• Progress in Medical Physics
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• v.28 no.3
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• pp.129-133
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• 2017

The machine log files recorded by a scanning control unit in proton beam therapy system have been studied to be used as a quality assurance method of scanning beam deliveries. The accuracy of the data in the log files have been evaluated with a standard calibration beam scan pattern. The proton beam scan pattern has been delivered on a gafchromic film located at the isocenter plane of the proton beam treatment nozzle and found to agree within ${\pm}1.0mm$. The machine data accumulated for the scanning beam proton therapy of five different cases have been analyzed using a statistical method to estimate any systematic error in the data. The high-precision scanning beam log files in line scanning proton therapy system have been validated to be used for off-line scanning beam monitoring and thus as a patient-specific quality assurance method. The use of the machine log files for patient-specific quality assurance would simplify the quality assurance procedure with accurate scanning beam data.

• Current Optics and Photonics
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• v.7 no.6
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• pp.665-672
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• 2023

This study focuses on investigating the impact of the spectral linewidth of a seed laser in a master-oscillator power amplifier (MOPA) configuration on stimulated Brillouin scattering and the beam quality of the output diffracted by a grating. To conduct the study, a distributed feedback (DFB) laser is modulated in a pseudorandom binary sequence (PRBS) and amplified by a two-stage Yb-doped fiber amplifier to achieve an output power of over 1 kW. The spectral linewidth of the seed laser is systematically varied from 1 to 12 GHz in the frequency domain by varying the PRBS modulation parameters. The experimental results reveal a tradeoff between suppressing stimulated Brillouin scattering and enhancing beam quality with increased spectral linewidth. Therefore, the study provides valuable insights into optimizing spectral beam combining to achieve high beam quality and scalable power upgrade in fiber lasers.

• Journal of the Korea Institute of Military Science and Technology
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• v.10 no.4
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• pp.160-167
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• 2007

In this paper, we presented the development results of high speed wavefront sensor which is used in diagnosing the beam quality of He-Ne laser for adaptive optics system. The beam quality information of laser in AO system is necessarily required for diagnosing the optical components or correcting the distorted wavefront afterward. According to system requirements, normally, it is requested that there are high precision of measurement and real time processing speed. The developed wavefront sensor in this paper achieved maximum 30Hz of measurement rate and ${\lambda}/20(\;{@}\;{\lambda}=0.6328{\mu}m)$ of measurement precision in RMS. We also applied the developed into an experimental adaptive system and verified the performance of it by correcting the aberrated wavefront with a rate of 30Hz and $\lambda$/20 precision using the combination of the developed and PID control algorithm.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.249-250
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• 2009

Recently, the interest on self-compacting concrete (SCC) without any mechanical vibration is increasing as the demand for high-strength and high surface quality of precast element increased. In this work, precast beam element with 7m length was manufactured using high-strength SCC with design strength of 60MPa, resulting in high-strength and high surface quality was obtained from the precast beam cast by high-strength SCC.

• Journal of Welding and Joining
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• v.21 no.5
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• pp.568-574
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• 2003

In the welding for the steel structure of H-beam with mild steel and 490N/$\textrm{mm}^2$ high tensile steel, we applied the fillet weld mostly and 6-8mm weld length(AISC-spec.). And a new developed metal-cored-wire is used in automatic welding as well as semi-automatic welding. In this study we have attempted to raise the welding productivity and to stabilize the quality on horizontal positions of fillet welding with the following items: - We improved the weld productivity using metal based cored wire with a high deposition rate in the steel structure of H-beam. - We tested the weldability and evaluated the quality of the weldmetal by horizontal fillet $CO_2$ welding. The process is carried out in combination with a special purpose metal-based FCW with excellent resistance to porosity and high welding speed. - We studied the micro structure of the weldmetal by the various welding conditions. - We studied the effect of welding residual stress by the welding conditions in T-joint. Therefore, it can be assured that more productive and superior quality of the weldmetal can be taken from this study results.

• International Journal of Precision Engineering and Manufacturing
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• v.8 no.4
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• pp.10-15
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• 2007

Taguchi methods have been used for a long time to improve the product quality and process performance of a manufacturing system, Few researchers have applied this methodology in laser beam cutting (LBC) of sheet metals and found the considerable improvement in cut qualities. In all experimental investigations of LBC so far, the objective was to optimize the single quality characteristic at a time. In this paper the simultaneous optimization of multiple quality characteristics such as Kerf width and material removal rate (MRR) during pulsed Nd:YAG LBC of thin sheet of magnetic material (high Silicon-steel) has been presented using Taguchi's quality loss function. The results show the considerable improvement in multiple S/N ratio as compared to initial cutting condition. Also, the comparison of results from single and multi-objective optimization have been presented and it was found that the loss in quality is always possible shifting from single quality to multiple quality optimization.

• Nuclear Engineering and Technology
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• v.38 no.4
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• pp.319-326
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• 2006

A brief review is presented on the ion beam application in science and technology. ion beams are used very effectively in various fields of science and technology, on the basis of advance in accelerator technology and experimental techniques for ion beam utilization. Recent progress in this field is reviewed in terms of the direct ion beam utilization like ion beam analysis, and the utilization of neutrons as secondary particles.

• Journal of Welding and Joining
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• v.31 no.4
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• pp.28-33
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• 2013

The effects of laser welding beam quality is very large. However, not an analysing case was found for the difference on the plasma emission signal during laser welding according to the beam quality. Therefore, in this study, we compared and evaluated penetration and signal change according to the beam quality at the a similar wavelength band by using a fiber laser and Nd:YAG laser. In addition, we took high speed videography in order to make sure that FFT analysis reflects the actual motion period of keyhole and found the period of video analysis and FFT mostly matched. As a result, it is expected to secure higher reliability than evaluating signal intensity when appling FFT to monitoring.

• Proceedings of the KAIS Fall Conference
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• 2011.12b
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• pp.481-484
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• 2011

The increasing interest in the laser beam welding is placing stringent demands on the manufacturing techniques and performance requirements, and the manufacture employs the high quality and efficiency laser beam welding technology. This paper covers recent research trends of the laser beam welding technology including the laser beam surfacing and laser beam cladding technology.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.359-359
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• 2011

Many research applications in basic sciences and biology such as protein crystallography require hard x-rays in the range of 3-20 keV with high brightness. A medium energy storage ring as PLS-II with a beam energy of 3 GeV can meet such high photon energies. In-vacuum undulators (IVU) with a period length of 20 mm and a peak field of 0.97 T are used in the PLS-II ring to produce such X-rays in the fundamental or higher harmonics. Due to the many poles and high fields, insertion devices like wigglers and undulators have a significant impact on the stability of the electron beam with potential degradation of beam quality and life time. Therefore, nonlinear fields must be determined by measurement and evaluated as to their impact on beam stability. Specifically, transverse field roll-off can be a serious detriment to injection in top-up mode and must be corrected. We use magnetic field measurement data to evaluated beam stability by tracking particles using an explicit symplectic integrator in both, transverse and longitudinal planes.