• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 추계학술대회 논문집 학회본부 B
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• pp.348-351
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• 2000

There have been significant advances in thyratron performance in recent years. these advanced waveforms have increased the complexity and cost of drive circuits. Thyratrons can reliably switch anode voltages up to 40kV and conduct peak currents up to 10kA or more. So stable thyratron drivers are essential for reliable high voltage pulse modulators. In order to operate thyratron well, thyratron driver need high repetition rate, fast rising time and low jitter. In this paper, used power MOSFET/transformer combinations. Designed thyratron driver is satisfied requirements and experimental results are presented to confirm.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2005년도 추계학술발표회
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• pp.915-916
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• 2005

The high power RF system for the PEFP 20MeV proton accelerator composed of the 3MeV RFQ and the 20MeV DTL has been installed. The klystron for the RFQ was tested up to 600kW and operated routinely to drive the RFQ in a pulse mode operation. The klystron for the DTL which consists of 4 tanks was tested up to 800kW in pulse mode operation. The pulse width and repetition rate was 50${\mu}s$ and 1Hz respectively. The high power RF system has been operated to drive each accelerating structure and will be used to accelerate 20MeV proton beam.

• 한국정보통신학회논문지
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• 제11권12호
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• pp.2343-2351
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• 2007

본 논문은 시변 펄스형 자기장(Time-varying Magnetic field)을 반복적으로 발생시키는 전원장치 및 전원장치에서 발생된 에너지를 자기장으로 발생키시기 위한 자기유도 코일 probe의 설계 및 구현을 통하여 짧은 시간($300{\mu}s$이하) 동안 고자기장(${\sim}1.2Tesla$)을 발생시켰다. 시간과 펄스 주기를 순차적으로 조정 할 수 있는 다단 메쉬 방식으로 설계하여 고반복적($0.1Hz{\sim}20Hz$)으로 스위칭했을 경우에도 동일한 출력세기를 발생시킬 수 있는 자기장 의료기기 시스템을 구현하였다.

• Journal of Electrochemical Science and Technology
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• 제12권2호
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• pp.257-265
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• 2021

In this study, we report niobium (Nb) with hierarchical porous structure produced by a one-pot, HF-free electrochemical etching process. It is proved experimentally that a well-defined hierarchical porous structure is produced from the combination of a limited repetition of pulse etching and high concentration of aggressive anion (i.e., SO₄^2-), which results in hierarchical pores with high order over 3. A formula is derived for the surface area of porous Nb as a function of the hierarchical order of pores while the experimental surface area is estimated on the basis of the electrochemical gas evolution rate on porous Nb. From the comparison of the theoretical and experimental surface areas, an in-depth understanding was gained about porous structure produced in this work in terms of the actual pore shape and hierarchical pore order.

• 한국정밀공학회지
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• 제30권10호
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• pp.1009-1015
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• 2013

Ultra-short laser pulses are effective, when high requirements concerning accuracy, surface roughness and heat affected zone are demanded for surface structuring. In particular, picosecond laser systems that are suited to be operated in industrial environments are of great interest for many practical applications. This paper focused on inducing optimum process parameters for higher volume ablation rate by analyzing a relationship between crater diameter and optical spot size. In detail, the dependency of the volume ablation rate, penetration depth and threshold fluence on the pulse duration 8 ps and wavelength of 515 nm was discussed. The experimental results showed that wavelength of 515 nm resulted in less threshold fluence ($0.075J/cm^2$) on copper than IR wavelength ($0.3J/cm^2$). As a result, it was possible that optimum fluence for higher volume ablation rate was achieved with $0.28J/cm^2$.

• 한국통신학회논문지
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• 제34권4C호
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• pp.476-483
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• 2009

마이크로파 탐색기를 이용하여 표적을 탐지, 추적하는 경우 하방 표적에 대해서는 지표면에서 반사되는 클러터 신호의 영향을 받는다. HPRF (high pulse repetition frequency) 모드를 사용하는 마이크로파 탐색기에서 부엽클러터 영역에 나타나는 퇴각표적을 탐지하기 위해서는 여러 지형과 상황에 따른 지표면 부엽클러터 전력의 통계적인 특징을 파악하여야 한다. HPRF 모드를 사용하는 탐색기의 항공기 탑재시험에서 지상 클러터의 전력을 측정한 자료를 기반으로, 각 지형과 안테나 시선각 등의 상황에 따라 부엽클러터의 확률분포 특성을 가장 근접하게 표현하는 확률밀도함수를 구하고 그 확률밀도함수의 매개변수를 추정하였다. 확률밀도함수 및 매개변수를 추정한 자료를 이용하여, 퇴각표적을 탐지할 때에 원하는 수준의 표적탐지 오류 확률을 가지는 표적탐지 임계값 설정에 관하여 분석하였다. 본 논문의 지표면 부엽클러터 전력의 확률분포 특성 분석과 표적탐지 임계값 설정에 관한 분석 자료는 표적탐지 방법 개발 및 일정 오경보 처리 등의 다양한 분야에 이용될 수 있다.

• 한국통신학회논문지
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• 제28권3C호
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• pp.224-231
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• 2003

본 논문에서는 FCC에서 제정한 허용 주파수 3.1~10.6 GHz 대역 내에서 IR 시스템 설계를 위한 특성 파라미터를 유도하고, 다원접속 간섭 환경에서 IR 시스템의 오율 성능을 분석하였다. 결과에 의하면, FCC에서 제정한 허용 주파수 범위 내에서 적용 가능한 펄스 주기($t_{n}$) 는 0.04~0.0326 ns로 매우 한정됨을 알 수 있었다. 또한, 시스템 성능 변화에 있어서 펄스 주기보다는 펄스반복개수($N_{s}$ )에 의해서 시스템 성능이 크게 변화되는 것을 알 수 있었다. 따라서, 다원접속 시스템 설계 시 동시 사용자 수에 따라 모노 펄스의 주기 및 프레임 단위 시간(Τ$_{f}$ )의 설정이 필요하고 전송율에 따른 적정한 펄스 반복 개수를 설계해야 함을 알 수 있었다. 다원접속 간섭 발생 시에는 50Mbps 이상의 고속 전송을 요하는 IR 시스템에서 다원접속 간섭 자체로 인해 매우 심각한 성능 열화가 발생하는 것을 알 수 있었고, 따라서, 고속 전송 다원접속 IR 시스템 설계 시에는 다원접속 간섭을 제거할 수 있는 추가적인 보상기법이 동시에 설계되어야 함을 알 수 있었다.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.I
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• pp.583-588
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• 2005

Indium tin oxide (ITO) is a commonly used conducting transparent oxide film (CTO) used in flat panel display applications. Direct write laser ablation is sometimes employed for ITO patterning and it is important that the substrate material and remaining ITO be affected as little as possible by the laser ablation. In this investigation, femtosecond laser ablation of ITO was studied to identify laser processing parameters which cleanly ablated ITO with a minimum of damage to a glass substrate and surrounding ITO. The Ti:Sapphire chirp pulse amplified femtosecond laser used for the experiments had a wavelength of 775nm and produced pulses with a duration of 150fs at a rate of 2 kHz. Ablation was carried out at a sufficiently high panel scanning speed that single ablation spots could be studied. The pulse energy was adjusted to determine feasible spot diameters and depths which could be ablated into the ITO without damaging the glass substrate. Next, ablation of lines without glass damage was also demonstrated. Experiments were also performed with a high repetition rate (100kHz) femtosecond laser.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 봄 학술논문 발표대회
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• pp.345-346
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• 2023

As the shape and size of detectable objects diversifying recognition and segmentation algorithms have been developed to acquire accurate shape information. Although a high density of data captured by the repetition of scanning improves the accuracy of algorithms the high dense data decreases the efficiency due to its large size. This paper proposes standardization algorithms using the feature of structural members on indoor point cloud data to improve the process. First of all we determine the reduction rate of the density based on the features of the target objects then the data reduction algorithm compresses the data based on the reduction rate. Second the data arrangement algorithm rotates the data until the normal vector of data is aligned along the coordinate axis to allow the following algorithms to operate properly. Final the data arrangement algorithm separates the rotated data into their leaning axis. This allows reverse engineering of indoor point clouds to obtain the efficiency and accuracy of refinement processes.

• Journal of Magnetics
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• 제17권1호
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• pp.27-32
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• 2012

Transcranial magnetic stimulation requires an electric field composed of dozens of V/m to achieve stimulation. The stimulation system is composed of a stimulation coil to form the electric field by charging and discharging a capacitor in order to save energy, thus requiring high-pressure kV. In particular, it is charged and discharged in capacitor to discharge through stimulation coil within a short period of time (hundreds of seconds) to generate current of numerous kA. A pulse-type magnetic field is formed, and eddy currents within the human body are triggered to achieve stimulation. Numerous pulse forms must be generated to initiate eddy currents for stimulating nerves. This study achieved high internal pressure, a high number of repetitions, and rapid switching of elements, and it implemented numerous control techniques via introduction of the half-bridge parallel load method. In addition it applied a quick, accurate, high-efficiency charge/discharge method for transcranial magnetic stimulation to substitute an inexpensive, readily available, commercial frequency condenser for a previously used, expensive, high-frequency condenser. Furthermore, the pulse repetition rate was altered to control energy density, and grafts compact, one-chip processor with simulation to stably control circuit motion and conduct research on motion and output characteristics.