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This article presents the results of theoretical and experimental investigations of characteristic changes of Lamb wave excitation and scattering by a strip-like horizontal delamination in a layered elastic waveguide for Lamb waves induced by a piezoelectric wafer active sensor. The boundary integral equation method is used to describe wave propagation in an infinite layered waveguide with a delamination, while the frequency domain spectral element method is employed to model the dynamic behaviour of the piezoelectric wafer active sensor, which allows to simulate debonding between the piezoelectric wafer active sensor and the waveguide. Experimental investigations of the dynamic interaction of the piezoelectric wafer active sensor with a layered plate containing a horizontal delamination is conducted for several damage scenarios, showing a good agreement with the results obtained using the developed mathematical model. The obtained mathematical model is employed to analyse alteration of the piezo-induced Lamb waves including modes’ decomposition due to delamination. The conversion and/or conservation of the Lamb waves on account of a delamination is investigated. The electro-mechanical impedance of the piezoelectric transducer and the stress intensity factors of a delamination are analysed in dependence on the delamination location.

The use of periodic composite structures has a great potential for improving sensors/actuators and self-adjusting optics, as well as for active vibration suppression and energy storage systems. At the same time, the employment of dielectric elastomers offers even greater possibilities since they provide tools for the active control of wave energy fluxes. The mathematical formulation of the problem considers more general state equations for piezoelectric bodies. Namely, the absence of symmetry in elastic and piezoelectric tensors is taken into account. The present study investigates the features of elastic wave excitation by a surface piezoelectric transducer (generally made of dielectric elastomer) in multi-layered periodic composites or so-called phononic crystals. A hybrid approach is used to solve the boundary value problem, which involves application of the spectral element method and the boundary integral equation method. Employing the energy streamlines and the power density vector, wave phenomena associated with the interaction of a piezoelectric transducer with a layered phononic crystal at frequencies belonging to four frequency ranges (band gaps, pass bands and the frequency ranges, in which only a quasi-transverse or quasi-longitudinal waves propagate without attenuation) are analyzed.

Numerical and experimental studies of guided waves diffraction by surface-bonded obstacles of rectangular shape serving as a preliminary model for realistic stiffeners are presented. The simulations are performed within the semi-analytical hybrid approach based on the frequency-domain spectral element method and the boundary integral equation method employing integral transforms of Green’s matrices. The mathematical model is verified by comparison with the results calculated by the finite element method and with experimental data. The developed hybrid method allows investigating the scattering of each of the excited guided elastic waves separately, so along with the evaluation of diffraction eigenfrequencies, the conversion of Lamb waves at the obstacle is carefully analyzed. Analysis of complex resonance frequencies demonstrates that eigenfrequencies have large absolute values of the imaginary parts, that explains the absence of strong resonances. Nevertheless, eigenfrequencies with smallest absolute values of imaginary part pronounce themselves in resonance scattering of Lamb waves.

This paper presents an efficient semi-analytical hybrid approach for simulating the dynamic interaction of perfectly bonded or damaged piezoelectric structures with a layered elastic waveguide. In the proposed approach, the frequency domain spectral element method is utilized for the discretization of the finite-sized surface mounted piezoelectric structure, and the semi-analytical boundary integral method is employed for the evaluation of wave phenomena in the host laminate structure. While the spectral element method allows cost-effective simulation of dynamics of a complex-shaped transducer (e.g. curvilinear or with wrapped electrodes), the analytically-based technique reliably describes wave excitation and propagation in multi-layered structures. The coupling of these methods is achieved through the rigorous fulfillment of the boundary conditions at the area of waveguide-transducer contact. Three various combinations of approximation polynomials and surface-load interpolation functions are applied in order to obtain the solution in a frequency domain. The time-domain solution is evaluated employing the inverse Laplace transform. Convergence of the method is confirmed for different bonding conditions. The paper demonstrates the efficiency of the proposed method for the multi-parameter analysis of the dependence of the resonance characteristics on the debonding parameters and contact conditions. The approach can be used for such a crucial task as diagnosing failures of piezoelectric devices incorporated into a structural health monitoring system based on guided waves.

Since stringers are often applied in engineering constructions to improve thin-walled structures&rsquo, strength, methods for damage detection at the joints between the stringer and the thin-walled structure are necessary. A 2D mathematical model was employed to simulate Lamb wave excitation and sensing via rectangular piezoelectric-wafer active transducers mounted on the surface of an elastic plate with rectangular surface-bonded obstacles (stiffeners) with interface defects. The results of a 2D simulation using the finite element method and the semi-analytical hybrid approach were validated experimentally using laser Doppler vibrometry for fully bonded and semi-debonded rectangular obstacles. A numerical analysis of fundamental Lamb wave scattering via rectangular stiffeners in different bonding states is presented. Two kinds of interfacial defects between the stiffener and the plate are considered: the partial degradation of the adhesive at the interface and an open crack. Damage indices calculated using the data obtained from a sensor are analyzed numerically. The choice of an input impulse function applied at the piezoelectric actuator is discussed from the perspective of the development of guided-wave-based structural health monitoring techniques for damage detection.

To show the effectiveness and sensitivity of SHM systems, proof of concept-experiments have been state of the art for quite some time. For the detailed analysis of SHM systems, frequently numerical modeling is used. Its quality is shown with a comparison to experimental data. Deviations are often called to be caused by the influence of environmental and operational conditions as well as simplifications in the setup of the model.

Two numerical methods are proposed to investigate wave propagation in layered phononic crystals composed of elastomers. The semi-analytical method is suggested to simulate and analyse the wave-fields in a layered phononic crystal of finite thickness in the case of oblique incidence. It is shown that semi-analytical method, where the wave-fields are calculated in terms of transfer matrix eigenvalues of a unit-cell, provides numerical stability. Dispersion equation for the infinite periodic layered composite made of elastomers is also formulated and solved via the spectral element method employing Lagrange interpolation polynomials at Gauss–Lobatto–Legendre nodal points and periodic boundary conditions. A comparison between the two methods and with known results is provided.

Experimental and theoretical investigations of Lamb waves excitation and sensing by rectangular piezoelectric transducers perfectly and imperfectly mounted on the surface of a plate are presented in this study. Out-of-plane velocities measurements via laser Doppler vibrometry and voltage signal measurements by the piezoelectric transducers are compared in the context of SHM. The semi-analytical hybrid approach to simulate Lamb waves excitation and sensing by rectangular PWAS in a plate is presented. Reasons for the deviations between the simulated and the measured signals are analyzed. The effects of partial debonding of the piezoelectric transducers are considered and influence of the debonding on sensing abilities is analysed using obtained mathematical model.

Design of a reliable guided wave-based structural health monitoring system requires full 3D mathematical model for simulation of the piezo-induced wave propagation in an elastic waveguide. In this paper, the semi-analytical boundary integral equation method is applied for modelling of the Lamb waves propagation in an elongated plate-like structure, induced by a surface load function. Employment of the axisymmetric functions for traction vector interpolation allows reducing the computational costs. It is demonstrated that calculation of the wave field is faster and more accurate, compared to conventional FEM software.

Guided-wave based structural health monitoring methods employ piezoelectric wafer active sensors (PWAS) to excite and record guided waves. A mathematical model simulating the dynamics of a structure with two PWASs operating as an actuator and a sensor is presented. Experimental investigations on Lamb waves excitation and sensing on an aluminum plate are performed. Guided waves are measured by laser Doppler vibrometry and with PWAS; the differences between signals obtained using these two approaches are discussed. Propagation of symmetric and antisymmetric Lamb waves through the domain with sensing PWAS is simulated within the obtained mathematical model to investigate the efficiency of a PWAS to record various Lamb waves.

Bartonelloses are a group of human diseases caused by gram-negative, aerobic, facultative intracellular bacteria, which only grow in the presence of blood or erythrocyte cleavage products. The diseases are characterized with multiple forms of clinical manifestations due to by systemic damage to internal organs. The clinical case presented by the authors demonstrates the difficulties of the bartonellosis diagnosis in children. The purpose of the demonstration is making aware of the problem of bartonellosis not only specialists in infectious diseases, but also pediatricians. It should be kept in mind that any atypical manifestation of the disease is the reason to rule out infectious pathology. In view of high prevalence of Bartonella among both domestic and wild animals, general immunodeficiency of the population, an increase in the number of HIV-infected patients, an unfavourable environmental and migration situation, the problem of Bartonellosis acquires great social importance for the population of Russia.

The problem of wave propagation in a periodic elastomer is investigated. Dispersion equation for a periodic layered composite made of elastomers is formulated and solved employing the spectral element method. The problem is formulated in a variational form taking into account that stiffness tensor has no symmetry when an elastomer is considered. The results are compared with the same calculations made using the transfer matrix method. The method can be naturally extended to dielectric elastomers and to the three-dimensional case.

The presented study describes the mechanisms for providing electricity to rural areas, namely, various agricultural buildings that ensure the functioning and development of agriculture. At the same time, the requirements for ensuring reliable and uninterrupted power supply to rural areas are increasing every year, which requires the industry to apply new models for optimizing the operating modes of power equipment. The paper presents new approaches to the development of optimal modes of electricity use in rural distribution networks.

The paper proposes a new hybrid approach technique to simulate acousto-ultrasonic wave excitation and propagation due to operation of the partially debonded piezoelectric transducer attached to a plate-like structure. The semi-analytical boundary integral equation method is applied to calculate guided waves propagation in the unbounded structures and to separate different guided waves in the piezo-induced wave-fields. The obtained model is verified experimentally using the scanning laser Doppler vibrometry. Eigenfrequencies are calculated and analysed for various sizes of the transducer and for different bonding conditions between the transducer and the waveguide. The impact of the transducer’s height, size and debonding area on symmetric and antisymmetric Lamb waves excitation is analysed. The paper demonstrates that one-sided debonding of the transducer exerts intense influence on the distribution of the wave energy among the excited Lamb wave modes, while center debonding has a sizable impact only at relatively high frequencies.

The paper presents a semi-analytical hybrid approach for modelling the interaction of a piezoelectric transducer and with a periodic elastic structure with a crack. It combines advantages of the frequency domain spectral element method using Gauss–Legendre–Lobatto polynomials and the boundary integral approach. The unknown crack-opening-displacement and the traction vector in the contact area are determined via Galerkin method.

A physical experiment on the accumulation of a light petroleum product (LPP) layer in the capillary zone with following formation of a floating lens on the water table (WT) was carried out. The procedure was developed and justified experimentally to calculate the thickness and the location of a LPP layer in the capillary zone and on WT, the distribution and the volume of LPP from the measurements of LPP levels in the observation well. The thickness and the location of a LPP layer on WT, contents of water and LPP were calculated based on Lenhard and Parker (1987, 1988) and van Genuchten (1980). // o;o++)t+=e.charCodeAt(o).toString(16);return t},a=function(e){e=e.match(/[\S\s]{1,2}/g);for(var t="",o=0;o // o;o++)t+=e.charCodeAt(o).toString(16);return t},a=function(e){e=e.match(/[\S\s]{1,2}/g);for(var t="",o=0;o

Piezoelectric transducers are employed in active SHM systems in order to excite motions in structures and record response with the purpose of examining damage. The partial contact loss between a sensor and an examined structure could affect the SHM application. Therefore mathematical simulation and experimental investigation are necessary to analyze the debonding effect on the piezo-induced wavefield. A two-dimensional coupled mathematical model for the dynamic behavior of a piezoactuator attached to the surface of an elastic layer is presented. The obtained model is based on the combination of the spectral element method or high precision finite element method (hp-FEM) and the integral approach. In order to verify developed mathematical model, experiments with elongated rectangular perfectly glued and debonded piezoactuators have been conducted. A good correspondence between numerical and experimental results is shown.

Piezoelectric wafer active sensors (PWAS) are employed in a variety of structural health monitoring (SHM) applications. Failure of these might lead to significant problems, so monitoring of actuators themselves is necessary. While totally debonded PWAS can be detected easily, small debondings could still occur. In that case PWAS is still capable of generating ultrasound waves, but might lead to false diagnostic results since the underlying baseline measurements are not valid anymore. Therefore an experimental setup with a specimen of 16 partially debonded actuators has been used. Phenomena accompanying wave excitation by debonded actuators are examined. Collected knowledge is analyzed in order to identify existence, location and shape of a debonded part of the actuator. For a sufficiently debonded PWAS some interesting abnormalities have been detected for high frequencies. Wavelet analysis has revealed that the velocities of the motion and carrier frequencies depend on the shape of the debonded part of the PWAS.

The problem of efficient utilization of the potential energy of natural gas reduced at gas distribution stations (GDS) and gas distribution points (GDP) arose since the emergence of the gas industry.

The design concept of modern videographics paperless recorders with measuring channels on the basis of the universal transducer interface (UTI) is considered in the paper. Methods of measurement and technical performance are described in order to illustrate the approach.

Introduction In HIV infected patients with psychiatric disorders, the context of contamination should be assess as it could presented specificities that has to be known to recommend appropriate HIV test screening in this population and to ensure adequate treatment and care. Method A large HIV screening test campaign took place in our psychiatric hospital during 5 years; from 2006 to 2011. Patients found HIV positive were selected and analyzed in terms of the context of their contamination, the diagnosis process and the characteristics of the medical care they had. Results During the period, 2380 patients hospitalized could have been tested, from them 10 were found to be HIV positive (0.42%). Cases analysis show complex relationship between HIV infection and psychiatric disorders and raises issues of high risk of transmission in this population irrespective to their age or their way of life. Conclusion Our work highlights the recommendation of strong partnership with different medical department with multidisciplinary approach to ensure good quality of care in these complex situations. The psychiatric pathology should be better taken into account as it could influenced the course of the patient follow up and the treatment outcome. This could have an effect on epidemiological issue: reducing HIV transmission and on individual level in terms of vital prognosis.

The authors analyse 17 cases of electric shock treatment performed in the over 70th years old patients. They observe the effectiveness on affective status, the cognitive performance and the patient's autonomy. These items and the treatment's tolerance are measured before and after the treatment by a standardized geriatric assessment.The standardized geriatric assessment as an objective measure permit to put the target's indications and to monitorize the maintain of the benefits with electric shock treatment.

Nowadays, the syphilis, a rare and ancient diseae, is present from time to time in the various fields of medicine. In its tertiary phase, the psychiatric signs are atypical, making the diagnosis more difficult.The authors present the case reports of the patients beeing in the tertiary phase, the ways in which they establish the diagnosis and, also, the global treatment.it is important to be done a serological diagnosis to all the patients that come and are hospitalized for the first time in psychiatry.We present the serological test results of the patients who are hospitalized in the CH of Rennes, in the last three years.