ABSTRACT
The non-contact three-dimensional measurement and reconstruction techniques have played a significant role in the packaging and transportation of precious cultural relics. This paper develops a structured light based three-dimensional measurement system, with a low-cost for cultural relics packaging. The structured light based system performs rapid measurements and generates 3D point cloud data, which is then denoised, registered and merged to achieve accurate 3D reconstruction for cultural relics. The multi-frequency heterodyne method and the method in this paper are compared. It is shown that the relative accuracy of the proposed low-cost system can reach a level of 1/1000. The high efficiency of the system is demonstrated through experimental results.
ABSTRACT
Ordered two-dimensional (2D) arrays of ß-HgS nanocrystal aggregates were prepared successfully at the air/water interface through the interfacial reaction between Hg(2+) ions in the subphase and H(2)S in the gaseous phase under the direction of liquid-expanded monolayers of arachidic acid (AA). These 2D arrays are composed of hexagonal or quasi-hexagonal aggregates with the size of several hundreds of nanometers that consist of several tens of HgS nanocrystals with the size of several nanometers. The formed HgS nanocrystals together with AA molecules self-assembled into round aggregates due to the interactions between the species, and the aggregates self-assembled into 2D arrays further due to the attractions between them. During the self-assembly process, the soft round aggregates transformed into hexagonal or quasi-hexagonal ones. The experimental conditions, especially the phase states of the AA monolayers and temperature, have great influences on the formation of the 2D arrays. To the best of our knowledge, this is the first case to get 2D ordered arrays at the air/water interface through a one-step synthesis and assembly process.
ABSTRACT
The stem radius growth (SRG) of six samples of Picea meyeri and five samples of Larix principis-rupprechtii nearby the tree-line of Luya Mountain in North China was measured by the dendrometer in the summer phase from July 15 to August 7 and the autumn phase from September 5 to October 9, 2007, with the environmental factors measured simultaneously. In the summer phase, there was no significant difference in the sensitivity of SRG to the environmental factors fluctuation between the two species; but in the relatively cold and dry autumn phase, the SRG of P. meyeri was more sensitive to the fluctuation of environmental factors. The accumulated SRG of the two species increased linearly in summer phase, but decreased first and kept stable then in autumn phase, with the growth increment of P. meyeri fluctuated more than that of L. principis-rupprechtii. The SRG of the two species correlated positively with hydrological factors and negatively with thermal factors, and the SRG of P. meyeri was strongly affected by air humidity and temperature, while that of L. principis-rupprechtii was mainly affected by soil moisture.
