• KIEE International Transactions on Electrophysics and Applications
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• v.4C no.2
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• pp.55-59
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• 2004

Throughout manufacturing processes, pulse shaping is required for material processing and it is regarded as an important (actor according to the specific characteristics of materials. Therefore, this study suggests a highly appropriate pulse shaping technique using a multi-switching method. This is a pulse superposition method in which one flash lamp can consecutively turn on by the double switching of the discharging system. It is possible to construct a variety of pulse shapes and pulse widths by the consecutive trigger of the silicon-controlled rectifiers (SCR) of a PIC (program integrated circuit) one-chip microprocessor. The use of this technique can provide a number of advantages to people who require suitable pulse shaping for particular applications such as welding, cutting, and drilling.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.6 no.3
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• pp.111-121
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• 2007

In this paper, we propose a TH-Multiband-UWB system through pulse shaping to fit in domestic UWB spectrum regulation. We propose the transmission pulse of Multi-Carrier type for pulse shaping and use Cognitive Radio to detect interfering frequency. We use Genetic Algorithm in Cognitive Radio's calculation propose and propose solution of interference problem between TH-UWB using Cognitive Radio and typical MB-OFDM UWB system or other communication systems. In this paper, we explain how Cognitive Engine detects the interfering frequency. The technique of TH-Multiband-UWB system using Cognitive Radio shows a good performance in interference condition.

• Journal of the Korean Society of Marine Environment & Safety
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• v.3 no.2
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• pp.13-21
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• 1997

This paper describes the effectiveness of laser pulse shaping in eliminating weld defects such as porosity, cracks and undercuts in pulsed Nd:YAG Laser welding. A large porosity was formed in a keyhole mode of deep penetration weld metal of any stainless steel. Solidification cracks were present in Type 303 with about 0.3%s. The conditions for the formation of porosity were determined in further detail in Type 316. With the objectives of obtaining a fundamental knowledge of formation and prevention of weld defects, the fusion and solidification behavior of a molten puddle was observed during laser spot welding of Type 310S. through high speed video photographing technique. It was deduced that cellular dendrite tips grew rapidly from the bottom to the surface, and consequently residual liquid remained at the grain boundaries in wide regions and enhanced the solidification cracking susceptibility. Several laser pulse shapes were investigated and optimum pulse shapes were proposed for the reduction and prevention of porosity and solidification cracking.

• Proceedings of the IEEK Conference
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• 2002.06a
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• pp.263-266
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• 2002

Many methods have been Proposed to reduce the PAPR of the OFDM signal. Among them a method that uses the time waveform of the different sub-carriers. The method is referred to as pulse shaping and it works with arbitrary number of sub-carriers and my type of base-band linear modulation. It has been shown, using this technique, that it is possible to design a set of time waveforms that reduce the PAPR of the OFDM transmitted signal and improve its power spectrum simultaneously. In this paper, we investigate the effect of some of these sets of time waveforms on the OFDM system performance in terms of Bit Error Rate (BER).

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.8
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• pp.1270-1278
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• 2004

This paper describes the effectiveness of laser pulse shaping in eliminating weld defects such as porosity, cracks and undercuts in pulsed Nd:YAG laser welding. A large porosity was formed in a keyhole mode of deeply penetrated weld metal of any stainless steel. Solidification cracks were present in STS 310S with above 0.017%P and undercuts were formed in STS 303 with about 0.3%S. The conditions for the formation of porosity were determined in further detail in STS 316. With the objectives of obtaining a fundamental knowledge of formation and prevention of weld defects, the fusion and solidification behavior of a molten puddle was observed during laser spot welding of STS 310S through a high speed video photographing technique. It was deduced that cellular dendrite tips grew rapidly from the bottom to the surface, and consequently residual liquid remained at the grain boundaries in wide regions and enhanced the solidification cracking susceptibility. Several laser pulse shapes were investigated and optimum pulse shapes were proposed for the reduction and prevention of porosity and solidification cracking.

• Korean Journal of Optics and Photonics
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• v.21 no.6
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• pp.254-258
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• 2010

We investigate an optical technique for beam shaping and optical amplification of a pulsed laser diode without variation of its original properties, such as repetition rate and pulse duration. The horizontal and longitudinal sizes of the pulsed laser diode are 300 and $2{\mu}m$, respectively, and its output power is $1.1mW/cm^2$. The multimodal and elliptical pulse shape of the laser diode is converted to the single-modal and Gaussian pulse shape by using a lensed optical fiber. Since the single-modal lensed fiber coupling from the multimodal pulsed laser diode degrades the output power severely, the output power of the pulsed laser diode is dramatically enhanced by using an optical amplification method based on master oscillated power amplification (MOPA). The pulse qualities of the laser diode are not changed after amplifying the pulse power and the output power was finally measured to be $29mW/cm^2$.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.14 no.4
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• pp.8-15
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• 2000

In this paper, we realize the active PFC(Power Factor Correction) system of BF(Boost Forward) converter with PWM-PFM(Pulse Width Modulation-Pulse Frequency Modulation) control technique to control DC output voltage, to remove the noise like harmonics at output voltage, and to control the input current with sinusoidal wave synchronized by the source voltage.To achieve the desired load voltage and improved PFC, we first implement current shaping control at the inverting stage and make the converted output DC voltage with forward converter. After making the ratio of output voltage to current as 50V/1A and the duty ratio greater than 0.5. When input voltage is 30V and boost inductance is 1.1mH. we control the voltage changing rate according to the variation of load resistance using a PWM-PFM control technique. And finally we prove experimentally, we attenuated its harmonics and improved PF up to 0.96 using the current shaping technique.

• Journal of the Optical Society of Korea
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• v.18 no.5
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• pp.449-452
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• 2014

We present a multi-tap microwave photonic filter with high selectivity through applying time-to-frequency mapping and optical frequency comb shaping techniques. When arranged in the time-to-frequency mapping stage, by a Fourier transform, the deviation of the optical taps to the target profile is significantly reduced while maintaining the apodization profile, resulting in high sidelobe suppression in the filters. By applying a simple time-to-frequency mapping stage to the conventional optical frequency combs, we demonstrate a substantially enhanced (>10dB) sidelobe suppression, resulting in filter lineshapes exhibiting a significantly high (>40dB) main lobe to sidelobe suppression ratio. These results highlight the potential of the technique for implementation in various passband filters with high sidelobe suppression.

• Nuclear Engineering and Technology
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• v.39 no.6
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• pp.717-724
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• 2007

A measurement-based time-domain noise simulation of radiation detector-preamplifier (front-end) noise in nuclear spectroscopy is described. The time-domain noise simulation was performed by generating "noise random numbers" using Monte Carlo's inverse method. The probability of unpredictable noise was derived from the empirical cumulative distribution function via the sampled noise, which was measured from a preamplifier output. Results of the simulated noise were investigated as functions of time, frequency, and statistical domains. Noise behavior was evaluated using the signal wave-shaping function, and was compared with the actual noise. Similarities between the response characteristics of the simulated and the actual preamplifier output noises were found. The simulated noise and the computed nuclear pulse signal were also combined to generate a simulated preamplifier output signal. Such simulated output signals could be used in nuclear spectroscopy to determine energy resolution degradation from front-end noise effect.

• Proceedings of the KIPE Conference
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• 2003.11a
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• pp.1-5
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• 2003

The random pulse width modulation(RPWM) on the noise and vibration abatement in inverter-fed induction motor drive is presented. This paper describes a RPWM technique based on space vector PWM strategy for shaping the switching noise spectrum in such a way it can merge with the natural system noise. To verify the validity of the proposed RPWM scheme, the experiment based on the TMS320 C3l microprocessor was executed. Finally, the simulation and experimental results will be given to demonstrate the effectiveness of the proposed RPWM technique.