• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.11a
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• pp.204-211
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• 2001

For the treatment of high compressibility number in the Reynolds equation, a new class of exponential high-order shape functions has been recently introduced in the literatures. In this paper a FE lubrication analysis method of high speed gas mechanical face seals is developed, implementing these shape functions. Their validity and usefulness are presented using 1-D gas bearing models. And a validation of developed 2-D analysis code is shown with a gas flat and spiral groove face seal models.

• Tribology and Lubricants
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• v.32 no.4
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• pp.119-124
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• 2016

In the sapphire wafering process, lapping is a crucial operation in order to reduce the damaged layer and achieve the target thickness. Many parameters, such as pressure, velocity, abrasive, slurry and plate, affect lapping characteristics. This paper presents an experimental investigation on the effect of the plate groove on the material removal rate and roughness of the wafer. We select the spiral pattern and rectangular type as the groove shapes. We vary the groove density by controlling the groove shape dimension, i.e., the groove width and pitch. As the groove density increases to 0.4, the material removal rate increases and gradually reaches a saturation point. When the groove density is low, the pressing load is mostly supported by the thick film, and only a small amount acts on the abrasives resulting to a low material removal rate. The roughness decreases on increasing the groove density up to 0.3 because thick film makes partial participations of large abrasives which make deep scratches. From these results, we could conclude that the groove affects the contact condition between the wafer and plate. At the same groove density, the pitch has more influence on reducing the film thickness than the groove width. By decreasing the groove density with a smaller pitch and larger groove width, we could achieve a high material removal rate and low roughness. These results would be helpful in understanding the groove effects and determining the appropriate groove design.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2000.11a
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• pp.419-420
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• 2000

The present study introduces and describes the characteristics of the spiral guide and groove body cyclones for the first time. The spiral guide was set inside the cyclone body or the inside of the cyclone body was grooved circumferentially or vertically. Except for the cyclone body, all configurations were the same. The particle collection efficiency for a conventional cyclone (Figure 1) was measured under a series of flow rates ranging from 15 L/min up to 80 L/min, and was compared with that yielded using existing theories. (omitted)

• Restorative Dentistry and Endodontics
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• v.30 no.1
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• pp.31-37
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• 2005

The aim of this study was to evaluate the effectiveness of sealer placement in simulated root canal extensions. Forty resin blocks were attained from the Endo-training Bloc. In each block. The simulated root canal was made with $\#20$, 80taper GT file. After each block was longitudinally split into two halves, a standardized groove was prepared on one canal wall of two halves to simulate the canal extensions with various irregularities. The two halves of each block were assembled and all simulated root canals were obturated by single cone method with AH26 sealer. Four different methods of sealer placement were used: group A, $\#20$ K-file; group B, ultrasonic file; group C, lentulo spiral; group D, EZ-Fill bi-directional spiral. All obturated blocks were stored in $100\%$ humidity at $37^{\circ}C$ for 1 week, Using a low speed saw, each block was sectioned horizontally. Images of the sections were taken using a stereomicroscope at $\times$ 30 magnification and a digital camera. The amount of the sealer in the groove was evaluated using a scoring system, a higher score indicated better sealing effectiveness. The data was statistically analysed by Fisher's Exact Test. The sealing score was the lowest, specially at the middle area of canal extensions in group A, and that was statistically significant difference from other groups. In conclusion, the ultrasonic file, lentulo spiral and EZ-Fill bi-directional spiral were effective methods of sealer placement in simulated canal extensions. The K file was the least effective method, specially at the middle area of canal extensions.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.4
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• pp.123-129
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• 2018

A rotational drawing die which can form a long tube with spiral grooves on the surface is presented. The main feature of the proposed die is a rotation insert that is embedded into the die container for the die to freely rotate with respect to the drawing centerline as the materials are drawn. We employed a three-dimensional finite element model to investigate the effects of the rotational die on the material filling of spiral grooves. The material used in the finite element analysis was stainless 304. We also performed a pilot drawing test to verify the usefulness of the proposed rotational drawing die. Results reveal that the material filling of spiral grooves by the proposed rotational drawing die was in good agreement for both the finite element analysis and the drawing test. We found that the underfill in a conventional drawing die was reduced in the proposed rotational drawing die.

• Progress in Superconductivity and Cryogenics
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• v.3 no.1
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• pp.16-21
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• 2001

Bubble behavior is studied with an electrode system which consists of coaxial spiral coil-to-cylindrical electrode with an insulation barrier and spacers and is immersed in liquid nitrogen for simulation of insulation environments in high temperature superconducting(HTS) coils The results show that the bubble behavior Is affected severely by electric field: (1) under low applied voltage bubbles rise by buoyancy, but at higher applied voltage they are trapped in a lower electric field region below the coil electrode, and (2) the trapped bubble flows along the downside of coil electrode if no obstruction is in a groove between coil turns. but it splashes out of the groove after its growing if the obstruction such as spacer-exists.

• KSTLE International Journal
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• v.4 no.1
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• pp.18-26
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• 2003

Recently, fluid dynamic bearings (EDBs) have important applications in miniature rotating machines such as those found in the computer information storage industry, due to their outstanding low acoustic noise and NRRO (Non-Repeatable Run Out) characteristics. This research investigates the dynamic behavior of fluid dynamic bearings composed of hydrodynamic herringbone groove journal and spiral groove thrust bearing. The five degrees of freedom of FDB are considered to describe the real motion of a general rotor bearing system. The Reynolds equation and five nonlinear equations of motion for the dynamic behavior are solved simultaneously, The incompressible Reynolds equation is solved by using the finite element method (FEM) in order to calculate the pressure distribution in a fluid film and the five equations of motion by using the Runge-Kutta method. The reaction forces and moments are obtained by integrating the pressure along the fluid film. Numerical results are validated by comparing with the previously published experimental and numerical results. As a result the dynamic behavior of FDB spindle such as orbit, floating height, and angular orbit is investigated by considering the conical motion under the static and dynamic load conditions.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.498-501
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• 2000

Air dynamic bearings are inherently unstable in dynamic behavior due to the varying angle of a force produced and the nonlinear characteristics of stiffness. In this study, such dynamic behavior is obtained and compared with experimental results. A body axis coordinate system is employed to avoid the change of a moment of inertia. FDM is used to calculate the pressure distribution on the bearing surface and then the force acting on the rotor was calculated by integrating the pressure distribution. By integrating accelerations which are calculated from the equations of motion using the 4th order Runge-Kutta method, the pose of the bearing at each time step is obtained.

• Korean Journal of Poultry Science
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• v.25 no.3
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• pp.113-118
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• 1998

These experiments were conducted to develope the artificial insemination methods of wild duct (Anas platyhychis platylyachos) . The characteristics of erect phallus and semen collected by the abdominal massage method were investigated in wild duck. The erection and withdrawal time of phallus were 50.70${\pm}$18.66 and 92.58${\pm}$51.95 sec. , respectively, in wild duck. The length, long and short diameter of erect phallus were 3.98${\pm}$0.49crn, 1.53${\pm}$0.15cm and 1.05${\pm}$0.04 cm, respectively, and the spiral grooves of erect phallus were 4 in wild duck. The volume of semen, concentration of spermatozoa and total sperm of an ejaculate were 0.18${\pm}$0.06 ml, 2.84${\pm}$0.03 x 10 9 /ml and 0.52${\pm}$0.21 x 10 cells, respectively, in wild duck. The motility of sperm and pH of semen were 49.06${\pm}$14. 35 and 7.6${\pm}$0.14 in wild duck.

• 한국정보통신설비학회:학술대회논문집
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• 2009.08a
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• pp.54-58
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• 2009

In this paper, the ECT(eddy current testing) signal analysis of eddy current array probe for inspection of SG(steam generator) tube in NPP(nuclear power plant) using electromagnetic FEM(finite element method) was performed. To obtain the electromagnetic characteristics of probes, the governing equation was derived from Maxwell's equation, and the problem was solved by using the 3-dimensional FEM. The types of defects were FBH(flat bottomed hole) and OD groove, Spiral groove, natural defects(pitting, SCC, multiple SCC, wear). The depth of FBH defects were 20%, 40%, 60%, 80%, 100 of SG tube thickness, and it was assumed that the defects were located on the tube outside. And the operation frequency of 100kHz, 300kHz and 400kHz were used. Material of specimen was Inconel 600 which is usually used for SG tubes in NPP. The signal difference could be observed according to the variation of size and depth on FBH defects and operation frequencies. The results in this paper can be helpful when the ECT signals from EC array probe are evaluated and analyzed.