 T-Junction으로 구성되어 있다. 차단영역 도파관 등가회로를 이용하여 stepped-impedance 필터를 설계하였고, T-Junction은 반사손실을 -20 dB 이하로 최적화하였다. 듀플렉서를 제작하여 측정한 결과 응답특성이 시뮬레이션 결과와 일치함을 확인하였다.

• Current Optics and Photonics
• /
• 제2권4호
• /
• pp.308-314
• /
• 2018

Visible light communication (VLC) is considered a strong future candidate for indoor wireless communication. However, its performance seems to be relatively unsatisfactory when compared to wireless local area network (WLAN) communication using millimeter waves. To improve the performance of VLC, numerous technologies have been proposed so far, in both electrical and optical domains. Among the proposals, optical beamforming (OB) is an optical-domain technology that can concentrate light in a specific direction or on a target spot. It can significantly improve VLC performance and can be widely used, because it does not depend on electrical modulation schemes. Therefore, this review discusses the concept, principle, and types of OB, the structure of a VLC system using OB, performance results of OB, and the combination of OB with electrical signal modulation in VLC. OB is expected to be one of the key techniques in future VLC implementations, similar to radio-frequency beamforming in millimeter-wave communication.