• Title/Summary/Keyword: pulse cycle

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An Experimental Study on the Heat Exchangers in the Pulse Tube Refrigerator (맥동관 냉동기 열교환기에 관한 실험적 연구)

  • 남관우;정상권;정은수
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.12 no.3
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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.

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Pulse reverse current 을 이용한 Cu mesh 도금의 표면형상 개선

  • Lee, Jin-Hyeong;Lee, Ju-Yeol;Kim, Man
    • Proceedings of the Korean Institute of Surface Engineering Conference
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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.

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A Method for the high speed selection of information in the magnetic memory core (기억자심에서의 정보선택의 고속화방법)

  • 이주근
    • Journal of the Korean Institute of Telematics and Electronics
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    • v.6 no.3
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    • pp.1-7
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    • 1969
  • The Series RC load is connected with the word line in an attempt to select with high speed the information from the coincident current magnetie memory core. By taking the small time constant of the RC load, the cycle time of the output pulse is shortened by about 2 microseconds to 3 micro seconds. For this purpose, the analytical study are accomplished and the optimum circuit parameters are determined. Furthermore, the thermal problems occuring from the high speed switching of the magnetic memory core have been clarified.

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A Comparative Study of TiN Coatings Deposited by DC and Pulsed DC Asymmetric Bipolar Sputtering (DC 스퍼터법과 비대칭 바이폴라 펄스 DC 스퍼터법으로 증착된 TiN 코팅막의 물성 비교연구)

  • Chun, Sung-Yong
    • Journal of the Korean institute of surface engineering
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    • v.44 no.5
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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.

Illumination Control of LEDs in Visible Light Communication Using Manchester Code Transmission

  • Lee, Seong-Ho
    • Journal of Sensor Science and Technology
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    • v.25 no.5
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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.

A Comparative Study of NbN Coatings Deposited by DC and Pulsed DC Asymmetric Bipolar Magnetron Sputtering (DC 스퍼터법과 비대칭 바이폴라 펄스 DC 스퍼터법으로 증착된 NbN 코팅막의 물성 비교연구)

  • Chun, Sung-Yong;Oh, Bok-Hyun
    • Journal of the Korean institute of surface engineering
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    • v.48 no.4
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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.

A Comparative Study of TiAlN Coatings Deposited by DC and Pulsed DC Asymmetric Bipolar Magnetron Sputtering (DC 스퍼터법과 비대칭 바이폴라 펄스 DC 스퍼터법으로 증착된 TiAlN 코팅막의 물성 비교연구)

  • Chun, Sung-Yong;Lee, Tae Yang
    • Journal of the Korean institute of surface engineering
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    • v.47 no.4
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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.

Pulse Plasma Assisted Atomic Layer deposition 장치의 제작과 특성

  • 박지호;김희준;이창우;김용태
    • Proceedings of the Korean Society Of Semiconductor Equipment Technology
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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$$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.

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Various Pulse Forming of Pulsed $CO_2$ laser using Multi-pulse Superposition Technique

  • Chung, Hyun-Ju;Kim, Hee-Je
    • KIEE International Transactions on Electrophysics and Applications
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    • v.11C no.4
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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 $mutextrm{s}$.

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Effect of Pulse Plating on the Hardness and Ductility of Electroplated Fe-C (펄스전류에 의해 제조된 Fe-C 도금층의 경도 및 인성에 대한 연구)

  • 오영주;하헌필;변정수
    • Journal of the Korean institute of surface engineering
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    • v.35 no.3
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    • pp.141-148
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    • 2002
  • Fe-C alloy layers were produced by pulse plating and the properties were compared with those produced by D.C. plating. When the pulse on time ($T_{on}$ ) was the same, both the duty cycle and peak current density($I_{p}$ ) had little influence on the carbon content and the hardness of the layer. The structure and hardness of the direct current plating were similar to those of the pulse current plating. However, the ductility was enhanced when the pulse current was applied due to the release of residual stress during the pulse off time($T_{off}$).).