• Journal of applied mathematics & informatics
• /
• v.6 no.2
• /
• pp.649-659
• /
• 1999

This paper presents a parallel implementation of stiff-ness matrix calculation based on the processor farm model on a net-work of workstations running PVM programming environment. As the computational characteristics of stiffnes matrix exhibits good po-tentials for effective prallel computation the performance improve-ment is show to be almost linear with the number of sorkstations involved in the computation.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.14 no.6
• /
• pp.1487-1494
• /
• 1990

In this paper the dynamic characteristics of self acting air lubricated slider bearing of hard disk/head system are investigated. The dynamic equations of magnetic head mechanism considering both parallel and pitch motion and the time dependent modified Reynolds equation are analyzed and the dynamic pressure distribution of air film is numerically calculated in frequency domain by small perturbation method and finite difference scheme with variable grid. The dynamic response of the slider spacing is obtained accordingly as the moving recording surface vibrates in parallel mode.

• Journal of Advanced Marine Engineering and Technology
• /
• v.23 no.4
• /
• pp.504-513
• /
• 1999

Usually bellows are designed for the purpose of absorbing axial movement. To find out axial stiffness of bellows the axisymmetric shell theory using the finite element method is adopted in this paper. Bellows can be idealised by series of conical frustum-shaped elements because it is axisymmetric shell structure. The force required to deflect bellows axilly is a function of the dimensions of the bellows and the materials from which they are made. The displancements of nodal points due to small increment of force are calculated by the finite element method and the calculated nodal displacements are added to r-z cylinderical coordinates of nodal points. The new stiffness matrix of the system using the new coordinates of nodal points is adopted to calculate the another increments of nodal dis-placements that is the step by method is used in this paper. spring constant is analyzed according to the changing geometric factors of u-shaped bellows. The FEM results were agreed with experiment. Using developed FORTRAN PROGRAM spring constant can be predicted by input of a few factors.

• Journal of Fashion Business
• /
• v.8 no.1
• /
• pp.141-155
• /
• 2004

Chitosan, the natural biodegradable polymer derived from chitin by de- acetylation, has been widely applied to the textile finishing processes for excellent anti-microbial characteristic and handle improvement of fabric. The purpose of this study is to investigate the change of handle when cotton fabric is treated with chitosan-polyurethane mixed solution. The viscosity values of chitosan solutions were 8cps and 50cps, and the wet-pick-up% was maintained at 90%. In case of mixing with water soluble polyurethane, the mixture ratio of chitosan and polyurethane was settled on the solid content ratio of 1:0, 1:0.5, 1:1, 1:2. Also the change of physical properties by neutralization in NaOH solution was studied. The results can be summarized up as follows : 1. Extensibility(EM) and tensile energy(WT) of cotton fabric treated with chitosan are decreased, but bending rigidity(B) is remarkably increased. With the addition of polyurethane, the decrease of EM and WT is weakened and the increase of B is weakened. The case of neutralization is similar to the case of polyurethane addition. 2. By treating fabric with chitosan, FUKURAMI(Fullness and softness) is decreased, but KOSHI(Stiffness), SHARI(Crispness), HARI(Anti-drape Stiff ness) are increased. With the addition of polyurethane, the decrease of FUKURAMI is diminished and the increase of KOSHI, SHARI, HARI are diminished. 3. As the viscosity of chitosan solution increased, the air permeability value increased. The addition of polyurethane decreased the air permeability.

• Tribology and Lubricants
• /
• v.31 no.6
• /
• pp.294-301
• /
• 2015

In this paper, we predict the rotordynamic force coefficients of tilting pad journal bearings (TPJBs) with rocker-back pivots, and we compare the predictions to recently published predictions and test data. The present TPJB model considers the rocker-back pivot stiffness calculated based on the Hertzian contact-stress theory, which is nonlinear with the application of a force . For the five-pad TPJB in load-between-pad and load-on-pad configurations, the predictions show the pressure- and film-thickness distributions, the deflection and stiffness of the individual pivots, and bearing stiffness and damping coefficients. The minimum film thickness and peak pressure occur at the bottom pad on which the applied load is directed. Because of the preload, the pres- sure is positive even at the upper pad in the opposite direction to the applied load. The pivot deflection and stiff- ness are maximum at the bottom pad that receives the heaviest pressure load. The predicted stiffness coefficients increase as the static load and rotor speed increase, while the damping coefficients decrease as the rotor speed increases, but increase as the static load increases. In general, the predicted stiffness coefficients agree well with the test data. The predicted damping coefficients overestimate the test data, particularly for large static loads. In general, the current predictive model considering the pivot stiffness improves the accuracy of the rotordynamic performance compared to previously reported models.

• Journal of the Korean Society for Railway
• /
• v.11 no.5
• /
• pp.489-498
• /
• 2008

In general, deflection limit criteria of bridge design specifications have been considered based on static serviceability and structural stability. Dynamic serviceability induced from bridge vibration actually has not been included in the criteria. Thus, it is necessary for deflection limit to be considered in order to check dynamic service- ability on bridge vibration. In this study, The allowable displacement of Korea Railway Bridge Design Specifications is compared to the frequency domain comfort limit and analyzed france code and japanese code. Korea Railway Bridge Design Specifications is regulated based on the train speed. Such is because the vibration time duration is partly considered. but this criteria is not satisfied with comfort limit. and, it is estimated to be capable to provide deflection limit considering dynamic serviceability. In order to evaluate the dynamic serviceability of various types of railway bridges in current public were selected and their dynamic signals were measured. and the result of the bridge-train interaction analysis according to the changes in bridge stiffness was compared to the comfort limit to suggest the stiff-ness limit to the dynamic serviceability, which should conveniently be applied at the field.