• Journal of the Korean Society for Precision Engineering
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• 제15권4호
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• pp.7-14
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• 1998

Noncircular gears have been used for obtaining the modified anglualr velocity ratio between parallel axes. The elliptical gear, which is a kind of noncircular gears, makes use of ellipse as a pitch curve, and is applied for the measurement of the discharge of liquid. The applications of an elliptical gear are more advantageous than any other mechanism as like a crank-slider linkage or a cam mechanism in view of the accuracy and the reliability to transmit the prescribed motion. In this paper, acceding to the theoretical involute tooth profile, two pairs of the elliptical gears were manufactured by using CNC wire electronic discharge machine. The proper ranges of the operating pressure angle and of module not to generate under cutting are studied on the change of the eccentricity, because it is the eccentricity of the pitch curve that determines most of the characteristics of the elliptical gear and then the vibration analysis is executed for the verification of harmonious rotating.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2000년도 유체기계 연구개발 발표회 논문집
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• pp.285-292
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• 2000

Numerical calculation is applied to centrifugal pump at design condition by using commercial code STAR-CD and Tascflow, and these results are compared with experimental data at impeller outlet. Numerical analysis is also performed by changing turbulence model and discretization scheme at design condition using Tascflow. Turbulence model and discretization scheme used to Tascflow are k-$\epsilon$, k-$\omega$ turbulence model and upwind, modified linear profile scheme. W;th the same turbulence model and discretization scheme, two results of STAR-CD and Tascflow are very similar. But there is significant difference in numerical results near hub and shroud of impeller with different kinds of turbulent model and discretization scheme at design condition. And with k- $\omega$ turbulence model and modified linear profile scheme, it is showed that numerical results are very similar to experimental results of impeller outlet

• Proceedings of the Korean Society of Precision Engineering Conference
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.476-479
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• 1997

A Knowledge of friction force in pneumatic cylinders makes it possible to improve cylinder description during simulation and to asses performance under changing operating conditions more accurately. Such knowledge is particularly useful, for example, when modeling continuous pneumatic positioning systems or predicting the operating conditions under which stick slip may occur, as well as in establishing preventive maintenance procedures for pneumatic cylinders. Friction force depends on a number of factors, including operating pressure, seal running speed on the cylinder barrel and rod, barrel material and surface roughness, seal dimensions and profile, seal material, lubrication conditions, cylinder distortion during assembly, and the operating temperature of cylinder components. This paper shows a system for measuring the friction force caused by a seal used in pneumatic cylinders. Results of experimental tests show that seal friction forces for grease lubricated service are clearly dependent on speed and pressure and are les sensitivity to other parameter. i.e., barrel material and roughness, seal material, and profile.

• Journal of Mechanical Science and Technology
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• 제20권3호
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• pp.345-357
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• 2006

By employing the concept of equivalent linkage, this paper presents an analytical method for analyzing the mechanical errors of disk cam mechanisms with a flat-faced follower. The resulting error equations do not really involve the location of the curvature center of the cam profile, and locating the curvature center of the cam profile is not essential. The resulting errors are significantly affected by the pressure angle, and the smaller pressure angle will result in the smaller mechanical error. In the worst case, owing to the joined effects of various design parameters, the accuracy of the follower motion may degrade considerably. For the oscillating follower case, all acceleration error functions have a sudden change at every beginning and at every end of the motion even though the theoretical follower displacement is cycloidal motion.

• KSTLE International Journal
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• 제5권1호
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• pp.14-22
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• 2004

The sub-surface stress field beneath the gear's contact surface caused by the surface pressure in lubricated condition is analyzed. To evaluate the influence of the clearances between a gear tooth and a pinion tooth on the stress field, two kinds of tooth profile models - conventional cylinder contact model and new numerical model - were chosen. Kinematics of the gear is taken into account to obtain the numerical model which is the accurate geometric clearances between a gear tooth and a pinion tooth. Transient elasto-hydrodynamic lubrication (EHL) analysis is performed to get the surface pressure. The sub-stress field is obtained by using Love's rectangular patch solution. The analysis results show that the sub-surface stress is quite dependent on both the surface pressures and the profile models. The maximum effective stress of the new model is lower than that of the old model. The depth where the maximum effective stress occurs in the new model is not proportional to the intensity of the external load.

• Tribology and Lubricants
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• 제20권3호
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• pp.157-162
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• 2004

The cam curve of a balance type vane pump consists usually of circular arcs and Archimedes' spirals. However, if they are connected directly together, the curve must have a few discontinuous points of the gradients and the motion of the vanes is no longer smooth. Designing data for an oil hydraulic vane pump used in power steering system were obtained by the acquisition of optimum cam profile data which can be available to reduce noises and vibrations through the minimization of cavitation with the improvement of suctional performance. The performance test is carried on the trial manufactures by measuring the volumetric and the mechanical efficiency. And from that result, maintaining the same characteristic as the conventional one in the relief pressure and noise level, the experimental pump discharges 0.7 $\ell$/min and shows nearly 3.5% enhancement in the total efficiency more than the conventional one.

• Journal of the Korea Institute of Military Science and Technology
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• 제5권2호
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• pp.207-216
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• 2002

In this paper, the study on the behavior of the deformation of brittle material, such as concrete, ceramic, was peformed by comparison of Lagrangian technique and Smoothed Particle Hydrodynamics using commercial nonlinear hydrodynamic numerical program, Autodyn_2D. The effect of SPH technique was proved by investigating the behavior of material deformation, velocity profile and pressure profile.

• Proceedings of the KSME Conference
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• 대한기계학회 2004년도 추계학술대회
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• pp.1069-1074
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• 2004

This study investigated the effect of pressure variations on augmentation of heat transfer when the ultrasonic waves were applied. The augmentation ratio of heat transfer was experimentally investigated and was compared with the profiles of pressure distributions calculated applying a coupled finite element-boundary element method (coupled FE-BEM). As the ultrasonic intensities increase from 70W to 340W, the velocity of the liquid paraffin is found to increase as well as kinetic energy, This physical behavior known as quasi-Eckart streaming results from acoustic pressure variations in the liquid. Especially, the higher acoustic pressure distribution near two ultrasonic transducers develops more intensive flow (quasi-Eckart streaming), destroying the flow instability. Also, the profile of acoustic pressure variation is consistent with that of augmentation of heat transfer. This mechanism is believed to increase the ratio of hear transfer coefficient.

• Proceedings of the KSCN Conference
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• 대한지역사회영양학회 1998년도 추계학술대회 및 제3차 정기총회
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• pp.97-97
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• 1998

• New & Renewable Energy
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• 제9권2호
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• pp.23-29
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• 2013

Furnace and laser is currently the most important doping process. However furnace is typically difficult appling for selective emitters. Laser requires an expensive equipment and induces a structural damage due to high temperature using laser. This study has developed a new atmospheric pressure plasma source and research atmospheric pressure plasma doping. Atmospheric pressure plasma source injected Ar gas is applied a low frequency (a few 10 kHz) and discharged the plasma. We used P type silicon wafers of solar cell. We set the doping parameter that plasma treatment time was 6s and 30s, and the current of making the plasma is 70 mA and 120 mA. As result of experiment, prolonged plasma process time and highly plasma current occur deeper doping depth and improve sheet resistance. We investigated doping profile of phosphorus paste by SIMS (Secondary Ion Mass Spectroscopy) and obtained the sheet resistance using generally formula. Additionally, grasped the wafer surface image with SEM (Scanning Electron Microscopy) to investigate surface damage of doped wafer. Therefore we confirm the possibility making the selective emitter of solar cell applied atmospheric pressure plasma doping with phosphorus paste.