[en] The hydriding performance, electrochemical properties and structure of MlNi_5-xSn_x (x=0-0.5) hydrogen storage alloys containing La-rich mischmetal were investigated by the use of pressure-composition isotherms, electrochemical measurements, and XRD, XPS, SEM and atomic parameters to improve properties and reduce cost. The substitution of Ni by Sn leads to an increase of the unit cell volume and charge-discharge cycle life and decrease of the plateau pressure, hysteresis and the hydrogen storage capacity. The standard enthalpy of hydride formation decreases with increasing tin substitution. The main factor which influences the standard enthalpy of the hydriding reaction is the number of the outer orbit electrons and not the atomic size factor. With a small amount of tin substitution, the cycle life increases by 52% (0.5C) and 42% (1.0C), but maximum discharge capacity decreases only by 3.0 and 3.5%, respectively. The cycle life is obviously improved by the low volume expansion and the formed SnO₂ surface layers upon electrochemical cycling

[en] La_2_/_3Ba_1_/_3MnO_3: wt%Ag_x (LBMO:Ag_x, x=0.04) films were prepared on single crystalline (001)-orientated LaAlO_3 substrates by pulsed laser deposition technique. All the samples show along the (00l) orientation in rhombohedral structure with R3c space group. The surface roughness (Ra), insulator-metal transition temperature (Tp) and resistivity at Tp (ρ_T_p) of the LBMO:Ag_0_._0_4 films reached optimal values of 3.29 nm, 288 K and 0.033 Ω cm at 740 °C, respectively. The improvement of electrical transport properties in the films are attributed to the optimal growth temperature and Ag-doping improve the microstructure of the surfaces, grain boundaries (GBs) in connectivity and better crystallization. In addition, the electrical conduction behaviors can be well fitted with the grain/domain boundary, electron–electron and magnon scattering mechanisms in the ferromagnetic metallic region (T< Tp), as well as with the adiabatic small polaron hopping mechanism in the paramagnetic insulating region (T>Tp).

[en] The littlest Higgs (LH) model predicts the existence of the doubly charged scalars Φ^±±, which generally have large flavor changing couplings to leptons. We calculate the contributions of Φ^±± to the lepton flavor violating (LFV) processes l_i→l_jγ and l_i→l_jl_kl_k, and we compare our numerical results with the current experimental upper limits on these processes. We find that some of these processes can give severe constraints on the coupling constant Y_ij and the mass parameter M_Φ. Taking into account the constraints on these free parameters, we further discuss the possible lepton flavor violating signals of Φ^±± at high energy linear e⁺e^- collider (ILC) experiments. Our numerical results show that the possible signals of Φ^±± might be detected via the subprocesses e^±e^±→l^±l^± in future ILC experiments. (orig.)

[en] Highlights: • A new CG-CLH integrated with oxy-fuel combustion for producing 99.4% H₂ is proposed. • Exergy efficiency of the new process is 2.4% higher than CG-CLHwS1. • CO₂ capture of the new process is 26.7% higher than CG-CLHwS1. - Abstract: Coke-oven gas (COG) is largely by-produced in coking plants, being most burnt and resulting in serious energy waste and air pollutant emissions. Producing high-value hydrogen from COG is therefore promising, however, the traditional processes via steam methane reforming still suffer from high energy consumption and CO₂ emissions. In this work, we propose efficient COG-to-hydrogen processes by chemical looping hydrogen technology. Parameter optimization of the proposed systems without and with support has also been conducted for the optimum COG utilization and maximum hydrogen production. The optimum molar ratios for the oxygen carrier/COG, steam/oxygen carrier, and air/oxygen carrier were found to be 2.0, 1.2, and 0.81, respectively, for the process without support. In the supported system, due to the presence of the high-temperature support, the optimum molar ratio of the oxygen carrier/COG is decreased to 1.1, while the steam/oxygen carrier ratio is increased to 3.9. The exergy efficiency, and CO₂ capture efficiency, and hydrogen purity of the system with support are 63.8%, 73.3%, and 99.4 mol.%, respectively. It was found that the process including an intercooling between fuel reactor and steam reactor, and oxygen-enriched combustion in the heating air reactor provides a further improved exergy efficiency of 66.2% and CO₂ capture efficiency of about 100%.

[en] The signal collected by current sensor will contain various noises, which will have a negative impact on the its accuracy and calibration. In order to remove unwanted noises, an extended Kalman filter (EKF) method based on backpropagation (BP) neural network is proposed in this paper. BP neural network has good adaptive ability and non-linear mapping ability. EKF can effectively filter noise and improve the calibration accuracy for non-linear systems. The signal collected by current sensor is processed by EKF and is used as the input signal of BP neural network. The trained neural network can modify the output signal of EKF, so as to improve the calibration accuracy. The angle difference and ratio difference of current sensor calibration are below 0.1, which meets the national standard and shows the effectiveness of this method. (paper)

[en] The stability and the Hopf bifurcation of a nonlinear electromechanical coupling system with time delay feedback are studied. By considering the energy in the air-gap field of the AC motor, the dynamical equation of the electromechanical coupling transmission system is deduced and a time delay feedback is introduced to control the dynamic behaviors of the system. The characteristic roots and the stable regions of time delay are determined by the direct method, and the relationship between the feedback gain and the length summation of stable regions is analyzed. Choosing the time delay as a bifurcation parameter, we find that the Hopf bifurcation occurs when the time delay passes through a critical value. A formula for determining the direction of the Hopf bifurcation and the stability of the bifurcating periodic solutions is given by using the normal form method and the center manifold theorem. Numerical simulations are also performed, which confirm the analytical results. (paper)

[en] Highlights: • Novel family of estimators for controlling efficiency. • Rigorous derivations and proofs. • Proof of principle established using multilayer transport problems. • Several numerical examples exhibit gains in efficiency. This paper introduces a new family of hybrid estimators aimed at controlling the efficiency of Monte Carlo computations in particle transport problems. In this context, efficiency is usually measured by the figure of merit (FOM) given by the inverse product of the estimator variance $\mathrm{Var}[\xi ]$ and the run time T: $\mathrm{FOM}:={(\mathrm{Var}[\xi ]T)}^{-1}$. Previously, we developed a new family of transport-constrained unbiased radiance estimators (T-CURE) that generalize the conventional collision and track length estimators [1] and provide 1–2 orders of magnitude additional variance reduction. However, these gains in variance reduction are partly offset by increases in overhead time [2], lowering their computational efficiency. Here we show that combining T-CURE estimation with conventional terminal estimation within each individual biography can moderate the efficiency of the resulting “hybrid” estimator without introducing bias in the computation. This is achieved by treating only the refractive interface crossings with the extended next event estimator, and all others by standard terminal estimators. This is because when there are index-mismatched interfaces between the collision location and the detector, the T-CURE computation rapidly becomes intractable due to the large number of refractions and reflections that can arise. We illustrate the gains in efficiency by comparing our hybrid strategy with more conventional estimation methods in a series of multi-layer numerical examples.

[en] The structural and energetic properties of bimetallic Ag_mCu_n clusters (m + n ≤ 5) in the cationic and anionic charged states have been investigated by density functional theory with relativistic effective core potentails. The stable cationic pentamers have three-dimensional structures in contrast to anionic clusters assume planar structures. For the given cluster size the electron affinities decrease as the Cu content increases, while no clear trend can be found in adiabatic ionization potentials. The binding energy per atom also increases with the increasing Cu content and follows the order anion < cation. The most probable dissociation channels of the clusters considered are also discussed. (atomic and molecular physics)

[en] Single production of the doubly charged scalars Φ^±± via eγ, ep and pp collisions is studied in the context of the little Higgs (LH) model. Our numerical results show that the new particles Φ^±± can be abundantly produced and their possible signatures should be detected in future high energy linear e⁺e^- collider (ILC). The cross section for single production of Φ^±± at the LHC is much smaller than that at the ILC or the THERA

[en] Grazing bifurcation of a relative rotation system with backlash non-smooth characteristic is studied along with the change of the external excitation in this paper. Considering the oil film, backlash, time-varying stiffness and time-varying error, the dynamical equation of a relative rotation system with a backlash non-smooth characteristic is deduced by applying the elastic hydrodynamic lubrication (EHL) and the Grubin theories. In the process of relative rotation, the occurrence of backlash will lead to the change of dynamic behaviors of the system, and the system will transform from the meshing state to the impact state. Thus, the zero-time discontinuous mapping (ZDM) and the Poincare mapping are deduced to analyze the local dynamic characteristics of the system before as well as after the moment that the backlash appears (i.e., the grazing state). Meanwhile, the grazing bifurcation mechanism is analyzed theoretically by applying the impact and Floquet theories. Numerical simulations are also given, which confirm the analytical results. (paper)