The Variable-Atmosphere Wave Tank

A facility was constructed for the study of water-entry, water-exit, and underwater trajectory behavior of small momentum-propelled missiles for varied trajectory launching angles, missile accelerations and velocities, wave fields and conditions of cavitation. A unique feature is the electromagnetic missile propulsion system. The facility is made principally of non-magnetic and electrically non-conducting materials to permit the determination of missile accelerating force from the reactive force on the launching coil

Magnetic Resonance

Contains reports on one research project

Fluid Free Surface Proximity Effect on a Sphere Vertically Accelerated from Rest

Theory is developed to estimate the effect of free surface proximity on the initial added mass of a sphere accelerated vertically upward from rest in an ideal fluid. It is assumed that the acceleration regime is sufficiently brief that inertial forces predominate and gravitational effects may be neglected. Results of tests in water indicate that while there are slight viscous and gravitational effects over the acceleration regime, the agreement between theory and experiment is good. It is concluded that over briefer acceleration regimes these effects would decrease and the agreement would improve

Consistent thermodynamics for spin echoes

Spin-echo experiments are often said to constitute an instant of anti-thermodynamic behavior in a concrete physical system that violates the second law of thermodynamics. We argue that a proper thermodynamic treatment of the effect should take into account the correlations between the spin and translational degrees of freedom of the molecules. To this end, we construct an entropy functional using Boltzmann macrostates that incorporates both spin and translational degrees of freedom. With this definition there is nothing special in the thermodynamics of spin echoes: dephasing corresponds to Hamiltonian evolution and leaves the entropy unchanged; dissipation increases the entropy. In particular, there is no phase of entropy decrease in the echo. We also discuss the definition of macrostates from the underlying quantum theory and we show that the decay of net magnetization provides a faithful measure of entropy change.Comment: 15 pages, 2 figs. Changed figures, version to appear in PR

Real Fluid Effects on an Accelerated Sphere Before Boundary-Layer Separation

Studies were made on the apparent increase in mass on acceleration (added mass) of a sphere accelerated from rest and before boundary-layer separation, in cylinders of various diameters filled with water or oil. From a comparison of theoretical and experimentally obtained added masses, the following conclusions were drawn: In the absence of wall effects on the boundary layer, the wall shear stress over elements of the sphere can be approximated by the solution for the flat plate moving parallel to itself and the potential flow over the elements outside the boundary layer. The impulse on the elements is obtained by integration with respect to time, and the wall drag and drag impulse on the sphere by integration over the sphere surface. Good theoretical and experimental agreement obtains under the assumption that a mass of fluid, estimated from the wall drag impulse, is carried in the boundary layer and may be university distributed over the sphere

Refractory composite materials for spacecraft thrust chambers Final report, 23 Jul. 1968 - 22 Feb. 1970

Hot firing tests with FLOX/methane propellants for evaluating pyrolytic refractory composite materials for thrust chamber

Strong Tunneling in Double-Island Structures

We study the electron transport through a system of two low-capacitance metal islands connected in series between two electrodes. The work is motivated in part by experiments on semiconducting double-dots, which show intriguing effects arising from coherent tunneling of electrons and mixing of the single-electron states across tunneling barriers. In this article, we show how coherent tunneling affects metallic systems and leads to a mixing of the macroscopic charge states across the barriers. We apply a recently formulated RG approach to examine the linear response of the system with high tunnel conductances (up to 8e^2/h). In addition we calculate the (second order) cotunneling contributions to the non-linear conductance. Our main results are that the peaks in the linear and nonlinear conductance as a function of the gate voltage are reduced and broadened in an asymmetric way, as well as shifted in their positions. In the limit where the two islands are coupled weakly to the electrodes, we compare to theoretical results obtained by Golden and Halperin and Matveev et al. In the opposite case when the two islands are coupled more strongly to the leads than to each other, the peaks are found to shift, in qualitative agreement with the recent prediction of Andrei et al. for a similar double-dot system which exhibits a phase transition.Comment: 12 page