• 동력기계공학회지
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• 제13권6호
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• pp.57-62
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• 2009

Unsteady flows in a semi-induction system was investigated to verify their characteristics. A semi-induction system was designed and made to verify the Sow characteristics in an intake system. To attain an intact wave of an intake pulse, a single semi-intake system was adopted as a test rig. The system consists of an intake pipe and a rotary valve as a pulse generator, and a variable volume Helmholtz resonator. The variable volume Helmholtz resonator was mounted in the intake pipe to enhance a breathing capacity and engine performance. The phase and amplitude of the pulsating flow in an unsteady flow system were found to affect the charging capacity significantly. The behavior of pressure wave, their phase and amplitude were investigated in various regions. Some of the results obtained from experiments were described.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 C
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• pp.1533-1535
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• 2000

The design and fabrication technologies of pulse power reversely switched-on dynistor have been developed 1200V/120kA pulse power reversely switched-on dynistor device have been designed by analytically and numerically using commercial modeling S/W The important characteristics of reversely switched-on dynistors are breakover voltage $V_{BO}$, commutative peak voltage before steady state $V_m$, on-state voltage in steady state $V_o$, turn-off time $t_q$, dV/dt capability.

• 한국표면공학회지
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• 제43권3호
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• pp.154-158
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• 2010

Numerical analysis is done to investigate the effects of pulse bias on the plasma processing characteristics like ion doping and ion nitriding by using fluid dynamic code with a 2D axi-symmetric model. For 10 mTorr of Ar plasma, -1 kV of pulse bias was simulated. Maximum sheath thickness was around 20 mm based on the electric potential profile. The peak electron temperature was about 20 eV, but did not affect the averaged plasma characteristics of the whole chamber. Maximum ion current density incident on the substrate was 200 $A/m^2$ at the center, but was decreased down to 1/10th at radius 100 mm, giving poor radial uniformity.

• Archives of Pharmacal Research
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• 제23권3호
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• pp.197-201
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• 2000

In an aqueous piperacillin sodium solution, a well-defined single wave or single peak was observed by direct current(DC) polarography or differential pulse polarography(DPP). The peak potential change per pH unit was -54 mV in the phosphate buffer at $18^{\circ}C$, which indicated that protons were involved in the electrochemical reduction of the 2,3-dioxopiperazine moiety of piperacillin sodium with a $H^{+}e^{-}$ ratio of one. Using a phosphate buffer of pH 4.3, the $1.0{times}10^{-7}$ M piperacillin sodium single peak could be determined by DPP with relative standard deviation of 1.6 %(n=3). Piperacillin sodium could be analyzed with-out interference from penicillin G-potassium, which enabled the employment of DPP as a fast and simple technique for monitoring the synthetic process of the antibiotic.

• Progress in Superconductivity
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• 제3권1호
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• pp.17-22
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• 2001

Practical implementation of the SFQ technology in most application requires more than single-chip-level circuit complexity. Multiple chips have to be integrated with a technology that is reliable at cryogenic temperatures and supports an inter-chip data transmission speed of tens of GHz. In this work, we have studied two basic issues in building large RSFQ circuits. The first is the reliable inter-chip SFQ pulse transfer technique using Multi-Chip-Module (MCM) technology. By noting that the energy contained in an SFQ pulse is less than an attojoule, it is not very surprising that the direct transmission of a single SFQ pulse through MCM solder bump connectors can be difficult and an innovative technique is needed. The second is the recycling of the bias currents. Since RSFQ circuits are dc current biased the large RSFQ circuits need serial biasing to reduce the total amount of current input to the circuit.

• Nuclear Engineering and Technology
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• 제51권3호
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• pp.776-783
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• 2019

Laser welding is usually a more effective method than electron-beam one since a vacuum chamber is not required. It is important for joining Zr-1%Nb (E110) alloy in a manufacturing process of nuclear fuel rods. In the present work, effect of energy parameters of pulsed laser welding on properties of butt joints of sheets with a thickness of 0.5 mm is investigated. The most efficient combination has been found (8-11 J pulse energy, 10-14 ms pulse duration, 780-810 W peak pulse power, 3 Hz pulse frequency, 1.12 mm/s welding speed). The results show that ultimate strength under static loading can not be used as a quality criterion for zirconium alloys welds. Increased shielding gas flow rate does not allow to protect weld metal totally and contributes to defect formation without using special nozzles. Several types of imperfections of the welds have been found, but the major problem is branching microcracks on the surface of the welds. It is difficult to identify the cause of their appearance without additional research on improving the welding zone protection (gas composition and flow rate as well as nozzle configuration) and studying the hydrogen content in the welds.

• 한국위성정보통신학회논문지
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• 제9권3호
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• pp.1-4
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• 2014

무선통신 시스템은 동일채널 또는 인접채널에서 동작하는 무선 송신기에 의해서 간섭을 받는다. 때문에 새로운 서비스를 도입할 경우에는 도입하는 시스템과 기존 시스템 상호 간에 미치는 간섭분석을 통해서 서로 공존할 수 있는 기술기준을 마련해야 한다. FTS(Flight Termination System)는 공공의 안전을 보장하고 발사체의 비정상적인 임무수행을 막기 위해서 사용된다. 최근에는 보안성을 높이고 여러 발사체나 비행체에서 동시에 운용할 수 있는 차세대 FTS에 대한 연구가 진행 중이며, EFTS(Enhanced FTS)는 이러한 목적에 적합하다. 본 논문에서는 간섭신호가 EFTS의 성능에 미치는 영향을 분석하였다. EFTS의 변조방식으로는 비동기 DPSK(Differential PSK)와 비동기 CPFSK(Continuous Phase FSK)를 고려하였고, 간섭원으로는 FMCW(Frequency Modulated Continuous Wave) 신호와 펄스레이더를 고려하였다. 간섭원의 전력은 FMCW의 경우 원신호보다 20.3dB가 작고, 펄스레이더의 경우에는 원신호보다 19.1dB가 작은 것으로 설정하고 간섭 영향을 시뮬레이션하였으며, 시뮬레이션 결과 FMCW 간섭의 경우 $E_b/N_o$가 1dB 정도 악화되었고, 펄스레이더 간섭 신호의 경우 $E_b/N_o$가 약 0.5dB 악화되었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 A
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• pp.514-517
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• 1996

Zero current switching(ZCS) series resonant converter is used to control laser power density in a pulsed Nd:YAG laser power supply. The high power and high repetition rate paused Nd:YAG laser is designed and fabricated to control current pulse width and pulse repetition rate in the double elliptical laser oscillator. In order to find out operational characteristics of pulsed Nd:YAG laser, the electrical properties of driving power supply and laser output power are investigated and experimented by changing of the current pulse width from 200uS to 350uS(step 50uS) and pulse repetition rate range of 500pps(pulse per second) to 1150pps. From that result, we obtaind maximum efficiency of 1.83% and maximum laser output or 220W at the condition of 350 uS and 1150pps with one Nd:YAG rod), and obtained that of more than 400W with two laser head connecting series.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2006년도 하계종합학술대회
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• pp.149-150
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• 2006

In this paper, design, simulation, fabrication method, and measured results of a digital frequency discriminator(DFD) operating in E, F, and G band are introduced. We describe the direct conversion scheme(DCS) with microwave integrated-circuit(MIC) developed for the small-area and high-speed system. When the input signal is the pulse with a pulse width of 100 ns, accuracy of frequencies measured by the DFD has 1.335 MHz RMS at no noise and 2.64 MHz RMS at signal-to-noise(S/N) ratio within 3 dB in E, F, and G band, which nearly satisfy the specification of 2.5 MHz RMS.

• Transactions on Electrical and Electronic Materials
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• 제16권6호
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• pp.308-311
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• 2015

V₂O₅/Mn₃O₄/Nb₂O₅ codoped zinc oxide varistor ceramics were sintered at a temperature range as low as 875~950℃. The voltage clamping characteristics of V₂O₅/Mn₃O₄/Nb₂O₅ codoped zinc oxide varistor ceramics were investigated at a pulse current range of 1~50 A. The sintering temperature had a significant effect on clamp voltage ratio, which exhibits surge protection capabilities. The varistor ceramics sintered at 875℃ exhibited the best clamping characteristics, in which the clamp voltage ratio was 2.69 at a pulse current of 50 A. The varistor ceramics sintered at 900℃ exhibited the highest electrical stability, where = 3,824 V/cm (initial 3,909 V/cm), and E_{1 mA/cm²} = 27 (initial 39) after application of a pulse current of 100 A.