• Restorative Dentistry and Endodontics
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• v.12 no.2
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• pp.111-116
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• 1987

The experimental study was made to evaluate the influence of retentive grooves on the canal wall upon the retention of post, using different type of cements. Ninety periodontally involved anterior teeth were extracted and divided into six groups of 15 teeth. The groups were labeled as follows: Group I: Dentatus post cemented zincphosphate cement into post hole with smooth wall. Group II: Dentatus post cemented with zincphosphate cement into post hole with retentive grooves. Group III: Dentatus post cemented with glass-ionomer cement into post hole with smooth wall. Group IV: Dentatus post cemented with glass-ionomer cement into post hole with retentive grooves. Group V: Dentatus post cemented with composite resin adhesive into post hole with smooth wall. Group VI: Dentatus post cemented with composite resin adhesive into post hole with retentive grooves. The tensile strength was tested by an Instron type tester with cross-head speed of 5mm per minute. The results were as follows: In the group without retentive grooves, three kinds of cement have little effect upon retentive capacity of Dentatus post. The Dentatus post cemented on the canal wall with retentive grooves is more retentive than Dentatus post without retentive grooves.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.2
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• pp.235-243
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• 2001

This paper describes a design study of the cylindrical multi-hole premixed burner to be used for condensing gas boiler which can raise performance and reduce NOx emission. In this study, specifications of the multi-hole burner (hole diameters and arrangement) are investigated using model flat burners in terms of flame stability, and combustion characteristics for stability and NOx emission are examined for cylindrical multi-hole burner. As a result, the equivalence ratio for optimum operation condition of the cylindrical burner is around 0.72(0.7∼0.75). In this condition, turn-down ratio becomes 3 : 1 at least which is suitable for proportional control. The NOx and CO emission is less than 40ppm and 25ppm(0$_2$0% basis), respectively. This burner can be applied LPG as well as NG because there is no difference for stable combustion region.

• The Journal of the Korean dental association
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• v.15 no.11
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• pp.763-766
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• 1977

The Purpose of this study was to observe force required to remove some kinds of pin from dentin. The teeth were embedded within a resin cylinder and the occlusal surface was sectioned at a right angle to the axis of the cylinder to expose dentin surface. Thread mate system pin (minim and regular), friction Iocked pin and cemented pin were tested Pin holes were drilled by handpiece and depths of pin holes were tested 1,2 and 3mm. After insertion of the pins into pinhole, tensile loading was performed on the Instron testing machine at the speed of 0.5 inch/min. Results were follewed: 1. In retention, the cemented pins are the least, the friction locked pins intermediate and the self threading pins the greatest in all pins. In self threading pins, regalar pin has greater retention than minim pin 2. The deeper the depth of the pin hole is, the more the retention of the pin increases.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.481-485
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• 2000

A new type of compliant press-fit pin has been developed and evaluated for use packaging of electronic telecommunications equipments. Main requirements for design are defined the upper limit of pin insertion force and the lower limit of pin retention force. Upper limit of pin insertion force is set to protect the copper plate of the inner PTH wall. Lower limit of pin retention force is set to satisfy a wire-wrapping specification. Results are represented by insertion force and retention force variations according to the front angle, rear angle and material, etc.

• Composites Research
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• v.36 no.4
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• pp.259-263
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• 2023

This study investigated the open hole tensile (OHT) properties of carbon fiber/epoxy composites and compared them to bolt joint tensile (BJT) properties. The net nominal modulus and strength (1376 MPa) were found to be higher than the gross nominal strength (1041 MPa), likely due to increasing hole size. The OHT and BJT specimens exhibited similar stiffness, as expected without bolt rotation causing secondary bending. OHT specimens experienced a sharp drop in stress indicating unstable crack propagation, delamination, and catastrophic failure. BJT specimens failed through shear out on the bolt side and bearing failure on the nut side, involving fiber kinking, matrix splitting, and delamination, resulting in lower strength compared to OHT specimens. The strength retention of carbon fiber/epoxy composites with open holes was 66%. Delamination initiation at the hole's edge caused a reduction in the stress concentration factor. Filling the hole with a bolt suppressed this relieving mechanism, leading to lower strength in BJT specimens compared to OHT specimens. Bolt joint efficiency was calculated as 15%. The reduction in strength in bolted joints was attributed to fiber-matrix splitting and delamination, aligning with Hart Smith's bolted joint efficiency diagram. These findings contribute to materials selection and structural reliability estimation for carbon fiber/epoxy composites. They highlight the behavior of open hole and bolt joint configurations under tensile loading, providing valuable insights for engineering applications.

• Journal of Korean Society on Water Environment
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• v.28 no.5
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• pp.686-692
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• 2012

This study illustrates how to design and evaluate a non-point sources management detention pond using SWMM. In particular, special attention is given to the orifice design. In SWMM, orifice properties that need to be defined include its height above the bottom of the storage unit, its type, its geometry and its hydraulic properties. Among the various characteristics of orifice, the orifice hole size which is closely related to hydraulic retention time is focused in this study. Sensitivity analysis of orifice size in annual non-point sources reduction efficiency is carried out. In addition, a methodology which can be used to design a virtual junction in SWMM has been proposed to quantify water quality improvement triggered by the detention pond installation. As a result, it is recommended that a detention outlet should be designed to be about 2 to 3 days of hydraulic retention time.

• Journal of Korean Society of Water and Wastewater
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• v.27 no.1
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• pp.49-58
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• 2013

A selected halogenated organic contaminant, monochlorophenol was successfully degraded by photocatalytic reaction in a circulating batch system. The photocatalytic degradation in most cases follows first-order kinetics. The photocatalytic reaction rate increased in the $TiO_2$ dosage range of 0.1 g/L to 0.4 g/L, then decreased with further increase of the dosage. Also the degradation rate increased over the range of the retention time from 0.49 min. to 0.94 min., then decreased with further increase of the retention time in the circulating batch reactor. The photocatalytic activity was enhanced by addition of metal impurities, platinum(Pt) and palladium(Pd) onto the photocatalysts. The photocatalytic degradation rate increased with the increase of Pt and Pd in the content range of 0 to 2wt %, then decreased with further increase of the metal contents. Therefore the metal loading to $TiO_2$ influence the degradation rate of a halogenated organic compound by acting as electron traps, consequently reducing the electron/positive hole pair recombination rate.

• JSTS:Journal of Semiconductor Technology and Science
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• v.1 no.1
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• pp.40-49
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• 2001

We have developed a repeatable process of forming uniform, small-size and high-density self-assembled Si nano-crystals. The Si nano-crystals were fabricated in a conventional LPCVD (low pressure chemical vapor deposition) reactor at $620^{\circ}c$ for 15 sec. The nano-crystals were spherical shaped with about 4.5 nm in diameter and density of $5{\times}l0^{11}/$\textrm{cm}^2$. More uniform dots were fabricated on nitride film than on oxide film. To take advantage of the above-mentioned characteristics of nitride film while keeping the high interface quality between the tunneling dielectrics and the Si substrate, nitride-oxide tunneling dielectrics is proposed in n-channel device. For the first time, the single electron effect at room temperature, which shows a saturation of threshold voltage in a range of gate voltages with a periodicity of ${\Delta}Ｖ_{GS}\;{\approx}\;1.7{\;}V$, corresponding to single and multiple electron storage is reported. The feasibility of p-channel nano-crystal memory with thin oxide in direct tunneling regime is demonstrated. The programming mechanisms of p-channel nano-crystal memory were investigated by charge separation technique. For small gate programming voltage, hole tunneling component from inversion layer is dominant. However, valence band electron tunneling component from the valence band in the nano-crystal becomes dominant for large gate voltage. Finally, the comparison of retention between programmed holes and electrons shows that holes have longer retention time.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.36 no.3
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• pp.52-59
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• 2004

The greater Increase of the demand for environmental friendly materials especially for packaging industry leads to the larger interest in the reusable and recycable materials such as pulp mold. Although the pulp mold has great characteristics for packaging, some deficiency compared with other packaging material like EPS(Expandable Polystyrene) need to be overcome, for example, the relative higher cost. In this report, since the water drainage rate at the forming zone of a wet pulp mold process could have a great influence on the economical efficiency not only by increasing machine speed but also reducing the drying energy, the optimum ways for increasing drainage were investigated The mechanism of vacuum drainage In pulp mold forming was successfully evaluated by using RDA(Retention and Darinage Analyzer). Since the conditions of stock were greatly affected by the pulping time of low consistency pulper, the optimum pupling time was investigated with considerations of all stock preparation processes. The change of stock temperature and the addition of polyelectrolyte could improve the vacuum drainage rate. It was founded that the wire mesh types of mold former had a little influence on the retention because of the relatively mild vacuum drainage. However, the bigger size of dewatering hole showed better drainage rate and could reduce the plugging and con lamination of mold.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.28 no.3
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• pp.213-221
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• 2006

Purpose This study was aimed to evaluate the effect of the location and angle of drilling on the changes of the distance between the two block specimens. Materials and methods In experimental group 1, the screw holes were prepared by drilling in the distal portion of compression part of the plate at $90^{\circ}$. In experimental group 2, the drilling was performed at an angle of $30^{\circ}$ proximal to the miniplate, and in experimental group 3, at $30^{\circ}$ distal respectively. In control group, the drilling was performed to the center of hole at $90^{\circ}$. The fixation screw length was 5 mm, 7 mm, and 9 mm in all groups. The results were as follows. Results 1. In control group, the mean changes between two specimens were 0.01 mm, 0.02 mm, and 0.00 mm in 5 mm, 7 mm, and 9 mm screws respectively. 2. In experimental group 1, the compression part was moved toward the retention part. The range of mean changes were from -0.39 mm to -0.43 mm. 3. In experimental group 2, the compression part was moved toward the retention part. The range of mean changes were from -0.51 mm to -0.56 mm. 4. In experimental group 3, the compression part was moved apart from the retention part and the range of mean changes were from 0.55 mm to 0.56 mm. 5. The changes were significantly different between all groups(p<0.01). Conclusion These results suggest that 0.4$\sim$0.5 mm of compressive effect can be achieved by drilling on the distal area of the screw hole at an angle of $90^{\circ}$ and by the proximal angulation to the miniplate, and the gap between specimens can be increased by distal angulation to the miniplate during drilling.