2,527 research outputs found

### Enhancing the Quality of Data on Income: Recent Developments in Survey Methodology

In this paper, we evaluate two survey innovations aimed at improving income measurement. These innovations are (1) integrating the question sequences for income and wealth which may elicit more accurate estimates of income from capital than has been true in the past, and (2) changes in the periodicity over which income flows are measured, which may provide a closer match between what the survey respondent knows best and the periodicity contained in survey measurement. These innovations have been introduced into both the Health and Retirement Study (HRS) and the study of Asset and Health Dynamics Among the Oldest Old (AHEAD). Based on the results reported in this paper, the potential return in quality of income measurement from these innovations is substantial.

### Tunneling spectra for ($d_{x^2-y^2}+is$)-wave superconductors versus tunneling spectra for ($d_{x^2-y^2}+id_{xy}$)-wave superconductors

The tunneling conductance spectra of a normal metal / insulator / singlet
superconductor is calculated from the reflection amplitudes using the
Blonder-Tinkham-Klapwijk (BTK) formulation. The pairing symmetry of the
superconductor is assumed to be $d_{x^2-y^2}+is$, or $d_{x^2-y^2}+id_{xy}$. It
is found that in the ($d_{x^2-y^2}+is$)-wave case there is a well defined
conductance peak in the conductance spectra, in the amplitude of the secondary
s-wave component. In the ($d_{x^2-y^2}+id_{xy}$)-wave case the tunneling
conductance has residual values within the gap, due to the formation of bound
states. The bound state energies depend on the angle of the incident
quasiparticles, and also on the boundary orientation. On the basis of this
observation an electron focusing experiment is proposed to probe the
($d_{x^2-y^2}+id_{xy}$)-wave state.Comment: 17 pages with 9 figure

### Intercontinental antenna arraying by symbol stream combining at ICE Giacobini-Zinner encounter

Deep space tracking stations on different continents were arrayed during the encounter of the International Cometary Explorer (ICE) spacecraft with the comet Giacobini-Zinner during September 9 through 12, 1985. This is the first time that telemetry signals received on different continents have been combined to enhance signal to noise ratio. The arraying was done in non-real time using the method of symbol stream combining. The improvement in signal to noise ratio was typically 2 dB over the stronger of the two stations in each array

### Attractions between charged colloids at water interfaces

The effective potential between charged colloids trapped at water interfaces
is analyzed. It consists of a repulsive electrostatic and an attractive
capillary part which asymptotically both show dipole--like behavior. For
sufficiently large colloid charges, the capillary attraction dominates at large
separations.
The total effective potential exhibits a minimum at intermediate separations
if the Debye screening length of water and the colloid radius are of comparable
size.Comment: 8 pages, 1 figure, revised version (one paragraph added) accepted in
JPC

### Analytical and experimental study of stratification and liquid-ullage coupling, 1 June 1964 - 31 May 1965

Closed-form solution for stratification of subcooled fluids in containers subjected to heating, and for liquid-ullage vapor couplin

### High-purity silicon crystal growth investigations

The study of silicon sheet material requirements for high efficiency solar cells is reported. Research continued on obtaining long lifetime single crystal float zone silicon and on understanding and reducing the mechanisms that limit the achievement of long lifetimes. The mechanisms studied are impurities, thermal history, point defects, and surface effect. The lifetime related crystallographic defects are characterized by X-ray topography and electron beam induced current

### A precursor state to unconventional superconductivity in CeIrIn${_5}$

We present sensitive measurements of the Hall effect and magnetoresistance in
CeIrIn${_5}$ down to temperatures of 50 mK and magnetic fields up to 15 T. The
presence of a low temperature coherent Kondo state is established. Deviations
from Kohler's rule and a quadratic temperature dependence of the cotangent of
the Hall angle are reminiscent of properties observed in the high temperature
superconducting cuprates. The most striking observation pertains to the
presence of a \textit{precursor} state--characterized by a change in the Hall
mobility--that appears to precede the superconductivity in this material, in
similarity to the pseudogap in the cuprate high $T_c$ superconductors.Comment: 4 figure

### Hamiltonian approach to the ac Josephson effect in superconducting-normal hybrid systems

The ac Josephson effect in hybrid systems of a normal mesoscopic conductor
coupled to two superconducting (S) leads is investigated theoretically. A
general formula of the ac components of time-dependent current is derived which
is valid for arbitrary interactions in the normal region. We apply this formula
to analyze a S-normal-S system where the normal region is a noninteracting
single level quantum dot. We report the physical behavior of time-averaged
nonequilibrium distribution of electrons in the quantum dot, the formation of
Andreev bound states, and ac components of the time-dependent current. The
distribution is found to exhibit a population inversion; and all Andreev bound
states between the superconducting gap $\Delta$ carry the same amount of
current and in the same flow direction. The ac components of time-dependent
current show strong oscillatory behavior in marked contrast to the subharmonic
gap structure of the average current.Comment: 23 pages, 10 figures, LaTe

### Matching concepts across HOL libraries

Many proof assistant libraries contain formalizations of the same
mathematical concepts. The concepts are often introduced (defined) in different
ways, but the properties that they have, and are in turn formalized, are the
same. For the basic concepts, like natural numbers, matching them between
libraries is often straightforward, because of mathematical naming conventions.
However, for more advanced concepts, finding similar formalizations in
different libraries is a non-trivial task even for an expert.
In this paper we investigate automatic discovery of similar concepts across
libraries of proof assistants. We propose an approach for normalizing
properties of concepts in formal libraries and a number of similarity measures.
We evaluate the approach on HOL based proof assistants HOL4, HOL Light and
Isabelle/HOL, discovering 398 pairs of isomorphic constants and types

- …