Damage quantification techniques in acoustic emission monitoring

Acoustic emission (AE) analysis is one of the several diagnostic techniques available nowadays for structural health monitoring (SHM) of engineering structures. Some of its advantages over other techniques include high sensitivity to crack growth and capability of monitoring a structure in real time. The phenomenon of rapid release of energy within a material by crack initiation or growth in form of stress waves is known as acoustic emission (AE). In AE technique, these stress waves are recorded by means of suitable sensors placed on the surface of a structure. Recorded signals are subsequently analysed to gather information about the nature of the source. By enabling early detection of crack growth, AE technique helps in planning timely retrofitting or other maintenance jobs or even replacement of the structure if required. In spite of being a promising tool, some challenges do still exist behind the successful application of AE technique. Large amount of data is generated during AE testing, hence effective data analysis is necessary, especially for long term monitoring uses. Appropriate analysis of AE data for quantification of damage level is an area that has received considerable attention. Various approaches available for damage quantification for severity assessment are discussed in this paper, with special focus on civil infrastructure such as bridges. One method called improved b-value analysis is used to analyse data collected from laboratory testing

Review: Acoustic emission technique - Opportunities, challenges and current work at QUT

Acoustic emission (AE) is the phenomenon where high frequency stress waves are generated by rapid release of energy within a material by sources such as crack initiation or growth. AE technique involves recording these stress waves by means of sensors placed on the surface and subsequent analysis of the recorded signals to gather information such as the nature and location of the source. AE is one of the several non-destructive testing (NDT) techniques currently used for structural health monitoring (SHM) of civil, mechanical and aerospace structures. Some of its advantages include ability to provide continuous in-situ monitoring and high sensitivity to crack activity. Despite these advantages, several challenges still exist in successful application of AE monitoring. Accurate localization of AE sources, discrimination between genuine AE sources and spurious noise sources and damage quantification for severity assessment are some of the important issues in AE testing and will be discussed in this paper. Various data analysis and processing approaches will be applied to manage those issues

Machine condition prognosis based on regression trees and one-step-ahead prediction

Predicting degradation of working conditions of machinery and trending of fault propagation before they reach the alarm or failure threshold is extremely importance in industry to fully utilize the machine production capacity. This paper proposes a method to predict future conditions of machines based on one-step-ahead prediction of time-series forecasting techniques and regression trees. In this study, the embedding dimension is firstly estimated in order to determine the necessary available observations for predicting the next value in the future. This value is subsequently utilized for regression tree predictor. Real trending data of low methane compressor acquired from condition monitoring routine are employed for evaluating the proposed method. The results indicate that the proposed method offers a potential for machine condition prognosi

Experimental Study on Condition Monitoring of Low Speed Bearings : Time Domain Analysis

In condition monitoring of low speed rolling element bearings (REBs), traditional techniques involving vibration acceleration may not be able to detect a growing fault due to the low impact energy generated by the relative motion of the components. This study presents an experimental evaluation for incipient fault detection of low speed REBs by using an acoustic emission (AE) sensor and an accelerometer. A low speed fault simulation test rig was developed to simulate common machine faults with shaft speeds as low as 10rpm under loading conditions. Tests were conducted on the rig with various seeded defect bearings. This study reveals the best frequency bandwidth and suitable parameters for condition monitoring using AE signal for early detection of low speed bearing defects by means of statistical parameters in time domain

Patient-Provider Discussions about Lung Cancer Screening Pre- and Post-Guidelines: Health Information National Trends Survey (HINTS)

Objective In 2013, the USPSTF issued a Grade B recommendation that long-term current and former smokers receive lung cancer screening. Shared decision-making is important for individuals considering screening, and patient-provider discussions an essential component of the process. We examined prevalence and predictors of lung cancer screening discussions pre- and post-USPSTF guidelines. Methods Data were obtained from two cycles of the Health Information National Trends Survey (2012; 2014). The analyzed sample comprised screening-eligible current and former smokers with no personal history of lung cancer (n = 746 in 2012; n = 795 in 2014). Descriptive and multiple logistic regression analyses were conducted; patient-reported discussion about lung cancer screening with provider was the outcome of interest. Results Contrary to expectations, patient-provider discussions about lung cancer screening were more prevalent pre-guideline, but overall patient-provider discussions were low in both years (17% in 2012; 10% in 2014). Current smokers were more likely to have had a discussion than former smokers. Significant predictors of patient-provider discussions included family history of cancer and having healthcare coverage. Conclusions The prevalence of patient-provider discussions about lung cancer screening is suboptimal. Practice implications There is a critical need for patient and provider education about shared decision-making and its importance in cancer screening decisions

Cancer-Related Direct-To-Consumer Advertising - A Study of its Antecedents, Influence on Patient Information Seeking Behaviors, and Contingent Effects

Direct-to-consumer advertising (DTCA) of prescription medications and healthcare facilities has generated much debate over the potential benefits and adverse consequences for the public at large, patients, clinician-patient relationships, and the overall healthcare system. This dissertation is aimed at contributing to this debate through studying the impact of DTCA in the context of cancer treatment. Study 1 assessed the reliability and validity of three candidate measures of patient-reported exposure to cancer-related DTCA across seven criteria. The study found that all three measures performed well in terms of convergent, nomological, discriminant, and face validity. Findings from this study offer support for utilizing these survey measures in future studies targeting cancer patients. Next, Study 2 examined the prevalence and correlates of cancer-related DTCA exposure in a sample of patients in Pennsylvania diagnosed with breast, prostate, or colorectal cancers. On average, patients reported modest exposure to such DTCA (median exposure was once per week). Significant correlates of exposure included cancer type, age, stage of disease, and ethnicity. Study 3 investigated the relationships between DTCA exposure and subsequent information seeking behaviors. The analyses detected a significant association between DTCA exposure and cancer patients\u27 subsequent information engagement with their clinicians at one-year follow-up. Exposure to DTCA was marginally significant in predicting information seeking from non-clinician (lay media and interpersonal) sources. Based on the Integrative Model of Behavioral Prediction, a focused analysis showed a significant indirect path between DTCA exposure and subsequent information seeking from non-clinician sources, mediated through attitudes and intention to seek from these sources. Study 4 was guided by the Structural Influence Model of Communication to explore disparities in health information seeking behaviors arising from DTCA exposure. The study found that the associations between DTCA exposure and active information seeking behaviors were not moderated by patients\u27 age, educational level, race/ethnicity, or cancer type. To conclude, these studies would likely inform the ongoing debate and future research regarding the impact of cancer-related DTCA exposure on communication outcomes and disparities