• Journal of the Semiconductor & Display Technology
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• v.10 no.2
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• pp.115-119
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• 2011

A tip-type carbon nanotube(CNT)-based field emitter was studied to consider it as electron source for micro-focused x-ray tube. The CNT was grown directly on a metal (tungsten) substrate by using an inductively coupled plasma-chemical vapor deposition (ICP-CVD) method. Prior to CNT growth, the metal substrate was etched to have various tip angles from $10^{\circ}$ to $180^{\circ}C$ (flat-type). The morphologies and microstructures of all the grown CNTs were analyzed via field-emission SEM. Furthermore, the effects of substrate tip-angles on the emission properties of CNT-based field emitters were characterized to estimate the maximum current density, the turn-on voltage, and the spatial distribution of electron beams. Prolonged long-term stability testing of the CNT emitters was also performed. All the experiment results obtained from this study indicated why a tip-type CNT emitter, compared with a flat-type CNT emitter, would be more desirable for a micro-focused x-ray system, in terms of the emission current level, the focused beam area, and the emission stability.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.3
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• pp.207-212
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• 2019

A flat-type piezoelectric ceramic ultrasonic transmitter was successfully fabricated for application in acoustic devices with cone-free diaphragms. The transmitter, possessing a center frequency of 40.6 kHz, exhibited a higher displacement characteristic for a multilayer type compared with a single layer type. Surface roughness treatment of an Al elastic diaphragm influenced a slight increase (1.1 dB) in the sound pressure level (SPL) at $10V_{rms}$ due to the enlarged surface area. The fabricated multilayer piezoelectric ceramic ultrasonic transmitter showed increasing SPL with increasing input voltage, with a maximum SPL of approximately 123.6 dB at $10V_{rms}$. This implies a doubly increased SPL density of $3.6dB/mm^3$, superior to that of a commercial open-type transmitter with a cone.

• Journal of the Korean Institute of Navigation
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• v.17 no.3
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• pp.77-83
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• 1993

The goal of this research is to get a measuring system for absorption characteristics over the frequency band with 30MHz to 1, 000MHz concerning the ferrite electromagnetic wave absorbers, for example, grid-type and sintered flat type, etc. It is, however, very difficult to measure the absorption characteristics as in low frequency as in 30 MHz. In this research, therefore, we propose a standing wave method using parallel striplines, fabricate the measuring system, and measure the characteristic of ferrite microwave absorbers using the proposed mea-suring system.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.1880-1883
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• 1997

An Parallax-Barrier type autostereoscopic display system is implemented to overcome the handicap of current glass-typed stereo imaging system which gives operators unnatural feeling and reluctance. This system is composed of image mixing part of two input images, A/D transformation part, scan conversion part to eliminate the rainbow interference phenomenon, and pin-hole type barrier lens. For the fine display the accurate slit width of barrier is calculated in consideration of retina size, and the samsung 10.4" TFT-LCO was used as flat display monitor.itor.

• Journal of KSNVE
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• v.1 no.2
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• pp.107-113
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• 1991

When non-contact type vibration probes are used for the precision measurement of shaft vibration, they can induce the measurement errors due to the shaft curvature since they have been calibrated for the flat plate. In this study the errors due to the shaft radius and the misalignment between the shaft and probe centerlines are analyzed, and an in-situ calibration tool, which can be conveniently used for calibration independent of the shaft curvature and material, is introduced.

• Publications of The Korean Astronomical Society
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• v.16 no.1
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• pp.7-10
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• 2001

In the framework of the C-gauge condition for the perturbed variables and the linear approximation for the anisotropy of the spacetime, we studied the formulae for the Sachs-Wolfe effect in dust filled and perturbed Bianchi type I universe model. The results were compared with those of the flat Friedmann model.

• Proceedings of the KIEE Conference
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• 2009.04b
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• pp.79-81
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• 2009

튜블러 선형 동기발전기는 간단하고 안정적인 구조이며, 구조적으로 수직력이 발생하지 않는다. 본 논문에서는 파력발전에 튜블러 선형 동기발전기를 소개한다. 또한 flat type과 특성비교를 통하여 튜블러 발전기가 파력발전에 적합함을 증명하였다.

• Journal of the Korean earth science society
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• v.22 no.2
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• pp.120-129
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• 2001

A sand shoal (1300 m long and 400 m wide) with an orientation of north-south is formed on the lower tidal flat of Gomso Bay, southwestern coast of Korea. Surface bedforms, sedimentary structures, sedimentation rate, grain size distribution and can-corer sediments have been measured and analysed along the sand shoal proper zone B and its offshore zone A and onshore zone C during the period of 14 months. These three zones can be differentiated based on sedimentological characteristics: A zone - fine sand (3${\varphi}$ mean), linguoid-type ripples, 70 mm/month in sedimentation rate and no bioturbation, B zone - medium sand (2.5${\varphi}$ mean), dunes (4${\sim}$5 m in wavelength), 30 mm/month in sedimentation rate and no bioturbation, and C zone - coarse silt (5${\varphi}$ mean), sinuous-type ripples, 10 mm/month in sedimentation rate and well-developed bioturbation. These characteristics indicate that the zone C represents a relatively low-energy regime environment whereas the zone A corresponds to a relatively high-energy environment. The zone B would play an important role for a barrier to dissipate the approaching wave energy, resulting in maintaining of low-energy conditions in the inner part of Gomso-Bay intertidal flat behind.

• Journal of Conservation Science
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• v.36 no.6
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• pp.440-455
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• 2020

This study aims to examine the material characteristics of bowls and compare the making techniques of flat cup with cover and jar coffin from the Oryang-dong kiln site, Naju. Bowls, the most frequently excavated small pottery have similar material characteristics, including gray surface, fine-grained texture, and small-sized tempers such as quartz and feldspar, regardless of the excavation slopes. However, the firing temperature of the bowls mostly ranges from 950 to 1,100 ℃. It is estimated that the bowls had formalized making techniques, owing to the similar material composition and firing technique regardless of the excavation slope. The flat cups with cover have similar texture and mineral phases, except their poorly sorted inclusions. However, the jar coffins contain not only fine-grained minerals but also medium-grained quartz, feldspar, and biotite, showing a relatively wide range of firing temperatures. According to the geochemical results of pottery by type, it is assumed that chemical compositions are classified into two groups: small pottery(bowl and falt cup with cover) and jar coffins. In conclusion, small potteries such as bowls and flat cups with cover were made by removing the heavy minerals from raw materials, whereas jar coffins were made by adding medium-grained minerals to raw materials to maintain and support their structures, despite the same source materials. In addition, it is presumed that pottery making proceeded by selecting the source materials, preparing according to their use and controlling the firing temperature and environment.

• Bulletin of the Korean Mathematical Society
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• v.52 no.1
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• pp.335-344
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• 2015

We characterize a homogeneous real hypersurface of type (A) or a ruled real hypersurface in a non-flat complex space form, respectively.