On the stored and dissipated energies in heterogeneous rate-independent systems: theory and simple examples

The aim of the present work is to determine the amount of dissipated and stored energies in structures containing frictional cracks and elasto-plastic zones. The proposed theory combines micromechanical and thermodynamic tools to calculate both energies. Using simple examples, it is shown that the Taylor–Quinney coefficient is not a constant, and can be much less than the values usually considered (i.e. close to unity).      

Two-fluid non-linear model for flow in catheterized blood vessels

Blood flow through a catheterized artery is analyzed, assuming the flow is steady and blood is treated as a two-fluid model with the suspension of all the erythrocytes in the core region as a Casson fluid and the plasma in the peripheral region as a Newtonian fluid. The expressions for velocity, flow rate, wall shear stress and frictional resistance are obtained. The variations of these flow quantities with yield stress, catheter radius ratio and peripheral layer thickness are discussed. It is noticed that the velocity and flow rate decrease while the wall shear stress and resistance to flow increase when the yield stress or the catheter radius ratio increases while all the other parameters were held fixed. It is found that the velocity and flow rate increase while the wall shear stress and frictional resistance decrease with the increase of the peripheral layer thickness. The estimates of the increase in the frictional resistance are significantly very small for the present two-fluid model than those of the single-fluid Casson model.     

Prediction of Friction and Wear of Sliding Contacts,Based on Generalizational Theory of Thermal Dynamics and Modelling of Friction and Wear of Tribosystems

On the basis of electrofriction interaction analysis of high current sliding electric contacts and experimental verification of the theoretical prerequisites, a method, has been elaborated to assess the tribotechnica characteristics which allows one to make an optimal choice of materials for contact pairs in high-current sliding electric contacts at the designing stage.     

The work function of hydrothermally synthesized UO2 and the implications for semiconductor device fabrication

The photoelectric work function of nearly stoichiometric (111) and (100) hydrothermally grown UO₂ was measured to be 6.28 ± 0.36 eV and 5.80 ± 0.36 eV, respectively. Candidate metals for electrical contacts are identified for both rectifying and non‐rectifying contacts based on work function, lattice compatibility, and electrical conductivity.     

What is novel in quantum transport for mesoscopics?

The understanding of mesoscopic transport has now attained an ultimate simplicity. Indeed, orthodox quantum kinetics would seem to say little about mesoscopics that has not been revealed — nearly effortlessly — by more popular means. Such is far from the case, however. The fact that kinetic theory remains very much in charge is best appreciated through the physics of a quantum point contact. While discretization of its conductance is viewed as the exclusive result of coherent, single-electron-wave transmission, this does not begin to address the paramount feature of all metallic conduction: dissipation. A perfect quantum point contact still has finite resistance, so its ballistic carriers must dissipate the energy gained from the applied field. How do they manage that? The key is in standard many-body quantum theory, and its conservation principles.     

Surface Modification and Contact Interaction of Particles

Abstract

The effects of particle surface modification by ambient media and surfactant adsorption on the cohesive forces in the immediate contacts between individual particles have been studied with the CF (cohesive force) apparatus. The values of the free energy of interaction in direct coagulation contacts between particles of various types in liquids of different polarity and in the presence of various surfactants have been measured. They cover a broad range of several orders of magnitude; these interactions define the rheological properties of concentrated thixotropic systems and their stability with respect to peptization. A similar experimental technique has been used for studying active media influences on various physico‐chemical processes of particle bridging and formation of the phase contacts responsible for the mechanical properties of related solid structures and their resistance to fracture. The effect of the adsorption induced decrease in strength and durability of such porous structures with phase contacts and compact solids is considered.     

In Situ Corrosion Fabrication of NaNbO3/Nb3O7F Heterojunctions with Optimized Band Realignment for Enhanced Photocatalytic Hydrogen Evolution

Heterostructured photocatalysis is a significant issue owing to the unique band alignment, improved spectrum absorption, and enhanced photocatalytic activity. However, the construction of uniform, controllable, and effective heterojunctions is still a huge challenge. Herein, NaNbO₃/Nb₃O₇F heterojunctions are fabricated through an in situ corrosion technique for the first time. The influence of phase transformation on the hydrogen evolution reaction (HER) activity is investigated systematically in terms of photocatalytic water splitting for H₂ production. Interestingly, the band realignment and good interfacial contact endow the NaNbO₃/Nb₃O₇F heterojunctions with a high HER activity (43.3 mmol g⁻¹ h⁻¹), which is about 2.4 times that of pure Nb₃O₇F and 1.36 times that of pure NaNbO₃. The results may provide some new insights into the corrosion technique and HER activity of novel heterostructured catalysts.     

Hydrogen versus fluorine: effects on molecular structure and intermolecular interactions in a platinum isocyanate complex

At the molecular level, the enantiomerically pure square‐planar organoplatinum complex (SP‐4‐4)‐(R)‐[2‐(1‐aminoethyl)‐5‐fluorophenyl‐κ²C¹,N][(R)‐1‐(4‐fluorophenyl)ethylamine‐κN](isocyanato‐κN)platinum(II), [Pt(C₈H₉FN)(NCO)(C₈H₁₀FN)], and its congener without fluorine substituents on the aryl rings adopt the same structure within error. The similarities between the compounds extend to the most relevant intermolecular interactions, i.e. N—H…O and N—H…N hydrogen bonds link neighbouring molecules into chains along the shortest lattice parameter in each structure. Differences between the crystal structures of the fluoro‐substituted and parent complex become obvious with respect to secondary interactions perpendicular to the classical hydrogen bonds; the fluorinated compound features short C—H…F contacts with an F…H distance of ca 2.6 Å. The fluorine substitution is also reflected in reduced backbonding from the metal cation to the isocyanate ligand.     

A dynamic frictional contact problem for piezoelectric materials

We consider a mathematical model which describes the frictional contact between a piezoelectric body and an electrically conductive foundation. The process is dynamic, the material's behavior is modeled with an electro-viscoelastic constitutive law and the contact is described by subdifferential boundary conditions. We derive the variational formulation of the problem which is in the form of a system involving a second order evolutionary hemivariational inequality for the displacement field coupled with a time-dependent hemivariational inequality for the electric potential field. Then we prove the existence of a unique weak solution to the model. The proof is based on arguments of abstract second order evolutionary inclusions with monotone operators.     

Involvement of organic fluorine substitution in the crystalline packing structures of tricyclic Diels-Alder adducts derived from diarylfulvenes and N-arylimides

Fluorinated tricyclic Diels-Alder adducts derived from corresponding diarylfulvenes and N-arylmaleimides, each of different degree and positions of the fluorine substituents, and including the non-fluorinated parent compound, have been synthesized. Their X-ray crystal structures were determined in order to study the effect of fluorine substitution on the solid state organization in competition with other weak intermolecular interactions. A balanced interplay of C-H?O, C-H?F and especially C-H?π contacts is typical of the crystal packings while other potential interactions such as C-F?F, C-F?π^F, π^H?π^F and Br?Br are secondary or not to be found. Isostructurality calculations and comparison of molecular conformations have been performed in order to structurally classify the compounds depending on the number and mode of fluorination.