Damage localization of closing cracks using a signal decomposition technique

Fatigue cracks are a common occurrence in engineering structures subjected to dynamic loading and need to identify at its earliest stage before it leads to catastrophic failure. The presence of fatigue-breathing crack or closing cracks is usually characterised by the presence of sub, super-harmonics, and inter-modulation in the response of the structure subjected to harmonic excitation. It should be mentioned here that the amplitude of nonlinear harmonics are of very less order in magnitude when compared to linear or excitation component. Further, these nonlinear components often get buried in noise as both are having matched (low) energy levels. The present work attempts to decompose the acceleration time history response using singular spectrum analysis and propose a strategy to extract the nonlinear components from the residual noisy time history component. A new damage index based on these extracted nonlinear features is also proposed for closing crack localization. The effectiveness of the proposed closing crack localization approach is illustrated using detailed numerical studies and validated with lab level experimentation on the simple beam-like structure. It can be concluded from the investigations that the proposed signal decomposition based damage localization technique can detect and locate more than one crack present in the structure

Damage localization of closing cracks using a signal decomposition technique

Fatigue cracks are a common occurrence in engineering structures subjected to dynamic loading and need to identify at its earliest stage before it leads to catastrophic failure. The presence of fatigue-breathing crack or closing cracks is usually characterised by the presence of sub and super-harmonics in the response of the structure subjected to harmonic excitation. It should be mentioned here that the amplitude of nonlinear harmonics are of very less order in magnitude when compared to linear or excitation component. Further, these nonlinear components often get buried in noise as both are having matched (low) energy levels. The present work attempts to decompose the acceleration time history response using singular spectrum analysis and propose a strategy to extract the nonlinear components from the residual noisy time history component. A new damage index based on these extracted nonlinear features is also proposed for closing crack localization. The effectiveness of the proposed closing crack localization approach is illustrated using detailed numerical studies and validated with lab level experimentation on the simple beam-like structure. It can be concluded from the investigations that the proposed signal decomposition based damage localization technique can detect and locate more than one crack present in the structure

Temporal Resolution and Active Auditory Discrimination Skill in Vocal Musicians

Introduction Enhanced auditory perception in musicians is likely to result from auditory perceptual learning during several years of training and practice. Many studies have focused on biological processing of auditory stimuli among musicians. However, there is a lack of literature on temporal resolution and active auditory discrimination skills in vocal musicians. Objective The aim of the present study is to assess temporal resolution and active auditory discrimination skill in vocal musicians. Method The study participants included 15 vocal musicians with a minimum professional experience of 5 years of music exposure, within the age range of 20 to 30 years old, as the experimental group, while 15 age-matched non-musicians served as the control group. We used duration discrimination using pure-tones, pulse-train duration discrimination, and gap detection threshold tasks to assess temporal processing skills in both groups. Similarly, we assessed active auditory discrimination skill in both groups using Differential Limen of Frequency (DLF). All tasks were done using MATLab software installed in a personal computer at 40dBSL with maximum likelihood procedure. The collected data were analyzed using SPSS (version 17.0). Result Descriptive statistics showed better threshold for vocal musicians compared with non-musicians for all tasks. Further, independent t-test showed that vocal musicians performed significantly better compared with non-musicians on duration discrimination using pure tone, pulse train duration discrimination, gap detection threshold, and differential limen of frequency. Conclusion The present study showed enhanced temporal resolution ability and better (lower) active discrimination threshold in vocal musicians in comparison to non-musicians

replies_to_reviewers_comments_sage_shm-30_May_2018 – Supplemental material for A method for detecting damage-induced nonlinearity in structures using weighting function augmented curvature approach

<p>Supplemental material, replies_to_reviewers_comments_sage_shm-30_May_2018 for A method for detecting damage-induced nonlinearity in structures using weighting function augmented curvature approach by J Prawin and A Rama Mohan Rao in Structural Health Monitoring</p

Thoracoscopic repair of iatrogenic bronchial injury in a neonate during bronchogenic cyst excision

Thoracoscopic surgery was not previously accepted in the neonatal population due to inappropriate instrumentation and lack of experience. However, our experience in the last few decades has slowly yet steadily established its safety and efficacy. The major advantages that thoracoscopy offers are early recovery and fewer long-term complications. However, we are aware that this comes at the cost of a steep learning curve and the potential challenge of facing certain complications which may compel a conversion to open. There is a paucity of literature regarding intraoperative complications of neonatal thoracoscopy and its management. Conversion to open thoracotomy is appropriate, keeping patient safety in mind, and any decision made to continue management of a complication thoracoscopically is technically demanding. Iatrogenic bronchial injury is one such rare complication of thoracoscopy with a limited mention in literature. We describe below a 25-day-old patient with a bronchogenic cyst who sustained injury to the left bronchus during thoracoscopic cyst excision, which was successfully repaired thoracoscopically