6,035 research outputs found
Cyclic Permutations in Kazama-Suzuki String Models
Moddings by cyclic permutation symmetries are performed in 4-dimensional
strings, built up from N=2 coset models of the type . For some exemplifying cases, the massless chiral and antichiral states
of are computed. The extent of the equivalence between different
conformal invariant theories which possess equal chiral rings is analyzed.Comment: 26 pages, LaTex fil
Influence of atomic polarization and horizontal illumination on the Stokes profiles of the He I 10830 multiplet
The polarization observed in the spectral lines of the He I 10830 multiplet
carries valuable information on the dynamical and magnetic properties of plasma
structures in the solar chromosphere and corona, such as spicules, prominences,
filaments, emerging magnetic flux regions, etc. Here we investigate the
influence of atomic level polarization on the emergent Stokes profiles for a
broad range of magnetic field strengths, in both 90 degree and forward
scattering geometry. We show that, contrary to a widespread belief, the
selective emission and absorption processes caused by the presence of atomic
level polarization may have an important influence on the emergent linear
polarization, even for magnetic field strengths as large as 1000 G.
Consequently, the modeling of the Stokes Q and U profiles should not be done by
taking only into account the contribution of the transverse Zeeman effect
within the framework of the Paschen-Back effect theory, unless the magnetic
field intensity of the observed plasma structure is sensibly larger than 1000
G. We point out also that in low-lying optically thick plasma structures, such
as those of active region filaments, the (horizontal) radiation field generated
by the structure itself may substantially reduce the positive contribution to
the anisotropy factor caused by the (vertical) radiation field coming from the
underlying solar photosphere, so that the amount of atomic level polarization
may turn out to be negligible. Only under such circumstances may the emergent
linear polarization of the He I 10830 multiplet in such regions of the solar
atmosphere be dominated by the contribution caused by the transverse Zeeman
effect.Comment: Accepted for publication in The Astrophysical Journal (It is
tentatively scheduled for the ApJ January 20, 2007 issue
Experimental study of laser dissimilar joining for Usibor 2000 and Al-T7075 with Tepex 102
Due to the needs of weight reduction in the automobile structures and of time reduction in the Body-In-White (BIW) manufacturing stage, effective and accurate dissimilar joining is demanded to take advantage of metal-polymer structures. Automotive industry is highly interested in the combination of metal alloys and composite materials; however, dissimilar joining of this type of materials without using mechanic or adhesive joining is a challenge. As an alternative to the classical joining techniques, laser technology can be used to join dissimilar materials. In laser direct joining, a laser beam is used to heat the metal and by conduction to heat the polymer up to melting temperature in the interface without reaching degradation temperature. In this work, an experimental procedure is proposed to set the basis of dissimilar joining between metal and composite parts for the automobile industry. To do that, laser texturing on metallic parts was studied and a wide battery of experimental test were performed to obtain the proper joining process parameters for dissimilar joining between Usibor 2000 and Al-T7075 with Tepex 102. Results show that is possible to reach over 17 MPa in lap shear adhesion test which is similar to the performance of typical adhesives used in automotive industry.Authors wish to thank Basque Country Government for financial support provided through MULTIMAT project Elkartek KK2017/00088 as well as the Spanish Industry ministry for support provided in INTEGRADDI project DPI 2016-79889
Shalamov\u27s Testament: Pushkinian Precepts in Kolyma Tales
In a letter from 1972, the author of Kolyma Tales and survivor of the gulag Varlam Shalamov, declared “In my prose, I consider myself the inheritor of the Pushkinian tradition \u3c…\u3e.” Indeed, in Kolyma Tales, Shalamov exhibited a studied understanding of Pushkin’s artistic technique. Through his implementation of Pushkinian artistic principles, Shalamov was seeking to restore the poet’s image to what it had been prior to the Soviet Union’s politicized interpretation while simultaneously revealing the truth about life in the labor camps to a readership that could not otherwise fathom what the inmates endured on day-to-day basis. In writing this paper, my aim is to demonstrate how Shalamov manifests Pushkinian narrative strategies in his work of documentary prose. I first consider how the Soviet writer, in response to Pushkin’s poem, “I have raised a monument to myself,” formulated his authorial mission. I follow this up with a comparison of Pushkin’s Belkin Tales with several of Shalamov’s short stories. I emphasize Shalamov’s implementation of the principles of “the poetization of prose,” as outlined by Wolf Schmid. I conclude my analysis with a look at Pushkin’s historical works, in particular The History of the Pugachev Rebellion, and how he defined the role of the historian. I then compare Pushkin’s views on the subject of history to those of Shalamov and Alexander Solzhenitsyn. Ultimately, I hope to have proven that Shalamov’s commitment to Pushkin’s legacy resulted in a canonical body of work unsurpassed in its honesty, clarity and artistic and civic merit
Diffusion of Hydrogen in Pd Assisted by Inelastic Ballistic Hot Electrons
Sykes {\it et al.} [Proc. Natl. Acad. Sci. {\bf 102}, 17907 (2005)] have
reported how electrons injected from a scanning tunneling microscope modify the
diffusion rates of H buried beneath Pd(111). A key point in that experiment is
the symmetry between positive and negative voltages for H extraction, which is
difficult to explain in view of the large asymmetry in Pd between the electron
and hole densities of states. Combining concepts from the theory of ballistic
electron microscopy and electron-phonon scattering we show that H diffusion is
driven by the -band electrons only, which explains the observed symmetry.Comment: 5 pages and 4 figure
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