Search results

1

Mechanical Response in an N-Electrode Piezo-Quartz Bar under Electrical and Thermal Excitations

100%

Munshi T., Kundu K., Mahalanabis R.

Acta Physica Polonica A

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1995

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vol. 87

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issue 6

995-1002

EN

The mechanical response in an N-electrode piezo-quartz bar where two consecutive electrodes are separated by an unelectroded region has been studied under electrical and thermal excitations. The bar is subjected to a periodic polarization gradient and a constant flow of heat. The method of operational calculus and Green's function has been used to solve the problem. For time scale ranging from 0.1 to 1.0 s the response becomes a linear function of time and is of the order of 10^{-8} m.

2

Effect of Nonlinear Elasticity on Interband and Intersubband Transition Energies in GaN/AlN Superlattices

80%

Łepkowski S.

Acta Physica Polonica A

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2007

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vol. 112

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issue 2

315-319

EN

We present a theoretical study of the effect of nonlinear elasticity on interband and intersubband transition energies in wurtzite GaN/AlN superlattices. The effect of nonlinear elasticity is considered by taking into account the changes of elastic constants caused by the intrinsic hydrostatic pressure, originating from lattice misfit between constituents of the superlattice. We show that the influence of the effect of the nonlinear elasticity on the interband and intersubband transition energies in the GaN/AlN superlattices depends crucially on the strain state of structures, in particular on the in-plane lattice constant of the buffer or the substrate. For the superlattices strained to AlGaN buffers with small aluminum concentrations, the effect of nonlinear elasticity increases significantly the interband transition energy and decreases the intersubband transition energy. For the superlattices strained to AlGaN buffers with large aluminum concentrations, the effect of nonlinear elasticity leads to a decrease in the interband transition energy and an increase in the intersubband transition energy.

3

Acousto-Electric Interaction in Magnetised Piezoelectric Semiconductor Quantum Plasma

80%

Ghosh S., Muley A.

Acta Physica Polonica A

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2016

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vol. 130

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issue 6

1401-1405

EN

Amplification of an acoustic wave is considered in magnetised piezoelectric n-type semiconductor plasma under quantum hydrodynamic regime. The important ingredients of this study are the inclusion of quantum diffraction effect via the Bohm potential, statistical degeneracy pressure, and externally applied magnetostatic field in the momentum balance equation of the charged carriers. A modified dispersion relation is derived for evolution of acoustic wave by employing the linearization technique. Detailed analysis of quantum modified dispersion relation of acoustic wave is presented. For a typical parameter range, relevant to n-InSb at 77 K, it is found that the non-dimensional quantum parameter H reduces the gain while magnetic field enhances the gain of acoustic wave. The crossover from attenuation to amplification occurs at (ϑ₀/ϑₛ)=1 and this crossover point is found to be unaffected by quantum correction and magnetic field. It is also found that the maximum gain point shifts towards lower drift velocity regime due to the presence of magnetic field while quantum parameter H shifts this point towards higher drift velocity. Numerical results on the acoustic gain per radian and acoustic gain per unit length are also illustrated. Our results could be useful in understanding acoustic wave propagation in magnetised piezoelectric semiconductor in quantum regime.

4

Infrared Spectroscopy in Molecular Study of the Piezoelectric Effect in Pig's Shin Bone

80%

Lipiec E., Kowalska J., Wiecheć A., Zieliński P., Kwiatek W., Iwaniec M.

Acta Physica Polonica A

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2012

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vol. 121

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issue 2

539-542

EN

Despite growing number of literature demonstrating the piezoelectric effect in bones at macro level there's still a lack of papers describing this effect at molecular level. In order to examine this effect more specifically, a study has been conducted to show the possibility of using infrared spectroscopy on samples contained in the electric field. This is the first known research on applying infrared spectroscopy to study the influence of electric field and compressive stress on bones' structure represented by the molecular IR spectrum. The samples used in this experiment as a model were prepared in pellet form, made from powdered pig's shin bone mixed with KBr (mass ratio of about 1:100). The spectra were obtained in transmission mode. Three different types of experiments were performed at each sample, which were subjected to: (a) fixed electric field (E < 40 kV/m), (b) variable electric field (0-40 kV/m), (c) compressive stress (P < 100 MPa). The obtained data have shown that the electric field and compressive stress on sample modified infrared spectra of the bone. Qualitative as well as quantitative changes in the spectral range between 900 cm^{-1} and 1200 cm^{-1} and the band at 562 cm^{-1} (PO_4^{3-} asymmetric and symmetric stretching, respectively) were observed. The relative area obtained by decomposition of the PO_4^{3-} band reaches an extreme value in the external compressive stress (10 MPa), that occur under physiological conditions. Based on presented data, it was proved that the applied factors (electric field, compressive stress) can change the oscillation energy and the number of molecule's degrees of freedom.

5

Effects of Nonlinear Elasticity and Electromechanical Coupling on Optical Properties of InGaN/GaN and AlGaN/AlN Quantum Wells

80%

Łepkowski S., Majewski J.

Acta Physica Polonica A

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2006

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vol. 110

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issue 2

237-242

EN

We present theoretical studies of effects of the nonlinear elasticity and the electromechanical coupling on the optical properties of InGaN/GaN and AlGaN/AlN quantum wells. In these structures, due to the lattice misfit between constituents, the quantum wells are compressively strained and the intrinsic hydrostatic pressure is present. Therefore, the nonlinear elasticity is investigated by taking into account the pressure dependence of elastic stiffness tensor for the strained quantum wells. We show that this effect leads to (i) decrease in the volumetric strain and (ii) increase in the polarization-induced built-in electric field in the quantum wells. Consequently, the interband transition energies in the quantum wells decrease when the nonlinear elasticity of nitrides is considered. On the other hand, we show that the effect of electromechanical coupling, i.e., co-existence of ordinary and converse piezoelectric effects results in increase in the interband transition energies in the considered quantum wells. It turns out that the influence of the nonlinear elasticity on the optical properties is stronger than the influence of electromechanical coupling for InGaN/GaN quantum wells, while for AlGaN/GaN the opposite situation is observed.

6

Analytical Determination of the PZTs Distribution in Active Beam Vibration Protection Problem

70%

Brański A., Lipiński G.

Acta Physica Polonica A

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2011

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vol. 119

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issue 6A

936-941

EN

The paper concerns an active vibration protection (p-reduction) of the structure via piezoelectric transducers; p-reduction corresponds to an active vibration reduction (a-reduction). The quantity and effectiveness of the (a- or p-) reduction, among other parameters, depend on the piezoelectric transducers distribution on the structure. The best results are obtained bonding piezoelectric transducers to the structure in the sub-domains with the largest curvatures; it is so-called quasi-optimal distribution of the piezoelectric transducers. Up to now, the quasi-optimal distribution was determined based on heuristic reasons only. The aim of the paper is to confirm quasi-optimal distribution in analytical way. The beam clamped at one end, vibrating with first three modes separately, is chosen as the research object. It is assumed that the piezoelectric transducers are exactly the same. Demanding the vibration amplitude to be equal to zero (i.e. p-reduction condition), the general formula for interacting forces piezoelectric transducers-beam is derived. Next, such an appropriate distribution of piezoelectric transducers is searched analytically, that the minimal forces are achieved; it leads to the best reduction effectiveness. It turned out that the analytical method pointed out quasi-optimal distribution of the piezoelectric transducers. The validation of theoretical considerations is confirmed numerically.

7

Modelling and Simulation of 3 Blade Helicopter's Rotor Model

61%

Latalski J., Bocheński M., Warmiński J., Jarzyna W., Augustyniak M.

Acta Physica Polonica A

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2014

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vol. 125

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issue 6

1380-1384

EN

Results of model tests of a rotating composite beam with integrated piezoelectric active element are presented in the paper. A proposed electromechanical system is a simplified model of the structure of a modern helicopter rotor blade. Numerical analysis of the considered system is developed by means of the finite element method. In addition, the laboratory setup has been built in order to perform real experimental studies. Selected static and dynamic characteristics of the object are determined by a series of numerical simulations. The results are compared with the outcomes of tests performed on the experimental setup. A very good agreement between numerical simulation and experiment results is observed.

8

Effectiveness Analysis of the Beam Modes Active Vibration Protection with Different Number of Actuators

61%

Brański A.

Acta Physica Polonica A

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2013

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vol. 123

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issue 6

1123-1127

EN

This paper deals with an active vibration protection (p-reduction) of the beam-actuators mechanical system, hence it concerns separate modes. The paper's aim is an effectiveness analysis of the p-reduction assuming different number of actuators. It is assumed a priori that actuators are bonded to the beam in the sub-domain with the largest curvatures and they are exactly the same. The beam clamped at one end is chosen as the research object. Next, as required by the p-reduction condition, the number and distribution of actuators are changed. It turns out that the best reduction effectiveness, measured via any effectiveness coefficient, is obtained for one actuator bonded in the sub-domain with the largest curvature. The validation of theoretical considerations is confirmed numerically.

9

Analytical Determination of Optimal Actuators Position for Single Mode Active Reduction of Fixed-free Beam Vibration Using the Linear Quadratic Problem Idea

61%

Żołopa E., Brański A.

Acta Physica Polonica A

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2014

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vol. 125

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issue 4A

A-155-A-158

EN

An analytical solution is obtained, based on linear quadratic problem well-known in the control theory. The problem is formulated for fixed-free beam vibration (fourth order partial differential equation) in Hilbert space and the point control and distributed output is considered. Beam deflection at any point is chosen as a criterion of optimization. In this case it means the linear quadratic problem. Up to now, the linear quadratic problem was formulated many times, but only for the time-dependent equation. The aim of the paper is to obtain the value of the cost functional formulated as the function of distribution of actuators. The minimum of this function leads to the optimal actuators location. The results obtained with this method confirm the results obtained in heuristic way and pure analytical one for separate mode; it is pointed out that the actuators ought to be bonded on the beam sub-regions in which the mode curvatures take their local maximums and the highest value.

Refine search results

Mechanical Response in an N-Electrode Piezo-Quartz Bar under Electrical and Thermal Excitations

Effect of Nonlinear Elasticity on Interband and Intersubband Transition Energies in GaN/AlN Superlattices

Acousto-Electric Interaction in Magnetised Piezoelectric Semiconductor Quantum Plasma

Infrared Spectroscopy in Molecular Study of the Piezoelectric Effect in Pig's Shin Bone

Effects of Nonlinear Elasticity and Electromechanical Coupling on Optical Properties of InGaN/GaN and AlGaN/AlN Quantum Wells

Analytical Determination of the PZTs Distribution in Active Beam Vibration Protection Problem

Modelling and Simulation of 3 Blade Helicopter's Rotor Model

Effectiveness Analysis of the Beam Modes Active Vibration Protection with Different Number of Actuators

Analytical Determination of Optimal Actuators Position for Single Mode Active Reduction of Fixed-free Beam Vibration Using the Linear Quadratic Problem Idea