• Journal of Powder Materials
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• v.29 no.4
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• pp.314-319
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• 2022

The effect of the laser beam diameter on the microstructure and hardness of 17-4 PH stainless steel manufactured via the directed energy deposition process is investigated. The pore size and area fraction are much lower using a laser beam diameter of 1.0 mm compared with those observed using a laser beam diameter of 1.8 mm. Additionally, using a relatively larger beam diameter results in pores in the form of incomplete melting. Martensite and retained austenite are observed under both conditions. A smaller width of the weld track and overlapping area are observed in the sample fabricated with a 1.0 mm beam diameter. This difference appears to be mainly caused by the energy density based on the variation in the beam diameter. The sample prepared with a beam diameter of 1.0 mm had a higher hardness near the substrate than that prepared with a 1.8 mm beam diameter, which may be influenced by the degree of melt mixing between the 17-4 PH metal powder and carbon steel substrate.

• Applied Microscopy
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• v.36 no.spc1
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• pp.25-33
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• 2006

Nanofabrication with finely focused ion and electron beams is reviewed, and position and size controlled fabrication of nano-metals and -semiconductors is demonstrated. A focused ion beam (FIB) interface attached to a column of 200keV transmission electron microscope (TEM) was developed. Parallel lines and dots arrays were patterned on GaAs, Si and $SiO_2$ substrates with a 25keV $Ga^+-FIB$ of 200nm beam diameter at room temperature. FIB nanofabrication to semiconductor specimens caused amorphization and Ga injection. For the electron beam induced chemical vapor deposition (EBI-CVD), we have discovered that nano-metal dots are formed depending upon the beam diameter and the exposure time when decomposable gases such as $W(CO)_6$ were introduced at the beam irradiated areas. The diameter of the dots was reduced to less than 2.0nm with the UHV-FE-TEM, while those were limited to about 15nm in diameter with the FE-SEM. Self-standing 3D nanostructures were also successfully fabricated.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.1089-1092
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• 2001

In the stereolithography process, build parameters are laser power, scan velocity, scan width, bean diameter, layer thickness and so on. These values are determined according to product accuracy and build time. Build time can be reduced by improving of scan velocity, laser power, layer thickness, hatching space and so on. But variation of these parameters influence part accuracy, surface roughness, strength. This paper observed cure properties in various beam diameter. In order to examine these, relationships of scan velocity and cure depth, scan velocity and cure width according to various beam diameter in one scan line are measured. And cure thickness is measured according to beam diameter and scan velocity in scan surface of one layer. For reduction of build time, beam diameter and scan velocity is proposed in stereolithography process.

• Korean Journal of Optics and Photonics
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• v.11 no.2
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• pp.73-79
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• 2000

We measure a beam diameter of scan and sub-scan direction of LSD (Laser Scanning Urnt) which uses $fheta$ lens produced by injecLion molding method as a scanning lens. While the measured beam diameter in scan direction, which is $62muextrm{m}$ to $68\mu\textrm{m}$, shows similar size comparing to the design beam diameter, the sub-scan beam diameter shows sIzable beam diameter deviation as much as 37 11m ranging from $78\mu\textrm{m}$ to $115\mu\textrm{m}$. Injection molding lens has the surface figure error due to the shrinkage III the cooling time and the internal distortion (birefringence) due to the uneven cooling conditIOn so that these bring about wavefront aberration (i.e., the enlargement of beam size), and are eventually expre~sed as the deterioration of the pdnting image. In this paper. we first measure and analyze beam diameter, birefringence (polanzation ratio), and asphedcal figure error of mIens in order to know the principle cause of the beam diameter deviation in sub-scan directIOn. And Lhen. through the analysis of a designed depth of focus and a calculated field curvature (imaging position of the optical axis directIon) using the above figure elTor data, we know Lhat the birefringence IS the main factor of sizable beam diameter deVIation in sub-scan direction. ction.

• Journal of the Korea Furniture Society
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• v.13 no.2
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• pp.11-18
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• 2002

This study was carried out to investigate the strength and technical feasibility of glulam from small diameter Pinus densiflora and Larix kaempferi. Small diameter logs are currently not used in structural laminated beam construction, but it is suggested that its properties may be feasible for this purpose. The glulam combinations were designed with high grade laminae located at outer laminations (face) and low grade laminae located at center laminations. Important problems of finger jointed glulam as a structural beam are the small modulus of rupture (MOR). One solution for this problem Mi to use veneer and solid wood as the face laminae. The MOE values were predicted for each beam from laminae. The results showed that actual beam MOE values exceeded slightly the predicted values. Based on the evaluation and analysis of Pinus and Larix glulam, the maximum load of Larix kaempferi glulam indicated large values. The bending properties of A and E types glulam were superior to others. It is suggested that this small diameter log can be a candidate for structural glulam construction, providing the proper combinations of face laminae.

• Structural Engineering and Mechanics
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• v.89 no.2
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• pp.155-170
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• 2024

Several types of column-beam connections are used in the design of steel structures. This situation causes different cross-section effects and, therefore, different displacements and deformations. In other words, connection elements such as welds, bolts, continuity plates, end plates, and stiffness plates used in steel column-beam connections directly affect the section effects. This matter reveals the necessity of knowing the steel column-beam connection behaviours. In this article, behaviours of bolted column-beam connection with end plate widely used in steel structures are investigated comparatively the effects of the stiffness plates added to the beam body, the change in the end plate thickness and bolt diameter. The results obtained reveal that the moment and force carrying capacity of the said connection increases with the increase in the end plate thickness and bolt diameter. In contrast, it causes the other elements to deform and lose their capacity. This matter shows that optimum dimensions are very important in steel column-beam connections. In addition, it has been seen that adding a stiffness plate to the beam body part positively contributes to the connection's moment-carrying capacity.

• Journal of the Korean Society of Safety
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• v.20 no.4 s.72
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• pp.54-62
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• 2005

This Study is to find out how RC beam mixed with sawdust acts comparing with normal beam without sawdust mixture, and how they can be applied to the actual structural frame, despite a Int that they are mixed with waste material : saying sawdust. ED3H1, ED3H2, ED5H1, ED5H2, ED3H1UB, ED5H1UB, ED3H2L, ED5H2L and Normal without sawdust mixture are main factor to be tested here in order to apply them to the actual case. D and H means diameter 3cm or 5cm, and holes one and two respectively. And all variables are tested with each two for one variables. Test results are compared using crack diagrams and strain & loads. There are eleven(11)% capacity decrease between ED 3H1 and ED5H1 in rebar, strain. Left and right side crack shapes are much similar in variable ED3H2L having maximum capacity 14.5 tone. ED5H2L having maximum capacity thirteen(13)tone, in case of normal 19.6 tone. Two holes in beam rather on the longitudinal direction than on the forcing direction can be more effective to keep the original capacity of the beam because this case can distribute load more uniformly. There is 33% capacity decreased in case of diameter five(5)cm, compared to diameter three(3)cm. Two holes give thirty nine(39) percent capacity decrease than one of diameter three(3)cm.

• Journal of Sensor Science and Technology
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• v.8 no.3
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• pp.219-225
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• 1999

The purpose of this study is to measure such parameters as TMR, OAR, TSF for small beams ranging in size from 12.5mm to 40mm by diode, ionization chamber, film, TLD and to determine proper detectors for the measurement of 6MV small x-ray beams. Diode and film show good results within 2% error for the TMR measurement of the beam as small as beam with diameter 12.5mm. Diode and film have excellent spatial resolution in the OAR measurement and the comparison between two detectors shows the error within 3%. But TMR and OAR can not be measured accurately by the ionization chambers. The TSF by diode and TLD records 0.890.96 for the beams with diameter 12.5mm 40mm. The TSF determined by 0.125cc ionization chamber and markus ionization chamber for the larger beams than the beams with diameter 25mm agrees within 2% comparing with that of diode and TLD.

• Proceedings of the Optical Society of Korea Conference
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• 1989.02a
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• pp.76-80
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• 1989

Spatial filters were designed for 1 TW high power phosphate glass laser development. Laser beam should be expanded from 1 mm diameter to 200mm diameter. Pin hole size should be determined and most of incident energy should be transmitted through out to final spatial filter. Each pin hole size is determined by calculating encircled energy for Gaussian beam from the oscillator. The optical tube length of each spatial filter is corrected to have the best collimating quality by scew raytracing through the total system.

• Journal of the Korean Vacuum Society
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• v.20 no.6
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• pp.403-408
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• 2011

To develop the MFX (Micro-Focus X-ray) tube, the trajectories of electrons emitted from the field emission cathode was simulated using SIMION program. Regardless of starting position of the electron in emitter, we found out the fact that there is the optimum extractor voltage Ve, which can focus the electron beam on one place. Extractor voltage Ve varies depending on the source voltage Vs, but the ratio of two voltages (Ve/Vs) is always constant, its value was 99.4%. When the ratio of two voltages (Ve/Vs) was 99.4%, the beam diameter in the cross-over point was $1.2{\mu}m$. Because the focal spot size in MFXG (Micro-Focus X-ray Generator) can not be less than the cross-over diameter within MFX tube, it is important to find out the conditions that can make a smaller beam diameter. Therefore, the above results is considered to be a very important ones in the development of the MFXG.