Transfer matrix analysis of a duct with gradually varying arbitrary cross-sectional area.

A method is presented to determine the low-frequency sound field in a duct with a cross-section of arbitrary shape and area that varies gradually without discontinuities. The duct is modeled as several fictitious segments, each of which has a cross-sectional area that is a quadratic function of position along its axis. A closed-form solution does not exist for arbitrary quadratic variation.

Design and optimization of piezoelectric unimorph beams with distributed excitation.

A method is presented to design an optimal unimorph beam that flexes and generates voltage in response to a distributed load acting over its length using an analytical model. The objective is to design a beam that resonates at a specified frequency at which there is a peak in the excitation. The associated open-circuit voltage sensitivity and gain bandwidth product are functions to be maximized.

Analytical model of mechanically excited piezoelectric unimorph beams.

A model is presented of a composite beam with one elastic and one piezoelectric layer. A reduced set of piezoelectric equations of state that has only the longitudinal components of stress and strain and the transverse components of electric field and charge density is consistently used to include the effect of piezoelectric coupling in all the equations. The equi-potential boundary conditions on the electrodes, the open-circuit condition, and the Gauss condition are satisfied.

Management of large preiapical lesion with the combination of second generation platelet extract and hydroxyapatite bone graft: a report of three cases.

The pulp tissue necrosis and extensive periodontal diseases leads to the development of the inflammatory periapical lesion which causes a local response of bone around the apex of the tooth. Depends upon the nature of wound and available biological growth factors the outcome will be either regeneration or repair. Being a rich source of growth factors, platelet rich fibrin (PRF) posses many advantages in bone regeneration.