• ETRI Journal
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• 제20권1호
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• pp.46-54
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• 1998

An analysis method of electromagnetic scattering from periodic patch array of double-dipole elements on a grounded dielectric substrate in case of oblique incident and arbitrary polarization is considered. The basis functions are chosen to be entire consinusoidal functions are chosen to be entire consinusoidal functions covering the rectangular shaped domain in which the original dipoles are inscribed, unlike the conventional method in which basis functions are defined only for the conducting element region. To confirm the validity of the proposed analysis method, we calculate the normalized scattered power for two propagating modes and compare the results with those obtained by the previous numerical method for the double dipole elements of rectangular type and parallelogram type which have the property of frequency scanned reflection and polarizer. Good correspondence has been observed between them. Some numerical results such as variation of power and axial ratio of first-order diffracted wave by a periodic array of double-dipole elements are compared with previous results.

• Journal of the Optical Society of Korea
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• 제17권3호
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• pp.242-248
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• 2013

Full color holographic optical element fabrication using a photopolymer is proposed for a waveguide-type head mounted display. The fabricated full color holographic optical elements can be attached to the waveguide to replace the conventional couple-in and couple-out optics in the head mounted display. To implement the system, this study analyzed the optical characteristics of the photopolymer using three lasers (red, green and blue). Considering the color uniformity, a new laminated structure for a full color holographic optical element was also designed. The proposed system was confirmed experimentally.

• 제어로봇시스템학회논문지
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• 제4권6호
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• pp.747-752
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• 1998

Ultrasonic sensors have been widely used to recognize the working environment for a mobile robot. However, their intrinsic problems, such as specular reflection, wide beam angle, and slow propagation velocity, require an excessive number of sensors to be integrated for achieving the sensing goal. This paper proposes a new measurement scheme which uses only two sets of ultrasonic sensors to determine the location and the type of a target surface. By measuring the time difference between the returned signals from the target surface, which are generated by two transmitters with 1 ㎳ difference, it classifies the type and determines the size of the target surface. Since the proposed sensor system uses only two sets of ultrasonic sensors to recognize and localize the target surface, it significantly simplifies the sensing system and reduces the signal processing time so that the working environment can be recognized in real time.

• 한국공작기계학회논문집
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• 제11권3호
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• pp.33-38
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• 2002

This paper deals with pressure ripple attenuation far separated-type Hydrostatic Transmission (HST) consisting ova variable axial piston pump connected in an open loop to a fried displacement axial piston motor. Pressure ripples in HST is major source of vibration which can lead to fatigue failure of components and cause noise. In order to reduce the pressure ripple, an annular tube tripe hydraulic filter is proposed to attenuate pressure ripples with the high frequencies components to achieve better noise reduction in HST. The basic principle of a hydraulic filter is allied to propagation of pressure wave, reflection, absorption in cross section of discontinuity and resonance in the hydraulic pipeline. It is experimentally shown that the hydraulic filter attenuates about 30∼40dB of pressure ripple with high frequencies. These results will assist in modeling and design of noise reduction in hydraulic control systems, and provide a means of designing a quieter HST.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 1992년도 정기총회 및 추계학술발표회
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• pp.2-29
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• 1992

According to the increase of occupation density of microwave frequency band on use microwave environments have been congested extensively. For shielding unnecessary electromagnetic wave of preventing the electromagnetic wave reflection a good conductor a low resistive material or a lossy material is mainly used. As a method to measure the absorbing characteristics of microwave absorber the fundamental microwave measuring method can be used. There is however a big problem in measuring errors since the wavelength of microwave is very short especially as in the case as microwave absorber for RADAR. Therefore this research aimed to a converting adaptor of 20mm${\Phi}$ coaxial tube from a Type-N connector to 20mm${\Phi}$ coaxial tube and to use it for designing microwave absorber and evaluating absorbing characteristics. Furthermore the measurements of absorbing characteristics and material constants have performed and reviewed which were carried out by using the coaxial tube in the short type and by using rectangular waveguide respectively As a result the validity of the measured values have been confirmed.

• 한국소음진동공학회논문집
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• 제15권9호
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• pp.1060-1069
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• 2005

Silencers are engineering devices that are designed to attenuate sound waves propagating in a flowing medium. The muffler type silencer has a series of chambers in parallel or series utilizing the reflection and expansion characteristics of the expansion chambers, sidetubes, branch resonators, and tailpipes to attenuate the sound. To Improve the performance of industrial blower silencer of muffler type which is employed in petrochemical plant, this paper seeks its optimal arrangement of buffs by experimental method and suggests optimal arrangement of buffs. Experimental results show that the optimal one suggested can reduce the noise level as much as 14 dB (or 18 dB(A)) in the laboratory and as much as 4 dB(A) compared to that of the existing silencer on the ground.

• 한국염색가공학회지
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• 제23권2호
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• pp.83-89
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• 2011

Poly(vinyl alcohol) (PVA), PVA/Montmorillonite (MMT), PVA/Silver (Ag), and PVA/MMT/Ag nanocomposite nanowebs were prepared by electrospinning technique in aqueous solution. In order to investigate the effect of inorganic materials on the morphology and thermal properties of PVA based nanocomposite nanowebs, experiments were performed with 5 wt.% of MMT and Ag. Field emission type scanning electron microscopy, transmission electron microscopy (TEM), reflection type X-ray diffraction (XRD), and thermal gravimetric analyzer were utilized to characterize nanocomposite nanowebs. TEM and XRD results show MMT and Ag were well dispersed in PVA nanowebs. Those inorganic nanoparticles enhanced thermal property of the nanocomposite nanowebs.

• 센서학회지
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• 제14권3호
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• pp.169-179
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• 2005

A multiplexed bend loss type single-mode fiber-optic sensor system was prepared to measure the displacement of several cm of the civil engineering structures such as many bridges, tunnels and various buildings. This bend loss type fiber-optic sensor used the signal difference between two reflection signals due to various bend losses generating at a pair of optical connectors by using OTDR (optical time domain reflectometer) for measuring displacements. And the experiments were conducted for showing the measurement feasibility on the range of 10 cm, and the multiplexing experiments were also performed to measure the displacements of 5 measuring positions of an object by setting these 5 fiber-optic sensors on a single mode fiber simultaneously.

• 세라미스트
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• 제22권4호
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• pp.429-451
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• 2019

Quartz glass is a key material for making semiconductor process components because of its purity, low thermal expansion, high UV transmittance and relatively low cost. Domestic quartz glass has a market worth about 500 billion won in 2018, and the market power of Japanese materials is very high. Quartz glass for semiconductor process can be divided into general process and exposure. For general process, molten quartz glass is mainly used, but synthetic quartz glass with higher purity is preferred. Synthetic quartz glass is used as the photomask for the exposure process. Recently, as semiconductors started the sub-nm process, the transition from the transmission type using ArF ultraviolet (194 nm) to the reflection type using EUV ultraviolet (13.5 nm) began. Therefore, the characteristics required for the synthetic quartz glass substrates used so far are also rapidly changing. This article summarizes the current technical trends of quartz glass and recent technical issues. Lastly, the present situation and development possibility of quartz glass technology in Korea were diagnosed.

• 한국전기전자재료학회논문지
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• 제28권1호
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• pp.21-27
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• 2015

We propose a fabrication process of a 3-electrode type reflective display and ascertain the realized color panel. The first design is proceeded with basis on Ti electrode for fast panel fabrication, easy align process, and high reflection of a white image. To observe the particle movement at the lower electrodes and optimize the space between electrodes, we design the second patterns, from which we establish a fabrication process with the mixing of electronic ink, loading of this ink, electronic ink assembly, driving, and packaging. After aging process, we ascertain a normally driving panel with black, white, and blue color.