• Proceedings of the KWS Conference
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• 2002.10a
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• pp.583-588
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• 2002

The purpose of the study is to evaluate fracture toughness on the Laser and the electron beam welded joints of high tensile steels (HT500, HT550, HT650) by using 3-point bend CTOD and Charpy impact test. WM (weld metal) CTOD tests have been carried out using two kinds of CTOD specimen, the Laser beam welding (108mm length, and 24mm width, and 12mm thickness) and the electron beam welding (l71mm length, and 38mm width, and 19mm thickness). WM Charpy impact specimen is a standard V-notch type, and the temperature of the experiment is changed from -45 to 20 degree of centigrade. FE-analysis is also performed in order to investigate the effect of stress-strain fields on fracture characteristics. Results of the standard V-notch Charpy test are influenced by strength mis-match effect and the absorbed energy vE depends on crack path, and The transition temperature of Laser beam welded joints is more higher than that of electron beam welded joints. Results of the 3-point bend test give low critical CTOD and the crack path is in the weld metal of al specimens. These results indicate fracture toughness characteristics of the welded joints and transition temperature of HT500 are similar both a Laser beam welded joint and an electron beam welded joint. But the fracture toughness and the transition temperature of the electron beam welded joints of HT550 and HT650 are higher than those o the Laser beam welded joints.

• Applied Microscopy
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• v.38 no.4
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• pp.285-291
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• 2008

We have evaluated the effects of experimental factors on transmitted electron beam intensities for quantitative analysis in electron tomography. For the correct application of Beer's law in electron tomography, the transmitted beam intensity should reflect the net effect of mass properties on beam path. So, the any other effects of the objective aperture and the specimen holder on beam path should be removed. The cut-off effects of objective aperture were examined using Quanti-foil holey carbon film and a transmission electron microscope operated at 120 kV. The transmitted beam intensities with $30{\mu}m$ objective aperture dropped about 16.7% compared to electron beam intensities without the objective aperture. Also, the additional losses of about 14.2% at high tilt angles were occurred by cut-off effects of the objective apertures. For the precise quantitative analysis in electron tomography, the effect of the objective aperture on transmitted electron beam intensities should be considered. It is desirable that 2-D tilt series images are obtained without the objective aperture for correct application of Bee's law.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.8
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• pp.721-728
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• 2014

In this paper, it is proposed a method of optimizing path parameters for large-area laser processing. On-the-fly system is necessary for large-area laser processing of uniform quality. It is developed a MOTF(Marking On-The-Fly) board for synchronizing the stage and scanner. And it is introduced the change of the error due to the change of parameters and algorithm for large-area laser processing. This algorithm automatically generates stage path and a velocity profile using acceleration and deceleration parameters. Since this method doesn't use a G-code, even if without expert knowledge, it has an advantage that can be accessed easily. Angle of one of the square of $350{\times}350mm$ was changed from $50^{\circ}$ to $80^{\circ}$ and analyzed the error corresponding to the value of Ta. It is calculated the value of Ta of the best with a precision of 20um through measurement of accuracy according to the Ta of each angle near the edge.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.6
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• pp.153-158
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• 2007

The present study covers numerical analysis of a thermionic scanning electron microscope(SEM) column. The SEM column contains an electron optical system in which electrons are emitted and moved to form a focused beam, and this generates secondary electrons from the specimen surfaces, eventually making an image. The electron optical system mainly consists of a thermionic electron gun as the beam source, the lens system, the electron control unit, and the vacuum unit. For a systematic design of the electron optical system, the beam trajectories are investigated through numerical analyses by tracing the ray path of the electron beams, and the quality of resulting image is evaluated from the analysis results.

• Journal of the Korean Society of Radiology
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• v.15 no.1
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• pp.79-83
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• 2021

In radiation therapy, electron beam is often used in the treatment of superficial lesion. Accurate measurements are required because electron beam interacts with them in the beam path and affects dose measurements. However, no research has been conducted on electron beam quality assurance. in this study, PbO-based dosimeter was fabricated as a basic study for electron beam quality assurance. Thus, the reproducibility and linearity of the energy of 6, 9, and 12 MeV were analyzed to evaluate measurement accuracy and precision. Reproducibility measurements show RSD value of 1.024%, 1.019% and 0.890%, respectively, at 6, 9, and 12 MeV. linearity measurements show 0.9999 R2 at 6, 9, and 12 MeV altogether. Both evaluations show that the PbO dosimeter has very good measurement accuracy and precision with excellent results.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.859-860
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• 2009

• Journal of the Korean Society for Precision Engineering
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• v.26 no.11
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• pp.92-98
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• 2009

The scanning electron microscope (SEM) contains an electron optical system in which electrons are emitted and moved to form a focused beam, and generates secondary electrons from the specimen surfaces, eventually making an image. The electron optical system usually contains two condenser lenses and an objective lens. The condenser lenses generate a magnetic field that forces the electron beams to form crossovers at desired locations. The objective lens then focuses the electron beams on the specimen. The present study covers the design and analysis of an objective lens for a thermionic SEM. A finite element (FE) analysis for the objective lens is performed to analyze its magnetic characteristics for various lens designs. Relevant beam trajectories are also investigated by tracing the ray path of the electron beams under the magnetic fields inside the objective lens.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2003.09a
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• pp.71-71
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• 2003

The study on magnetic field combined radiation therapy, as a new technique to modify the dose distributions using external magnetic field, has been investigated. The goal of the study is to develop the techniques for dose localization, as a particle beam, from the strong magnetic fields. In this study, in order to study the principle of dose deposition in external fields, as a basic approach, we have calculated approximately the paths of traveling electrons in water under external magnetic fields with numerical methods. The calculations are performed for a primary particle by cumulating the steps which are defined as small path lengths which energy loss can be ignored. In this calculation, the energy loss and direction change for a step was calculated by using total stopping power and Lorentz force equation respectively. We have examined the deflected paths of the electron through water as a function of external magnetic field and incident electron s energy. Since we did not take account of the multiple scattering effects for electrons through water, there are errors in this calculation. However, from the results we can explain the principle of dose variation and dose focusing for electron beams under strong magnetic fields in water.

• Progress in Medical Physics
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• v.7 no.2
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• pp.57-65
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• 1996

Total Skin Electron Beam Therapy (TSEBT) is one of the most effective treatment methods for superficially disseminated skin cancer or cutaneous T-cell lymphoma. We have treated a patient with cutaneous T-cell lymphoma. We have used Stanford technique using six dual field. The nominal energy of electron beam was 4MeV. SSD was 390cm and the gantry angles of dual fields were 76$^{\circ}$ and 104$^{\circ}$. The dose profiles of single field and dual fields were measured with films and a Farmer type ion chamber. The field uniformity was 10％ over the patient's surface. During treatment, the patient was placed in six different positions for homogenous dose distribution over the body surface. The areas not directly exposed to the path of the electron beam (soles of feet, perineum and vertex of scalp) were boosted with 7MeV electron beam. During the treatment, lens, fingernails and toenails were shielded.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.311-311
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• 2013

The resistance switching memory devices have several advantages to take breakthrough for the limitation of operation speed, retention, and device scale. Especially, the metal-oxide materials such as ZnO are able to fabricate on the flexible and visible transparent plastic substrate. Also, the quantum dots (QDs) embedded in dielectric layer could be improve the ratio between the low and the high resistance becauseof their Coulomb blockade, carrier trap and induced filament path formation. In this study, we irradiated 0.2-MeV-electron beam on the ZnO/QDs/ZnO structure to control the defect and oxygen vacancy of ZnO layer. The metal-oxide QDs embedded in ZnO layer on Pt/glass substrate were fabricated for a memory device and evaluated electrical properties after 0.2-MeV-electron beam irradiations. To formation bottom electrode, the Pt layer (200 nm) was deposited on the glass substrate by direct current sputter. The ZnO layer (100 nm) was deposited by ultra-high vacuum radio frequency sputter at base pressure $1{\times}10^{-10}$ Torr. And then, the metal-oxide QDs on the ZnO layer were created by thermal annealing. Finally, the ZnO layer (100 nm) also was deposited by ultra-high vacuum sputter. Before the formation top electrode, 0.2 MeV liner accelerated electron beams with flux of $1{\times}10^{13}$ and $10^{14}$ electrons/$cm^2$ were irradiated. We will discuss the electrical properties and the physical relationships among the irradiation condition, the dislocation density and mechanism of resistive switching in the hybrid memory device.