• Journal of the Korea institute for structural maintenance and inspection
• /
• v.25 no.6
• /
• pp.95-102
• /
• 2021

Elastometic bearings using flexible rubber materials have recently been widely applied for seismic retrofit of bridges. However, due to various factors, the aging of the rubber material progresses, which causes the shear stiffness change of the bearing, which affects the seismic performance of the bridge. For natural rubber, accelerated heat aging test was performed with variables of heating temperatures and exposure time to analyze shear characteristics. As aging progresses (i.e. increase of temperature and exposure time), the maximum shear stress and shear strain decrease. Also, the shear stiffness is greatly increased at the same shear strain. This means that the rubber material is hardened, implying that the seismic performance of the elastomeric bearing becomes poor.

• Animal cells and systems
• /
• v.5 no.1
• /
• pp.1-9
• /
• 2001

Terebelliphilus simplex n. gen., n. sp. and Myxomolgus invulgus n. sp. are described from the tubicolous polychaetes found in the intertidal shores in the Yellow Sea. The new genus Terebelliphilus belongs to the family Sabelliphilidae but is characteristic in bearing the reduced segmentations In legs 1-4, an unusual sexual dimorphism in antennule, and the ventral location of genital areas. Myxomolgus invulgus is readily distinguishable from its congeners by the morphological features of rostrum, antennule, mandible, maxilla, leg 4 and female leg 5.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2006.10a
• /
• pp.411-412
• /
• 2006

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2010.05a
• /
• pp.262-263
• /
• 2010

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2000.10a
• /
• pp.332-336
• /
• 2000

Cooling characteristics of cooling jacket for spindle system with built-in motor are studied. For the analysis, three dimensional model for the cooling jacket is built by using finite volume method. The three dimensional model includes the estimation on the amount of heat generation of bearing and built-in motor and the thermal characteristic values such as heat flux on the boundary. Numerical results show that flow rate are important factors for cooling characteristics of cooling jacket.

• Animal cells and systems
• /
• v.12 no.3
• /
• pp.157-163
• /
• 2008

Paradexamine jindoensis n. sp. belonging to family Dexaminidae was collected from Jindo Island, Korea. The new species is fully illustrated and compared with related congeners. The new species resembles highly P. houtete, in having the tooth formulae of dorsal pleonites, 1-3-3-3, rear to front and in bearing short spines on the mandible. However, it is characteristic in having the several morphological differences of mouth parts, slender appendages, and longer peduncular article 2 of antenna 1 than article 1.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 1996.03a
• /
• pp.47-51
• /
• 1996

Unsteady-state temperature distributions and thermal deformations of a spindle system are studied in this paper. Three dimensional model is built for analysis, and the amount of heat generation of bearing and the thermal characteristic values including heat transfer coefficient are estimated. Temperature distributions and thermal deformations of a model are analyzed using the finite element method and the termal boundary values. Numerical results are compared with the measured data. The results show that thermal deformations and temperature distributions of a high precision spindle system can be reasonably estimated using the three dimensional model and the finite element method.

• 제어로봇시스템학회:학술대회논문집
• /
• 2004.08a
• /
• pp.990-994
• /
• 2004

This paper presents a method to predict the transient characteristic of the air lubricated slider head in a hard disk drive by using optimization technique. The time dependent modified Reynolds equation based on the molecular slip flow approximation equations was used to describe the fluid flow within the air bearing and the implicit finite difference scheme is applied to calculate the pressure distribution under the slider head. The exhaustive search combined with the Broyden-Fletcher-Goldfarb-Shanno method were employed to obtain optimum design variables which are taper angle, rail width and taper length in order to keep the forces and moments acting on the slider head in dynamic equilibrium. The results show that the optimal head slider of the magnetic head has good stability characteristic that can reach the steady state within 0.5 microsecond.

• Journal of the Korean Society for Precision Engineering
• /
• v.23 no.1 s.178
• /
• pp.193-200
• /
• 2006

To perform the finish grinding process of ferrules which are widely used as fiber optic connectors, a high-precision centerless grinding machine is necessary. The high-precision centerless grinding machine is consisted of the hydrostatic GW and RW spindle systems, hydrostatic RW feeding mechanism, RW swivel mechanism, on-machine GW and RW dressers, and concrete-filled steel bed. In this study, the thermal characteristics of the high-precision centerless grinding machine such as the temperature distribution, temperature rise and thermal deformation, are estimated based on the virtual prototype of the grinding machine and the heat generation rates of heat sources related to the machine operation conditions. The reliability of the predicted results is demonstrated by the temperature characteristics measured from the physical prototype. Especially, the predicted and measured results show the fact that the high-precision centerless grinding machine has very stable thermal characteristics.

• International Journal of Precision Engineering and Manufacturing
• /
• v.8 no.1
• /
• pp.32-37
• /
• 2007

The outer diameter finishing grinding process required for ferrules, which are widely used as fiber optic connectors, is carried out by high-precision centerless grinding machines. In this study, the thermal characteristics of such a machine, for example, the temperature distribution, temperature rise, and thermal deformation, were estimated based on a virtual prototype and the heat generation rates of heat sources related to normal operating conditions. The prototype consisted of a concrete-filled bed. hydrostatic grinding wheel (GW) and regulating wheel (RW) spindle systems, a hydrostatic RW feed mechanism, a RW swivel mechanism, and on-machine GW and RW dressers. The reliability of the predicted results was demonstrated using temperature characteristics measured from a physical prototype. The predicted and measured results indicated that this particular high-precision centerless grinding machine had very stable thermal characteristics.