7,547 research outputs found
Many-body system with a four-parameter family of point interactions in one dimension
We consider a four-parameter family of point interactions in one dimension.
This family is a generalization of the usual -function potential. We
examine a system consisting of many particles of equal masses that are
interacting pairwise through such a generalized point interaction. We follow
McGuire who obtained exact solutions for the system when the interaction is the
-function potential. We find exact bound states with the four-parameter
family. For the scattering problem, however, we have not been so successful.
This is because, as we point out, the condition of no diffraction that is
crucial in McGuire's method is not satisfied except when the four-parameter
family is essentially reduced to the -function potential.Comment: 8 pages, 4 figure
Outdoor Recreation Expenditures: A Nationwide Study
Outdoor recreation expenditures are examined in this paper. Data from the 1982-83 Nationwide Recreation Survey are used to determine the nature and extent of expenditures for outdoor recreation by a nationally representative sample of individuals. In addition, anticipated future expenditures by the same group are reported. The implications of these data for the leisure industry are discussed
Structural and physical properties of layered oxy-arsenides LnRuAsO (Ln = La, Nd, Sm, Gd)
Polycrystalline samples of LaRuAsO, NdRuAsO, SmRuAsO, and GdRuAsO have been
synthesized and studied using powder x-ray diffraction, electrical transport,
magnetization, and heat capacity measurements. Variations in structural
properties across the series reveal a trend toward more ideal tetrahedral
coordination around Ru as the size of the rare earth element is reduced. The
lattice parameters of these Ru compounds show a more anisotropic response to
variation in Ln than their Fe analogues, and significant anisotropy in thermal
expansion is also observed. Transport measurements show metallic behavior, and
carrier concentrations near 10^21 - 10^22 electrons per cm^3 are inferred from
simple analysis of Hall effect measurements. Anomalies in resistivity,
magnetization, and heat capacity indicate antiferromagnetic ordering of rare
earth moments at 5 K for GdRuAsO, 4.5 K for SmRuAsO, and <2 K for NdRuAsO.
Magnetization measurements on LaRuAsO show no evidence of a magnetic moment on
Ru. Observed behaviors are compared to those reported for similar Fe and Ru
compounds
Thermoelectric properties of Co, Ir, and Os-Doped FeSi Alloys: Evidence for Strong Electron-Phonon Coupling
The effects of various transition metal dopants on the electrical and thermal
transport properties of Fe1-xMxSi alloys (M= Co, Ir, Os) are reported. The
maximum thermoelectric figure of merit ZTmax is improved from 0.007 at 60 K for
pure FeSi to ZT = 0.08 at 100 K for 4% Ir doping. A comparison of the thermal
conductivity data among Os, Ir and Co doped alloys indicates strong
electron-phonon coupling in this compound. Because of this interaction, the
common approximation of dividing the total thermal conductivity into
independent electronic and lattice components ({\kappa}Total =
{\kappa}electronic + {\kappa}lattice) fails for these alloys. The effects of
grain size on thermoelectric properties of Fe0.96Ir0.04Si alloys are also
reported. The thermal conductivity can be lowered by about 50% with little or
no effect on the electrical resistivity or Seebeck coefficient. This results in
ZTmax = 0.125 at 100 K, still about a factor of five too low for solid-state
refrigeration applications
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