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In this paper, we used CALYPSO program which is conjuncted with DFT to investigate Li doped small-sized neutral Bn clusters. From ground-state and low energy structures, the properties and geometric significance of Li-doped boron clusters are greatly affected. Except for LiB9, which adds a B atom on preceding LiB8 boron wheel, the ground-state clusters of LiBn are formed by replacing the terminal boron atom of the Bn+1 clusters in the same size with a Li atom or by adding a Li atom to the Bn clusters. The transition point from 2 to 3D configuration of LiBn clusters appears at n = 5. The stability of LiBn clusters was analyzed by calculating the average binding energy, Gibbs free energy, first-order differential energy, second-order differential energy, HOMO–LUMO gap (the energy gap between the highest occupied and lowest unoccupied molecular orbital) and charge transfer. The results show that the LiB11 cluster with excellent symmetry and planar structure is the relative most stable structure. Molecular orbital and chemical bonding analysis indicated that the main reason for the stability of the LiB11 cluster is mainly due to the strong s-p bonding of B–B. [ABSTRACT FROM AUTHOR]

Projects about magnesium-based doped of transition metal have constantly attracted much attention in cluster science, while the research of Co, Fe, Ni doped Mid-Sized Mg16 clusters has not been reported. Here, the geometric construction and electronic properties of neutral and negative Mg16X (X = Co, Fe, Ni) clusters were researched by unbiased CALYPSO structure search codes and subsequent DFT calculations at the B3PW91 level. The results show that Fe and Co atoms are more likely to replace the central bits of the caged Mg170/− cluster, but the excellent and stable configuration of the Mg170/− cluster is perfectly maintained. Simultaneously, the doping of Co and Fe can cause the cluster to produce the corresponding magnetic moment. The caged Mg16Co− clusters with a central Co atom have good binding energy, local charge transfer and HOMO–LUMO gap according to stability analysis, which indicates that Mg16Co− clusters has better relative stability. In addition, it is found that there is an intense interaction between Mg-3s, p and Co-3d AO (molecular orbitals) through the analysis of molecular orbitals and adaptive natural density partitioning (AdNDP), which may be the main reason for the high stability of Mg16Co− clusters. [ABSTRACT FROM AUTHOR]

Divalent metal clusters, such as alkaline-earth metal clusters, have drawn extensive attention because of the appealing size-evoked nonmetal-to-metal transition and attractive characters related to the size, shape, and doping of clusters. Herein, the structural properties of small-size neutral and anionic Mgn+1 and BaMgn (n = 2–10) clusters are investigated thoroughly through a combination of the CALYPSO software package and DFT optimization. The final calculation results indicate that with the increase in Mg atom number, Ba atoms are inclined to substitute Mg atoms located at the skeleton convex cap. What is worth mentioning is that BaMg9 cluster which presents tower framework possesses excellent stability in specified size range on account of the detailed analysis of bond energy, second-order energy difference, and the charge transfer. In addition, the analysis of the bonding characteristics manifests that the strong s–p interaction between Ba and Mg atomic orbitals is conducive to the improvement in the stability of BaMg9. [ABSTRACT FROM AUTHOR]

Ammonium nitrate/fuel oil (ANFO) explosive vehicle is the most common equipment in the mining machinery. The pharmaceutical system is the most important system of the whole mechanical system, its performance and reliability determine the reliability of the whole system. However, there is little literature on reliability analysis of ANFO explosive vehicle. In this paper, ANFO explosive vehicle pharmaceutical system is regarded as the research object. The pharmaceutical system presents complex dynamic characteristics. The electronic control subsystem, for example, contains function dependency gate, and the sensitizer system includes warm spare parts. In this paper, the related theories and methods of dynamic fault tree and Bayesian network were applied to the reliability research of the pharmaceutical system. By analyzing the principle of the system, dynamic fault tree model was established. By mapping relation, it was transformed into Bayesian network. The marginal probability distribution and the conditional probability distribution of each node are determined, and the prior probabilities and the posterior probabilities of the pharmaceutical system are obtained. Compared with the results of Markov's analysis, there are some deviations between them. According to the sequencing result of the influence degree of parts on the reliability, the fuel flow-meter, oil filter element, sensitizer flow-meter, line interface, and oil pipe are the weak links of the pharmaceutical system. They can be regarded as important objects of system improvement, fault maintenance and health management. The sensitizer system is the most reliable subsystem of the pharmaceutical system. Because of the existence of spare part logic in this subsystem, it has the least influence on the pharmaceutical system. In addition, it is necessary to reduce the impact of the operating environment in the reliability analysis of similar systems. The result can improve maintenance efficiency and provide theoretical support for the system improvement. [ABSTRACT FROM AUTHOR]

A convolution perfectly matched layer (CPML) can efficiently absorb boundary reflection in numerical simulation. However, the CPML is suitable for the first-order elastic wave equation and is difficult to apply directly to the second-order elastic wave equation. In view of this, based on the first-order CPML absorbing boundary condition, we propose a new CPML (NCPML) boundary which can be directly applied to the second-order wave equation. We first systematically extend the first-order CPML technique into second-order wave equations, neglecting the space-varying characteristics of the partial damping coefficient in the complex-frequency domain, avoiding the generation of convolution in the time domain. We then transform the technique back to the time domain through the inverse Fourier transform. Numerical simulation indicates that the space-varying characteristics of the attenuation factor have little influence on the absorption effect and increase the memory at the same time. A number of numerical examples show that the NCPML proposed in this study is effective in simulating elastic wave propagation, and this algorithm is more efficient and requires less memory allocation than the conventional PML absorbing boundary. [ABSTRACT FROM AUTHOR]

The anisotropic properties of subsurface media cause waveform distortions in seismic wave propagation, resulting in a negative influence on seismic imaging. In addition, wavefields simulated by the conventional coupled pseudo-acoustic equation are not only affected by SV-wave artifacts but are also limited by anisotropic parameters. We propose a least-squares reverse time migration (LSRTM) method based on the pure qP-wave equation in vertically transverse isotropic media. A finite difference and fast Fourier transform method, which can improve the efficiency of the numerical simulation compared to a pseudo-spectral method, is used to solve the pure qP-wave equation. We derive the corresponding demigration operator, migration operator, and gradient updating formula to implement the LSRTM. Numerical tests on the Hess model and field data confirm that the proposed method has a good correction effect for the travel time deviation caused by underground anisotropic media. Further, it significantly suppresses the migration noise, balances the imaging amplitude, and improves the imaging resolution. [ABSTRACT FROM AUTHOR]

Full waveform inversion (FWI) is an extremely important velocity-model-building method. However, it involves a large amount of calculation, which hindsers its practical application. The multi-source technology can reduce the number of forward modeling shots during the inversion process, thereby improving the efficiency. However, it introduces cross-noise problems. In this paper, we propose a sparse constrained encoding multi-source FWI method based on K-SVD dictionary learning. The phase encoding technology is introduced to reduce crosstalk noise, whereas the K-SVD dictionary learning method is used to obtain the basis of the transformation according to the characteristics of the inversion results. The multi-scale inversion method is adopted to further enhance the stability of FWI. Finally, the synthetic subsag model and the Marmousi model are set to test the effectiveness of the newly proposed method. Analysis of the results suggest the following: (1) The new method can effectively reduce the computational complexity of FWI while ensuring inversion accuracy and stability; (2) The proposed method can be combined with the time-domain multi-scale FWI strategy flexibly to further avoid the local minimum and to improve the stability of inversion, which is of significant importance for the inversion of the complex model. [ABSTRACT FROM AUTHOR]

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Least squares reverse-time migration (LSRTM) is an inversion method that removes artificial images and preserves the amplitude of reflectivity sections. LSRTM has been used in reservoir exploration and processing of 4D seismic data. LSRTM is, however, a computationally costly and memory-intensive method. In this study, LSRTM in the pseudodepth domain was combined with the conjugate gradient method to reduce the computational cost while maintaining precision. The velocity field in the depth domain was transformed to the velocity field in the pseudodepth domain; thus, the total number of vertical sampling points was reduced and oversampling was avoided. Synthetic and field data were used to validate the proposed method. LSRTM in the pseudodepth domain in conjunction with the conjugate gradient method shows potential in treating field data. [ABSTRACT FROM AUTHOR]

Employing a polarization-entangled $$\chi $$ state, which is a four-photon genuine entangled state, we propose a protocol teleporting a general two-photon polarization state. Firstly, the sender needs to perform one Controlled-NOT gate, one Hadamard gate, and one Controlled-NOT gate on the state to be teleported in succession. Secondly, the sender performs local nondemolition parity analyses based on cross-Kerr nonlinearities and publicizes the achieved outcomes. Finally, conditioned on the sender's analysis outcomes, the receiver executes the single-photon unitary transformation operations on his own photons to obtain the state originally sit in the sender's location. Due to the employment of nondemolition parity analyses rather than four-qubit joint measurement, it can be realized more feasible with currently available technologies. Moreover, the resources of Bell states can be achieved because the nondestructive measurement is exploited, which facilitates other potential tasks of quantum information processing. [ABSTRACT FROM AUTHOR]

The mapping method is a forward-modeling method that transforms the irregular surface to horizontal by mapping the rectangular grid as curved; moreover, the wave field calculations move from the physical domain to the calculation domain. The mapping method deals with the irregular surface and the low-velocity layer underneath it using a fine grid. For the deeper high-velocity layers, the use of a fine grid causes local oversampling. In addition, when the irregular surface is transformed to horizontal, the flattened interface below the surface is transformed to curved, which produces inaccurate modeling results because of the presence of ladder-like burrs in the simulated seismic wave. Thus, we propose the mapping method based on the dual-variable finite-difference staggered grid. The proposed method uses different size grid spacings in different regions and locally variable time steps to match the size variability of grid spacings. Numerical examples suggest that the proposed method requires less memory storage capacity and improves the computational efficiency compared with forward modeling methods based on the conventional grid. [ABSTRACT FROM AUTHOR]

Taking collective noise into account, a feasible protocol for distributing a multi-photon polarization-entangled state is presented assisted with spatial degree of freedom. The compositions of polarization beam splitters and half-wave plates with tilted $$\pi /4$$ functioning as NOT gates convert the entanglement modes between the polarization and spatial degree of freedom. The appropriate and available optical elements are applied, by which the protocol can be feasibly implemented without the influence resulting from arbitrary collective noise. Furthermore, the successful probability of the entangled state distribution equals to unity for unitary collective noise model. [ABSTRACT FROM AUTHOR]