BACKGROUND RECTIFICATION AND FEATURE EXTRACTION OF IMAGE IN A SPOT WELD OF AL ALLOY X-RAY DETECTION

A primary study on Processing in X - ray inspection of spot weld for aluminum alloy spot welding,in- cluding for background simulation,acquisition of ideal binary image, and extraction and identifi- cation of defect features was presented.

Fast X-ray imaging beamline at SSRF

The fast X-ray imaging beamline(BL16U2)at Shanghai Synchrotron Radiation Facility(SSRF)is a new beamline that provides X-ray micro-imaging capabilities across a wide range of time scales,spanning from 100 ps toμs and ms.This beamline has been specifically designed to facilitate the investigation of a wide range of rapid phenomena,such as the deformation and failure of materials subjected to intense dynamic loads.In addition,it enables the study of high-pressure and high-speed fuel spray processes in automotive engines.The light source of this beamline is a cryogenic permanent magnet undulator(CPMU)that is cooled by liquid nitrogen.This CPMU can generate X-ray photons within an energy range of 8.7-30 keV.The beamline offers two modes of operation:monochromatic beam mode with a liquid nitrogen-cooled double-crystal monochromator(DCM)and pink beam mode with the first crystal of the DCM out of the beam path.Four X-ray imaging methods were implemented in BL16U2:single-pulse ultrafast X-ray imaging,microsecond-resolved X-ray dynamic imaging,millisecond-resolved X-ray dynamic micro-CT,and high-resolution quantitative micro-CT.Furthermore,BL16U2 is equipped with various in situ impact loading systems,such as a split Hopkinson bar system,light gas gun,and fuel spray chamber.Following the completion of the final commissioning in 2021 and subsequent trial operations in 2022,the beamline has been officially available to users from 2023.

Ray tracing particle image velocimetry-Challenges in the application to a packed bed

Ray tracing Particle Image Velocimetry(RT-PIV)is an optical technique for high resolution velocity measurements in challenging optical systems,such as transparent packed beds,that uses ray tracing to correct for distortions introduced by transparent geometries in the light paths.The ray tracing based correction is a post processing step applied to the raw PIV particle images before classical PIV evaluation.In this study,RT-PIV is performed in the top layer of a body centred cubic(bcc)sphere packing with gaseous flow,where optical access is obtained by the use of transparent N-BK7 glass balls with a diameter of d=40 mm.RT-PIV introduces new experimental and numerical challenges,for example a limited field of view,illumination difficulties,a very large required depth of field and high sensitivity to geometric parameters used in the ray tracing correction.These challenges and their implications are the main scope and discussed in the present work.Further,the validation of the ray tracing reconstruction step is presented and examples for the obtained corrected vector fields in a packed bed are given.The results show the strength of the method in reconstructing velocity fields behind transparent spheres that would not have been accessible by optical measurement techniques without the ray tracing correction.

CT and MRI diagnosis of acute traumatic hepatic rupture:analysis of ten cases

In order to verify whether magnetic resonance imaging (MRI) is superior to computed tomography (CT) in the detection and characterization of intrahepatic hematoma in its acute stage, the MRI and CT features of acute traumatic hepatic rupture (ATHR) were retrospectively studied and compared. Methods: In the 10 cases of ATHR admitted to our institute, 3 were examined with CT, 1 with MRI and 6 with both CT and MRI in the first 24 hours post injury and 9 cases out of the 10 were checked up with MRI in the first week after injury of surgery. The shape of the traumatic lesions, the damages of the intrahepatic vessels and the severity of hepatic rupture displayed with CT and MRI were compared. Results: It was found that in the first 24 hours post injury, 66.6% of hepatic injuries were shown as hypointensity on T1 weighted images and low or high density on noncontrast CT. 100% of the lesions were identified as well marked hyperintensity on T2 weighted images. Damages of the hepatic and/or portal veins were observed in 7, 4 and 3 cases on T2 and T1 weighted images and noncontrast CT figures respectively. The severity of hepatic injuries were graded in 100%, 66.7% and 44.4%of cases with these 3 procedures respectively. Conclusions: On the basis of our findings, it is concluded that T2 weighted MRI is a more sensitive and reliable imaging modality in the detection and differentiation of the type and severity of acute hepatic rupture than T1 weighted imaging and noncontrast CT.