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The development of Ni-based single crystal superalloys relies heavily on the composition design with the addition of critical alloying elements, e.g., Re and Ru. Understanding the role of alloying effects require to know the configurations of the alloying element distribution between γ-Ni and γ′-Ni3Al phases and among various non-equivalent sites. This work employed first-principles density functional theory calculations to study the preference of phase and site occupancy of 11 alloying elements including Al and transition metal elements: 3d (Ti, Cr, Co, Ni), 4d (Mo, Ru), and 5d (Hf, Ta, W, Re) in Ni and Ni3Al. We calculated the substitution energies of 1298 triple-site doping configurations including 286 NiNiNi site doping of Ni, 726 AlNiNi site doping, and 286 NiNiNi site doping of Ni3Al with alloying elements Ni, Co, Ru, Cr, Re, Mo, W, Al, Ti, Ta, and Hf. In the dual-site and triple-site doping of Ni and Ni3Al, all studied alloying elements preferred to occupy Ni phase rather than Ni3Al phase. We found that the most stable defect complexes often contained the favorable substitutions of Al, Ti, Ta, and Hf for the Ni sites that stabilized the alloying elements doping at the other one or two nearest neighbor sites. The co-substitutions of various alloying elements at multiple sites are critical to understanding the strengthening mechanism of alloying elements in Ni-based single crystal superalloys. [ABSTRACT FROM AUTHOR]

Atmospheric gas discharge is very likely to constrict into filaments and diffuse plasma formation is inefficient in most cases. Developing cost-efficient atmospheric diffuse plasma devices represents a significant challenge for high performance in biomedical decontamination and material processing. Here, we propose an alternative roadmap to produce a diffuse argon plasma jet by expanding and quenching the existing filamentary discharge at the initial or middle stage of streamer development. Possible mechanisms are summarized. With the gas flow velocity comparable to the ion drift one, enhancing ambipolar diffusion near the edge of the positive-streamer channel promotes the radial diffusion of newly-produced electrons, realizing the radial expansion of channel. Weakening electric field in front of the streamer head through head expansion and field offset, prevents the further development of streamer, leading to a positive-pseudo-streamer discharge. Reducing electric field in front of the negative-streamer head through ion compensation, impedes the initial growth of streamer, resulting in a negative pulseless glow discharge. The positive-pseudo-streamer and negative pulseless glow discharges function together to form the diffuse plasma jet. Streamer coupling theory is traditionally used to engineer the generation of diffuse plasmas in the regime preceding filamentary discharge, but this method remains inefficient. Here, an alternative route to cost-efficient diffuse plasma generation is proposed, involving the expansion and quenching of existing filamentary discharge. [ABSTRACT FROM AUTHOR]

Introduction: A large number of studies have shown that, for severe lumbar spinal stenosis, decompression surgery can often obtain better results than non-surgical treatment. However, whether the lumbar spine is fixed after decompression is still controversial. The results of biomechanical studies indicate that there is a correlation between the range of decompression and postoperative spinal instability. Methods: The multiple databases like Pubmed, Embase, Cochrane databases and China National Knowledge database were used to search for the relevant studies, and full-text articles involved in the evaluation of fusion and nonfusion surgery for lumbar spinal stenosis. Review Manager 5.2 was adopted to estimate the effects of the results among selected articles. Forest plots, sensitivity analysis and bias analysis for the articles included were also conducted. Results: A total of nine relevant studies were eventually satisfied the included criteria. There were significant differences in length of stay [mean difference (MD) = 3.04, 95% CI (2.00, 4.08), P < 0.000]1), but there were no differences in Oswestry Disability Index (ODI score) [MD = − 1.14, 95% CI (− 2.92, 0.63), P = 0.21; I2 = 87%] and complications [RR = 1 with 95% CI (0.69, 1.46), P value of overall effect was 0.98]. The study was robust and limited publication bias was observed in this study. Conclusion: Our research supported that fusion and nonfusion surgeries had no differences in clinical effects and complications for lumbar spinal stenosis, while fusion surgery involved a longer length of stay than nonfusion surgery. [ABSTRACT FROM AUTHOR]

We propose a protocol of asymmetric controlled bidirectional quantum teleportation of two- and three-qubit states. That is to say, Alice wants to teleport an arbitrary two-qubit state to Bob, and Bob wants to teleport an arbitrary three-qubit state for Alice via the control of supervisor Charlie. By using the eleven-qubit entangled state as the quantum channel, Alice can teleport an arbitrary two-qubit state for Bob and Bob can teleport an arbitrary three-qubit state for Alice simultaneously. [ABSTRACT FROM AUTHOR]

Knowledge of the mechanical properties of structural materials is essential for their practical applications. In the present work, three-hundred and sixty data samples on four mechanical properties of steels—fatigue strength, tensile strength, fracture strength and hardness—were selected from the Japan National Institute of Material Science database, comprising data on carbon steels and low-alloy steels. Five machine learning algorithms were used to predict the mechanical properties of the materials represented by the three-hundred and sixty data samples, and random forest regression showed the best predictive performance. Feature selection conducted by random forest and symbolic regressions revealed the four most important features that most influence the mechanical properties of steels: the tempering temperature of steel, and the alloying elements of carbon, chromium and molybdenum. Mathematical expressions were generated via symbolic regression, and the expressions explicitly predicted how each of the four mechanical properties varied quantitatively with the four most important features. This study demonstrates the great potential of symbolic regression in the discovery of novel advanced materials. [ABSTRACT FROM AUTHOR]

The interaction between mechanics and chemistry plays an essential and critical role in the behaviors and properties of materials, especially in nanoscale alloys. Based on the classical Gibbs and McLean adsorption isotherms, the present study takes the freestanding nanometer thick films of Pd-H solid solutions as a typic example to investigate surface segregation of hydrogen. The surface eigenstress model is further developed here to give analytic formulas, which have the capability to quantitatively predict the size-dependent surface segregation. Molecular dynamics (MD) simulations are conducted on free-standing Pd-H nanofilms. The MD simulations verify the theoretical analytic results and determine the values of parameters involved in the theoretical analysis. The integrated theoretical and numerical study exhibits that both surface excess H concentration and apparent biaxial Young's modulus of Pd-H thin films depend on the nominal H concentration and the film thickness. The MD simulations determine the values of three parameters involved in the theoretical analysis. Especially, the parameter of the differentiation in reference chemical potential behaves like the molar free energy of segregation in the McLean adsorption isotherm. [ABSTRACT FROM AUTHOR]

Grüneisen parameter is one of the most valuable quantities in thermodynamics, which links the material properties of bulk modulus, heat capacity at constant volume, thermal expansion coefficient, and volume together. A new thermodynamic model of temperature-dependent potential energy is proposed here to investigate the temperature dependent Grüneisen parameter of bulk material. The newly developed thermodynamic model leads to temperature dependent analytical solutions of Grüneisen parameter and other thermo-mechanical properties including the Grüneisen equation of state. Molecular dynamics simulations are conducted on single crystalline Ni, Cu, and Au bulk crystals and the simulation results verify the newly developed thermodynamic model and quantitively evaluate the theoretically derived physical quantities. In addition, the Debye model is also employed in the study of temperature dependent Grüneisen parameter and the results also verify the theoretical approach. [ABSTRACT FROM AUTHOR]

Surface eigenstress and eigendisplacement models were used to investigate the surface stress, surface relaxation and surface elasticity of thin films with different surface orientations. Molecular dynamics simulations and first-principles calculations were conducted on face-centered cubic Au films with the focus on relaxation induced nonlinear initial deformation. The simulation results verify the theoretical predictions of the size dependency of surface energy density and surface stress, and the nonlinear scaling law of the size-dependent Young's modulus of thin films. The mechanism of the size-dependent behaviors was further explored at the atomic bonding level with the charge density field. The Au atomic bonding at surfaces is enhanced compared to its interior counterpart and therefore the nominal Young's modulus of the Au thin films is larger when the film thickness is smaller. [ABSTRACT FROM AUTHOR]

The effect of electrostatic tractions on the fracture behavior of a dielectric material under mechanical and/or electric loading is analyzed, by studying a pre-cracked parallel-plate capacitor, and illustrated by plots. The results indicate that electrostatic tractions on the electrodes compress the material in front of the crack tip, while electrostatic tractions on the crack faces have the tendency to close the crack and stretch the material behind the crack tip. Mechanical load is the driving force to propagate the crack, while applied electric field retards crack propagation due to the electrostatic tractions. As a direct consequence, the fracture criterion is composed of two parts: the energy release rate must exceed a critical value and the mechanical load must be higher than the critical value for crack opening. [ABSTRACT FROM AUTHOR]

We theoretically study the propagations and interactions of an Airy beam, soliton, and nonlinear self-accelerating beam in LiNbO3 crystal modulated by a shorter wavelength background beam. Simulations indicate that the self-accelerating beam and Airy beam can effectively propagate even in self-defocusing media, and the finite-energy Airy beam can generate bright solitons in a self-focusing medium. When two counter-shift Airy beams interact under appropriate conditions, fusion solitons, breathing solitons, and soliton pairs are generated. If we allow a photovoltaic soliton to collide with an Airy beam, X-type waves and soliton deflection occur at a specific phase shift and beam interval. Moreover, we find that the dynamics of two truncated nonlinear self-accelerating beams tend to exhibit straight propagation with attraction and repulsion in the in- and out-of-phase cases, respectively. These results are significant for applications related to optical routing and optical switches. [ABSTRACT FROM AUTHOR]