• 한국공작기계학회논문집
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• 제11권6호
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• pp.1-9
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• 2002

This study describes the geometric characteristics and the 5-axis machining method in order to make end mill cutter coming with insert tips. End mill geometry is consisted of flute part and insert tip part. Flute part modeled by using ruled surfaces with constant helix angle, and insert tip part modeled by rectangular planes containing tapped hole of specified direction in its center. In this study, the modeled insert tip part considered both of a radial rake angle and a axial rake angle, because they were important cutting conditions. In order to machining the virtual end mill defined from geometric characteristics, we programmed a special software to machining the end mill considered in this study. This software can generate NC-codes about following processes, end milling or ball end milling of flute part end milling of rectangular plane, centering of hole, drilling of hole, and tapping of hole. Ant sampled end mills were modeled and machined on 5-axis CNC machining center with two index tables. Since machined end mills were very agreeable to designed end mills, we saw that the method proposed in this study can be very useful for manufacturing of end mill body with insert tip.

• Tribology and Lubricants
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• 제25권1호
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• pp.1-6
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• 2009

In this paper, the minimum oil film thickness and the maximum oil film pressure of engine bearings have been analyzed by using the elastohydrodynamic theory and Taguchi's design method as functions of the oil groove width, oil hole diameter, oil hole position, and oil supply pressure. The optimized design of the engine bearing f3r an automotive Diesel engine is very important for supporting a load-carrying capacity due to gas pres-sures from the engine combustion chamber and inertia forces of the piston. The optimized design data of engine bearings indicated that the optimized oil groove width and an oil diameter of a engine bearing are 8mm at the speed of 2,000 rpm for a given 4-cylinder Diesel engine. Thus, the oil groove oil groove and an oil hole for high performances of an engine bearing may be considered as major design parameters compared to other design factors, which are strongly related to the minimum oil film thickness and the maximum oil pressure distribution of the engine oil.

• 한국전산유체공학회지
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• 제21권1호
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• pp.64-71
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• 2016

This research is to numerically investigate the convective cooling performance in the Disk brake. Research concentrates on the heat transfer coefficient and cooling performance which are selected with cooling local locations. Cooling performance of the Hole disk has been compared by Ventilated Disk. According to the results of heat transfer on the disk brake, activated velocity distributions more appear in the Hole disk. This is due to the fact that a number of hole units have exactly 120 on the surface of the hole disk. Therefore, velocity distributions of hole disk brake is better activated than Ventilated disk. According to the calculations of Nusselt number between surface and atmosphere in the interested cooling area, average value of cooling effect has been increased 13.5% by the hole disk at driving of speed 65 km/h situation and grown 18% by the hole disk at driving speed of 100 km/h. Due to the flow of air through the hole route, cooling performance of the hole disk was very excellent. In addition, cooling effect on edge of the bottom is better than the vicinity of center.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2000년도 추계학술대회 논문집
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• pp.49-52
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• 2000

The hole flanging experiments are performed on a flat circular plates with a hole in the center and the flangeability and fracture behavior of TRIP steel and ferrite-bainite duplex steel were examined. Over the ranges of conditions investigated, the flangeability of ferrite-bainite duplex steel is better than TRIP steel and the term 'hole flanging capacity' introduced in this study. Fracture behavior of TRIP steel and ferrite-bainite duplex steel was characterized by petal formation at the edge of flange. In case of crack propagation, crack tip diversion that is supposed to be responsible for flangeability occurs more severely on HSLA Steel.

• 소성∙가공
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• 제10권6호
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• pp.465-470
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• 2001

Hole flanging experiments are performed on flat circular plates with a hole in the center and the flangeability and fracture behaviors of TRIP steels and ferrite-Bainite duplex steels were examined. In the hole flanging, deformation by lip and petalling occurs when plates are struck by punches of various shapes and high circumferential strains induced in the target material cause radial cracking and the subsequent rotation of the affected plate material in a number of symmetric petals. In all cases, failure of the plate was due to lip fracture that results from multiple localized neckings that take place around the hole periphery where straining is most severe and a somewhat regular pattern was observed in a fracture shape. The neck characteristics in flange formation and the transition from the lip to petal mode at which fracture occurs were compared with two materials.

• Clinics in Shoulder and Elbow
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• 제25권3호
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• pp.224-229
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• 2022

Background: Most acromioclavicular joint (ACJ) injuries are caused by direct trauma to the shoulders, and various methods and techniques are used to treat them; however, none of the options can be considered the gold standard. This study examines the horizontal stability of the ACJ after a complete dislocation was repaired using one of two Ethibond suture techniques, the loop technique and the two holes in the clavicle technique. Methods: In this single-blind, randomized clinical trial, 104 patients diagnosed with complete ACJ dislocation type V were treated using Ethibond sutures with either the loop technique or the two holes in the clavicle technique. Horizontal changes in the ACJ were radiographically assessed in the lateral axial view, and shoulder function was evaluated by the Constant (CS) and Taft (TS) scores at intervals of 3, 6, and 12 months after surgery. Results: The horizontal stability of the ACJ was better with the two-hole technique than the loop technique at all measurement times. CS and TS changes showed a significant upward trend over time with both techniques. The mean CS and TS at the final visit were 95.2 and 11.6 with the loop technique and 94.0 and 11.9 with the two-hole technique, respectively. The incidence of superficial infections caused by the subcutaneous pins was the same in the two groups. Conclusions: Due to the improved ACJ stability with the two-hole technique, it appears to be a more suitable option than the loop technique for AC joint reduction.

• 천문학회지
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• 제29권spc1호
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• pp.119-122
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• 1996

The case for a massive black hole in the center of the Galaxy is reassessed using improved modeling techniques and observational data. A dark mass of ${\~}{\times} 10^6$ Mo is present within 0.2 pc of the Galactic center. However, the available data can be modeled, without appealing to a massive black hole, using an extended distribution of dark stellar remnants (neutron stars and stellar mass black holes) provided that the stellar initial mass function in the central parsec is deficient in stars less massive than $\~$1 Mo. Such a situation may be a natural consequence of repeated gas build-up followed by starbursts in the central region. A clear distinction between this and the massive central black hole model cannot be made using red giant tracers outside 0.2 pc due to uncertainties in the radial velocity dispersion distribution. The cluster of massive early-type emission-line stars in the central parcsec more effectively probe the mass distribution close to Sgr A $\ast$, but their small number and partial rotational support complicate mass determinations. Proper motion determinations for stars within 0.5' of Sgr A$\ast$ may be the most effective means of unambiguously determining the mass distribution in the immediate vicinity of the Galactic center.

• Journal of Information Display
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• 제12권1호
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• pp.47-50
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• 2011

Highly stable amorphous indium.gallium.zinc-oxide (a-IGZO) thin-film transistors (TFTs) were fabricated with an etchstopper and via-hole structure. The TFTs exhibited 40 $cm^2$/V s field-effect mobility and a 0.21 V/dec gate voltage swing. Gate-bias stress induced a negligible threshold voltage shift (${\Delta}V_{th}$) at room temperature. The excellent stability is attribute to the via-hole and etch-stopper structure, in which, the source/drain metal contacts the active a-IGZO layer through two via holes (one on each side), resulting in minimized damage to the a-IGZO layer during the plasma etching of the source/drain metal. The comparison of the effects of the DC and AC stress on the performance of the TFTs at $60^{\circ}C$ showed that there was a smaller ${\Delta}V_{th}$ in the AC stress compared with the DC stress for the same effective stress time, indicating that the trappin of the carriers at the active layer-gate insulator interface was the dominant degradation mechanism.

• Advanced Composite Materials
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• 제18권1호
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• pp.43-59
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• 2009

The current study assessed the effect of a bolt hole on tensile fatigue properties of CFRP laminates. Two specimens, i.e. $[(0/90)_3]S$, $[(0/45/90/-45)_2]_S$, were analyzed using a finite element method and were experimentally tested for cases, both with and without a hole, whose diameter corresponded to 0.12 times the specimen width. Delamination positions predicted by a 3-dimensional static finite element analysis were matched well to those observed by an ultrasonic imaging system in the middle of fatigue test. A hole whose diameter corresponds to 0.12 times the specimen width caused the fatigue strength to decrease by 9% and 11% under 5 Hz loading frequency, and by 22% and 25% under 10 Hz loading frequency for $[(0/90)_3]_S$ and $[(0/45/90/-45)_2]_S$, respectively. Because the decrease in sectional area due to the hole was normalized in calculation of the tensile strength, a stress concentration around the hole is believed to induce the strength degradation of fatigue specimens. From the finite element analyses, the stress concentration factor around a hole was expected as 8.8 and 9.5 for $[(0/90)_3]_S$ and $[(0/45/90/-45)_2]_S$, respectively.

• 한국정밀공학회지
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• 제33권2호
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• pp.121-128
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• 2016

The mechanical jointing method is very important in the machine parts and structure. They are used by the bolts and rivet because it is very convenient to replace the parts and the structure. However, the mechanical jointing methods using the bolt and rivet needed the open hole. The machine parts life cycle is reduced because this open hole created the stress concentration. Therefore, the measurement methods are needed to evaluate phenomenon of the stress concentration. This paper discusses the development of the measurement algorithm using the digital image correlation methods to measure the strain distribution of the open hole. To implement the measurement algorithm using the DIC, the LabVIEW 2010 programming tool was used. To measure the strain distribution of the open hole, the tensile specimens having an open hole are made by using the aluminum 6061-T6. To secure the reliability of measurement result using the DIC, the DIC measurement results and FEM analysis results were compared.