• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.753-756
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• 1992

The piezoelectric ceramics of PMS-PZT was made in the radial mode disk. As the results, in the application of filter required conditions: that is, higher-values for piezoelectric properties($K_p$, $Q_m$) and lower-values for stabilities of $F_{\tau}$(temp. coefficient, aging rate), 5PMS-51PT-44PZ composition statified well. This composition was made in the dot-ring type. Asthe results, with increasing $n^2$ both $Q_m$ and S had high values, decreasing $n^2$ both $K_p$ and BW had low values when the diameter of sintered bodies were constant. Therefore, curve of filter characteristic have sharped with increasing $n^2$ and BW broadened with decreasing $n^2$.

• Journal of Biosystems Engineering
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• v.11 no.1
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• pp.8-16
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• 1986

This study was carried out to develop a microcomputer-based data acquisition system for engine performance test. A low-cost data acquisition system was developed utilizing an "APPLE II PLUS" microcomputer. The developed system consists of microcomputer, RPM counter included frequency-to-voltage converter, preamplifier for two load cells and 8-bit analog-to-digital converter with 16 chnnels. The system simultaneously measures engine speed by means of photointerrupter, torque and fuel consumption by means of load cells with variable sample numbers, sampling intervals and repetitions. The system collects, processes and provides data for storing on the $4{\frac{1}{4}}$ inch floppy disk as well as for writing out on the printer.

• Bulletin of the Korean Space Science Society
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• 2008.10a
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• pp.32.2-32.2
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• 2008

A major solar radio burst can disturb many kinds of radio instruments, including cellular phone, GPS, and radar. Korea Astronomy and Space Science Institute (KASI) is developing Korean Solar Radio Burst Locator (KSRBL) in collaboration with New Jersey Institute of Technology. KSRBL is a single dish radio spectrograph, which records the spectra of microwave (0.5 - 18 GHz) bursts with 1 MHz spectral resolution and 1 s time cadence, and locates their positions on the solar disk within 2 arcmin. Hardware manufacturing is almost completed including 4-channel digitizer/FPGA. The system is currently installed at Owens Valley Radio Observatory (OVRO), and test of the operation is in progress. It will be installed at KASI in 2009. We report current status and test results of KSRBL.

• Proceedings of the Korea Multimedia Society Conference
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• 2012.05a
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• pp.238-241
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• 2012

모든 기록매체의 장기보존성과 신뢰성은 보존에 있어 중요한 요소 중 하나이다. DVD 광기록매체 또한 신뢰성을 평가하기 위한 다양한 국제표준 및 연구가 진행되었다. 국가기록원은 각급 기관에서 생산되어 이관된 다양한 종류의 DVD 광매체를 보존하고 있으며, 이에 대한 상태평가를 위해 선행된 표준 및 연구 내용을 바탕으로 이관된 광매체에 대한 상태를 측정을 하였다. 본 연구에서는 이관된 DVD 매체에 대한 평가 기준을 8개의 연속된 ECC블럭의 PI 에러값을 사용하였다. 측정된 PI 에러 값은 생산년도, 제조회사, 에러 발생 위치로 분류하였으며 시간에 따른 열화 정도, 기록 품질 그리고 에러 발생 위치에 따른 매체 상태와의 연관성을 연구하였다.

• Electrical & Electronic Materials
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• v.11 no.10
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• pp.72-77
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• 1998

The effects of Al micro-bumps on the magnetic properties of CoCr(Pt)Ta/Cr films deposited on glass substrates were investigated. The coercivity increased and the coercivity squareness decreased by incorporating Cr/Al underlayers. The cause of the coercivity increase is attributed to the reduction of Co(0002) texture, the increase of magnetic isolation of CoCr(Pt)/Ta grains, and the refinement of CoCr(Pt)/Ta grains deposited on Cr/Al underlayers. The effects of an Al overlayer on the magnetic properties of CoCr(Pt)Ta/Cr films were also studied. The decrease of coercivity squareness is ascribed to the magnetic isolation of CoCr(Pt)Ta grains.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.223-224
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• 2006

This paper present a new disk-type piezoelectric transformer. The input side of the transformer has a crescent-shaped electrode and the output side has a focused poling direction. This transformer has multi-layered structure. The piezoelectric transformers operated m each transformer's resonance vibration mode. The electrodes and poling directions on commercialy available piezoelectric ceramic disks were designed so that the planar or shear mode coupling factor ($k_p,\;k_{15}$) becomes effective rather than the transverse mode coupling factor ($k_{31}$). The Resonance frequency is 65.22[kHz] and maximum voltage step-up ratio is 149. Multi-layered transformer has better efficiency and step-up ratio than the single-layered transformer.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.4
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• pp.462-466
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• 2010

A new buffer cache management scheme that aims at reducing power consumption in mixed HDD and NAND flash memory storage systems is presented. The proposed scheme reduces power consumption by considering different energy-consumption rate of storage devices, I/O operation type (read or write), and reference potential of cached blocks in terms of both recency and frequency. Simulation shows that the proposed scheme reduces power consumption by 18.0% on average and up to 58.9%.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.10a
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• pp.21-24
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• 2000

Ultra-fine grains were produced in pure Al using an Accumulative Rolling-Bonding (ARB) process. After several cycles of the ARB process, pure Al sheets were filled with the ultra-fine grains whose diameters were several hundred nano-meters. With ARB cycles, the nature of grain boundaries of the ultra-fine grains changed from diffusive sub-boundaries to well-defined high angle boundaries. After 7 cycles, ultra-fine polycrystals with large misorientations between neighboring grains were obtained. Sliding wear tests using a pin-on-disk type wear tester were co ducted on the ultra-fine grained pure Al. Wear rates of pure Al increased with the increase of ARB cycle numbers in spite of the increase in hardness. Worn surfaces and cross-sections were examined with optical microscopy (OM) and scanning electron microscopy (SEM) In investigate the wear mechanism of the ultra-fine grained pure Al.

• Publications of The Korean Astronomical Society
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• v.13 no.1 s.14
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• pp.123-128
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• 1998

The Blandford-Znajek process, which extracts the rotational energy of the supermassive black hole at the center of an active galactic nucleus, is now well explained and educated through the electronic circuit analysis established by Macdonald and Thorne. The Macdonald-Thorne circuits consist of the batteries and resistances of the central black hole and the astrophysical region around the accretion disk. In this letter we will consider the possibility whether we can connect coils and condensers in such circuits or not. If possible, that may explain a sudden corona-phenomenon in an active galactic nucleus. We conclude that a flash of order $\~5\times10^{40}\;ergs\;s^{-1}$ can occur around a $\~10^9M_\bigodot$ black hole through this process.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.2
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• pp.67.2-67.2
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• 2016

The Sun has diverse variations in solar atmosphere's layers due to solar activity. This solar variations can be recognized easily by sunspots which appear on the solar photosphere. Thus the sunspot on the photosphere is utilized by direct index of the solar activity. The other variation of the photosphere is center-to-limb variation (CLV). In this study, we analyze the relative intensity observed by SOHO, SDO. The data of photospheric intensity are from full disk images of SOHO/MDI intensity ($6768{\AA}$, from May 1994 to March 2011) and of SDO/HMI intensity ($6173-6174{\AA}$, from May 2010 to June 2016). As the result, we found the latitudinal variation of the intensity. The daily photospheric intensity showed the solar cyclic variation with sunspot number. It has a little difference of phase with sunspot number.