Forced vibration analysis of rotating cyclic structures in NASTRAN

A new capability was added to the general purpose finite element program NASTRAN Level 17.7 to conduct forced vibration analysis of tuned cyclic structures rotating about their axis of symmetry. The effects of Coriolis and centripetal accelerations together with those due to linear acceleration of the axis of rotation were included. The theoretical, user's, programmer's and demonstration manuals for this new capability are presented

On the nucleon-nucleon interaction leading to a standing wave instability in symmetric nuclear matter

We examine a recently proposed nucleon-nucleon interaction, claimed by its authors both realistic and leading to a standing wave instability in symmetric nuclear matter. Contrary to these claims, we find that this interaction leads to a serious overbinding of 4He, 16O and 40Ca nuclei when the Hartree-Fock method is properly applied. The resulting nuclear densities contradict the experimental data and all realistic Hartree-Fock results.Comment: 4 pages, 1 figur

Co-occurrence pattern of ground beetle (Coleoptera, Carabidae) assemblages along pollution gradient in scotch pine forest

Over the last 30 years there has been a great deal of interest in investigating patterns of species co-occurrence across space and time, which may be shaped by interspecific competition for shared resources. A good model of co-occurrence mechanisms is developed among predatory animals along a pollution gradient, where shared resources become more limited in more contaminated areas and the energy budget for detoxification is much higher. Community disassembly by heavy metal pollution may occur when the presence of toxic elements shifts patterns of species co-occurrence from structured to random. On the other hand, limited resources on a pollution gradient should lead to higher competition between dominant species. Disassembly may entail the loss of existing co-evolved interactions among species, which has ramifications for community dynamics and the quality of the functioning of polluted ecosystems. We expect an assemblage dominated by competitive species interactions to exhibit a significant segregation of taxa, whereas one dominated by mutualistic or syntrophic interactions would exhibit an aggregation of taxa. Responses of Carabidae co-occurrence patterns and changes in body size measures to heavy metal concentrations were investigated in a zinc contamination gradient in a Scots pine forest in the vicinity of Olkusz (southern Poland), at 12 study sites. The zinc concentration in the humus layer varied between 108 mg kg-1 dw to 6150 mg kg-1 dw. We used the C-score index, between all possible species pairs in a matrix. The ground beetle assemblages from the reference sites showed a significant segregation pattern. Community disassembly occurred only among assemblages in heavily polluted sites. The average value of skewness and kurtosis were significantly higher in the highly contaminated sites, indicating the greater proportion of small-bodied species in contaminated areas. The Gini coefficient was highest in the low contaminated sites, indicating the body-size inequality of carabid assemblages was greatest in the uncontaminated areas. Our data suggest that increased pollution contributes to the extinction of sensitive forest specialists with large body size and higher competitive abilities, leading to replacement by less sensitive generalists, with smaller body size and that the co-occurrence of species on heavily polluted sites is a result of unstable interactions between species in communities

Building a Socialist Neighborhood: Efforts at Integration among Poland, East Germany, and Czechoslovakia, 1969-1989

In the 1970s, the countries of the Eastern Bloc exhibited an increased interest in integration. Unlike the previous forms of cooperation centered on politics and economics, this new model of socialist integration focused on human interactions. Through open borders, guest worker programs, and youth exchanges, it aimed to bind the socialist community into an inseparable alliance. Despite imperfect conditions for such an arrangement, it worked for some time and contributed to better understanding among the neighbors. Nevertheless, the incompatible policies of socialist patriotism and communist internationalism, the economic inequalities of shortage economies, and the rise of antisystemic opposition brought tensions to the fore that eventually tore the Bloc apart. This dissertation explores the entangled history of Poland, East Germany, and Czechoslovakia by analyzing the functioning of integration, its shortcomings, and consequences. It reveals that the simultaneous pursuit of national interests aimed at preserving the regimes’ hold on power weakened whatever progress socialist integration might have achieved. This study concludes that the communists’ use of nationalism to legitimize their rule permeated the transborder relations developed in these two decades and not only revealed ideological fractures among them, but also made the disintegration of the Bloc possible after 1989.Doctor of Philosoph

Bladed-shrouded-disc aeroelastic analyses: Computer program updates in NASTRAN level 17.7

In October 1979, a computer program based on the state-of-the-art compressor and structural technologies applied to bladed-shrouded-disc was developed. The program was more operational in NASTRAN Level 16. The bladed disc computer program was updated for operation in NASTRAN Level 17.7. The supersonic cascade unsteady aerodynamics routine UCAS, delivered as part of the NASTRAN Level 16 program was recorded to improve its execution time. These improvements are presented

Classical mappings of the symplectic model and their application to the theory of large-amplitude collective motion

We study the algebra Sp(n,R) of the symplectic model, in particular for the cases n=1,2,3, in a new way. Starting from the Poisson-bracket realization we derive a set of partial differential equations for the generators as functions of classical canonical variables. We obtain a solution to these equations that represents the classical limit of a boson mapping of the algebra. The relationship to the collective dynamics is formulated as a theorem that associates the mapping with an exact solution of the time-dependent Hartree approximation. This solution determines a decoupled classical symplectic manifold, thus satisfying the criteria that define an exactly solvable model in the theory of large amplitude collective motion. The models thus obtained also provide a test of methods for constructing an approximately decoupled manifold in fully realistic cases. We show that an algorithm developed in one of our earlier works reproduces the main results of the theorem.Comment: 23 pages, LaTeX using REVTeX 3.

Effect of Magnetic Impurity Correlations on Josephson Tunneling

The ordering trend of magnetic impurities at low temperature results in the frustration of the pair-breaking effect and induces a ``recovery'' of superconducting properties. We show that this effect manifests itself in the deviation of the Josephson current amplitude from the values obtained within the Ambegaokar-Baratoff and the Abrikosov-Gor'kov models. We consider both weak and strong-coupling cases. The theory is applied to describe the experimental data obtained for the low-$T_c$ superconductor SmRh$_4$B$_4$. We further predict a ``recovery'' effect of the Josephson current in high-temperature superconductors.Comment: 7 pages, 4 figures. Accepted for publication in Physica

Superfluid density and penetration depth in Fe-pnictides

We consider the superfluid density $\rho_s (T)$ in a two-band superconductor with extended s-wave symmetry ($s^+$) in the presence of non-magnetic impurities and apply the results to Fe-pnictides. We show that the behavior of the superfluid density is essentially the same as in an ordinary s-wave superconductor with magnetic impurities. We show that, for moderate to strong inter-band impurity scattering, $\rho_s (T)$ behaves as a power-law $T^n$ with $n\approx 1.6\div2$ over a wide range of $T$. We argue that the power-law behavior is consistent with recent experiments on the penetration depth $\lambda (T)$ in BaFe$_2$As$_2$, but disagree quantitatively with the data on LaFePO.Comment: 4 pages, 2 figures; replaced with updated versio

Microscopic Structure of High-Spin Vibrational Excitations in Superdeformed 190,192,194Hg

Microscopic RPA calculations based on the cranked shell model are performed to investigate the quadrupole and octupole correlations for excited superdeformed bands in 190Hg, 192Hg, and 194Hg. The K=2 octupole vibrations are predicted to be the lowest excitation modes at zero rotational frequency. At finite frequency, however, the interplay between rotation and vibrations produces different effects depending on neutron number: The lowest octupole phonon is rotationally aligned in 190Hg, is crossed by the aligned two-quasiparticle bands in 192Hg, and retains the K=2 octupole vibrational character up to the highest frequency in 194Hg. The gamma vibrations are predicted to be higher in energy and less collective than the octupole vibrations. From a comparison with the experimental dynamic moments of inertia, a new interpretation of the observed excited bands invoking the K=2 octupole vibrations is proposed, which suggests those octupole vibrations may be prevalent in SD Hg nuclei.Comment: 22 pages, REVTeX, 12 postscript figures are available on reques