Modeling and simulation allow methodical variation of material properties beyond the capacity of experimental methods. Due to the hexagonal structure of graphene, it is considered as frame-like structure. In the frame...Modeling and simulation allow methodical variation of material properties beyond the capacity of experimental methods. Due to the hexagonal structure of graphene, it is considered as frame-like structure. In the frame, covalent C-C bonds are taken as beams joined together with carbon atoms placed at the joints. Uniaxial beam elements, defined by their cross-sectional area, material properties, and moment of inertia represent the covalent bonds. The parameters of the beam elements are determined by establishing equivalence between structural and computational mechanics. However, the bonds connecting the carbon atoms do not have physical existence as they are a compromise between attractive and repulsive forces. Also, defects at nanoscale make graphene different from frame-like structure. In addition, the topography of graphene makes it non-linear structure and even the axial loading changes to eccentric loading. Here we show that, by using basic statics principles, disparities between graphene and frame-likes structures can be highlighted.展开更多
As an important geomorphological divide in the hilly Loess Plateau, valley boundary plays a pivotal role in the construction of distributed models for studying the processes and mechanism of soil erosion, sediment tra...As an important geomorphological divide in the hilly Loess Plateau, valley boundary plays a pivotal role in the construction of distributed models for studying the processes and mechanism of soil erosion, sediment transfer and runoffs within a watershed. In the past, this boundary manually interpreted from large scale maps and aerial photographs. In this paper, the authors first present a simple and practical definition for topographic structures unique to the highly dissected topography in the hilly Loess Plateau in DEMs; then define the valley boundary cells in a DEM with the following features: 1) they are most likely located on a concave slope, 2) these cells have the sharpest transition in slope, 3) those cells on the downward side of the valley boundary should have a slope gradient larger than 20° ,4) as the boundary of the entire valley in a basin valley boundary must be continuous; then devise an algorithm to automatically delineate valley boundary from DEMs and implement it in a computer. This algorithm was applied to detect drainage networks and the valley boundary in the Wangjiagou basin in the hilly loess area of Lishi County, Shanxi Province, China from a 10 m DEM. The extracted results are highly comparable to those manually interpreted from aerial photographs.展开更多
文摘Modeling and simulation allow methodical variation of material properties beyond the capacity of experimental methods. Due to the hexagonal structure of graphene, it is considered as frame-like structure. In the frame, covalent C-C bonds are taken as beams joined together with carbon atoms placed at the joints. Uniaxial beam elements, defined by their cross-sectional area, material properties, and moment of inertia represent the covalent bonds. The parameters of the beam elements are determined by establishing equivalence between structural and computational mechanics. However, the bonds connecting the carbon atoms do not have physical existence as they are a compromise between attractive and repulsive forces. Also, defects at nanoscale make graphene different from frame-like structure. In addition, the topography of graphene makes it non-linear structure and even the axial loading changes to eccentric loading. Here we show that, by using basic statics principles, disparities between graphene and frame-likes structures can be highlighted.
文摘As an important geomorphological divide in the hilly Loess Plateau, valley boundary plays a pivotal role in the construction of distributed models for studying the processes and mechanism of soil erosion, sediment transfer and runoffs within a watershed. In the past, this boundary manually interpreted from large scale maps and aerial photographs. In this paper, the authors first present a simple and practical definition for topographic structures unique to the highly dissected topography in the hilly Loess Plateau in DEMs; then define the valley boundary cells in a DEM with the following features: 1) they are most likely located on a concave slope, 2) these cells have the sharpest transition in slope, 3) those cells on the downward side of the valley boundary should have a slope gradient larger than 20° ,4) as the boundary of the entire valley in a basin valley boundary must be continuous; then devise an algorithm to automatically delineate valley boundary from DEMs and implement it in a computer. This algorithm was applied to detect drainage networks and the valley boundary in the Wangjiagou basin in the hilly loess area of Lishi County, Shanxi Province, China from a 10 m DEM. The extracted results are highly comparable to those manually interpreted from aerial photographs.
