• Laser Solutions
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• v.2 no.3
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• pp.11-18
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• 1999

This paper describes the weldability of carbon steel and stainless steel using 5㎾ $CO_2$ laser system with nearly multi-mode beam and a parabolic focusing mirror. In the laser welding of steels, major welding parameters are focal point, travel speed, beam power, shield gas and gap tolerance, etc.. Two kinds of gases(Ar, He) were used as a assist gas and supplied through the external nozzle. It is very important for optimum condition to remove plasma plume which absorbs laser beam and to obtain deep penetration and sound weld bead. Bead-on-plate welding tests were carried out for the experiments. Penetration data were obtained with various welding parameters and the effects of welding parameters were discussed. Butt welding tests were performed with various conditions. Only the optimum laser parameters assured good weld quality As a result of this study, We achieve the fundamental weldabilities using a high power $CO_2$ laser for carbon steel and stainless steel.

• Korean Journal of Optics and Photonics
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• v.7 no.2
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• pp.136-141
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• 1996

We present a novel description of TE nonlinear guided waves in planar waveguides with two nonlinear bounding thin films. The nonlinear dispersion relations of the nonlinear waveguides are obtained by adopting the nonlinear transfer matrix. The optical properties obtained from these equations include: the power dependence of mode indices, the transition of the field maximum location, and the power distribution. The planar waveguide with self-focusing nonlinear layers shows the optical bistability of power-dependent mode indices, and the critical powers for the optical bistability increase with decreasing thickness of the nonlinear layers. The power distributions display the optical bistabilities, similar to those of nonlinear Fabry-Perot etalon.

• Bulletin of the Korean Chemical Society
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• v.34 no.1
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• pp.207-210
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• 2013

We report the construction of a MALDI imaging mass spectrometer equipped with a specially designed laser focusing lens, a compact aspherical singlet lens, that obtains a high-lateral imaging resolution in the microprobe mode. The lens is specially designed to focus the ionization laser (${\lambda}$ = 355 nm) down to a $1{\mu}m$ diameter with a long working distance of 34.5 mm. With the lens being perpendicular to the sample surface and sharing the optical axis with the ion path, the imaging mass spectrometer achieved an imaging resolution of as good as $5{\mu}m$ along with a high detection sensitivity of 100 fmol for peptides. The mass resolution was about 900 (m/${\Delta}m$) in the linear TOF mode. The high-resolution capability of this instrument will provide a new research opportunity for label-free imaging studies of various samples including tissues and biochips, even for the study at a single cell level in the future.

• The Research Journal of the Costume Culture
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• v.19 no.1
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• pp.71-82
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• 2011

This paper examined the kinds and characteristics of leather and also analyzed the expression techniques and characteristics of leather in contemporary fashion. The objective of this study lies in re-interpreting the current location of leather in contemporary fashion design, enlarging unlimited potential expression fields of leather, and at the same time, helping create new viewpoints and expression types of leather. For this purpose, this paper examined the kinds and characteristics of leather through the existing literatures, and it also carried out positive analysis of the expression techniques and characteristics of leather clothes through local and foreign fashion magazines and collection papers, such as Gap, Vogue, and Mode & Mode, focusing on the works presented in the fashion collections after 2000. Leather in contemporary fashion is expressed in different colors through dyeing. Through various expression techniques such as wrinkles, ruffle, stitch, embossing, quilting, patchwork, holing, nailing, cutting, laser cutting, fringe, weaving, printing, and collage, leather breaks the fixed ideas of itself and further, it makes the images of fashion design affluent. Leather clothes, which are made through various expression techniques, have some characteristics. First, leather clothes emphasize women's voluptuous beauty. Second, leather clothes create a decorative effect through mixture of materials and various expression techniques. Third, through the feel of materials and the emphasis of shapes, primitive beauty is expressed.

• Journal of Korean Elementary Science Education
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• v.39 no.1
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• pp.15-25
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• 2020

In this study, we investigated elementary and preservice elementary school teachers' actual and preferred types of science assessment focusing on the purpose and the method of assessment. Participants were 75 elementary school teachers and 93 preservice elementary school teachers. The questionnaire adopted from previous relevant studies was administerd in order to examine the types of assessment which the teachers have actually implemented and the preferred types of assessment for hypothetical situations known as the prototypical examples of constructivist assessment. The results revealed that most teachers and preservice teachers tend to possess the summative-oriented purpose of assessment. An affective assessment purpose focused on evaluating students' interest, attitude, and curiosity toward science was newly identified in this study. In analyzing teachers' responses from the viewpoint of the method of science assessment, responses of an informal mode such as observation and portfolio were noticeable. However, most of them were found to correspond to the traditional summative-oriented purpose of assessment. For prototypical constuctivist assessment situations, teachers and preservice teachers were found to prefer the performance and the informal modes than the measurement mode of the assessment methods, whereas their purposes of the assessment were not found to be constructivist.

• Journal of Korean Institute of Industrial Engineers
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• v.42 no.2
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• pp.138-150
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• 2016

This study aims to analyze the structure and characteristics of the domestic online game industry using network analysis. In particular, two-mode network analysis is employed to measure the network structure, centrality, and cluster for two types of online game platforms, online games and mobile games, from 1996 to 2014. We also conduct a dynamic analysis to capture the structural changes in the ecosystem by internal and external environmental changes before and after turning point for each online game platform. It is revealed that the online game econsystem has the higher number of clusters and higher concentration ratio than those of mobile game ecosystem. In dynamic analysis, both platforms exhibit similar trends over time with the increasing number of clusters, enlargement of largest cluster's size, and decreasing concentration ratio. This study is expected to provide fruitful implications for strategic decision making of online game companies and policy making for the online game industry.

• Journal of Korean Association for Spatial Structures
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• v.22 no.3
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• pp.57-64
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• 2022

As earthquakes have increased in Korea recently, people are paying attention to the seismic performance of buildings built in the past. Many school buildings in Korea were built based on standard drawings before the seismic design was applied. However, since school buildings are often designated as emergency evacuation facilities in case of disasters such as earthquakes, seismic evaluation and retrofit must be done quickly. This study investigated the failure modes among structural components (beams, columns, and joints), focusing on 1980s standard drawings for school buildings. The effects of column axial force, partial masonry infills, and different material strengths for concrete and rebar were considered for detailed evaluation. As a result, most of the joints were found to be the weakest among structural components. Column axial forces tended to make the joints more vulnerable, and partial masonry infills increased the possibility of joint failure and shear failure in columns.

• Journal of the Korean Solar Energy Society
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• v.31 no.6
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• pp.1-7
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• 2011

Sound waves and acoustic energy generated by two identical TA (ThermoAcoustic) lasers were analyzed and studied. One end of the ceramic stack was heated by a thin NiCr wire wound around that end. The other end of the stack was cooled by natural convection of atmospheric air. The wavelength of the sound waves generated by a single TA laser was four times the tube length and the amplitude of the waves increased with the heating rate. SPL (SoundPressure Level) meters and microphones were employed to measure and study the sound waves at different distances from the glass tube opening and at the focusing point of the TA laser pair for different laser position arrangements. The sound waves of the two TA lasers at the focusing point were found to be almost 180 degrees out of phase when the openings of the two lasers were very close to each other and the angle between the laser axes was small. When the two TA lasers were placed far apart, the sound wave amplitudes and the phase difference between the two laser outputs varied periodically with time. The frequencies of the sound waves changed when the openings of the two TA lasers were in close vicinity and the angle between the laser axes exceeded a certain value. In this case, the glass tube opening was no longer a pressure anti-node and the wavelength of the fundamental mode was not equal to four times the tube length.

• Transactions on Electrical and Electronic Materials
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• v.3 no.1
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• pp.30-37
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• 2002

A focusing grating coupler (FGC) was not fabricated by the 'Continuous Path Control'writing strategy but by an electron-beam lithography system of more general exposure mode, which matches not only the address grid with the grating period but also an integer multiple of the address grid resolution (5 nm). To more simplify the fabrication, we are able to reduce a process step without large decrease of pattern quality by excluding a conducting material or layer such as metal (Al, Cr, Au), which are deposited on top or bottom of an e-beam resist to prevent charge build-up during e-beam exposure. A grating pitch period and an aperture feature size of the FGC designed and fabricated by e-beam lithography and reactive ion etching were ranged over 384.3 nm to 448.2 nm, and 0.5 $\times$ 0.5 mm$^2$area, respectively. This fabrication method presented will reduce processing time and improve the grating quality by means of a consideration of the address grid resolution, grating direction, pitch size and shapes when exposing. Here our investigations concentrate on the design and efficient fabrication results of the FGC for coupling from slab waveguide to a spot in free space.

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.6
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• pp.521-537
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• 2000

Ultrasonic imaging is the most widely used modality among modern imaging device for medical diagnosis and the system performance has been improved dramatically since early 90's due to the rapid advances in DSP performance and VLSI technology that made it possible to employ more sophisticated algorithms. This paper describes "main stream" digital signal processing functions along with the associated implementation considerations in modern medical ultrasound imaging systems. Topics covered include signal processing methods for resolution improvement, ultrasound imaging system architectures, roles and necessity of the applications of DSP and VLSI technology in the development of the medical ultrasound imaging systems, and array signal processing techniques for ultrasound focusing.