• 설비공학논문집
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• 제12권3호
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• pp.284-291
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• 2000

A basic pulse tube refrigerator has been constructed with extensive instrumentation to study the characteristics of the heat exchanger experimentally under the oscillating pressure and the oscillating flow. This paper describes the sequential experiments with the basic pulse tube refrigerator. The experiments were performed for various cycle frequencies under the square pressure wave forms. First, the heat flux was measured through the cycle at the both cold and warm end heat exchangers without the regenerator. In order to enhance the thermal communication capability of the heat exchanger with the gas at low operating frequencies, a unique design of the triangular shape radial fin concept was applied to the heat exchangers. For the fin heat exchanger, the measured heat flux and the calculated heat flux from the two well-known oscillating heat transfer correlations were compared and discussed. Second, the regenerator was added to the pulse tube to make a basic pulse tube refrigerator configuration. The experiment showed the great impact of the regenerator on the temperature and the heat flux profiles. At the warm-end, the cyclic averaged heat flux had its maximum value at the specific operating frequency. The paper presents the explanation of the surface heat pumping effect as well as the experimental data.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2009년도 춘계학술대회 논문집
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• pp.136-137
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• 2009

전자파 차폐재로 메쉬를 제작하는 기존의 배치 방식은 복잡한 작업공정과 비싼 설비로 인해 생산원가 높다. 그래서 pulse reverse current를 이용하여 Cu mesh 도금을 하였다. 정펄스의 전류밀도가 $31mA/cm^2$일일 때 역펄스의 전류밀도 및 duty cycle에 상관없이 표면은 매끄럽게 나왔다. 정펄스의 전류밀도가 $454mA/cm^2$일때는 duty cycle이 25%이하는 표면상태가 매끄럽게 나타났지만 33%이상에서 표면상태가 거칠게 도금이 되었다.

• 대한전자공학회논문지
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• 제6권3호
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• pp.1-7
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• 1969

전류일치방식의 기억자심으로부터 기억정보를 고속도로 선택하기 위한 방법으로서, Word선에 RC선형집중회로를 종단하고 이 회로의 시정수를 작은치로 설정하여 선택 Pulse의 Cycle time을 2∼3μs로 단축시킴으로써 자심의 고속구동화를 시도하였다. 이를 위한 계의 해석방법과 회로정수의 최적치를 결정하고, 또 Cycle time의 단축에 결정적 요인이 되는 자심의 열적문제점에 대해서도 평가하였다. 이론치와 측정치가 잘 일치하였으며 Cycle time의 현저한 개선을 보아 이 방법이 고속화에 간단하고도 유효한 방법임을 확인하였다.

• 센서학회지
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• 제25권5호
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• pp.303-309
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• 2016

In this paper, we introduce a new method for controlling the illumination of LEDs in visible light communication (VLC) by changing the duty cycle of Manchester code. When VLC data were transmitted in Manchester code, the average optical power of the LEDs was proportional to the duty cycle. In experiments, we controlled the illumination of a $3{\times}3$ LED array from 10% to 90% of its peak value by changing the duty cycle of the Manchester code. The synchronizing clocks required for encoding and decoding the Manchester code were supplied by pulse generators that were connected to a 220 V power line. All pulse generators made the same pulses with a repetition frequency of 120 Hz, and they were synchronized with the full-wave rectified voltage of the power line. This scheme is a very simple and useful method for constructing indoor wireless sensor networks using LED light.

• 한국표면공학회지
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• 제44권5호
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• pp.179-184
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• 2011

This work investigated the effect of duty cycle and pulse frequency on the microstructures and properties of titanium nitride thin films deposited by asymmetric bipolar pulsed DC sputtering system. Oscilloscope traces of the I-V waveforms indicate high power and high current density outputs during the asymmetric bipolar pulsed mode. The grain size decreases with decreasing duty cycle. The duty cycle has a strong influence not only on the microstructural properties but also on the mechanical properties of titanium nitride films. Comparing with the continuous DC sputtering, the titanium nitride films prepared by pulsed DC asymmetric bipolar process exhibit better properties.

• KIEE International Transactions on Electrophysics and Applications
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• 제11C권4호
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• pp.127-132
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• 2001

We describe the pulse forming of pulsed $CO_2$laser using multi-pulse superposition technique. A various pulse length, high duty cycle pulse forming network(PFN) is constructed by time sequence. That is, this study shows a technology that makes it possible to make various pulse shapes by turning on SCRs of three PFN modules consecutively at a desirable delay time with the aid of PIC one-chip microprocessor. The power supply for this experiment consists of three PFN modules. Each PFN module uses a capacitor, a pulse forming inductor, a SCR, a High voltage pulse transformer, and a bridge rectifier on each transformer secondary. The PFN modules operate at low voltage and drive the primary of HV pulse transformer. The secondary of the transformer has a full-wave rectifier, which passes the pulse energy to the load in a continuous sequence. We investigated laser pulse shape and duration as various trigger time intervals of SCRs among three PFN modules. As a result, we can obtain laser beam with various pulse shapes and durations from about 250 $mutextrm{s}$ to 600 $mutextrm{s}$.

• 한국표면공학회지
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• 제47권4호
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• pp.168-173
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• 2014

The paper presents the comparative results of TiAlN coatings deposited by DC and pulsed DC asymmetric bipolar magnetron sputtering systems. The results show that, with the decreasing duty cycle and increasing pulse frequency, the coating morphology changes from a columnar to a dense structure, with finer grains. Pulsed sputtered TiAlN coatings showed higher hardness, higher residual stress, and smaller grain sizes than dc prepared TiAlN coatings. Moreover residual stress of pulsed sputtered TiAlN coatings increased on increasing pulse frequency. Meanwhile, the surface roughness decreased continuously with increasing pulsed DC frequency up to 50 kHz.

• 한국표면공학회지
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• 제48권4호
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• pp.136-141
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• 2015

The paper presents the comparative results of NbN coatings deposited by DC and pulsed DC asymmetric bipolar magnetron sputtering systems. The results show that, with the decreasing duty cycle and increasing pulse frequency, the coating morphology changes from a columnar to a dense structure, with finer grains. The Pulsed sputtered NbN coatings showed higher hardness, higher residual stress, and smaller grain sizes than those of DC prepared NbN coatings. Moreover residual stress of pulsed sputtered NbN coatings increased on increasing pulse frequency. Meanwhile, the surface roughness decreased continuously with increasing pulsed DC frequency up to 50 kHz.

• 한국반도체및디스플레이장비학회:학술대회논문집
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• 한국반도체및디스플레이장비학회 2005년도 추계 학술대회
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• pp.78-82
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• 2005

펄스 플라즈마 원자층 증착 방법 (PPALD : Pulse Plasma Atomic Layer Deposition)을 이용하여 삼원계 박막인 W-C-N 박막을 ILD layer인 TEOS 위에 제조하였다. 실험은 $WF_6,\;N_2.\;CH_4$ 가스의 순차적 주입과 $N_2$를 이용한 퍼징으로 이루어지며 $N_2$와 $CH_4$ 가스 주입 시에 pulse plasma가 적용되었다. 일반적인 ALD 증착 기구를 그대로 따르는 PPALD 방법에 의해 제조된 W-C-N 박막은 $H_2/N_2$ 플라즈마 초기 표면 처리에 의해 incubation cycles 없이 초기 cycles부터 0.2 nm/cycle의 일정한 증착율을 가지고 증착되므로 정확한 두께의 control이 가능하며 $300\;{\mu}{\Omega}-cm$의 매우 낮은 비저항 특성을 나타내었다.

• Journal of the Optical Society of Korea
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• 제18권1호
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• pp.60-64
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• 2014

We report the generation of 3.3-mW single-cycle terahertz (THz) pulses at 1-kHz repetition rate via optical rectification in MgO-doped prism-cut stoichiometric LiNbO3. Efficient pulse-front tilting of 800-nm pulses was realized by an optimized single-lens focusing scheme for radially-symmetric propagation of THz beams. In this geometry, nearly-diffraction-limited THz Gaussian beams with electric field strength as high as 350 kV/cm were generated. The pump-to-THz energy conversion efficiency of $1.36{\times}10^{-3}$ and the extremely high signal-to-noise ratio of ~1:15000 achieved are among the best results for 1-kHz single-cycle terahertz pulse generation ever demonstrated in room temperature operation.