RESUMO
Randomly distributed topological defects created during the spontaneous symmetry breaking are the fingerprints to trace the evolution of symmetry, range of interaction, and order parameters in condensed matter systems. However, the effective mean to manipulate topological defects into ordered form is elusive due to the topological protection. Here, we establish a strategy to effectively align the topological domain networks in hexagonal manganites through a mechanical approach. It is found that the nanoindentation strain gives rise to a threefold Magnus-type force distribution, leading to a sixfold symmetric domain pattern by driving the vortex and antivortex in opposite directions. On the basis of this rationale, sizeable mono-chirality topological stripe is readily achieved by expanding the nanoindentation to scratch, directly transferring the randomly distributed topological defects into an ordered form. This discovery provides a mechanical strategy to manipulate topological protected domains not only on ferroelectrics but also on ferromagnets/antiferromagnets and ferroelastics.
RESUMO
Water pollution control and prevention require that the water quality testing is of real time, online and portability. The presejt paper provides a water detecting system based on UV-visible spectra. The R2 of the linear regression is greater than 0.99 between absorbance and COD of the samples. Single measurement is within 1 s. At the same time, two methods were presented for direct comparison and normalization of the spectra and their corresponding indicator parameters. By a large number of experiments with standard solution of the potassium hydrogen phthalate and water samples, we found that these methods can be used to classify samples, find suitable mathematical model of the test water from the database, to improve the universal ability of the UV water testing technology, and get other water quality indices.
