Uniform Confinement Research Articles

Twin target sputtering system with ladder type magnet array for direct Al cathode sputtering on organic light emitting diodes

Twin target sputtering (TTS) system with a configuration of vertically parallel facing Al targets and a substrate holder perpendicular to the Al target plane has been designed to realize a direct Al cathode sputtering on organic light emitting diodes (OLEDs). The TTS system has a linear twin target gun with ladder type magnet array for effective and uniform confinement of high density plasma. It is shown that OLEDs with Al cathode deposited by the TTS show a relatvely lower leakage current density (∼1×10−5mA/cm2) at reverse bias of ‐6V, compared to that (1×10−2∼10−3 mA/cm2 at ‐6V) of OLEDs with Al cathodes grown by conventional DC magnetron sputtering. In addition, it was found that Al cathode films prepared by TTS were amorphous structure with nanocrystallines due to low substrate temperature. This demonstrates that there is no plasma damage caused by the bombardment of energetic particles. This indicates that the TTS system with ladder type magnet array could be useful plasma damage free deposition technique for direct Al cathode sputtering on OLEDs or flexible OLEDs.

New Sample Holder for the Preparation of Undisturbed Fine-Grained Soil Specimens for Laboratory Element Testing

Abstract The paper describes a new soil sample holding device, the undisturbed soil sample holder (USSH), which has the ability to minimize potential sample disturbance during the preparation of relatively soft fine-grained cylindrical soil specimens. The USSH is capable of providing suitable external, uniform lateral confinement to a sample of soil extruded from a field sampling tube. The device comprises a split hollow cylindrical aluminum housing that is internally lined with a flexible synthetic foam material. The foam lining allows the diameter of the cylindrical cavity of the USSH to be variable, while maintaining the shape of the cavity cylindrical. The device has the ability to essentially eliminate the sample freestanding period that is commonly associated with conventional preparation methods and to reduce potentially significant soil deformations that occur due to the self-weight of the sample. The effectiveness of the USSH in minimizing sample disturbance is demonstrated using comparative laboratory tests conducted on relatively soft soil specimens prepared with and without the USSH. The observed axial strains during specimen preparation, volumetric strains during consolidation, and stress-strain-pore water pressure response during undrained triaxial shear testing show that the USSH contributes to the preparation of undisturbed soil specimens for element testing.

Integer spin Hall effect in ballistic quantum wires

We investigate the ballistic electron transport in a two dimensional Quantum Wire under the action of an electric field ($E_y$). We demonstrate how the presence of a Spin Orbit coupling, due to the uniform electric confinement field gives a non-commutative effect as in the presence of a transverse magnetic field. We discuss how the non commutation implies an edge localization of the currents depending on the electron spins also giving a semi-classical spin dependent Hall current. We also discuss how it is possible obtain a quantized Spin Hall conductance in the ballistic transport regime by developing the Landauer formalism and show the coupling between the spin magnetic momentum and the orbital one due to the presence of a circulating current.

Control of elongation for field-reversed configuration plasmas using axial field index of a mirror confinement field

The separatrix shape of a field-reversed configuration (FRC) plasma formed by a negative-biased theta-pinch is quite elongated due to a uniform confinement field, except at the end coils (simple mirror field). The elongation of the shape, which is the ratio of half the separatrix length to the separatrix radius, is about 5–10. The control of elongation is attempted by introducing a field gradient along the confinement field (axial field index) over the whole plasma region (smooth mirror field). Since mirror effects act on all portions of the plasma, the FRC plasma is compressed axially and expanded radially. As a result, the elongation becomes almost half that in the simple mirror field. It is found that a poloidal flux in the smooth mirror field is 2.6-fold the value in the simple mirror field.

Constitutive Model for Confined High Strength Concrete Subjected to Cyclic Loading

The paper presents a constitutive model developed for high strength concrete with uniform lateral confinement subjected to cyclic axial compression. It is based on the testing program carried out for normal and high strength concrete. Compressive strengths of concrete at the time of testing were 44, 58, 83, and 106 MPa. Uniform confining pressures applied were 4, 8, and 12 MPa. The stress–strain model presented in this paper was developed based on triaxial test results, which were obtained under well-controlled conditions, where direct measurement of axial and lateral strains were possible. Ability to predict the axial as well as lateral strains in confined concrete is a superior attribute of the proposed model. When concrete is analyzed for passive confinement (such as the one provided by reinforcement), estimating the lateral strain is important because the lateral confinement directly depends on it. The proposed model can be used for modeling high strength concrete in seismic analysis of structures, where confining of concrete by reinforcement is essential for ductility.

Scaling, Dimensionality Crossover, Surface and Edge Specific Heats in Confined4He

We have studied the superfluid transition of 4He in situations where the growth of the correlation length is limited by a uniform spatial confinement. Under these conditions the critical behavior attained in the thermodynamic limit is greatly modified. One expects that data for similar confinement should scale with the correlation length. This is found to be true for the specific heat in planar confinement, 2D crossover, except in the region of the specific heat maximum and on the superfluid side. The modifications due to confinement depend on the details of the geometry. Studies of the specific heat with 1D and 0D crossover show the important role played by the lower dimension. Far from the transition the details of the confining geometry reveal contributions to the specific heat which can be attributed to surfaces and edges. Comparison of experimental resugts with theoretical calculations show agreement in some areas and disagreement in others.

Potential Formation at Plasma Edge due to Suprathermal Particle Losses

AbstractGeneration of the edge radial electric field and corresponding plasma rotation is studied for both uniform magnetic field and toroidal confinement systems with separatrix configuration of magnetic surfaces. The equations describing the edge plasma rotation due to suprathermal particle losses are derived. The solution on this equations is found for the simplest case of collisionless plasma flow to the neutralizing wall perpendicular to the magnetic field. It is shown that classical acceleration of plasma by ion orbital losses is enough to explain electric field and plasma rotation observed near walls.

Strength and Ductility of Confined Concrete

An analytical model is proposed to construct a stress‐strain relationship for confined concrete. The model consists of a parabolic ascending branch, followed by a linear descending segment. It is based on calculation of lateral confinement pressure generated by circular and rectilinear reinforcement, and the resulting improvements in strength and ductility of confined concrete. A large volume of test data, including poorly confined and well‐confined concrete was evaluated to establish the parameters of the analytical model. Confined concrete strength and corresponding strain are expressed in terms of equivalent uniform confinement pressure provided by the reinforcement cage. The equivalent uniform pressure is obtained from average lateral pressure computed from sectional and material properties. Confinement by a combination of different types of lateral reinforcement is evaluated through superposition of individual confinement effects. The descending branch is constructed by defining the strain corresponding to 85% of the peak stress. This strain level is expressed in terms of confinement parameters. A constant residual strength is assumed beyond the descending branch, at 20% strength level. The model is compared against a large number of column tests. Circular, square, and rectangular columns, with spiral and rectilinear reinforcements, as well as welded wire fabric, are used for comparison. Comparisons include concentric and eccentric loadings, as well as slow and fast strain rates. The results indicate good agreement.

Statistical mechanics of a confinement electron gas in a uniform electromagnetic field

In this paper we study an ideal electron gas in the presence of a uniform electromagnetic field and confinement by a three-dimensional harmonic potential. We find the partition function of this system and in the sequel we examine the Boltzmann statistics and Fermi-Dirac statistics applying the grand canonical ensemble method.