14H, 18R and 24R long-period stacking ordered （LPSO） structures were observed in the as-cast Mg-3Cu-1Mn-2Zn-1Y damping alloy using transmission electron microscopy （TEM）. These LPSO structures contained Mg, Y, Cu ...14H, 18R and 24R long-period stacking ordered （LPSO） structures were observed in the as-cast Mg-3Cu-1Mn-2Zn-1Y damping alloy using transmission electron microscopy （TEM）. These LPSO structures contained Mg, Y, Cu and Zn and thus they were quaternary phases. Sharp diffraction pattern of the 24R structure was obtained and the angle between and g10024R was measured to be 5.03°. During high resolution TEM observations, lattice fringes with two characteristic spacings were observed within the 24R structure. Based on the experimental results, 6H, 7H and three 8H are suggested as the building blocks of 18R, 14H and 24R structures, respectively. The 24R unit cell can be interpreted as the stacking of 8H building blocks in the same shear direction with a shear angle of about 5.03°. The imperfect 24R structures are in order or disorder arrangements of principal 8H and minor 6H blocks. This double-block structure model is also applicable to other reported defects in LPSO structures.展开更多
The physical-mechanical,chemical,and durability characteristics of alkali-activated materials(AAMs)have been widely investigated.However,a critical gap in the literature is the lack of a comprehensive overview of rece...The physical-mechanical,chemical,and durability characteristics of alkali-activated materials(AAMs)have been widely investigated.However,a critical gap in the literature is the lack of a comprehensive overview of recently published literature regarding the life cycle assessment(LCA)of these binders.This study aims to fill that gap by conducting a systematic literature review of globally published literature on the topic.This paper consolidates knowledge by searching different databases,focusing on LCA studies that used AAMs as pastes,mortars,concretes,bricks,and rammed earth/soil blocks.The selected articles were reviewed and categorized based on precursors,alkaline activators,functional units,system boundaries,life cycle inventory databases,allocation,impact methodologies,and software used.Additionally,this paper also critically analyzes the key challenges of LCA for AAMs.The major challenges were identified as selecting a functional unit,subjectivity in boundary systems,and data interpretation.This work concludes that AAMs show substantial advantages in global warming potential compared to ordinary Portland cement-based materials;however,the average of other categories such as marine ecotoxicity and ozone layer depletion has been reported to be higher than for the reference samples.展开更多
An effective and flexible rotation and compensation scheme is designed to improve the accuracy of rotating inertial navigation system （RINS）. The accuracy of single-axial R1NS is limited by the errors on the rotatin...An effective and flexible rotation and compensation scheme is designed to improve the accuracy of rotating inertial navigation system （RINS）. The accuracy of single-axial R1NS is limited by the errors on the rotating axis. A novel inertial measurement unit （IMU） scheme with error compensation for the rotating axis of fiber optic gyros （FOG） RINS is presented. In the scheme, two couples of inertial sensors with similar error characteristics are mounted oppositely on the rotating axes to compensate the sensors error. Without any change for the rotation cycle, this scheme improves the system＇s precision and reliability, and also offers the redundancy for the system. The results of 36 h navigation simulation prove that the accuracy of the system is improved notably compared with normal strapdown INS, besides the heading accuracy is increased by 3 times compared with single-axial RINS, and the position accuracy is improved by 1 order of magnitude.展开更多
It has been widely accepted that spherical per- iodicity generally dominates liquid and amorphous structure formation, where atoms tend to gather near spherically peri- odic shells according to Friedel oscillation. He...It has been widely accepted that spherical per- iodicity generally dominates liquid and amorphous structure formation, where atoms tend to gather near spherically peri- odic shells according to Friedel oscillation. Here it is revealed that the same order is just hidden in the atomic global packing modes of the crystalline phases relevant to bulk metallic glasses. Among the multiple nearest-neighbor dusters devel- oped from all the non-equivalent atomic sites in a given phase, there always exists a principal duster, centered by which the spherical periodicity, both topologically and chemically, is the most distinct. Then the principal dusters plus specific glue atoms just constitute the cluster-plus-glue-atom structural units shared by both metallic glasses and the corresponding crystalline phases. It is further pointed out that the spherical periodicity order represents the common structural homology of crystalline and amorphous states in the medium-range through scrutinizing all binary bulk-glass-relevant phases in Cu-（Zr, Hf）, Ni-（Nb, Ta）, Al-Ca, and Pd-Si systems.展开更多
基金Project (2009CB623704) supported by the National Basic Research Program of ChinaProject (50971076) supported by the National Natural Science Foundation of China
文摘14H, 18R and 24R long-period stacking ordered （LPSO） structures were observed in the as-cast Mg-3Cu-1Mn-2Zn-1Y damping alloy using transmission electron microscopy （TEM）. These LPSO structures contained Mg, Y, Cu and Zn and thus they were quaternary phases. Sharp diffraction pattern of the 24R structure was obtained and the angle between and g10024R was measured to be 5.03°. During high resolution TEM observations, lattice fringes with two characteristic spacings were observed within the 24R structure. Based on the experimental results, 6H, 7H and three 8H are suggested as the building blocks of 18R, 14H and 24R structures, respectively. The 24R unit cell can be interpreted as the stacking of 8H building blocks in the same shear direction with a shear angle of about 5.03°. The imperfect 24R structures are in order or disorder arrangements of principal 8H and minor 6H blocks. This double-block structure model is also applicable to other reported defects in LPSO structures.
基金supported by the Alexander von Humboldt Foundation,International Climate Protection Fellowship(Ref 3.5—1157991-IRN-IKS)This financial support is gratefully appreciated by Morteza Nikravan.Rafia Firdous and Dietmar Stephan highly acknowledge Bundesministerium fur Wirtschaft und Energie(BMWi)for funding number 16KN046744.
文摘The physical-mechanical,chemical,and durability characteristics of alkali-activated materials(AAMs)have been widely investigated.However,a critical gap in the literature is the lack of a comprehensive overview of recently published literature regarding the life cycle assessment(LCA)of these binders.This study aims to fill that gap by conducting a systematic literature review of globally published literature on the topic.This paper consolidates knowledge by searching different databases,focusing on LCA studies that used AAMs as pastes,mortars,concretes,bricks,and rammed earth/soil blocks.The selected articles were reviewed and categorized based on precursors,alkaline activators,functional units,system boundaries,life cycle inventory databases,allocation,impact methodologies,and software used.Additionally,this paper also critically analyzes the key challenges of LCA for AAMs.The major challenges were identified as selecting a functional unit,subjectivity in boundary systems,and data interpretation.This work concludes that AAMs show substantial advantages in global warming potential compared to ordinary Portland cement-based materials;however,the average of other categories such as marine ecotoxicity and ozone layer depletion has been reported to be higher than for the reference samples.
基金supported by the National Natural Science Foundation of China (No.40904018)the Key Laboratory Foundation of the Ministry of Education of China (No.201001)the Doctoral Innovation Foundation of Naval University of Engineering (No.BSJJ2011008)
文摘An effective and flexible rotation and compensation scheme is designed to improve the accuracy of rotating inertial navigation system （RINS）. The accuracy of single-axial R1NS is limited by the errors on the rotating axis. A novel inertial measurement unit （IMU） scheme with error compensation for the rotating axis of fiber optic gyros （FOG） RINS is presented. In the scheme, two couples of inertial sensors with similar error characteristics are mounted oppositely on the rotating axes to compensate the sensors error. Without any change for the rotation cycle, this scheme improves the system＇s precision and reliability, and also offers the redundancy for the system. The results of 36 h navigation simulation prove that the accuracy of the system is improved notably compared with normal strapdown INS, besides the heading accuracy is increased by 3 times compared with single-axial RINS, and the position accuracy is improved by 1 order of magnitude.
基金supported by the Science Challenge Program (JCKY2016212A504)the National Natural Science Foundation of China(11674045)
文摘It has been widely accepted that spherical per- iodicity generally dominates liquid and amorphous structure formation, where atoms tend to gather near spherically peri- odic shells according to Friedel oscillation. Here it is revealed that the same order is just hidden in the atomic global packing modes of the crystalline phases relevant to bulk metallic glasses. Among the multiple nearest-neighbor dusters devel- oped from all the non-equivalent atomic sites in a given phase, there always exists a principal duster, centered by which the spherical periodicity, both topologically and chemically, is the most distinct. Then the principal dusters plus specific glue atoms just constitute the cluster-plus-glue-atom structural units shared by both metallic glasses and the corresponding crystalline phases. It is further pointed out that the spherical periodicity order represents the common structural homology of crystalline and amorphous states in the medium-range through scrutinizing all binary bulk-glass-relevant phases in Cu-（Zr, Hf）, Ni-（Nb, Ta）, Al-Ca, and Pd-Si systems.
