32 research outputs found
Air-Coupled Ultrasonic Testing of Rails
No full textUnder sponsorship by the Federal Railroad Administration (FRA), the University of California at San Diego is developing a system for non-contact rail integrity evaluation. The system uses ultrasonic air-coupled guided wave signal generation and air-coupled signal detection to detect transverse and longitudinal defects in the rail. The fully air-coupled ultrasound transduction presents an evolution over the previous-generation prototype that used pulsed laser ultrasound excitation and air-coupled detection. The system also features a real-time statistical data analysis that minimizes false positive rates and maximizes true detection rates, as well as a specialized filtering approach and impedance matching to overcome the inherently poor signal-to-noise ratio of air-coupled ultrasonic measurements in rail steel. Special targets of the inspection are Detail Fractures, Transverse Fissures and Vertical Split Head defects that were responsible for several accidents in recent years. The design of the prototype was guided by rigorous Finite Element Analysis simulations that revealed fundamental aspects of air-coupled wave propagation and interaction with internal defects in rails. The non-contact air-coupled prototype has been tested at the Transportation Technology Center in Pueblo, CO, in October 2014 (at walking speed) and in November 2015 (at speeds of 5 mph, 10 mph and 15 mph). Results from these tests are presented in terms of Receiver Operating Characteristic (ROC) curves that assess the performance of the system in terms of the unavoidable trade-off between true detection rates and false positive rates. The preliminary analysis of the ROC curves from the latest November 2015 tests is quite encouraging
Ultrasonic guided wave imaging of plates containing defects and inclusions
No full textThis paper addresses the nondestructive testing of platelike structural components that are widely used in aerospace, marine, and civil structures. The objective is not only to detect and localize possible defects, but to reconstruct a picture of the plate in terms of weakened areas, considering cases with multiple defects of different depths. To do so, the minimum-variance distortionless response (MVDR) beamforming processor is applied, using a new
set of weights, that improve the focus of the array by increasing the dynamic range and the spatial resolution of the image. These weights are based on the physics of the propagating Lamb modes, including the symmetric mode S0, the antisymmetric mode A0, and the shear horizontal mode SH0, taking advantage of their compounding too. The beamforming processor intensity enables to distinguish stiffer from weaker areas of the plate
Cost-effectiveness of adding zoledronic acid to endocrine therapy in premenopausal women with hormone-responsive early breast cancer in Portugal, Spain, and Italy, based on the ABCSG-12 Study.
No full textADDING ZOLEDRONIC ACID TO ENDOCRINE THERAPY IN PREMENOPAUSAL WOMEN WITH HORMONE-RESPONSIVE EARLY BREAST CANCER CAN BE COST-EFFECTIVE FROM ITALIAN, SPANISH, AND PORTUGUESE HEALTH-CARE PERSPECTIVES, BASED ON THE ABCSG-12 TRIAL
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Inspection of Structures by Passive Extraction of Acoustic Transfer Functions and Ultrasonic Imaging
No full textInspection of structures is a critical task that needs to be performed in order to guarantee the safety of structural components during their service life. Different Nondestructive Evaluation (NDE) techniques can be used to inspect aerospace, civil, and biological systems to ensure their structural integrity and to identify the presence of damages and defects, which could impair the correct functioning of the overall structure.The focus of this dissertation is the inspection of structures through the passive extraction of the acoustic transfer function of the medium under consideration, and the 2D and 3D characterization of defects by means of ultrasonic imaging. The first part of the dissertation addresses the issue of defect detection in railroad tracks by extracting the acoustic transfer function of rails through a normalized cross-correlation operator, which exploits the random acoustic vibrations generated by the train wheels. A technique to remove uncorrelated noise from the recorded signals is also introduced to make the transfer function reconstruction more robust. A statistical outlier analysis is used to detect any variation in the transfer function of the rail as the train moves along the track, in order to identify locations where discontinuities (joints, welds, defects) might be present. A prototype with multiple pairs of capacitive sensors was developed to perform the inspection in a non-contact, passive-only, high-speed manner. Results from fields tests performed at the Transportation Technology Center (TTC) in Pueblo, CO, will demonstrate the feasibility of the system for the reliable inspection of railroad tracks at speeds up to 80mph.The second part of the dissertation is focused on the characterization of defects using ultrasonic imaging to create 2D and 3D images of the inspected medium. Imaging in bulk solids and plates is performed using sensor arrays and an improved beamforming algorithm that uses information about the structure of the propagating acoustic wave modes to improve the defect characterization process. Furthermore, the experimental application to railroad tracks and the implementation on a Graphics Processing Unit (GPU) shows the potential for the accurate real-time imaging of rail flaws
On the identification of bridge decks aeroelastic coefficients: the covariance block hankel matrix method
No full textIl seguente elaborato si concentra sull'identifi�cazione strutturale di sistemi soggetti a sollecitazioni aeroelastiche e nello speci�fico l'attenzione viene rivolta ad impalcati da ponte. Si analizzano i concetti principali caratterizzanti il campo dell'aeroelasticità indagando i fattori dominanti che entrano in gioco sul piano teorico. In seguito, si considera il metodo di identifi�cazione strutturale chiamato Covariance Block Hankel
Matrix (CBHM) utilizzato come strumento di derivazione
dei coeffi�cienti aeroelastici propri della struttura. Infi�ne, si indaga il comportamento di questo metodo di identi�ficazione al variare di una serie di parametri chiave e all'interno di diversi scenari, visionando risultati ottenuti tramite una serie di test eff�ettuati per provare l'a�dattabilità del metodo stesso al variare delle condizioni che caratterizzano il sistema
Non-Contact Ultrasonic Guided Wave Inspection of Rails: Next Generation Approach
No full textThe University of California at San Diego (UCSD), under a Federal Railroad Administration (FRA) Office of Research and Development (R&D) grant, is developing a system for highspeed and non-contact rail defect detection. A prototype using an ultrasonic air-coupled guided wave signal generation and air coupled signal detection, paired with a real-time statistical analysis algorithm, has been realized. This system requires a specialized filtering approach based on electrical impedance matching due to the inherently poor signal-to-noise ratio of air coupled ultrasonic measurements in rail steel. Various aspects of the prototype have been designed with the aid of numerical analyses. In particular, simulations of ultrasonic guided wave propagation in rails have been performed using a Local Interaction Simulation Approach (LISA) algorithm. The system's operating parameters were selected based on Receiver Operating Characteristic (ROC) curves, which provide a quantitative manner to evaluate different detection performances based on the trade-off between detection rate and false positive rate. The prototype based on this technology was tested in October 2014 at the Transportation Technology Center (TTC) in Pueblo, Colorado, and again in November 2015 after incorporating changes based on lessons learned
High-speed non-contact ultrasound system for rail track integrity evaluation
No full textUltrasonic rail inspection is the most commonly implemented method for detecting internal rail defects. While the conventional ultrasound wheel probe has gained its popularity within rail maintenance community, it suffers from the limited test speeds (25 mph at most). This paper presents the state-of-the-art developments in ultrasonic rail inspection technique that utilizes non-contact receivers and no active transmitters. The transfer function between two points of the rail is reconstructed by deconvolutions of multiple pairs of receivers that sense the acoustics naturally excited in the rail by the running wheels. The deconvolution process eliminates the random effect of the excitation to reconstruct a stable acoustic transfer function of the rail. A fixed bulk delay and frequency selection technique are introduced to facilitate the power spectral density estimation for robust transfer function reconstruction. A multivariate analysis based on selected features extracted from various frequency bands is conducted on the signals recorded by multiple sensor pairs respectively. Furthermore, damage index traces based on data from different sensor pairs provide system redundancy for improved reliability with the voting logic for damage detection. The proposed approach lends itself to extremely high testing speeds (as fast as the service train speed, e.g. 60 mph and above), that would enable the real-time evaluation of rail track integrity at train operational speeds. A prototype based on this passive-only inspection idea has been constructed and tested with the DOTX216 testing vehicle of the Federal Railroad Administration at the Transportation Technology Center (TTC) in Pueblo, CO in September 2016. Test runs were made at various speeds from 25 mph to 80 mph (the maximum speed allowed on the test track). The results show the feasibility of stable reconstruction of the transfer function from the random wheel excitation, as well as the detection of joints and welds present in the track. Some tests were also conducted on TTC Defect Farm showing the potential for defect defection
Defect detection performance of the UCSD non-contact air-coupled ultrasonic guided wave inspection of rails prototype
No full textThe University of California at San Diego (UCSD), under a Federal Railroad Administration (FRA) Office of Research and Development (R& D) grant, is developing a system for high-speed and non-contact rail defect detection. A prototype using an ultrasonic air-coupled guided wave signal generation and air-coupled signal detection, paired with a real-time statistical analysis algorithm, has been realized. This system requires a specialized filtering approach based on electrical impedance matching due to the inherently poor signal-to-noise ratio of air-coupled ultrasonic measurements in rail steel. Various aspects of the prototype have been designed with the aid of numerical analyses. In particular, simulations of ultrasonic guided wave propagation in rails have been performed using a Local Interaction Simulation Approach (LISA) algorithm. The system's operating parameters were selected based on Receiver Operating Characteristic (ROC) curves, which provide a quantitative manner to evaluate different detection performances based on the trade-off between detection rate and false positive rate. The prototype based on this technology was tested in October 2014 at the Transportation Technology Center (TTC) in Pueblo, Colorado, and again in November 2015 after incorporating changes based on lessons learned. Results from the 2015 field test are discussed in this paper
Expression of the Bitter taste receptor, T2R38, in enteroendocrine cells of the colonic mucosa of overweight/obese vs. Lean subjects
No full textBitter taste receptors (T2Rs) are expressed in the mammalian gastrointestinal mucosa. In the mouse colon, T2R138 is localized to enteroendocrine cells and is upregulated by longterm high fat diet that induces obesity. The aims of this study were to test whether T2R38 expression is altered in overweight/obese (OW/OB) compared to normal weight (NW) subjects and characterize the cell types expressing T2R38, the human counterpart of mouse T2R138, in human colon. Colonic mucosal biopsies were obtained during colonoscopy from 35 healthy subjects (20 OW/OB and 15 NW) and processed for quantitative RT-PCR and immunohistochemistry using antibodies to T2R38, chromogranin A (CgA), glucagon like peptide-1 (GLP-1), cholecystokinin (CCK), or peptide YY (PYY). T2R38 mRNA levels in the colonic mucosa of OW/OB were increased (> 2 fold) compared to NW subjects but did not reach statistical significance (P = 0.06). However, the number of T2R38 immunoreactive (IR) cells was significantly increased in OW/OB vs. NW subjects (P = 0.01) and was significantly correlated with BMI values (r = 0.7557; P = 0.001). In both OW/OB and NW individuals, all T2R38-IR cells contained CgA-IR supporting they are enteroendocrine. In both groups, T2R38-IR colocalized with CCK-, GLP1- or PYY-IR. The overall CgA-IR cell population was comparable in OW/OB and NW individuals. This study shows that T2R38 is expressed in distinct populations of enteroendocrine cells in the human colonic mucosa and supports T2R38 upregulation in OW/OB subjects. T2R38 might mediate host functional responses to increased energy balance and intraluminal changes occurring in obesity, which could involve peptide release from enteroendocrine cells. © 2016 Latorre et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
