Активность

After validating the radiation pattern of SH wave generated by the APS, the properties of beam steering for the proposed phased array was investigated. Finally, experiments were carried out to validate its performance in detection of various defects. Results indicated that even for a 1 mm through-thickness hole 700 mm away, the proposed phased array system can still detect it accurately, which is much better than previous SHM systems. Dual defects including a crack and a hole can also be clearly detected without baseline. The high-sensitivity of the proposed system was attributed to the employed bidirectional transducer which can generate non-dispersive SH0 wave with high energy concentration. This proposed SH wave phased array system will provide a high-performance SHM method for plate-like structures.This paper derives the resonance conditions for one-way resonant mixing of nonlinear Lamb waves. Two mode triplets are identified that satisfy such resonance conditions. It is also found that, when the primary waves are pulses of finite duration, the signal envelope of the corresponding resonant mixed wave is either a diamond or an elongated hexagon. The dimensions of these shapes are obtained explicitly in terms of the pulse lengths and group velocities of the Lamb modes in the mode triplet. These analytical results are verified by numerical simulations using the finite element method. Finally, a nondestructive evaluation method based on one-way mixing of Lamb waves is proposed for the inspection of a large area of a plate for damage distribution via a single access point. Numerical simulations of this nondestructive evaluation technique are conducted. It is found that using shorter pulses gives better spatial resolution, thus better suited for locating and sizing the damage zone, while using longer pulses gives a higher signal to noise ratio, thus better suited for quantifying the degree of damage in the damage zone. Results of this paper clarify some of the confusion in the existing literature regarding the resonance conditions for one-way mixing of nonlinear Lamb waves. Oltipraz mouse They also provide a better understanding of the physical characteristics of the resonant mixed wave. Such understanding enables the design of optimal measurement systems for one-way mixing of Lamb waves for the purpose of conducting large area nondestructive evaluation of plate-like structures from a single access point. This proposed one-way mixing nondestructive evaluation technique can be extended to pipes.Among the renewable energy sources, wind power generation presents competitive costs and high installation potential in many countries. Ensuring the integrity of the generation equipment plays an important role for reliable energy production. Therefore, nondestructive test procedures are required, especially for turbine blades, which are subject to severe operational conditions due to phenomena such as lightning strikes, mechanical stress, humidity and corrosion. Nondestructive ultrasonic test techniques are commonly applied in their predictive maintenance. This work proposes the use of novelty detection methods combined with nondestructive ultrasound testing to identify structural problems in wind turbine blades. Ultrasound signals are preprocessed using both, wavelet denoising and principal component analysis. Novelty detection deals with the one-class classification problem, when only the normal condition signatures are required for the classification system design. For the nondestructive test of turbine blades, this is an interesting paradigm because it is not always possible to obtain test samples from all of the existing flaw conditions. Our experimental results indicate the efficiency of the proposed method.Background and purpose We evaluated optimal transcranial Doppler (TCD) measures for predicting delayed cerebral ischemia (DCI) after aneurysmal subarachnoid hemorrhage (aSAH). Material and methods Consecutive patients with aSAH and daily middle cerebral artery (MCA) TCD recordings were retrospectively analyzed. Change in TCD velocity was obtained by creating a smoothing curve. Change in TCD velocity was determined with a linear regression model that confirmed greatest change in velocity associated with DCI occurred at days 2-7. Multivariate logistic regression analysis was then completed. Results 95 patients were evaluated. Increase in TCD velocity at days 2-7 proved to be the best predictor for DCI with an optimal cutoff of 8.9 cm/s/day (p = .019) and AUC 0.651. Multivariate logistic regression analysis using DCI as outcome showed that poor admission Hunt-Hess scores (OR 5.02, 95%CI 1.22-22.67, p = .028) and increases in TCD velocity (OR 5.32, 95%CI 1.41-23.33, p = .018) were independently associated with DCI. Conclusions We found that relative increases in TCD velocities in the MCAs during the first 7 days (with a threshold increase of 53.4 cm/s from days 2 to 7) after aSAH admission were independently associated with DCI. This association requires independent confirmation.Background The dorsal premotor area (DPM) plays an important role in hand coordination and muscle recruitment for lifting activities. Lesions in the area have demonstrated that the DPM is critical in the integration of movements that require combinations of reaching, grasping, and lifting. While many have looked at its functional connectivity, few studies have shown the full anatomical connectivity of DPM including its connections beyond the motor network. Using region-based fMRI studies, we built a neuroanatomical model to account for these extra-motor connections. Objective In this study, we performed meta-analysis and tractography with the goal of creating a map of the dorsal premotor network using the Human Connectome Project parcellation scheme nomenclature (i.e. the Glasser Atlas). While there are other possible ways to map this, we feel that it is critical that neuroimaging begin to move towards all of its data expressed in a single nomenclature which can be compared across studies, and a potential frayrus, and insula were demonstrated. Connections to the contralateral supplementary motor area and premotor cortex were also identified. Conclusions We describe a preliminary cortical model for the underlying structural connectivity of the Dorsal Premotor Area. Future studies should further characterize the neuroanatomic underpinnings of this network.