This chapter introduces the finite element method (FEM) as a tool for solution of classical electromagnetic problems. Although we discuss the main points in the application of the finite element method to electromagnetic design, including formulation and implementation, those who seek deeper understanding of the finite element method should consult some of the works listed in the bibliography section.

Introduction to the Finite Element Method

http://ieeexplore.ieee.org/iel5/5/31047/01444179.pdf

Fundamentals of acoustics

Synthesis and biomedical applications of Cerium oxide nanoparticles - A Review.

Cerium oxide nanoparticles (nanoceria; CNPs) have been found to have both pro-oxidant and anti-oxidant effects on different cell systems or organisms. In order to untangle the mechanisms which underlie the biological activity of nanoceria, we have studied the effect of five different CNPs on a model relevant aquatic microorganism. Neither shape, concentration, synthesis method, surface charge (ζ-potential), nor nominal size had any influence in the observed biological activity. The main driver of toxicity was found to be the percentage of surface content of Ce3+ sites: CNP1 (58%) and CNP5 (40%) were found to be toxic whereas CNP2 (28%), CNP3 (36%) and CNP4 (26%) were found to be non-toxic. The colloidal stability and redox chemistry of the most and least toxic CNPs, CNP1 and CNP2, respectively, were modified by incubation with iron and phosphate buffers. Blocking surface Ce3+ sites of the most toxic CNP, CNP1, with phosphate treatment reverted toxicity and stimulated growth. Colloidal destabilization with Fe treatment only increased toxicity of CNP1. The results of this study are relevant in the understanding of the main drivers of biological activity of nanoceria and to define global descriptors of engineered nanoparticles (ENPs) bioactivity which may be useful in safer-by-design strategies of nanomaterials.

/pdf/untangling-the-biological-effects-of-cerium-oxide-2dqvinkcm6.pdf

Untangling the biological effects of cerium oxide nanoparticles: the role of surface valence states.

Casimir effect on the critical pull-in gap and pull-in voltage of nanoelectromechanical switches is studied. An approximate analytical expression of the critical pull-in gap with Casimir force is presented by the perturbation theory. The corresponding pull-in parameters are computed numerically, from which one can notice the nonlinear effect of Casimir force on the pull-in parameters. The detachment length has been presented, which increases with increasing thickness of the beam.

Casimir effect on the pull-in parameters of nanometer switches. Microsys Technol

Effect of temperature on pull-in voltage and natural frequency of an electrostatically actuated microplate

In this paper flexural vibrations of an electrostatically actuated cantilever microbeam in an incompressible inviscid stationary fluid have been studied. By applying “Three dimensional aerodynamic theory” pressure jump across the microbeam has been investigated and the inertial effects of fluid on microbeam dynamics have been modeled as a mass added to microbeam mass. Magnitude of the added mass has been calculated for various aspect ratios of cantilever microbeams and compared with those of clamped-clamped microbeams. To investigate the dynamic characteristics, it has been considered that the microbeam has been deflected by a DC voltage, V DC and then the dynamic characteristics and forced response of the system have been considered about these conditions. Galerkin-based step by step linearization method (SSLM) and Galerkin-based reduced order model have been applied to solve the nonlinear static and dynamic governing equations, respectively. Water by neglecting viscidity effects, as an instant has been considered as a surrounding fluid and the frequency response of the microbeam has been compared with that of vacuum conditions. It has been shown that because of the added mass effects in watery environment, the natural frequencies of the microbeam decrease. Because of the higher dielectric coefficient and increasing electrical stiffness and decreasing total stiffness consequently, maximum amplitude of the microbeam vibrations increases in watery environment, compared with vacuum. Moreover, it has been shown that increasing the DC voltage, increases the electrical stiffness and maximum amplitude of the microbeam vibrations, consequently, It has been shown that in higher voltages (near pull-in voltage), the rate of variation of resonance frequency and maximum amplitude is stronger than lower voltages.

Dynamic characteristics and forced response of an electrostatically-actuated microbeam subjected to fluid loading

In this paper, flutter and divergence instabilities of a cantilever, a clamped–clamped, and a cantilever with intermediate simply-support microbeam sandwiched by piezoelectric layers have been studied. By presenting a mathematical formulation and numerical solution, critical piezoelectric force for avoiding of the instability in a cantilever microbeam has been calculated and validated by known buckling capacity of Beck column. By applying a similar mathematical analysis it has been introduced a critical piezoelectric voltage for a clamped–clamped microbeam. It has been shown that for cantilever microbeams, increasing of the follower piezoelectric force leads to: first flutter and then divergence instabilities whereas in the clamped–clamped microbeams only divergence instability can be occurred. Also effects of the intermediate simply support position on the critical piezoelectric voltage of a cantilever microbeam have been investigated. It has been shown that for case when the intermediate simply support is near to the fixed end of the cantilever increasing of the follower piezoelectric force leads to flutter instability but for case when the intermediate simply support is near to the free end of the cantilever it leads to divergence instability.

Static and dynamic stabilities of a microbeam actuated by a piezoelectric voltage

In the present work, the cerium nitrate hexa-hydrate and ammonium hydroxide, used as the starting materials and the weakly agglomerated cerium oxide nanoparticles was synthesized by simple and cost effective reverse co-precipitation method. The effect of aging time and calcination temperature on structural properties of synthesized nanopowder was investigated by X-ray diffractometry (XRD), simultaneous thermal analysis (STA), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM) and transmission electron spectroscopy (TEM) analytical methods. The investigation showed that aging of the precipitated precursors has pronounced effect on the decreasing of the agglomeration, increase in the crystallinity and the crystallite size of the final product obtained after calcination. Also, increase in the calcination temperature led to the appreciable increase in the crystallite size as well as the crystallinity.

	 

	Key words: Aging time, ammonium hydroxide, calcination temperature, ceria nanoparticles, reverse co-precipitation.

/pdf/effect-of-aging-time-and-calcination-temperature-on-the-1vi73qwbsb.pdf

Mohammad Fathalilou

Papers

Effect of temperature on pull-in voltage and natural frequency of an electrostatically actuated microplate

Dynamic characteristics and forced response of an electrostatically-actuated microbeam subjected to fluid loading

Static and dynamic stabilities of a microbeam actuated by a piezoelectric voltage

Effect of aging time and calcination temperature on the cerium oxide nanoparticles synthesis via reverse co- precipitation method

Micro-inertia effects on the dynamic characteristics of micro-beams considering the couple stress theory