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Due to repeated heavy loads, environmental conditions and non-frequent monitoring, the rail is subjected to heavy damage resulting in sudden failure. Hence, a frequent, faster, and efficient monitoring strategy is required. This paper attempts to investigate the application of guided wave (GW) generated through surface-bonded piezo-electric wafer transducer (PWT) to detect damages in rail at high frequencies. Firstly, a combined experimental and simulation study is presented in an effort to understand the dispersion characteristics of guided wave and its interaction with head damages in a relatively small rail specimen. The numerical simulation results are validated with those obtained from the experiments showing a good agreement between them. Secondly, a framework based on the machine learning algorithm is proposed to efficiently detect damage in rail head. Numerous inseparable guided wave modes are observed at higher frequencies implying the inability to detect damage through specific mode. Therefore, a machine learning framework is trained using time, frequency, and time–frequency domain features of the signal. Total 672 numerical simulations of different types of damage with different severity and location in the rail head are carried out to train and validate the model. It is found that GW generated through surface bonded PWTs is able to detect minimum defect size of 5% of head area with 1 mm thickness. Finally, the proposed framework is tested using simulation and experiment results of arbitrary damage in the rail head. The error in estimating severity was found to be in the range from 2.00% to 16.67%.

This paper presents a comparative study of activity sensors: piezoelectric and accelerometer sensor, for the design of rate adaptive pacemaker. Activity sensors are incorporated with the demand mode pacemaker for achieving rate adaptiveness of the pacing. There is a conflict in selecting the activity sensors: accelerometer and piezoelectric. These sensors could monitor the physical activity of the patients and adapt the pacing rate to the needs of the activity of the patient. Implanting these physiological sensors into pacemakers made it possible for the physicians to individually optimize pacing parameters for each patient. Piezoelectric sensors may not response accurately for some kind of activities like cycling, walking down stairs etc. Accelerometer sensors have also the limitations for measuring prolonged duration activities. Clinically, accelerometer based activity sensors have dominated the piezoelectric based activity sensor for the design of rate adaptive pacemaker. Therefore, in this paper we have performed the frequency and time domain analysis for analyzing the technically suitable activity sensor for the design of rate adaptive pacemaker and it is found that accelerometer performs 90% faster than piezoelectric sensor.

Acoustic-structural properties of piezo-electric driven resonant cavities usually employed to generate the so-called synthetic jets are theoretically and numerically investigated in order to characterize the performances of such devices. It is shown that the actuator behaves as a two-coupled oscillators system and the dimensionless form of the governing equations allows one to identify various operating conditions, in particular those leading to their decoupling. The theoretical predictions are validated through analytical, numerical and experimental findings for devices having different mechanical and geometrical characteristics, designed to achieve an increasing coupling effect. Considerations about the strength of jet formation at the Helmholtz frequency are made as well.

In this paper, a study of effective parameters and wave properties of a slab of an artificial material comprised of alternating piezomagnetic and piezoelectric layers is presented. This kind of composite structure features new functionalities including effective magneto-electric coupling nonexistent in either constituent layer. In the first section, the equations of propagation of hybrid elasto-electro-magnetic waves in the equivalent homogeneous medium are derived by using a double scale method based on the periodical homogeneization. The wave length is considered to be much greater than the layer spatial periodicity and electromagnetic retardation is not taken into account. In the second section, dispersion relations for the hybrid waves travelling in a slab with previously established effective parameters are obtained. It was shown that although all three components, mechanic, electric and magnetic, contribute to the overall oscillatory behavior, the wave is predominantly elastic. At the same time, such composite media demonstrate double tunability, electric via the piezoelectric phase and magnetic through the piezomagnetic one, and can be regarded as novel functional materials.

A piezo electric particle monitor was used to record droplet size distributions at 5 bars with nitrogen as gas phase and Exxol D60 as liquid phase. The measurements were compared with a laser diffraction technique. A discussion of the limitations of the methods is given. The results show that the piezo electric particle monitor is a good method for measuring droplet size distributions at given conditions.

This paper describes a bedload trap designed to separate bedload from saltation load in aeolian environments. The trap is installed below the sand surface and features a chimney that can be adjusted to the height of the surface. The chimney houses an internal wall to separate saltation load from bedload. Bedload particles are funneled to a piezo-electric sensor that converts grain impacts to voltages that can be sampled at very high frequencies (44,000 Hz in this example). Grains are then collected in a container that is easily retrieved so that sand samples can be obtained for weighing and subsequent grain size analysis. An algorithm to isolate single grain impacts is described. The version of the trap presented here is intended for the study of the initiation of grain motion.

The XY table is composed of two piezo electric actuators (PEA) and a positioning mechanism (PM). Due to existence of hysteretic nonlinearity in the PEA and the friction in the PM, the high precision control for the XY table is a challenging task. This paper discusses the high precision adaptive control for the XY talbe, where the hysteresis is described by Prandtl-Ishlinskii model. The proposed control law ensures the global stability of the controlled stage, and the position error can be controlled to approach to zero asymptotically. Experimental results show the effectiveness of the proposed method.

Part supply is a major bottleneck for successful automation in micro assembly. So far, vibratory conveyors working according to the micro throw principle are applied predominantly. However, missing flexibility, fault liability and abrasive wear are significant disadvantages. In this paper, a multi body simulation model describing the micro slide principle including all major influencing parameters for micro parts is presented. By means of experiments with an especially designed piezoelectric conveyor, the functionality and advantages of this principle are demonstrated and the model is validated. Furthermore, optimization of the conveyor by automation, miniaturization and modularization is shown.

The paper examines the feasibility of piezo-electric control of stiffened plates carrying axial compression and subject to interaction of local and overall buckling. A simple control strategy involving piezo-electric patches along the tips of the stiffeners carrying equal and opposite electric fields to resist bending of the stiffeners was found to effectively counteract the adverse effects of mode interaction and imperfection-sensitivity. For the dynamic problem, this strategy needed to be supplemented with patches attached to the surfaces of the plate in the middle of the panel to damp out local buckling oscillations. Two panels were considered, these being scaled replicas of each other. This enabled an examination of the scaling laws of response with practical applications in view. The results demonstrate that the structural performance of optimally designed stiffened structures can be enhanced with minimal energy consumption by appropriately designed piezo-electric patch configuration.

Vapour sensors were produced by electrodeposition of poly(pyrrole) using different counter-ions onto both quartz crystal microbalance (QCM) electrodes and separate interdigitated microelectrodes. The ratio of the relative change of resistance to that of frequency on exposure to a vapour was measured and was found to be independent of vapour concentration over a wide range, but characteristic of the vapour for a given polymer. The multi-property measurement results have shown the feasibility of distinguishing odourants and mixtures using a significantly lower number of different types of sensing material.

The transition probability has been estimated in strained GaN/AlGaN quantum wells (QWs) taking into account a carrier separation caused by the piezo electric field. It is found that the decrease of transition probability is not significant under high-level carrier injection for weakly strained QWs as high as 0.2%. However, that decrease should be considered in strongly strained QWs as about 1%.

Exact closed-form solutions are obtained for the stress and induction field of a spheroidal piezo-electric inclusion in an infinite piezo-electric matrix subjected to spatially homogeneous mechanical and electrical loadings far away from the inclusion. Three types of loading are considered: axisymmetric, in-plane and out-of-plane shear. A limiting case of this solution allows us to determine the stress and induction field of a penny-shaped crack in a piezo-electric material. Closed-form expressions for the stress and induction intensity factors of a penny-shaped crack are obtained.

Wannier-Stark ladder transitions in the photocurrent spectra of (111)B InxGa1−xAsGaAs strained layer superlattices are reported. Both vertical transitions in the same well and diagonal transitions between adjacent wells are observed. In contrast to (100) superlattices, the Wannier-Stark spectra are observed for both senses of applied bias relative to zero potential drop across the superlattice. The observed transition energies are found to be in good agreement with the predictions of exciton calculations. The piezo-electric field is deduced in a simple and direct way from analysis of the spectra as a function of bias.

An optical study of a series of high quality piezo-electric (PZ) (111)B GaAs-(InGa)As strained multi-quantum wells is reported. Well defined Δn ≠0 transitions (E1HH2, E1HH3 and E2HH1) are observed with comparable strength to the Δn =0 transition, as a result of the asymmetric well profile induced by the piezo-electric field. In PLE the onset of the E1HH1 continuum is clearly seen, allowing the deduction of an exciton binding energy of 9 meV. Appyting a bias to oppose the PZ field reduces the field in the well, which decreases the quantum confined Stark shift and weakens the Δn ≠0 transitions. At high bias, corresponding to flat band in the well, strong lifetime broadening is observed. Good agreement between theory and experiment is found only by using a value for the PZ constant ∼30% smaller than the commonly accepted value.

A scheme for active control of nonlinear vibration of space-structures, wherein each member is modeled as a beam-column, is presented. The expressions for shear stresses transmitted to the structural member by the distributed segmented piezo-electric actuators, which are bonded on the surfaces of the member, are derived in the general case in which the structural member is subjected to moments, transverse shear forces and an axial force. Based on the weak form of the governing equations, and a complementary energy approach based on assumed stress fields, the viability of active control of nonlinear dynamic response of lattice-type space structures, using piezo actuators, is studied. Four examples are given to demonstrate the feasibility of the approaches presented in this paper.

Aim: pancreatic stones are frequently reported to be a factor of failure of endoscopic treatment of chronic pancreatitis. Our series tried to evaluate the efficacy of extracorporeal piezoelectric shock wave lithotripsy (ESWL) to disintegrate pancreatic stones in the main pancreatic duct. Methods- Patients: 51 patients (40 men, 11 women) with a mean age of 51 years, presenting with chronic pancreatitis, have been treated between May 1995 to January 1990. The mean number of sessions of lithotripsy was 4.96 per patient with the piezoelectric lithotriptor EDAP LT02. The mean cumul (power (%) x time (sec) x frequency (shock/sec.) /160) per patient was 70,5 +/- 40,5. The total or uncomplete success was defined by the feasibility ofpancreatic stenting. Results: The fragmentation of stones in the main pancreaticduct was achieved in 83,3 % of cases. The total success was achievedin 25 patients (49%), an uncomplete succcess in 11 patients (21%) and atotal failure in 15 patients (29%). Pancreatic stenting failed in 3/33patients after the ESWL and 10/33 patients before the ESWL. Pain disappearedin 72% of the cases after ESWL. There was a significant relationbetween the fragmentation of stones and the disappearance of pain. A significantrelationship was shown between the cumul value and the fragmentationrate. Conclusion: ESWL with the piezoelectric lithotriptor provides satisfactory results on the disappearance of the pain and on the fragmentation. ESWL seems helpful in the endoscopic treatment of chronic pancreatitis.

The measuring principle consists in using a piezoelectric PVDF-filter on which the aerosol particles are collected. The filter surface is then intermittently irradiated with light pulses of a wavelength which is absorbed by the particles but not by the electrode material. Therefore the energy absorbed in a thin layer is proportional to the particle mass (for a constant size distribution) and thermalized. By heat conduction, part of this energy is converted into a charge pulse by the above-described mechanisms. The filters are produced by heavy ion irradiation and subsequent nuclear track etching. (ITA)

Summary The development of a device for measuring raindrop impact force is described. The apparatus records the amplitude of voltage outputs produced by water-drops striking the surface of a piezo-electric transducer. Voltage output can be calibrated in terms of kinetic energy or impact force. The apparatus can record either the force of individual water-drop impacts or the integrated impact force exceeding a particular threshold value. Impact force and transducer output signal are linearly related to each other. The effect of the height of fall on impact force is discussed. Transducer measurements are compared with amounts of sand splashed by faling water-drops. The similarity of the results suggests that the apparatus is recording an important erosive property of the water-drops used in the experiments.

Mechanical actuators composed of material possessing piezo-electric properties have been tested with a view to assessing quantitatively the effectiveness of these actuators for use as displacement and/or correction devices in precise mechanical systems. Specifically, a mechanical system involving the Burleigh PZ40 pusher and PZ70 HV DC Op Amp was tested. Input-output measurements presented demonstrate the distortion, gain, and nonlinearities inherent in the application of these actuators to mechanical systems. Important parameters are considered and applicability is discussed.

Several efforts to utilize quartz crystals as detectors have been successful. After a particular coating is evaluated for detection of either a class of compounds or a specific compound, the coated crystal must then be incorporated within some type of instrumentation which will give the desired signal or response. The authors, in addition to efforts directed toward improving the triethanolamine coated crystal for SO 2 detection, have designed and constructed an instrument capable of utilizing such a detector. While the instrument is designed as a continuous monitor, it can also be used as an intermittent sampler. The instrument provides a millivolt readout for recording the signal.

Summary Thie piezo-electric charge of quarz for pressures up to 10 kg/cm2 was measured in absolute value with an accuracy of 0.1% by 17 °, 60 ° and 90 °C. A small coefficient of temperature was found.

A surface Acoustic wave technique of testing piezo-electric semiconductors is described. The various advantages of the techniques are also pointed out.

We show that the amplification of sound waves in a piezo-electric semiconductor may be greatly influenced by processes involving plasmons. For instance, for the case of GaAs the amplification factor for a sound wave with a wave number close to the Debye wave number may be four times as large as was previously estimated.