نتایج جستجو برای: van der waals force
تعداد نتایج: 388325 فیلتر نتایج به سال:
in this study a simple and general chemical association theory is introduced. the concept of infinite equilibrium model is re-examined and true mole fractions of associated species are calculated. the theory is applied to derive the distribution function of associated species. as a severe test the application of presented theory to the van der waals mixture model is introduced in order to perfo...
The one-dimensional model of Lippincott and Schroeder for hydrogen bond has Been re-examined and it has been shown that O-H bond distance depends on repulsive van der Waals and attractive electrostatic potentials.it has been shown that constant b in the van der Waals repulsion potential is not transferable to all hydrogen bonds. The possibility of obtaining the semi-empircal parameters i...
The Casimir attraction can significantly interfere the physical response of nanoactuators. The intensity of the Casimir force depends on the geometries of interacting bodies. The present paper is dedicated to model the influence of the Casimir attraction on the electrostatic stability of nanoactuators made of cylindrical conductive nanowire/nanotube. An asymptotic solution, based on path-integr...
The adhesion force due to capillary interaction between two hydrophilic surfaces is strongly dependent on the partial pressure of water and is often calculated using the Kelvin equation. The validity of the Kelvin equation is questionable at low relative humidity (RH) of water, like in high vacuum and dry nitrogen environments, where water is only present as layers of several molecules thick at...
The nature of the physical interactions between Escherichia coli JM109 and a model surface (silicon nitride) was investigated in water via atomic force microscopy (AFM). AFM force measurements on bacteria can represent the combined effects of van der Waals and electrostatic forces, hydrogen bonding, steric interactions, and perhaps ligand-receptor type bonds. It can be difficult to decouple the...
We have developed a model for the calculation of van der Waals force for layered systems with axial symmetry. Our result can be applied to compute the cohesion of a carbon nanotube to a substrate, the cohesion between nanotubes, and between shells of multiwall nanotubes. We have obtained unusal power laws for the distance dependence of the many-body van der Waals potential.
We investigate the role of weak clamping forces, typically assumed to be infinite, in carbon nanotube mechanical resonators. Due to these forces, we observe a hysteretic clamping and unclamping of the nanotube device that results in a discrete drop in the mechanical resonance frequency on the order of 5-20 MHz, when the temperature is cycled between 340 and 375 K. This instability in the resona...
In this paper, the long-range Van Der Walls dispersion force correction (vdW-DF) for a combined system consisting of an Ag-chain adsorbed on a monolayer of graphene is studied. Calculations are based on density functional theory (DFT) performed by using various LDA, PBE and BLYP approximations. Since Ag chain is weakly adsorbed on graphene sheet, the Van Der Waals contribution to the total adso...
Van der Waals forces are among the weakest, yet most decisive interactions governing condensation and aggregation processes and the phase behaviour of atomic and molecular matter. Understanding the resulting structural motifs and patterns has become increasingly important in studies of the nanoscale regime. Here we measure the paradigmatic van der Waals interactions represented by the noble gas...
We study the influence of von Karman nonlinearity, van der Waals force, and a athermal stresses on pull-in instability and small vibrations of electrostatically actuated mi-croplates. We use the Galerkin method to develop a tractable reduced-order model for elec-trostatically actuated clamped rectangular microplates in the presence of van der Waals forcesand thermal stresses. More specifically,...
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