Higher-Harmonic Generation Analysis in Complex Waveguides via a Nonlinear Semianalytical Finite Element Algorithm

Propagation of nonlinear guided waves is a very attracting phenomenon for structural health monitoring applications that has received a lot of attention in the last decades. They exhibit very large sensitivity to structural conditions when compared to traditional approaches based on linear wave features. On the other hand, the applicability of this technology is still limited because of the lack of a solid understanding of the complex phenomena involved when dealing with real structures. In fact the mathematical framework governing the nonlinear guided wave propagation becomes extremely challenging in the case of waveguides that are complex in either materials (damping, anisotropy, heterogeneous, etc.) or geometry (multilayers, geometric periodicity, etc.). The present work focuses on the analysis of nonlinear second-harmonic generation in complex waveguides by extending the classical Semianalytical Finite Element formulation to the nonlinear regime, and implementing it into a powerful commercial Finite Element package. Results are presented for the following cases: a railroad track and a viscoelastic plate. For these case-studies optimum combinations of primary wave modes and resonant double-harmonic nonlinear wave modes are identified. Knowledge of such combinations is critical to the implementation of structural monitoring systems for these structures based on higher-harmonic wave generation

Non-Destructive Inspection of Impact Damage in Composite Aircraft Panels by Ultrasonic Guided Waves and Statistical Processing.

This paper discusses a non-destructive evaluation (NDE) technique for the detection of damage in composite aircraft structures following high energy wide area blunt impact (HEWABI) from ground service equipment (GSE), such as heavy cargo loaders and other heavy equipment. The test structures typically include skin, co-cured stringers, and C-frames that are bolt-connected onto the skin with shear ties. The inspection exploits the waveguide geometry of these structures by utilizing ultrasonic guided waves and a line scan approach. Both a contact prototype and a non-contact prototype were developed and tested on realistic test panels subjected to impact in the laboratory. The results are presented in terms of receiver operating characteristic curves that show excellent probability of detection with low false alarm rates for defects located in the panel skin and stringers

On the existence of antisymmetric or symmetric Lamb waves at nonlinear higher harmonics

Abstract This article theoretically studies the symmetry characteristics of Rayleigh-Lamb guided waves in nonlinear, isotropic plates. It has been known that the nonlinearity driven double harmonic in Lamb waves does not support antisymmetric motion. However the proof of this has not been obvious. Moreover, little is known on nonlinearity driven Lamb harmonics higher than double. These gaps were here studied by the method of perturbation coupled with wavemode orthogonality and forced response. This reduced the nonlinear problem to a forced linear problem which was subsequently investigated to formulate an energy level constraint as the defining factor for the absence of antisymmetry at any order of higher harmonic. This constraint was then used to explain the reason behind the absence of antisymmetric Lamb waves at the double harmonic. Further, it was shown that antisymmetric motion is prohibited at all the higher-order even harmonics, whereas all the higher order odd harmonics allow both symmetric and antisymmetric motions. Finally, experimental results corroborating theoretical conclusions are presented

The role of evanescent modes in Global-Local analysis of UGW in plates with varying local zone-scatterer relations

In order to provide a reliable and robust SHM performance, Ultrasonic Guided Waves (UGWs) need to be analyzed and understood. Numerical modeling of UGW propagation and scattering by hybrid methods offers the possibility of simulating UGW interaction with waveguides of arbitrary cross-sections and discontinuities. Maximizing the accuracy of such methods is important to perform quantitative SHM, while maintaining minimum computational cost. This work investigates the role of evanescent modes in the numerical analysis of UGWs in aluminum and composite plates with defects, by the hybrid Global-Local method. The complex solutions to the UGW eigenvalue problem are found and the scattering spectra for A0 and S0 incident modes are calculated. The accuracy of the numerical solution is then studied by computing the error in terms of energy balance. Parametric studies with respect to the local zone size, defect dimensions and shape are conducted including and excluding evanescent modes in the analysis. Considerations are provided to obtain a solution with error no greater than 5%, in terms of varying local zone – scatterer relations within plate waveguides

Treatment of human brucellosis with rifampin plus minocycline

In order to evaluate the efficacy and tolerability of a high intravenous dose of rifampin plus oral minocycline (administered daily for 3 weeks) for the treatment of acute brucellosis, we retrospectively reviewed the outcome of 239 consecutive patients (135 adults and 104 children) diagnosed and treated over a 17-year period in Italy. The combination used resulted in 100% response and a relapse rate lower than 2%. Fifty-two (30 adults and 22 children) (29.8%) complained of mild adverse effects including an increase in aspartate aminotransferase (>250 IU) observed in 12 cases and considered related to rifampin and in 11 cases a reversible hyperpigmentation of the tongue attributed to minocycline. A randomized prospective comparative study should be performed to confirm our encouraging result

Human toxocariasis: a report of nine cases

Aim: Human toxocariasis is caused by infection with the larval stage of nematode parasites of dogs and cats, Toxocara canis or Toxocara cati. These helminths are not able to complete their life cycle in undefinitive hosts and so undergo aberrant migrations in the tissues causing a wide spectrum of signs and symptoms. Eosinophilia is often severe and sometimes represents the only sign of infection, except in ocular and neurological forms. Methods: We describe the clinical features of nine children affected by toxocariasis admitted to our Infectious Diseases department from 2004 to 2006. Results: Fever and hepatomegaly were the most common clinical findings. In two cases eosinophilia was not present. Diagnosis was performed by enzyme-linked immunosorbent assay employing excretory–secretory antigens of Toxocara. canis larvae. All patients were successfully treated with oral albendazole with no side effects

A case of Brucella endocarditis in association with subclavian artery thrombosis

Brucellosis is a common zoonosis, endemic in Mediterranean countries, and caused by bacteria of Brucella genus. Brucellosis is a systemic infection and the clinical presentation varies widely from asymptomatic and mild to severe disease. Cardiovascular complications are extremely rare. We present a case of arterial thrombosis in a previously healthy young patient with Brucella endocarditis. Careful attention must be paid to any sign or symptom of thrombosis in patients affected by brucellosis, regardless of the presence of endocarditis and cardiovascular risk factors. PMID:22844622[PubMed] PMCID:PMC3400327Free PMC Articl

Disseminated tuberculosis in a patient treated with a JAK2 selective inhibitor: a case report

Background Primary myelofibrosis is a myeloproliferative disorder characterized by bone marrow fibrosis, abnormal cytokine expression, splenomegaly and anemia. The activation of JAK2 and the increased levels of circulating proinflammatory cytokines seem to play an important role in the pathogenesis of myelofibrosis. Novel therapeutic agents targeting JAKs have been developed for the treatment of myeloproliferative disorders. Ruxolitinib (INCB018424) is the most recent among them. Case presentation To our knowledge, there is no evidence from clinical trials of an increased risk of tuberculosis during treatment with JAK inhibitors. Here we describe the first case of tuberculosis in a patient treated with Ruxolitinib, a male with a 12-year history of chronic idiopathic myelofibrosis admitted to our Institute because of fever, night sweats, weight loss and an enlarging mass in the left inguinal area for two months. Conclusion Treatment with Ruxolitinib may have triggered the reactivation of latent tuberculosis because of an inhibition of Th1 response. Our case highlights the importance of an accurate screening for latent tuberculosis before starting an anti-JAK 2 treatmen