To accurately analyze the impact of casting pores in steel,high-resolution 3D X-ray tomography technology was used to gather detailed statistical information about micropores.These micropores were classified as gas,sh...To accurately analyze the impact of casting pores in steel,high-resolution 3D X-ray tomography technology was used to gather detailed statistical information about micropores.These micropores were classified as gas,shrinkage,and gas-shrinkage pores depending on their formation origin and morphology.Clustering tendencies and affinity parameters were defined to characterize the spatial correlations among these three types of pores.The 3D data from X-ray tomography scans were then integrated into finite element analysis(FEA)software to predict how micropore shape,size,and distribution influence stress distribution within the material.The results show that certain inflection points with small local radii within the cast pores are major contributors to stress concentration.Therefore,cast pores cannot be simply modeled as ideal spherical pores.The sphericity and volume of pores have a significant impact on the stress concentration of the model.Specifically,lower sphericity and larger pore volumes result in higher stress concentrations.Moreover,the internal pores of steel castings exhibit specific global distribution characteristics.Pores located on the surface of the specimen lead to significantly higher stress concentrations compared to those located inside the specimen.展开更多
Development of inhomogeneous deformation is an interest matter in material engineering. Synchrotron radiation tomography provides 3D distribution map of local strain in polycrystalline aluminum alloy by tracking micro...Development of inhomogeneous deformation is an interest matter in material engineering. Synchrotron radiation tomography provides 3D distribution map of local strain in polycrystalline aluminum alloy by tracking microstructural features. To perform further deep analysis on development of inhomogeneous deformation, crystallographic grain orientation is necessary. Three-dimensional X-ray diffraction technique was developed. A new crystallographic orientation measurement method was described in 3D space, utilizing grain boundary tracking （GBT） information.展开更多
Pneumatosis cystoides intestinalis(PCI) is a rare condition that may be associated with a variety of diseases.The presenting clinical picture may be very heterogeneous and represent a challenge for the clinician.In th...Pneumatosis cystoides intestinalis(PCI) is a rare condition that may be associated with a variety of diseases.The presenting clinical picture may be very heterogeneous and represent a challenge for the clinician.In the present paper we describe both a common and an uncommon clinical presentation of PCI and review the pertaining literature.Our cases confirm that,apart from asymptomatic cases,the clinical presentation of PCI may be widely different and suggest that a new onset of stipsis might be the presenting symptom.Diagnosis might be suggested by a simple X-ray of the digestive tract showing a change in the characteristics of the intestinal wall in two-thirds of these patients.However,one third of the patients do not have a suggestive X-ray and require a computed tomography(CT) scan/nuclear magnetic resonance that may reveal a thickened bowel wall containing gas to confirm the diagnosis and distinguish PCI from intraluminal air or submucosal fat.CT also allows the detection of additional findings that may suggest an underlying,potentially worrisome cause of PCI such as bowel wall thickening,altered contrast mucosal enhancement,dilated bowel,soft tissue stranding,ascites and the presence of portal air.Our results also point out that clinicians and endoscopists should be aware of the possible presentations of PCI in order to correctly manage the patients affected with this disease and avoid unnecessary surgeries.The increasing number of colonoscopies performed for colon cancer screening makes PCI more frequently casually encountered and/or provoked,therefore the possible endoscopic appearances of this disease should be well known by endoscopists.展开更多
基金The National Natural Science Foundation of China(No.51578137).
文摘To accurately analyze the impact of casting pores in steel,high-resolution 3D X-ray tomography technology was used to gather detailed statistical information about micropores.These micropores were classified as gas,shrinkage,and gas-shrinkage pores depending on their formation origin and morphology.Clustering tendencies and affinity parameters were defined to characterize the spatial correlations among these three types of pores.The 3D data from X-ray tomography scans were then integrated into finite element analysis(FEA)software to predict how micropore shape,size,and distribution influence stress distribution within the material.The results show that certain inflection points with small local radii within the cast pores are major contributors to stress concentration.Therefore,cast pores cannot be simply modeled as ideal spherical pores.The sphericity and volume of pores have a significant impact on the stress concentration of the model.Specifically,lower sphericity and larger pore volumes result in higher stress concentrations.Moreover,the internal pores of steel castings exhibit specific global distribution characteristics.Pores located on the surface of the specimen lead to significantly higher stress concentrations compared to those located inside the specimen.
文摘Development of inhomogeneous deformation is an interest matter in material engineering. Synchrotron radiation tomography provides 3D distribution map of local strain in polycrystalline aluminum alloy by tracking microstructural features. To perform further deep analysis on development of inhomogeneous deformation, crystallographic grain orientation is necessary. Three-dimensional X-ray diffraction technique was developed. A new crystallographic orientation measurement method was described in 3D space, utilizing grain boundary tracking （GBT） information.
文摘Pneumatosis cystoides intestinalis(PCI) is a rare condition that may be associated with a variety of diseases.The presenting clinical picture may be very heterogeneous and represent a challenge for the clinician.In the present paper we describe both a common and an uncommon clinical presentation of PCI and review the pertaining literature.Our cases confirm that,apart from asymptomatic cases,the clinical presentation of PCI may be widely different and suggest that a new onset of stipsis might be the presenting symptom.Diagnosis might be suggested by a simple X-ray of the digestive tract showing a change in the characteristics of the intestinal wall in two-thirds of these patients.However,one third of the patients do not have a suggestive X-ray and require a computed tomography(CT) scan/nuclear magnetic resonance that may reveal a thickened bowel wall containing gas to confirm the diagnosis and distinguish PCI from intraluminal air or submucosal fat.CT also allows the detection of additional findings that may suggest an underlying,potentially worrisome cause of PCI such as bowel wall thickening,altered contrast mucosal enhancement,dilated bowel,soft tissue stranding,ascites and the presence of portal air.Our results also point out that clinicians and endoscopists should be aware of the possible presentations of PCI in order to correctly manage the patients affected with this disease and avoid unnecessary surgeries.The increasing number of colonoscopies performed for colon cancer screening makes PCI more frequently casually encountered and/or provoked,therefore the possible endoscopic appearances of this disease should be well known by endoscopists.
