Grzegorz Litak

Magnetopiezoelastic energy harvesting driven by random excitations

This letter considers a nonlinear piezomagnetoelastic energy harvester driven by stationary Gaussian white noise. The increase in the energy generated by this device has been demonstrated for harmonic excitation with slowly varying frequency in simulation and validated by experiment. This paper considers the simulated response of this validated model to random base excitation and shows that the system exhibits a stochastic resonance. If the variance of the excitation were known then the device may be optimized to maximize the power harvested, even under random excitation.

Non-linear piezoelectric vibration energy harvesting from a vertical cantilever beam with tip mass

A common energy harvesting device uses a piezoelectric patch on a cantilever beam with a tip mass. The usual configuration exploits the linear resonance of the system; this works well for harmonic excitation and when the natural frequency is accurately tuned to the excitation frequency. A new configuration is proposed, consisting of a cantilever beam with a tip mass that is mounted vertically and excited in the transverse direction at its base. This device is highly non-linear with two potential wells for large tip masses, when the beam is buckled. The system dynamics may include multiple solutions and jumps between the potential wells, and these are exploited in the harvesting device. The electromechanical equations of motion for this system are developed, and its response for a range of parameters is investigated using phase portraits and bifurcation diagrams. The model is validated using an experimental device with three different tip masses, representing three interesting cases: a linear system; a low natural frequency, non-buckled beam; and a buckled beam. The most practical configuration seems to be the pre-buckled case, where the proposed system has a low natural frequency, a high level of harvested power and an increased bandwidth over a linear harvester.

Chaotic vibrations in a regenerative cutting process

We have investigated nonlinear dynamic behaviour occurring during orthogonal metal cutting where primary or secondary chatter can be generated. The system is modeled as a simple one-degree-of-freedom model where nonlinearities are associated with the cutting force and can introduce a combination of dry friction and impacting oscillator behaviour. The results obtained for a set of typical technological parameters indicate a wide spectrum of responses ranging from periodic to chaotic.

Interlayer coupling and p -wave pairing in strontium ruthenate

On the basis of a three-orbital model and an effective attractive interaction between electrons, we investigate the possible superconducting states, with p- and f-wave internal symmetries, of

Vibration in gear systems

{\mathrm{Sr}}_{2}{\mathrm{RuO}}_{4}.

Performance of a piezoelectric energy harvester driven by air flow

For an orbital-dependent interaction which acts between in-plane and out-of-plane nearest-neighbor ruthenium atoms, we find a state for which the gap in the quasiparticle spectra has nodes on the

Energy harvesting by two magnetopiezoelastic oscillators with mistuning

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Chaotic Combustion in Spark Ignition Engines

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NONPERIODIC OSCILLATIONS OF PRESSURE IN A SPARK IGNITION COMBUSTION ENGINE

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Combustion process in a spark ignition engine: Dynamics and noise level estimation

sheets of the Fermi surface, but which is complex with no nodes on the