10,690 research outputs found
Universal scaling relations in molecular superconductors
Scaling relations between the superconducting transition temperature , the superfluid stiffness and the normal state conductivity
are identified within the class of molecular
superconductors. These new scaling properties hold as varies over
two orders of magnitude for materials with differing dimensionality and
contrasting molecular structure, and are dramatically different from the
equivalent scaling properties observed within the family of cuprate
superconductors. These scaling relations place strong constraints on theories
for molecular superconductivity.Comment: 4 pages, 4 figure
Unconventional Quantum Critical Points
In this paper we review the theory of unconventional quantum critical points
that are beyond the Landau's paradigm. Three types of unconventional quantum
critical points will be discussed: (1). The transition between topological
order and semiclassical spin ordered phase; (2). The transition between
topological order and valence bond solid phase; (3). The direct second order
transition between different competing orders. We focus on the field theory and
universality class of these unconventional quantum critical points. Relation of
these quantum critical points with recent numerical simulations and experiments
on quantum frustrated magnets are also discussed.Comment: 28 pages, 6 figures. Review article for Int. J. Mod. Phys.
Balancing Local Order and Long-Ranged Interactions in the Molecular Theory of Liquid Water
A molecular theory of liquid water is identified and studied on the basis of
computer simulation of the TIP3P model of liquid water. This theory would be
exact for models of liquid water in which the intermolecular interactions
vanish outside a finite spatial range, and therefore provides a precise
analysis tool for investigating the effects of longer-ranged intermolecular
interactions. We show how local order can be introduced through quasi-chemical
theory. Long-ranged interactions are characterized generally by a conditional
distribution of binding energies, and this formulation is interpreted as a
regularization of the primitive statistical thermodynamic problem. These
binding-energy distributions for liquid water are observed to be unimodal. The
gaussian approximation proposed is remarkably successful in predicting the
Gibbs free energy and the molar entropy of liquid water, as judged by
comparison with numerically exact results. The remaining discrepancies are
subtle quantitative problems that do have significant consequences for the
thermodynamic properties that distinguish water from many other liquids. The
basic subtlety of liquid water is found then in the competition of several
effects which must be quantitatively balanced for realistic results.Comment: 8 pages, 6 figure
Study and development of a mathematical analysis for the performance assessment of space communication system parameters
Electronic computer program user manual for optimum design of space communication syste
User's manual for COPTRAN, a method of optimum communication system design
User manual for COPTRAN /communication system optimization program translator
Digital adaptive controllers for VTOL vehicles. Volume 1: Concept evaluation
A digital self-adaptive flight control system was developed for flight test in the VTOL approach and landing technology (VALT) research aircraft (a modified CH-47 helicopter). The control laws accept commands from an automatic on-board guidance system. The primary objective of the control laws is to provide good command-following with a minimum cross-axis response. Three attitudes and vertical velocity are separately commanded. Adaptation of the control laws is based on information from rate and attitude gyros and a vertical velocity measurement. The final design resulted from a comparison of two different adaptive concepts--one based on explicit parameter estimates from a real-time maximum-likelihood estimation algorithm, the other based on an implicit model reference adaptive system. The two designs were compared on the basis of performance and complexity
COPTRAN - A method of optimum communication systems design
Single set of mathematical expressions describes system cost and probability of error of data transmission in terms of four basic parameters in the link equation. A Lagrange multiplier sets up equations whose solutions yield the optimum values for system design considerations and weight and cost values
Digital adaptive controllers for VTOL vehicles. Volume 2: Software documentation
The VTOL approach and landing test (VALT) adaptive software is documented. Two self-adaptive algorithms, one based on an implicit model reference design and the other on an explicit parameter estimation technique were evaluated. The organization of the software, user options, and a nominal set of input data are presented along with a flow chart and program listing of each algorithm
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