• Smart Structures and Systems
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• v.24 no.2
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• pp.267-292
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• 2019

The present article addresses the coupled free vibration problem of skew magneto-electro-elastic plates (SMEE) considering the temperature-moisture dependent material properties. The plate kinematics follows Reddy's higher order shear deformation theory. With the aid of finite element methods, the governing equations of motion are derived considering the Hamilton's principle and solved by adopting condensation technique. The influence of different temperature and moisture dependent empirical constants on the frequency response of SMEE plate has been assessed. In addition, the natural frequencies corresponding to various fields are evaluated and the effect of empirical constants on these coupled frequencies is determined. A detailed parametric study has been carried out to assess the individual effects of temperature and moisture dependent empirical constants along with their combined effect, aspect ratio, length-to-width ratio, stacking sequence and boundary conditions. The results reveal that the external environment as well as the geometrical skewness has a significant influence on the stiffness of the SMEE plates.

• Korean Journal of Computational Design and Engineering
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• v.8 no.4
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• pp.270-277
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• 2003

In two dimensional mechanical design analysis, quadrilateral element mesh is preferred because it provides more accurate result than triangular element mesh. However, automation of quadrilateral element mesh generation is much more complex because of its geometrical complexities. In this study, an automatic quadrilateral element mesh generation algorithm based on the boundary normal offsetting method and the boundary decomposition method is developed. In so doing, nodes are automatically placed using the boundary normal offsetting method and the decomposition method is applied to decompose the designed domain into a set of convex subdomains. The generated elements are improved by relocation of the existing nodes based on the four criteria - uniformity, aspect ratio, skewness and taper degree. The developed algorithm requires minimal user inputs such as boundary data and the distance between nodes.

• Progress in Medical Physics
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• v.13 no.4
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• pp.195-201
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• 2002

Several investigators have presented the effects of external magnetic fields on the dose distributions for clinical electron and photon beams. We focus the low energy electron beam with more lateral scatter In this study we calculated the beam profiles for an clinical electron beam of 6 MeV with longitudinal magnetic fields of 0.5 T-3.0 T using a Monte Carlo code. The principle of dose enhancements in the penumbra region is to deflect the laterally scattered electrons from its initial direction by the skewness of the laterally scattered electrons along the direction of magnetic field lines due to Lorentz force under longitudinal magnetic field. To discuss the dose enhancement effect on the penumbra area from the calculated results, we introduced the simple term of penumbra reduction ratio (PRR), which is defined as the percentage difference between the penumbra with and without magnetic field at the same depth. We found that the average PRR are 33%, and 49% over the depths of 1.5 cm, 2.0 cm, and 2.4 cm for the magnetic fields of 2.0 T and 3.0 T respectively. For the case of 0.5 T and 1.0 T the effects of magnetic filed were not observed significantly. In order to obtain the dose enhancement effects by the external magnetic field, we think that its strength should be more than 2 T approximately. We expect that the PRR would be saturated to 50-60% with magnetic fields of 3 T-5 T As a result of these calculations we found that the penumbra widths can be reduced with increased magnetic fields. This Penumbra reduction is explained as a result of electron lateral spread outside the geometrical edges of the beam in a longitudinal magnetic field. This means that the electron therapy benefits from the external magnetic fields.