An analytical model of transducer array arrangement for guided wave excitation and propagation on cylindrical structures

Ultrasonic guided wave (GW) inspection is one of the non-destructive testing (NDT) techniques available for the engineering structures. Compared with other NDT techniques, guided waves can propagate a long distance with a relatively high sensitivity to defects in the structure. In order to increase the performance for pipe inspections to meet higher requirements under different conditions, the optimisation of piezoelectric transducer array design is still a need, as the technique is currently subject to a complex analysis due to wide number of guided wave modes generated. This can be done by optimising the transducer array design. In this paper, it is described an analytical mode of a set of piezoelectric transducer arrays upon torsional wave mode T(0,1) excitation in a tubular structure. The proposed analytical model for predicting signal propagation is validated by using finite element analysis in ABAQUS and three-dimensional laser vibrometer experiments for transducer array characterisations. The proposed analytical model works well and very fast for simulating transducer excitation and wave propagation along cylindrical structures. This will significantly reduce the complexity of guided wave analysis, enhancing effectively the structural health of structures and subsequently reducing the industry maintenance cost

Electron Depletion Due to Bias of a T-Shaped Field-Effect Transistor

A T-shaped field-effect transistor, made out of a pair of two-dimensional electron gases, is modeled and studied. A simple numerical model is developed to study the electron distribution vs. applied gate voltage for different gate lengths. The model is then improved to account for depletion and the width of the two-dimensional electron gases. The results are then compared to the experimental ones and to some approximate analytical calculations and are found to be in good agreement with them.Comment: 16 pages, LaTex (RevTex), 8 fig

Ultramicroscopic observation of recombinant adenoassociated virus type 2 on the surface of formvarcarbon coated copper grids under different relative humidity and incubation time using negative stain transmission electron microscopy

The purpose of this investigation was to compare the effects of different relative humidity (RH) on the microcosmic conformation of the recombinant AAV-2 virion at 22°C. rAAV-2 virions prepared on copper grid were placed in a high, middle or low RH cabinet and incubated for 72, 48 and 24 h, respectively. The rAAV-2 virions were observed by transmission electron microscope and the values of major axis length, minor axis length and ellipticity of the rAAV-2 virions were obtained using the IMS cell imageanalysis system. After incubation for 48 and 72 h, the major axis length and minor axis length of the rAAV-2 virion started to rapidly decrease in high RH. Conversely, the axis lengths rapidly increased in low RH. Then, the ellipticity of the rAAV-2 virion would almost tend to approach the identical value of0.9 for 48 and 72 h incubations in high RH. The results suggest that the rAAV-2 virion tended to favor a smaller, round, more stable conformation in high RH compared to low RH which implied that the rAAV-2 virion was probably prone to living in high relative humidity conditions

Influence of metal elements on the evolution of CO and CH4 during the pyrolysis of sawdust

Metal elements in biomass ash have been considered to affect the decomposition of large molecule during the pyrolysis of biomass. In this paper, effect of metal elements on the evolution of carbon monoxide (CO) and methane (CH4) was investigated during the pyrolysis of sawdust in a fixed bed reactor and species were detected by Fourier Transform Infrared analyzer. Results showed that all the metal additions restrained the yields of CO and CH4 and the quantity order of production was Fe2O3<ZnO<NaCl<CaO<KCl< Al2O3<No-addition. The addition of Al2O3, Fe2O3 and ZnO shortened the completion time of CO and CH4. Statistical analysis demonstrated that all the metal additions lowered the reaction rate of biomass pyrolysis dynamically