• 전기학회논문지P
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• 제58권4호
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• pp.609-614
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• 2009

A fuel-cell power system among various alternative power sources has many advantages such as comparatively independable circumstances, high-efficient, and heat-recyclable, thus it is now able to be up to hundreds MWh-scaled through improving feasibility and longevity of it. During the last few decades, numerous research results has been investigated to expand interest in fuel-cell technology. This study presents pressure distribution on the geometrical manifold structures, which are U-type and Z-type, of a planar-type fuel-cell stack by simulated with computational fluid dynamics(CFD). Then, electrical performance of a 200W fuel-cell stack, which is U-type, was diagnosed after pre-conditioning operation. The stack has electrical characteristics ; 22V, 10A, 220W, and current density $200mA/cm^2$.

• Steel and Composite Structures
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• 제5권4호
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• pp.327-343
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• 2005

The European Standards Organisation (CEN) has planned to develop a complete set of harmonized European building standards. The Eurocodes, being the design standards, form part of this total system of European standards, together with standards for fabrication and erection and product standards. After a period of experimental use of the ENV(European Pre Standard)-versions of the Eurocodes, these are now converted into official EN's (European Standards). Design of composite steel and concrete buildings and bridges is covered by Eurocode 4. An overview will be given of the historic development of Eurocode 4, the structure and contents of the EN version and the present status and planning for completion. The Eurocode treatment of some selected technical items will be presented in more detail.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2001년도 학술대회 논문집
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• pp.89-91
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• 2001

For the development of a small-sized superconducting magnetic energy storage (SMES) system we designed, fabricated and tested the model coil consisting five coils with different features, e.g. winding tensions, bore diameters and materials, cooling channels. The results show that even in the highly pre-stressed small coil A, about 70 % of the coils critical current are degraded The quench current of the coils A, B and E with narrow cooling channels is two times as high as that of the coil C without them though they are similar except spacers. The test results also indicate that the usual training effect depends on the winding tensions of the coils but the quench characteristic does not change according to materials of a bobbin.

• International Journal of Precision Engineering and Manufacturing
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• 제1권2호
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• pp.61-66
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• 2000

In this paper, we discuss the machining characteristics of HDD glass. Glass is now being used globally as a data storage device, Such glasses are usually machined by lapping by this technique requires a long machining time, resulting in low productivity, For this reason, we examine the possibility of EILD grinding in HDD glass workpieces, A move to ELID grinding may result in substantial cost reduction. Our purpose is to investigate the grinding characteristics of HDD glass in ELID grinding. The bonding materials for fixing the abrasives of cast iron, cobalt and bronze are applied, and grinding conditions such as rotation speed and feeding are varied. Results show that with the use of ELID, mirror surfaces can be achieved with high efficiency.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1992년도 추계학술대회 논문집
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• pp.81-83
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• 1992

The superconducting thin films deposited on $SiO_x$ substrate by R.F magnetron sputter using $YBa_2Cu_3O_x$ single target have been made and annealed at $940^{\circ}C$ for 30 min. The thickness of films were 1000-2000${\AA}$ with a rate of 20-25${\AA}/min$ and superconducting properties of thin films depended on the compositions of pre-annealed the thin films. It has been analyzed by SEM photo-analysis and X-ray diffraction patterns of these samples obtained under the various conditions of this sputtering methods. and recognized the supperconducting thin films by electric properties.

• Progress in Superconductivity
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• 제3권2호
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• pp.247-251
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• 2002

In general, the bubbling, generated during the fabrication of the tapes, breaks the superconducting filament, and critical current of the tapes will be decreased. Heat-treatment schemes of Bi-2223/Ag HTS tapes were modified, such as pre-annealing of multi-stacked billet, 2-step main sintering and ramp rate etc. The generation of bubbling was drastically decreased from 20 bubbles/m to 0 ~ 1 bubble/m by the modified heat-treatment. Therefore, the value of critical current of the tapes without bubbling was increased almost twice higher than that of already existing tapes. Critical current up to 42 A in 40 m length Bi-22231Ag tapes have been measured at 77K, self-field, 1$mutextrm{V}$/cm criterion. It could be confirmed that elimination of bubbling is effective to maintain the superconducting property along the tape length.

• 한국세라믹학회지
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• 제40권10호
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• pp.981-984
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• 2003

본 논문에서는 고정민 위치제어가 가능한 선형초음과 모터를 설계 및 제작하였다. 제안된 선형 초음파 모터의 발파장 진동자에 진계(Usinwt, Ucoswt)를 인가했을때 진동법의 불출부에서 발생하는 타원궤직은 이동자를 구동시킨다. 제작된 선형 초음파 모터의 면위궤적은 시뮬레이션 결과와 일치했으며, 압차력이 50 N일 때 이동자에서 발생하는 최대 힘은 9 N, 최대속도는 0.9 ㎧이고 20 N일 때 최대 힘은 2.4 N, 최대 속도는 0.38 ㎧의 특성을 나타냈다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1996년도 추계학술대회 논문집
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• pp.353-356
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• 1996

Ultra-high-speed analog and digital ICs (integrated circuits) fur 10Gbit/sec optical communication systems have been designed, fabricated and analyzed in this research. These circuits, which are laser diode (LD) driver, pre-amplifier, automatic gain controlled (AGC) amplifier, limiting amplifier and decision circuit, have been implemented with AIGaAs/GaAs heterojunction bipolar transistors (HBTs). The optimized AIGaAs/GaAs HBTs for the 10Gbps circuits in this work showed the cutoff and maximum oscillation frequencies of 65㎓ and 53㎓, respectively. It is demonstrated in this paper that the 10Gbps optical communication system can be realized with the ICs designed and fabricated using AlGaAs/GaAs HBTs.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 E
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• pp.2038-2040
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• 1999

In this study, the design, the fabrication and the evaluation of Rogowski coil are presented for the measurement of the high current pulse (the order of 100kA, $\sim$100Hz, 0.1msec$\sim$a few msec). And the fabricated Rogowski coil is tested and compared with the pre-proved rogowski coil.

• 설비공학논문집
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• 제22권11호
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• pp.781-787
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• 2010

To improve the efficiency of piping, recently the pre-fabrication piping system has been introduced, and much attention has been paid to TBPs which can replace Tee-joint. Forming and forming analysis on TBPs made from Carbon steel pipes for pressure service(KS D 3562 Sch40) and Stainless steel pipes(KS D 3576 20S) have been conducted to determine working pressure. Forming and forming analysis objects are $32A{\times}25A$, $40A{\times}25A$, $40A{\times}32A$, $50A{\times}25A$, $50A{\times}32A$, $50A{\times}40A$ TBPs.