1,988,155 research outputs found
The effect of concurrent geometry and roughness in interacting surfaces
We study the interaction energy between two surfaces, one of them flat, the
other describable as the composition of a small-amplitude corrugation and a
slightly curved, smooth surface. The corrugation, represented by a spatially
random variable, involves Fourier wavelengths shorter than the (local)
curvature radii of the smooth component of the surface. After averaging the
interaction energy over the corrugation distribution, we obtain an expression
which only depends on the smooth component. We then approximate that functional
by means of a derivative expansion, calculating explicitly the leading and
next-to-leading order terms in that approximation scheme. We analyze the
resulting interplay between shape and roughness corrections for some specific
corrugation models in the cases of electrostatic and Casimir interactions.Comment: 14 pages, 3 figure
Damping and Pseudo-fermions
After a short abstract introduction on the time evolution driven by non
self-adjoint hamiltonians, we show how the recently introduced concept of {\em
pseudo-fermion} can be used in the description of damping in finite dimensional
quantum systems, and we compare the results deduced adopting the Schr\"odinger
and the Heisenberg representations.Comment: in press in Journal of Mathematical Physic
Vacuum fluctuations and generalized boundary conditions
We present a study of the static and dynamical Casimir effects for a quantum
field theory satisfying generalized Robin boundary condition, of a kind that
arises naturally within the context of quantum circuits. Since those conditions
may also be relevant to measurements of the dynamical Casimir effect, we
evaluate their role in the concrete example of a real scalar field in 1+1
dimensions, a system which has a well-known mechanical analogue involving a
loaded string.Comment: 8 pages, 1 figur
Baryogenesis via leptogenesis in SO(10) models
We discuss the baryogenesis via leptogenesis mechanism within the
supersymmetric and nonsupersymmetric SO(10) models. We find that the
nonsupersymmetric model, endowed with an intermediate scale, is generally
favoured, unless some fine tuning occurs in the supersymmetric case.Comment: 9 pages, RevTex, with 1 figur
Gas Requirements in Pressurized Transfer of Liquid Hydrogen
Of late, liquid hydrogen has become a very popular fuel for space missions. It is being used in such programs as Centaur and Saturn. Furthermore, hydrogen is the ideal working fluid for nuclear powered space vehicles currently under development. In these applications, liquid hydrogen fuel is generally transferred to the combustion chamber by a combination of pumping and pressurization. The pump forces the liquid propellant from the fuel tank to the combustion chamber; gaseous pressurant holds tank pressure sufficiently high to prevent cavitation at the pump inlet and to maintain the structural rigidity of the tank. The pressurizing system, composed of pressurant, tankage, and associated hardware can be a large portion of the total vehicle weight. Pressurant weight can be reduced by introducing the pressurizing gas at temperatures substantially greater than those of liquid hydrogen. Heat and mass transfer processes thereby induced complicate gas requirements during discharge. These requirements must be known to insure proper design of the pressurizing system. The aim of this paper is to develop from basic mass and energy transfer processes a general method to predict helium and hydrogen gas usage for the pressurized transfer of liquid hydrogen. This required an analytical and experimental investigation, the results of which are described in this paper
Space simulation and radiative property testing system and method Patent
Development of method and equipment for testing heat radiative properties of material under controlled environmental condition
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