Attractive Wall Research Articles

Repulsive and attractive planar walls in general relativity

The method of a previous paper is generalized to yield all solutions to Einstein's equations for planar-symmetric walls composed of surface energy density $\ensuremath{\sigma}$ and tension $\ensuremath{\tau}$, with constant ratios in the physical range $\frac{\ensuremath{\tau}}{\ensuremath{\sigma}}\ensuremath{\le}1$. Special cases include domain walls, walls of cosmic strings, dust walls, and (when $\ensuremath{\tau}<0$) pressure walls. Attention is focused on the sense in which a wall is gravitationally repulsive when the tension is strong, the sense in which repulsion gives way to attraction as $\frac{\ensuremath{\tau}}{\ensuremath{\sigma}}$ is reduced below the value \textonehalf{}, and the way in which these features are reflected in the motion of the wall. Also studied is the way in which the unique static planar-symmetric solution fits within the classes of solutions.

Concentration dependence of the effective viscosity of polymer solutions in small pores with repulsive or attractive walls

Polymer solutions are demonstrated to have apparent viscosities in small pores which depend on pore diameter (or the mean diameter of pore throats in irregular porous media) and which, therefore, can be considerably different from the viscosity of the same solution in an unbounded medium. The apparent viscosities in the pores can be greater or less than in bulk depending upon whether the pore wall is attractive or repulsive for the polymer. Specifically, if there is no adsorption (repulsive wall) we find that the solution viscosity is always less inside the pore than in bulk. On the other hand if the wall is attractive the apparent solution viscosity inside the pore may be greater or less, depending on the concentration of the flowing polymer solution. Data representing these effects are presented for aqueous solutions of hydrolyzed polyacrylamide and xanthan polysaccharide. The data are organized as suggested by a model recently proposed by Chauveteau for polymer solution flow in small pores.

Interaction Management — a case study

Programme implementation Let us turn now to how the training was organised (see Figure 1). Travel to the training site was not a problem, so we established a well‐equipped training room at the Technical Training School. We have now moved to our own Management Development Centre and have a fully dedicated training room for Interaction Management, with permanently‐mounted attractive wall charts and all the necessary video and film equipment to present the course in its best light. The Technical Training School where we started was well regarded, and the IM programme was under its control. This was quite helpful in getting IM off the ground. Participants came to IM in a familiar location, where they had received other training they had found useful in performing their jobs. We did decide to limit to one the number of units conducted in any one week. This was due to language issues, learning new concepts for the first time, and because of the nature of the organisation management style.

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A magnetic bubble memory has a first bubble propagation tack (6) formed with an ion-implanted pattern and a second bubble propagation track formed with permalloy members (8) connected to each other to form a storage loop. The arrangement is such that a position of an attractive magnetic pole created in one of the permalloy members coincides with a position of an attractive charged wall appearing in the ion-impianted layer at a junction of the first and second bubble propagation tracks when a driving magnetic field is in a particular range of direction.

The Lennard-Jones 9:3 adsorptive system. II. Prediction of the liquid density profiles by perturbation theory

To predict the density profiles of liquids adsorbed onto the Lennard-Jones 9:3 (LJ 9:3) wall, we derive here two new perturbation equations (called PYP and PYP1 equations) taking a simpler adsorptive system as reference. The derivation is based on the functional derivative formalism of Lebowitz and Percus for inhomogeneous systems. The generating functional is of Percus–Yevick (PY) type. The resulting expressions are first order theories. Previous known perturbation formulas, such as the blip function equation and the enhanced PY equation, are identified as special cases (zeroth order theories) of the present equations. Connections can also be made to the Ebner–Saam–Stroud density functional equation. Numerical calculations were carried out for liquid state adsorption of Lennard-Jones 12:6 molecules and hard spheres. Two types of perturbation are examined: (i) perturbation of the density profile from the hard spheres near a Weeks–Chandler–Andersen type repulsive wall to hard spheres near a Lennard-Jones 9:3 attractive wall, and (ii) perturbation of the density profile from hard spheres near a LJ 9:3 wall to Lennard-Jones 12:6 molecules near the LJ 9:3 wall. Comparison with Monte Carlo results shows that the PYP1 approach is the most satisfactory theory among all equations tested. The blip function results are inadequate for the attractive wall, while the PYP theory gives peculiar density profiles at intermediate distances despite good agreements at shorter and longer ranges.

Structure of dense liquids at solid interfaces

Detailed calculations of dense fluids of hard spheres, soft repulsive spheres and Lennard-Jones molecules between hard, soft repulsive and attractive solid walls reveals a pronounced stratification of the fluid’s density profile. The calculations have been performed using the NVT Monte Carlo method with about 200 fluid molecules. The results indicate that a very significant role is played by the attractive component in the intermolecular potentials, which suggests that the usual hard-sphere perturbation theories are not applicable in their present form.

Bose-Einstein condensation with attractive boundary conditions

The phenomena of Bose-Einstein condensation is discussed for particles in a box with attractive walls. Variation of the elasticity has the following effects, a) the critical temperature, fugacity, etc. vary, b) separation of phases occurs, c) condensation in one and two dimensions is possible.

Interaction of domain walls in thin magnetic films

Interactions of pairs of parallel Neel walls are investigated by means of Ritz's method calculations. In the case of the symmetric, thin-film mode of Neel walls, unwinding walls show an attractive and winding walls a repulsive interaction for all distances. The functional dependence of the interaction on the distance of the walls is strongly correlated with the wall profiles of the isolated walls with their characteristic extended tails. For the asymmetric Neel wall mode which occurs in thicker films, an additional repulsive interaction of the magnetization vortices in the wall core is found. This leads for unwinding walls to stable configurations of double walls with separations between two and three times the film thickness.

Structure of adsorbed film of a bose liquid

It is shown that the Hartree approximation, adopted to situations in which the many-body system has a bound ground state, is suitable for obtaining a qualitative description of the structure of an adsorbed He-II film in the presence of an attractive wall potential.