• Proceedings of the Korean Society of Precision Engineering Conference
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• 1991.04a
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• pp.321-327
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• 1991

High power laser beams are used in a wide variety of materials processing applications such as cutting, welding, drilling and surface treatment. The CO$\sub$2/ laser is increasingly used in laser beam welding because of the highly potential advantages. High power laser welding is a high energy density, no filler metals and low heat input process to join metals. As the comparison with the conventiona welding, precision work and good fit-up to join the metals are required and maintenance is expensive at present. The principal variables of laser beam welding are the laser beam power, travel speed and bean spot size. The penetration depth during laser beam welding is directly related to the power density of the laser beam. Generally, for a constant beam size, the penetration depth increases with increasing laser beam power.

• 연구논문집
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• s.30
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• pp.43-56
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• 2000

N-IR spectroscopy technology is very useful. And, the technology has wide application range. In the range, we know that single beam type silica analyzer has some handicap. So we were studied Splitted beam type silica analyzer. This dissertation have been discuss about system structure, system fundamentals and performance test. At the test, we were study in the spectral interference of NH3. We know that existing system had some problem. It is structural frailties of single beam type. Therefore we were study for Splitted beam type structure. And we obtain a good result. We have $\pm$5% accuracy and 0.5 ppb level measuring range. But, we have a question. It is ppt level measuring technology by the laser beam spectroscopy.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.10
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• pp.1061-1070
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• 2009

In this paper, we have designed TDL(True-time Delay Line) for eliminating beam-squint occurring in active phased array antenna with large electrical size operated in wide bandwidth, and have tested its electrical performance. The proposed TDL device is composed of 4-bit microstrip delay line structure and MMIC amplifier for compensation of the delay-line loss. The measured results of gain and phase versus delay state satisfy the electrical requirements, also P1dB output power and noise figure meet the requirement. To verify the performance of fabricated TDL, we have simulated the beam patterns of wide-band active phased array antenna using the measured results and have certified the beam pattern compensation performance. As a result of simulated beam pattern compensation with respect to the 675.8 mm size antenna which is operated in X-band, 800 MHz bandwidth, we have reduced the beam squint error of ${\pm}1^{\circ}$ with ${\pm}0.1^{\circ}$. So this TDL module is able to be applied to active phase array antenna system.

• Structural Engineering and Mechanics
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• v.26 no.5
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• pp.569-589
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• 2007

This paper presents an analytical model for RC beam-column connections that takes into account bond deterioration between reinforcing steel and concrete. The model is based on the Lumped Damage Mechanics (LDM) theory which allows for the characterization of cracking, degradation and yielding, and is extended in this paper by the inclusion of the slip effect as observed in those connections. Slip is assumed to be lumped at inelastic hinges. Thus, the concept of "slip hinge", based on the Coulomb friction plasticity theory, is formulated. The influence of cracking on the slip behavior is taken into account by using two concepts of LDM: the effective moment on an inelastic hinge and the strain equivalence hypothesis. The model is particularly suitable for wide beam-column connections for which bond deterioration dominates the hysteretic response. The model was evaluated by the numerical simulation of five tests reported in the literature. It is found that the model reproduces closely the observed behavior.

• Current Optics and Photonics
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• v.5 no.5
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• pp.500-505
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• 2021

We demonstrated a wide-fan-angle flat-top irradiance pattern with a very narrow linewidth by using an aspheric lens and a long-pitch reflective diffraction grating. First, we numerically designed a diffraction-based linear beam homogenizer. The structure of the Al diffraction grating with an isosceles triangular shape was optimized with 0.1-mm pitch, 35.5° slope angle, and 0.02-mm radius of the rounding top. According to the numerical results, the linear uniformity of the irradiance was more sensitive to the working distance than to the shape of the Al grating. The designed Al grating reflector was fabricated by using a conventional mold injection and an Al coating process. A uniform linear irradiance of 405-nm laser diode with a 100-mm flat-top length and 0.176-mm linewidth was experimentally demonstrated at 140-mm working distance. We believe that our proposed linear beam homogenizer can be used in various potential applications at a precise inspection system such as three-dimensional morphology scanner with line lasers.

• KCI Concrete Journal
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• v.13 no.2
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• pp.49-57
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• 2001

Flat-plate buildings are commonly modeled as two-dimensional frames to calculate unbalanced moments, lateral drift and shear at slab-column connections. The slab-column frames under lateral loads are analyzed using effective beam width models, which is convenient for computer analysis. In this case, the accuracy of this approach depends on the exact values of effective beam width to account for the actual behavior of slab-column connections. In this parametric study, effective beam width coefficients for wide range of the variations are calculated on the several types of slab-column connections, and the results are compared with those of other researches. Also the formulas for effective beam width coefficients are proposed and verified by finite element analysis. The proposed formulas are founded to be more suitable than others for analyzing flat-plate buildings subjected to lateral loading.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.10
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• pp.2535-2542
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• 1993

Two-noded curved beam elements, CMLC (field-consistent membrane and linear curvature) and IMLC(field-inconsistent membrane and linear curvature) are developed on the basis of Timoshenko's beam theory and curvilinear coordinate. The curved beam element is developed by the separation of the radial deflection into the bending deflection. In the CMLC element, field-consistent axial strain interpolation is adapted for removing the membrane locking. The CMLC element shows the rapid and stable convergence on the wide range of curved beam radius to thickness. The field-consistent axial strain and the separation of radial deformation produces the most efficient linear element possible.

• Applied Microscopy
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• v.48 no.4
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• pp.122-125
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• 2018

The focused ion beam (FIB) method is widely used to prepare specimens for observation by transmission electron microscopy (TEM), which offers a wide variety of imaging and analytical techniques. TEM has played a significant role in material investigation. However, the FIB method induces amorphization due to bombardment with the high-energy gallium ($Ga^+$) ion beam. To solve this problem, electron beam induced deposition (EBID) is used to form a protective layer to prevent damage to the specimen surface. In this study, we introduce an optimized TEM specimen preparation procedure by comparing the EBID of carbon and tungsten as protective layers in FIB. The selection of appropriate EBID conditions for preparing specimens for TEM analysis is described in detail.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.11
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• pp.1102-1107
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• 2009

An ultrasonic sensor has been widely used as a range sensor for its low cost and capability of detecting some obstacles, such as glasses and black surfaces, which are not well detected by a laser scanner and an IR sensor. Although low-cost sensors are preferred for practical service robots, they suffer from the inaccurate and insufficient range information. This paper proposes a novel approach to obstacle avoidance using low-cost anisotropic ultrasonic sensors with wide beam angle. In this paper, obstacles can be detected by the proposed sensor configuration which consists of one transmitter and three receivers. Because even wide obstacles are represented by a point, which corresponds to the intersection of range data from each receiver of the anisotropic sensor, a robot cannot avoid wide obstacles successfully. This paper exploits the probabilistic mapping technique to avoid collision with various types of obstacles. The experimental results show that the proposed method can robustly avoid obstacles in most indoor environments.

• Applied Microscopy
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• v.49
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• pp.4.1-4.2
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• 2019

We applied the advanced bitmap-assisted patterning function of focused ion beam to fabricate microscale sculpture of the 'BangTanSoNyeonDan' known as BTS members, the world-wide famous K-pop boyband. With the help of an electron microscope, you can carve your idols on your accessories at micro scale. Fun applications of electron microscopes are not limited to science.