• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.649-650
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• 2012

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.429-430
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• 2010

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.193-194
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• 2011

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.777-778
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• 2011

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.372.2-372
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• 2002

This paper presents an efficient modeling method fur open cracked beam structures. An equivalent bending spring model is introduced to represent the structural weakening effect in the presence of open cracks. The proposed method adopts the exact dynamic element method (EDEM) to avoid the difficulty and numerical errors in association with re-meshing the structure. The proposed method is rigorously compared with a commercial finite element code. (omitted)

• Korean Journal of Optics and Photonics
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• v.19 no.3
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• pp.229-236
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• 2008

The optimum conditions of second harmonic generation (SHG) can be successfully achieved experimentally using single pass and double pass methods of a pumping beam. The beam has a power of several Watts radiated by a DOFA (Diode Laser Oscillator & Fiber Amplifier) system, which is a high power CW wavelength tunable infrared laser system, in a PPLN (Periodically Poled MgO doped Lithium Niobate) nonlinear crystal. In the case of a single pass method, the parameters are the wavelength of 535 nm for SHG and the output power of 245 mW generated from the pumping input beam with wavelength of 1070 nm and the power of 2.45 W at phase matching temperature of $108.9^{\circ}C$. The conversion efficiency of SHG was 10%. In order to enhance the output of SHG, the double pass method of the SHG system of a PPLN using a concave mirror for the retroreflection and a pair of wedged flat windows for phase compensation was also presented. In this double pass system, we obtained the SHG output beam with the wavelength of 535 nm and the maximum power of 383 mW at optimum phase matching temperature of $108.5^{\circ}C$ by using an incident pumping beam with wavelength of 1070 nm and the power of 2.45 W. The maximum conversion efficiency is 15.6%, which is more than that of the single pass method.

• Journal of Korean Society of Steel Construction
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• v.13 no.4
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• pp.381-393
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• 2001

The current traffic situation in Korea can be described as rapid change in traffic volume and diversity in vehicle size from compact cars to large trucks. W-beam barrier most widely used in Korea was found not to satisfy the stiffness requirement for the Koran impact condition of 14 ton-60Km/h-15deg. and it was too stiff for small vehicles impacting with more realistic speed to satisfy the safety of vehicle occupants. To develop a guardrail system satisfying the two contradicting goals, a thrie-beam guardrail system, which had the beam thickness of 3.2mm and rubber cushions, was conceived. Even though the height of the thrie-beam(450mm) is increased by 100mm as compared to that of W-beam (350mm), there was only 2% increase in the weight of the thrie-beam. The new thrie-beam barrier system could contain more wide range of vehicle bumper heights, and showed better performance in the viewpoint of stiffness and energy absorbing capability than the W-beam system. The impact performance was evaluated from a crash test. The developed thrie-beam guardrail system satisfied all applicable criteria for NCHRP 350 test designation 3-10.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.6
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• pp.931-936
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• 2013

Recently, the use of large-electron-beam polishing for polishing complex metal surfaces has been proposed. In this study, the temperature induced by a large electron beam was predicted using the heat transfer theory. A finite element (FE) model of a continuous wave (CW) electron beam was constructed assuming Gaussian distribution. The temperature distribution and melting depth of an SUS304 sample were predicted by changing electron-beam polishing process parameters such as energy density and beam velocity. The results obtained using the developed FE model were compared with experimental results for verifying the melting depth prediction capability of the developed FE model.

• Journal of Biomedical Engineering Research
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• v.34 no.2
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• pp.73-79
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• 2013

Purpose: The purposes of this study were to measure the dose distribution of Photodynamic therapy(PDT) laser with 635 nm wavelength using GafChromic film. Method & Result: We made each output 300 J by changing mW and sec using the laser beam radiation mode such as C.W(Continuous Wave) mode, Pulse mode and Burst Pulse mode and measured the does at 0 mm and 5 mm of distance from optic fiber catheter end to the film, and at 5 mm distance by changing the angle of the end of the optic fiber catheter as $0^{\circ}$ and $0.5^{\circ}$. The radiated film was scanned and OD(Optical Density) was compared. And two-dimensional isodose curves were obtained and the consistency of shapes was compared. It was confirmed that there was consistency between optic density and the dose radiated on the film when we radiated GafChromic film by changing distance and angle of 300 J output in each radiation mode coordinating mW and sec. Conclusion: In this study, we could identify the stability according to changes in laser beam modes, changes in output according to distance, changes in uniformity according to angle, and beam profiles using GafChromic film, and we could also get two-dimensional isodose curve. It was found that small change in the distance and angle that is made when optic fiber catheter was contacted on the treatment area did not make big effects on the output of beam and the uniformity of dose, and it was also found that GafChromic film could be utilized for the purpose of QA of PDT laser beam.

• Journal of the Korean Society for Nondestructive Testing
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• v.26 no.3
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• pp.198-205
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• 2006

The necessity of nondestructively inspecting austenitic steels, fiber-reinforced composites, and other inherently anisotropic materials has stimulated considerable interest in developing beam models for anisotropic media. The properties of slowness surface playa key role in the beam models based on the paraxial approximation. In this paper, we apply a modular multi-Gaussian beam (MMGB) model to study the effects of material anisotropy on ultrasonic beam profile. It is shown that the anisotropic effects of beam skew and excess beam divergence enter into the MMGB model through parameters defining the slope and curvature of the slowness surface. The overall beam profile is found when the quasilongitudinal(qL) beam propagates in the symmetry plane of transversely isotropic austenitic steels. Simulation results are presented to illustrate the effects of these parameters on ultrasonic beam diffraction and beam skew. The MMGB calculations are also checked by comparing the anisotropy factor and beam skew angle with other analytical solutions.