• 한국전자파학회논문지
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• 제19권2호
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• pp.174-180
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• 2008

전원을 on/off하는 스위칭 방식을 이용한 펄스 증폭기는 입력 신호를 변조하는 방식에 비해 효율 및 잡음 특성이 우수하며, 입력단에 별도의 펄스 변조기가 필요 없어 회로가 간단하다. 현재 스위칭 방식의 펄스 증폭기는 스위칭 회로의 특성 상 rise 시간에 비해 fall 시간이 길어지는 단점이 있다. 본 논문에서는 fall 시간을 개선한 스위칭 회로를 제안하였다. 펄스 증폭기에 제안한 스위칭 회로를 적용하여 측정한 결과, 펄스 출력이 27 dBm에서 rise/fall 시간이 각각 5.7 ns, 21.9 ns인 결과를 얻었다.

• 대한전자공학회논문지SD
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• 제44권8호
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• pp.22-29
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• 2007

[ $0.18{\mu}m$ ] CMOS공정을 이용하여 supply voltage 1.8V에서 2.5Gb/s 이상의 데이터 처리속도를 가지는 2:1 Multiplexer(MUX) 설계를 하였다. High speed 동작을 위한 주파수의 한계를 극복하기 위해서 4.7 nH의 on-chip micro spiral micro inductor $(20\times20{\mu}m2)$가 설계 되었고, 10개 이상의 inductor를 사용하고도 칩 면적 증가가 거의 없으면서 inductive peaking 효과를 극대화할 수 있었다. 칩 측정은 on-wafer로 진행되었고, micro spiral inductor가 있는 2:1 MUX와 그것이 없는 2:1 MUX 각각 측정하여 그 결과를 비교하였다. 측정결과 micro spiral inductor를 가진 2:1MUX가 rise time과 fall time이 1.25Gb/s에서는 rise time이 23%, fall time은 3%의 peaking 개선 효과가 있는 것을 확인하였다. 2.5Gb/s에서는 fall time이 약 5.3%, rise time 3.5%의 개선 효과를 보았다. 전체 소비전력은 61.2mW, 2.5Gb/s에서 voltage output swing은 $180mV_{p-p}$로 측정되었다.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2006년도 6th International Meeting on Information Display
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• pp.426-429
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• 2006

We investigated the electrooptical properties of a carbon nanotube (CNT)-doped nematic liquid crystal (LC) cell. Experimental results reveal that the doped CNTs influence the elastic constant of LC-CNT dispersion. Using a small amount of CNT dopant, the rise time of the LC cell is nearly invariant; the threshold voltage of the cell increases due to the increase in the elastic constant of LC-CNT dispersion. At a higher CNT concentration, the marked increase in the dielectric anisotropy of LC-CNT dispersion markedly decreases the rise time and threshold voltage of the LC cell. The fall time of this cell decreases with increasing CNT concentration due to the increase in elastic constant and the slight increase in viscosity of LC-CNT dispersion. The rise time and the fall time of the LC cell are decreased simultaneously when the LC host is doped with a moderate amount of CNT dopant.

• 한국정밀공학회지
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• 제19권1호
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• pp.158-164
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• 2002

This paper proposes the optimization of ultrasonic signal recognition in ferrite carbon steel weld zone using neural networks. For these purposes, the ultrasonic signals for defects as porosity, incomplete penetration and slag inclusion in the weld zone are acquired in the type of time series data. And then their applications evaluated feature extraction based on the time-frequency-attractor domain(peak to peak, rise time, rise slope, fall time, fall slope, pulse duration, power spectrum, and bandwidth) and attractor characteristics (fractal dimension and attractor quadrant) etc. The proposed neural networks system in this study can enhances performance of ultrasonic signal recognition.

• 한국철도학회논문집
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• 제6권2호
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• pp.81-86
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• 2003

This study proposes the neural network simulator for the integrity evaluation of weld zone in railway rails. For these purposes, the ultrasonic signals for defects(crack) of weld zone in frames are acquired in the type of time series data and echo strength. The detection of the natural defects in railway truck is performed using the characteristics of echodynamic pattern in ultrasonic signal. And then their applications evaluated feature extraction based on the time-frequency-attractor domain(peak to peak, rise time, rise slope, fall time, fall slope, pulse duration, power spectrum, and bandwidth) and attractor characteristics (fractal dimension and attractor quadrant) etc. The constructed neural network simulator agrees fairly well with the measured results of test block(defect location, beam propagation distance, echo strength, etc). The Proposed neural network simulator in this study can be used for the integrity evaluation of weld zone in railway rails.

• 대한전자공학회논문지
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• 제24권4호
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• pp.701-707
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• 1987

This paper is concerned with an accurate delay time modling of the ED MOS logic gates and its application to the multiple delay logic simulator. The proposed delay model of the ED MOS logic gate takes account of the effects of not only the loading conditions but also the slope of the input waveform. Defining delay as the time spent by the current imbalance of the active inverter to charge and discharge the output load, with respect to physical reference levels, rise and fall model delay times are obtained in an explicit formulation, using optimally weighted imbalance currents at the end points of the voltage transition. A logic simulator which uses multiple rise/fall delays based on the model as decribed in the above has been developed. The new delay model and timing verification method are evaluated with repect to delay accuracy and execution time.

• 대한전자공학회논문지
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• 제22권2호
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• pp.75-81
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• 1985

저전류 범위에서 l2L은 연결되는 소자의 input capacitance, resistance 및 그 소자동작에 필요한 전류들에 의해 출력단의 신호가 손상을 입게 되어 logic기능이 방해를 받게 되며 그로 인한 회로의 불확실성이 증가될 수 있다. 본 논문은 이와같은 외부부하와 연결된 I2L-inverter의 기능에 관한 해석을 다루고 rise time과 fall time의 변화에 관한 simulation 및 실험을 통한 측정결과를 비교 분석하였다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제54권9호
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• pp.427-432
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• 2005

Ion migration characteristics of a rotary spark airgap of high voltage Pulse generator had been investigated. It was considered that the ion migration speed and the ions of the gases(atmosphere gases, $O_2,\;N_2,,\;and\;H_{2}O,\;etc$.) and the charged very fine particles(about $10\~100nm$ size) migrated through the upper stator ball and bottom stator ball of the rotary spark airgap would determined the rise and fall times of the output high voltage pulse. In this paper, a basic study on the ion migration characteristics of the rotary spark airgap between the spark stator ball and the ion-sensing electrode of the proposed high voltage pulse generator have been investigated experimentally. As a result, the three kinds of ion speeds were detected by the ion-sensing electrode installed at the position of the bottom stator ball of the ball type sparkgap high voltage pulse generator. The migration velocities, diameters, masses, charges, numbers of the ions and particles were obtained by experiments and calculations, which, however, would determine the rise and fall times of the output high voltage pulse.

• 한국광물학회지
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• 제9권1호
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• pp.1-6
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• 1996

Woolastonite from Susan occurs as intercalations in limestone beds of Lower Paleozoic Joseon Supergroup. It is a thermal metamorphic product of impure limestone. Electron microprobe analysis shows that it is considerably pure wollastonite. It has triclinic cell with a=7.932$\AA$, b=7.328$\AA$, c=7.069$\AA$, $\alpha$=89.995$^{\circ}$, $\beta$=$95.255^{\circ}$, and $ \Upsilon=103.367^{\circ}$.Dissolution behaviors of wollastonite have been studied conducting three different dissolution experiments; two different reactions with HC1 (one batch and one re-initialization experiment) and one traction with distilled water. In the batch type powder wollastonite-HCl reaction, pH of solution rapidly increases in the early stage and then its rate of increase slows down to reach plateau resulting in parabolic relationship with time. It is represented by the early rapid rise and fall in pH giving a sharp pH-edge and succeeding slow rise in the re-initialization experiment. The early rapid rise in pH is due to the rapid sorption of H- in solution to oxygens on the reactive surface of wollastonite and the fall in pH means that all reactive surface sites are occupied by H- ions and no more H- adsorption occurs. The slow rise in pH following the pH- edge is due to the dissolution of wollastonite as evidenced by the correlation of pH variation and cation concentration. Dissolution of powder wollastonite in HCl shows linear trend with time. Si is dissolved predominantly over Ca at a constant rate. Ca is dissolved predominantly in the very early stage. Dissolution rate of coarse-grained wollastonite fragments in distilled water is parabolic with times howing a rapid reaction in the early stage and a slow reaction in the advanced stage. The Ca/Si ratio in solution is high in the case of coarse-grained wollastonite fragment as compared with powder wollastonite. The coarse-grained wollastonite fragment-water (acid) reaction resulted in the solution with an elevated constant pH value (alkaline) giving an important significance on the environmental view point.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 추계종합학술대회 논문집
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• pp.287-290
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• 1999

In the transmitter of optical fiber transmission systems, a time-division multiplexer combines several parallel data streams into a single data stream with a high bit rate. In this paper, we design a 2:1 (2-channels) time-division multiplexer using SiGe HBT with emitter size of 2$\times$8${\mu}{\textrm}{m}$$^2$. The operation speed is 10Gbps, the rise and fall times of 20-80% are 34ps and 35ps, respectively and the dissipation of power is 0.86W.