Micro computed tomography (Micro-CT) was applied to obtain three-dimensional images of the microstructure of cement paste (water-to-cement mass ratio of 0.5) at different ages. By using the Amira software, component p...Micro computed tomography (Micro-CT) was applied to obtain three-dimensional images of the microstructure of cement paste (water-to-cement mass ratio of 0.5) at different ages. By using the Amira software, component phases of the cement paste such as pores, hydration products, and unhydrated clinker particles were segmented from each other based on their 3D image grey levels; their relative contents were also calculated with the software, and the data are 61.2%, 0% and 38.8% at the beginning of hydration and 11.8%, 78.5% and 9.7% at 28 d age, respectively. The hydration degree of cement paste at different ages was compared with the experimental data acquired by loss on ignition (LOI) tests. The results show that the calculated and measured data reasonably agree with each other, which indicates that micro-CT is a useful and reliable approach to characterize the micro structure evolution of hydrating cement paste.展开更多
目的初步探讨骨质疏松性椎体压缩骨折患者、骨质疏松患者以及无骨质疏松患者3者间椎体骨质的差别。方法对30例需要进行手术治疗的患者进行分组,分别为骨质疏松性椎体压缩骨折患者组、骨质疏松患者组及无骨质疏松患者组,每组10例。在术...目的初步探讨骨质疏松性椎体压缩骨折患者、骨质疏松患者以及无骨质疏松患者3者间椎体骨质的差别。方法对30例需要进行手术治疗的患者进行分组,分别为骨质疏松性椎体压缩骨折患者组、骨质疏松患者组及无骨质疏松患者组,每组10例。在术中分别取出3组患者少许椎体样本,椎体样本大小相等,不影响手术疗效的同时亦不会对患者造成不良影响,患者均表示知情同意。随后分别对取出的椎体标本进行显微计算机断层扫描术(micro-computed tomography,Micro-CT)检测,以了解及对比3组患者之间椎体骨密度(bone mineral density,BMD)、骨矿含量(bone mineral content,BMC)和骨小梁情况。结果骨质疏松性椎体压缩骨折患者组对比骨质疏松患者组、无骨质疏松患者组其椎体皮质骨BMD、松质骨BMD、骨小梁BMD和总体BMD以及皮质骨BMC、松质骨BMC和总BMC均有明显下降,差异具有统计学意义(P<0.05),其中骨小梁BMD、皮质骨BMC、松质骨BMC和总BMC下降显著(P<0.01);骨质疏松患者组对比无骨质疏松患者组其椎体皮质骨BMD、松质骨BMD、骨小梁BMD和总体BMD以及皮质骨BMC、松质骨BMC和总BMC均有下降,差异具有统计学意义(P<0.05),其中骨小梁BMD下降显著(P<0.01)。结论较低的椎体BMD和BMC是椎体压缩骨折发生发展的主要原因,骨质疏松患者和暂无骨质疏松人群需要预防BMD、BMC的下降,防止骨质疏松性椎体压缩骨折的发生。展开更多
Micro porosity in aluminum alloys may contribute to fatigue life degradation, which can largely limit the application of alloys. Therefore, the fatigue life of a commercial 7050-T7451 thick plate and an experimental p...Micro porosity in aluminum alloys may contribute to fatigue life degradation, which can largely limit the application of alloys. Therefore, the fatigue life of a commercial 7050-T7451 thick plate and an experimental plate with different porosities was compared in this study. The X-ray computed tomography(XCT) was utilized to characterize the size, number density and spatial distribution of porosity inside various samples, and the fracture surface of fatigued specimens was compared by using scanning electron microscope(SEM). The results showed that the fatigue cracks prefer to initiate from constituent particles in the commercial alloy. Whereas the micro porosity is the predominant site for crack nucleation and subsequent failure in the experimental one. The presence of micro porosity in experimental7050-T7451 thick plate may reduce the fatigue life by an order of magnitude or more compared with the defect-free alloy. The pores close to sample surface are the main fatigue crack initiation site, among which larger and deeper pore leads to a shorter fatigue life. The crack initiation is also affected by the pore geometry and direction. Besides, the overall porosity inside the bulk can affect the crack propagation during fatigue tests.展开更多
基金Project(2009CB623201) supported by the National Basic Research Program of ChinaProjects(50902106, 51272193) supported by the National Natural Science Foundation of ChinaProject(NCET-10-0660) supported by New Century Excellent Talents in Universities of China
文摘Micro computed tomography (Micro-CT) was applied to obtain three-dimensional images of the microstructure of cement paste (water-to-cement mass ratio of 0.5) at different ages. By using the Amira software, component phases of the cement paste such as pores, hydration products, and unhydrated clinker particles were segmented from each other based on their 3D image grey levels; their relative contents were also calculated with the software, and the data are 61.2%, 0% and 38.8% at the beginning of hydration and 11.8%, 78.5% and 9.7% at 28 d age, respectively. The hydration degree of cement paste at different ages was compared with the experimental data acquired by loss on ignition (LOI) tests. The results show that the calculated and measured data reasonably agree with each other, which indicates that micro-CT is a useful and reliable approach to characterize the micro structure evolution of hydrating cement paste.
文摘目的初步探讨骨质疏松性椎体压缩骨折患者、骨质疏松患者以及无骨质疏松患者3者间椎体骨质的差别。方法对30例需要进行手术治疗的患者进行分组,分别为骨质疏松性椎体压缩骨折患者组、骨质疏松患者组及无骨质疏松患者组,每组10例。在术中分别取出3组患者少许椎体样本,椎体样本大小相等,不影响手术疗效的同时亦不会对患者造成不良影响,患者均表示知情同意。随后分别对取出的椎体标本进行显微计算机断层扫描术(micro-computed tomography,Micro-CT)检测,以了解及对比3组患者之间椎体骨密度(bone mineral density,BMD)、骨矿含量(bone mineral content,BMC)和骨小梁情况。结果骨质疏松性椎体压缩骨折患者组对比骨质疏松患者组、无骨质疏松患者组其椎体皮质骨BMD、松质骨BMD、骨小梁BMD和总体BMD以及皮质骨BMC、松质骨BMC和总BMC均有明显下降,差异具有统计学意义(P<0.05),其中骨小梁BMD、皮质骨BMC、松质骨BMC和总BMC下降显著(P<0.01);骨质疏松患者组对比无骨质疏松患者组其椎体皮质骨BMD、松质骨BMD、骨小梁BMD和总体BMD以及皮质骨BMC、松质骨BMC和总BMC均有下降,差异具有统计学意义(P<0.05),其中骨小梁BMD下降显著(P<0.01)。结论较低的椎体BMD和BMC是椎体压缩骨折发生发展的主要原因,骨质疏松患者和暂无骨质疏松人群需要预防BMD、BMC的下降,防止骨质疏松性椎体压缩骨折的发生。
基金Project(2019KJ2X08-4) supported by Chinalco Technology Development Project Fund,China。
文摘Micro porosity in aluminum alloys may contribute to fatigue life degradation, which can largely limit the application of alloys. Therefore, the fatigue life of a commercial 7050-T7451 thick plate and an experimental plate with different porosities was compared in this study. The X-ray computed tomography(XCT) was utilized to characterize the size, number density and spatial distribution of porosity inside various samples, and the fracture surface of fatigued specimens was compared by using scanning electron microscope(SEM). The results showed that the fatigue cracks prefer to initiate from constituent particles in the commercial alloy. Whereas the micro porosity is the predominant site for crack nucleation and subsequent failure in the experimental one. The presence of micro porosity in experimental7050-T7451 thick plate may reduce the fatigue life by an order of magnitude or more compared with the defect-free alloy. The pores close to sample surface are the main fatigue crack initiation site, among which larger and deeper pore leads to a shorter fatigue life. The crack initiation is also affected by the pore geometry and direction. Besides, the overall porosity inside the bulk can affect the crack propagation during fatigue tests.
