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Rui Azevedo Guerreiro,Paula Fazendas,Ana Rita Pereira,Ana Marques,João Pais,Sofia Alegria,Kisa Hyde Congo,Ana Catarina Gomes,João Carvalho,Gonçalo Morgado,Inês Cruz,Ana Rita Almeida,Isabel João,Hélder 한국심초음파학회 2020 Journal of Cardiovascular Imaging (J Cardiovasc Im Vol.28 No.2
BACKGROUND: Stress echocardiography has a 72%–85% sensitivity and an 80%–95% specificity. In this study, we characterized patients who received a false-positive stress echocardiogram result. METHODS: A total of 5,256 patients underwent a stress echocardiogram (induced by exercise, dobutamine, or dipyridamole) between 2009 to 2018, and 405 patients (7.7%) received a positive result. Among the positive patients, 300 underwent coronary angiography within 12 months, and these patients were included in this study (mean age = 64.9 ± 9.4 years, 230 men [76.7%]). Coronary artery disease was diagnosed by stenosis ≥50% in any epicardial coronary artery. Clinical and echocardiographic variables were compared between patients with true- and false-positive stress echocardiogram results. RESULTS: Seventy-two patients (24%) had a false-positive stress echocardiogram, with similar rates across stressor types (p = 0.574). Patients with false positives were less frequently men (63.9% vs. 80.7%, p = 0.003), had lower diabetes mellitus prevalence (15.3% vs. 45.6%, p = 0.001), were similar to true positive patients with regard to body-mass index, arterial hypertension prevalence, hyperlipidemia and smoking, and had lower pre-test probability of coronary artery disease (23% vs. 32%, p = 0.016). The wall motion score index (WMSI) was higher in the true-positive stress group, and wall motion abnormalities were more frequent in the apical segments (70.5% vs. 56.7%, p = 0.034). In a multivariable predictive model, men (odds ratio [OR] = 2.994), diabetes (OR = 5.440), and peak WMSI (OR = 10.690) were associated with a true-positive result. CONCLUSIONS: Twenty-four percent of our study population received a false-positive stress echocardiogram result, with similar rates across stressor types. Patients with true-positive stress echocardiogram results are more likely to be men, diabetic, and have a high peak WMSI.
Measurement and Diagnostic of Engine Belt Physical Condition from Acoustic Signals
Bruno Fazenda,Fengshou Gu,Mark Avis,Andrew Ball 제어로봇시스템학회 2009 제어로봇시스템학회 국제학술대회 논문집 Vol.2009 No.8
This paper presents an investigation into the diagnosis of transmission belt condition through acousticmonitoring. A relevant belt model and laser interferometry measurements are used to guide the design and analysis of the acoustic monitoring system. The fault under scrutiny is the development of a loss of tension in the belt which mayoccur due to degradation of belt material. Results show that it is possible to diagnose this kind of fault using acoustic diagnostic techniques. Analysis of acoustic signals reveals changes in the natural frequencies of the belt which arematched by results for laser interferometry.
Acoustic Based Safety Emergency Vehicle Detection for Intelligent Transport Systems
Bruno Fazenda,Hidajat Atmoko,Fengshou Gu,Luyang Guan,Andrew Ball 제어로봇시스템학회 2009 제어로봇시스템학회 국제학술대회 논문집 Vol.2009 No.8
A system has been investigated for the detection of incoming direction of an emergency vehicle. Acoustic detection methods based on a cross microphone array have been implemented. It is shown that source detection based on time delay estimation outperforms sound intensity techniques, although both techniques perform well for the application. The relaying of information to the driver as a warning signal has been investigated through the use of ambisonic technology and a 4 speaker array which is ubiquitous in most modern vehicles. Simulations show that accurate warning information may be relayed to the driver and afford correct action.
Luyang Guan,Yimin Shao,Fengshou Gu,Bruno Fazenda,Andrew Ball 제어로봇시스템학회 2009 제어로봇시스템학회 국제학술대회 논문집 Vol.2009 No.8
In this paper, a new method is proposed by combining ensemble empirical mode decomposition (EEMD) with order tracking techniques to analyse the vibration signals from a two stage helical gearbox. The method improves EEMD results in that it overcomes the potential deficiencies and achieves better order spectrum representation for fault diagnosis. Based on the analysis, a diagnostic feature is designed based on the order spectra of extracted IFMs for detection and separation of gearbox faults. Experimental results show this feature is sensitive to different fault severities and robust to the influences from operating conditions and remote sensor locations.
Motor Current Signal Analysis using a Modified Bispectrum for Machine Fault Diagnosis
Fengshou Gu,Yimin Shao,Niaoqin Hu,Bruno Fazenda,Andrew Ball 제어로봇시스템학회 2009 제어로봇시스템학회 국제학술대회 논문집 Vol.2009 No.8
This paper presents the use of the induction motor current to identify and quantify common faults within a two-stage reciprocating compressor. The theoretical basis is studied to understand current signal characteristics when themotor undertakes a varying load under faulty conditions. Although conventional bispectrum representation of currentsignal allows the inclusion of phase information and the elimination of Gaussian noise, it produces unstable results dueto random phase variation of the sideband components in the current signal. A modified bispectrum based on theamplitude modulation feature of the current signal is thus proposed to combine both lower sidebands and highersidebands simultaneously and hence describe the current signal more accurately. Based on this new bispectrum a more effective diagnostic feature namely normalised bispectral peak is developed for fault classification. In association with the kurtosis of the raw current signal, the bispectrum feature gives rise to reliable fault classification results. Inparticular, the low feature values can differentiate the belt looseness from other fault cases and discharge valve leakage and intercooler leakage can be separated easily using two linear classifiers. This work provides a novel approach to theanalysis of stator current for the diagnosis of motor drive faults from downstream driving equipment.