CH(4) storage and CO(2) capture in highly porous zirconium oxide based metal-organic frameworks

A series of porous Zr oxoclusters-based MOFs was computationally explored for their gas storage/capture performances. The highly porous UiO-67(Zr) and UiO-68(Zr) solids show exceptionally high CH(4) and CO(2) adsorption capacities under operating conditions that make these thermal, water and mechanical resistant materials very promising for physisorption-based processes.     

Boundary Layer Stability¶in Real Vanishing Viscosity Limit

In the previous paper [20], an Evans function machinery for the study of boundary layer stability was developed. There, the analysis was restricted to strongly parabolic perturbations, that is to an approximation of the form u _t +(F(u)) _x =ν(B(u)u _x ) _x $ (ν≪1) with an “elliptic” matrix B. However, real models, like the Navier–Stokes approximation of the Euler equations for a gas flow, involve incompletely parabolic perturbations: B is not invertible in general. We first adapt the Evans function to this realistic framework, assuming that the boundary is not characteristic, neither for the hyperbolic first order system u _t +(F(u)) _x = 0, nor for the perturbed system. We then apply it to the various kinds of boundary layers for a gas flow. We exhibit some examples of unstable boundary layers for a perfect gas, when the viscosity dominates heat conductivity. Received: 27 November 2000/ Accepted: 16 March 2001     

Phenomenological continuous contact–impact modelling for multibody simulations of pedestrian–vehicle contact interactions based on experimental data

Multibody modelling of pedestrian collisions requires the definition of contact–impact between the pedestrian and the vehicle. An examination of relevant impact test data reveals large rate-dependent components of the reaction force, permanent indentation, and concomitant energy loss. Contact–impact models previously used in simulations of pedestrian impacts typically have not adequately modelled one, two or all three of these phenomena. This paper presents a phenomenological contact–impact model based on the Hunt–Crossley model of impact, which includes rate-dependent damping, and is extended to include permanent indentation. The proposed model suitably characterises impact test data in a form that can also be implemented in the multibody simulation code MADYMO (TASS-Safe, Netherlands). The proposed contact–impact model was used to characterise the impact between a legform and the bumper of a vehicle, based on two impact tests conducted at different impact speeds. A single contact–impact definition in MADYMO closely reproduced the dynamics of both tests. The proposed model may be suitable in a wide range of impact conditions where the impact is modelled using multibody techniques and it is practicable to conduct impact tests as part of the modelling process.     

Photoluminescence and structural defects in silicon layers implanted by iron ions

The photoluminescence spectra of silicon samples implanted by ⁵⁶Fe⁺ ions [energy, 170 keV; dose, 1×10¹⁶, (2–4)×10¹⁷ cm^?2] and annealed at temperatures of 800, 900, and 1000°C are measured. The structure of the samples at each stage of treatment is investigated using transmission electron microscopy (TEM). It is found that the phase formation and morphology of crystalline iron disilicide precipitates depend on the dose of iron ions and the annealing temperature. A comparison of the dependences of the intensity and spectral distribution of the photoluminescence on the measurement temperature, annealing temperature, and morphology of the FeSi₂ phase revealed the dislocation nature of photoluminescence.     

Memory effect in Ba<Subscript>0.85</Subscript>Sr<Subscript>0.15</Subscript>TiO<Subscript>3</Subscript> ferroelectric films on silicon substrates

Ba_0.85Sr_0.15TiO₃ ferroelectric films on single-crystal silicon wafers were grown and studied. X-ray diffraction and electron microscopy studies showed that the films are characterized by a limited texture with a perovskite structure. It was shown that the grown films can be used as recording media for nonvolatile rerecorded data carriers in kinematic-type external memory devices. A possible mechanism of data recording and storage in the structures was considered.     

Wigner liquid conductivity in a parallel magnetic field

It is assumed that comparatively low-mobility objects (clusters of a small number of electrons) can appear in a two-dimensional strongly correlated electronic system (Wigner liquid) against the background of mobile Fermi-type carriers. These formations can get “pinned” to inhomogeneities and play the role of additional scatterers. Clusters of two and three electrons are discussed (for a short-range order in the arrangement of electrons, as in a triangular lattice). The number of these clusters depends on both temperature and the parallel magnetic field. This results in the temperature and field dependences of the resistance and magnetization of the system. According to a simple model, resistance increases and the metal-dielectric transition occurs as the parallel magnetic field grows stronger. The model predicts a nonlinear magnetic field dependence of magnetization.