A study on acoustic emission signal propagation of a small size multi-cylinder diesel engine

Acoustic emission has been found effective in offering earlier fault detection and improving identification capabilities of faults. However, the sensors are inherently uncalibrated. This paper presents a source to sensor paths calibration technique which can lead to diagnosis of faults in a small size multi-cylinder diesel engine. Preliminary analysis of the acoustic emission (AE) signals is outlined, including time domain, time-frequency domain, and the root mean square (RMS) energy. The results reveal how the RMS energy of a source propagates to the adjacent sensors. The findings lead to allocate the source and estimate its inferences to the adjacent sensor, and finally help to diagnose the small size diesel engines by minimising the crosstalk from multiple cylinders

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

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

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

Machine prognostics based on health state estimation using SVM

The ability to accurately predict the remaining useful life of machine components is critical for continuous operations in machines which can also improve productivity and enhance system safety. In condition-based maintenance (CBM), effective diagnostics and prognostics are important aspects of CBM which provide sufficient time for maintenance engineers to schedule a repair and acquire replacement components before the components finally fail. All machine components have certain characteristics of failure patterns and are subjected to degradation processes in real environments. This paper describes a technique for accurate assessment of the remnant life of machines based on prior expert knowledge embedded in closed loop prognostics systems. The technique uses Support Vector Machines (SVM) for classification of faults and evaluation of health for six stages of bearing degradation. To validate the feasibility of the proposed model, several fault historical data from High Pressure Liquefied Natural Gas (LNG) pumps were analysed to obtain their failure patterns. The results obtained were very encouraging and the prediction closely matched the real life particularly at the end of term of the bearings

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

Investigations on road noise level spatial variability within a specially designed acoustic balcony

An investigation into the spatial distribution of road traffic noise levels on a balcony is conducted. A balcony constructed to a special acoustic design due to its elevation above an 8 lane motorway is selected for detailed measurements. The as-constructed balcony design includes solid parapets, side walls, ceiling shields and highly absorptive material placed on the ceiling. Road traffic noise measurements are conducted spatially using a five channel acoustic analyzer, where four microphones are located at various positions within the balcony space and one microphone placed outside the parapet at a reference position. Spatial distributions in both vertical and horizontal planes are measured. A theoretical model and prediction configuration is presented that assesses the acoustic performance of the balcony under existing traffic flow conditions. The prediction model implements a combined direct path, specular reflection path and diffuse reflection path utilizing image source and radiosity techniques. Results obtained from the prediction model are presented and compared to the measurement results. The predictions are found to correlate well with measurements with some minor differences that are explained. It is determined that the prediction methodology is acceptable to assess a wider range of street and balcony configuration scenarios

Nanofibers Reinforced Polymer Composite Microstructures

The book Advances in Nanofibers is a research publication that covers original research on developments within the Nanofibers field of study. The book is a collection of reviewed scholarly contributions written by different authors. Each scholarly contribution represents a chapter and each chapter is complete in itself but related to the major topics and objectives. The target audience comprises scholars and specialists in the field. Chapter 7 Nanofibers Reinforced Polymer Composite Microstructures, by Andy Alubaidy, Krishnan Venkatakrishnan, and Bo Tan is designed to be a comprehensive source for nanofibers reinforced polymer studies. The fundamental properties, manufacturing techniques, and applications of nanofibers reinforced polymer materials are discussed. In addition, this chapter introduce an in depth scientific framework for the advances in nanofibers reinforced polymer researches as well as scientific principles and mechanisms in relation to the methods of fabrication of reinforced microstructuring with a discussion on potential commercial applications. The mechanical, electrical, and magnetic properties of nanofibers reinforced polymer microstructures will be the focus of this chapter. It also offers an in depth discussion on methodology, modeling, characterization, fabrication, and applications for nanofibers reinforced polymers.https://source.sheridancollege.ca/fast_books/1000/thumbnail.jp

Unusual presentation of uterine rupture following laparoscopic myomectomy: a case report and literature review

Laparoscopic myomectomy is preferred to the laparotomy approach as the former promises a better postoperative course, with fewer complications and faster recovery. It is increasingly performed in younger women in recent years. However, although rare, uterine rupture is an important and dangerous complication. Authors report a case of 36-year-old lady who presented at 23 weeks and 4 days gestation of an in vitro fertilization (IVF) dichorionic diamniotic twin pregnancy with spontaneous uterine rupture. She underwent a laparoscopic myomectomy three year prior for a 4.5cm fundal fibroid. Her presenting symptoms include acute onset of epigastric pain. Uterine rupture was confirmed using Computed Tomography scan. She underwent an exploratory laparotomy and the placenta was found extruding from a 4cm defect on the posterior fundus along the previous myomectomy scar with active bleeding. Current literature suggests it is difficult to predict when uterine rupture may happen. Proper selection criteria for suitable cases may allow trial of labour after myomectomy to be a viable option. Potential considerations include interval between myomectomy and conception, scar integrity, method of repair, and the use of electrocoagulation. This case reports the worrying features of an early antepartum rupture presenting with atypical symptomatology. In pregnant patients presenting with abdominal pain or haemodynamic instability, it is imperative to consider uterine rupture so as to perform timely intervention. Those with a history of laparoscopic myomectomy should be considered high risk and counseled about the risk of rupture with extensive discussion about mode of delivery.

Editorial: Next generation γδ T cell-based tumor immunotherapy

The discovery of the gd T-cell receptor (TCR) and its ability to confer potent cytotoxic activity in CD3+ cells some 35 years ago sparked the initial proliferation in research that garnered widespread interest in the biology and function of gd T cells