69,081 research outputs found
Finite element analysis of laminated plates and shells, volume 1
The finite element method is used to investigate the static behavior of laminated composite flat plates and cylindrical shells. The analysis incorporates the effects of transverse shear deformation in each layer through the assumption that the normals to the undeformed layer midsurface remain straight but need not be normal to the mid-surface after deformation. A digital computer program was developed to perform the required computations. The program includes a very efficient equation solution code which permits the analysis of large size problems. The method is applied to the problem of stretching and bending of a perforated curved plate
Dynamic analysis of the GEOS satellite
The assumed modes method is used to investigate the stability of the GEOS satellite. The system is discretized by representing the continuous displacement by finite series of space-dependent admissible functions multiplied by time-dependent generalized coordinates. The spatial dependence is eliminated by integration over the elastic domains, so that the testing functional reduces to a testing function. The sign properties of the testing function are then tested and the equilibrium defined as nontrivial. In considering the stability of small motions about nontrivial equilibrium, it is shown that if the analysis performed by ignoring the motion of the mass center indicates stability, then the system remains stable if the motion of the mass center is included
Theory of magnetic excitons in the heavy-fermion superconductor
We analyze the influence of unconventional superconductivity on the magnetic
excitations in the heavy fermion compound UPdAl. We show that it leads
to the formation of a bound state at energies well below 2 at the
antiferromagnetic wave vector {\textbf Q}=. Its signature is a
resonance peak in the spectrum of magnetic excitations in good agreement with
results from inelastic neutron scattering. Furthermore we investigate the
influence of antiferromagnetic order on the formation of the resonance peak. We
find that its intensity is enhanced due to intraband transitions induced by the
reconstruction of Fermi surface sheets. We determine the dispersion of the
resonance peak near {\textbf Q} and show that it is dominated by the magnetic
exciton dispersion associated with local moments. We demonstrate by a
microscopic calculation that UPdAl is another example in which the
unconventional nature of the superconducting order parameter can be probed by
means of inelastic neutron scattering and determined unambiguously.Comment: 6 pages, 4 figure
Structure of the Partition Function and Transfer Matrices for the Potts Model in a Magnetic Field on Lattice Strips
We determine the general structure of the partition function of the -state
Potts model in an external magnetic field, for arbitrary ,
temperature variable , and magnetic field variable , on cyclic, M\"obius,
and free strip graphs of the square (sq), triangular (tri), and honeycomb
(hc) lattices with width and arbitrarily great length . For the
cyclic case we prove that the partition function has the form ,
where denotes the lattice type, are specified
polynomials of degree in , is the corresponding
transfer matrix, and () for ,
respectively. An analogous formula is given for M\"obius strips, while only
appears for free strips. We exhibit a method for
calculating for arbitrary and give illustrative
examples. Explicit results for arbitrary are presented for
with and . We find very simple formulas
for the determinant . We also give results for
self-dual cyclic strips of the square lattice.Comment: Reference added to a relevant paper by F. Y. W
Partition Function Zeros of a Restricted Potts Model on Lattice Strips and Effects of Boundary Conditions
We calculate the partition function of the -state Potts model
exactly for strips of the square and triangular lattices of various widths
and arbitrarily great lengths , with a variety of boundary
conditions, and with and restricted to satisfy conditions corresponding
to the ferromagnetic phase transition on the associated two-dimensional
lattices. From these calculations, in the limit , we determine
the continuous accumulation loci of the partition function zeros in
the and planes. Strips of the honeycomb lattice are also considered. We
discuss some general features of these loci.Comment: 12 pages, 12 figure
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