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Ping Huai

Publications and source records attributed to Ping Huai.

5 recordsLinked to original sources

Weakly supervised learning for pattern classification in serial femtosecond crystallography

Serial femtosecond crystallography at X-ray free electron laser facilities opens a new era for the determination of crystal structure. However, the data processing of those experiments is facing unprecedented challenge, because the total number of diffraction patterns needed to determinate a high-resolution structure is huge. Machine learning methods are very likely to play important roles in dealing with such a large volume of data. Convolutional neural networks have made a great success in the field of pattern classification, however, training of the networks need very large datasets with labels. Th is heavy dependence on labeled datasets will seriously restrict the application of networks, because it is very costly to annotate a large number of diffraction patterns. In this article we present our job on the classification of diffraction pattern by weakly supervised algorithms, with the aim of reducing as much as possible the size of the labeled dataset required for training. Our result shows that weakly supervised methods can significantly reduce the need for the number of labeled patterns while achieving comparable accuracy to fully supervised methods.

cond-mat.mtrl-sci

Irradiation effects in the Ni-17Mo-7Cr alloy bombarded with MeV Au ions

Irradiation effects in Ni-17Mo-7Cr alloy, which is an newly developed structural material for molten salt reactor (MSR), have been systematically investigated by using 3MeV Au ions at different fluences, corresponding to dpa number (displacement per atom) of 1~ 30. GIXRD measurement indicates that the microstrain of the irradiated samples increased from 0.14% to 0.22% as dpa increased from 1 to 30. In the meanwhile, nanoindentation results reveal the Ni-17Mo-7Cr alloy underwent radiation-induced hardening first and then softening at dpa of 30. The swelling rate of Ni-17Mo-7Cr alloy was found around 1.3% at 30 dpa, which means only 0.04% per dpa. Besides, Raman spectra shows that carbon segregation appeared after Au ions irradiation. Our results are very helpful for understanding irradiation damages in Nickel-base alloys, especially for those in purpose of being used in future MSR nuclear energy system.

cond-mat.mtrl-sci

Strong Adsorption between Uranium Dicarbide and Graphene Surface Induced by f Electrons

The interaction between gaseous uranium dicarbide and graphite is significant for the safety control and design of Gen-IV nuclear energy system. In this article, the interaction mechanism has been studied using a simplified model of adsorption of two typical UC2 isomers (linear CUC and symmetric triangular structures) on graphene based on density functional theory calculations. The results reveal strong chemisorption characteristics between the UC2 and graphene, which is found different from the conventional weak intermolecular interaction. Interestingly, although the CUC structure can induce a double sp3-hybridization at the graphene, the most stable adsorption structure is formed by the triangular UC2 adsorbed at the hollow site of the graphene. Further bonding analysis indicates that the U 5f orbitals of the triangular UC2 are more active than that in the CUC, providing a larger effective bonding area in the adsorption system. Our calculations are helpful for understanding the role of actinide compounds in adsorption on carbon nanomaterials surface, especially for elucidating the bonding properties of 5f electrons.

physics.atm-clus

Theory of Doping Induced High-Spin in a Model of Polyene-Based Molecular Magnets

Control of intramolecular spin alignment is studied theoretically in a model of polyene-based molecular magnets in which delocalized $π$ electrons are coupled with localized radical spins. In a previous paper [Phys. Rev. Lett. 90 (2003) 207203], we have demonstrated that charge doping is an effective way to realize controllable high-spin in the $π$-conjugated molecular magnets. In this paper, we clarify the dependence of spin-alignment on the exchange interaction between the localized spin and $π$ electron and the electron-electron interactions. The antiferromagnetic exchange interaction plays a role different from the ferromagnetic counterpart in doped molecules. To understand complex interplay of charge and spin degrees of freedom in the doped systems, we carry out a systematic study on the phase diagram of spin alignment in the parameter space. The mechanism of the spin alignment is discussed based on the spin densities of $π$ electrons. The calculated results are consistent with experiments, providing a theoretical basis for the control of spin alignment.

cond-mat.str-el

Electronic Control of Spin Alignment in pi-Conjugated Molecular Magnets

Intramolecular spin alignment in pi-conjugated molecules is studied theoretically in a model of a Peierls-Hubbard chain coupled with two localized spins. By means of the exact diagonalization technique, we demonstrate that a spin singlet (S=0) to quartet (S=3/2) transition can be induced by electronic doping, depending on the chain length, the positions of the localized spins, and the sign of the electron-spin coupling. The calculated results provides a theoretical basis for understanding the mechanism of spin alignment recently observed in a diradical donor molecule.

cond-mat.mtrl-sci