410 research outputs found
Finite difference approximation of electron balance problem in the stationary high-frequency induction discharges
© The Authors, published by EDP Sciences, 2017. The problem of finding the minimal eigenvalue corresponding to a positive eigenfunction of the nonlinear eigenvalue problem for the ordinary differential equation with coefficients depending on a spectral parameter is investigated. This problem arises in modeling the plasma of radio-frequency discharge at reduced pressures. The original differential eigenvalue problem is approximated by the finite difference method on a uniform grid. A sufficient condition for the existence of a minimal eigenvalue corresponding to a positive eigenfunction of the finite difference nonlinear eigenvalue problem is established. Error estimates for the approximate eigenvalue and the corresponding approximate positive eigenfunction are proved. Investigations of this paper generalize well known results for eigenvalue problems with linear dependence on the spectral parameter
PCT, spin and statistics, and analytic wave front set
A new, more general derivation of the spin-statistics and PCT theorems is
presented. It uses the notion of the analytic wave front set of
(ultra)distributions and, in contrast to the usual approach, covers nonlocal
quantum fields. The fields are defined as generalized functions with test
functions of compact support in momentum space. The vacuum expectation values
are thereby admitted to be arbitrarily singular in their space-time dependence.
The local commutativity condition is replaced by an asymptotic commutativity
condition, which develops generalizations of the microcausality axiom
previously proposed.Comment: LaTeX, 23 pages, no figures. This version is identical to the
original published paper, but with corrected typos and slight improvements in
the exposition. The proof of Theorem 5 stated in the paper has been published
in J. Math. Phys. 45 (2004) 1944-195
A specialized isotope mass spectrometer for noninvasive diagnostics of Helicobacter pylori infection in human beings
A specialized isotope mass spectrometer for noninvasive diagnostics of Helicobacter pylori infection in human beings based on the carbon-13 isotope breath test has been designed and constructed. Important stages of the work included (i) calculating a low-aberration mass analyzer, (ii) manufacturing and testing special gas inlet system, and (iii) creating a small-size collector of ions. The proposed instrument ensures 13C/12C isotopic ratio measurement to within 1.7‰ (pro mille) accuracy, which corresponds to requirements for a diagnostic tool. Preliminary medical testing showed that the mass spectrometer is applicable to practical diagnostics. The instrument is also capable of measuring isotopic ratios of other light elements, including N, O, B (for BF2+ ions), Ar, Cl, and
Iron based superconductors: magnetism, superconductivity and electronic structure
Angle resolved photoemission spectroscopy (ARPES) reveals the features of the
electronic structure of quasi-two-dimensional crystals, which are crucial for
the formation of spin and charge ordering and determine the mechanisms of
electron-electron interaction, including the superconducting pairing. The newly
discovered iron based superconductors (FeSC) promise interesting physics that
stems, on one hand, from a coexistence of superconductivity and magnetism and,
on the other hand, from complex multi-band electronic structure. In this review
I want to give a simple introduction to the FeSC physics, and to advocate an
opinion that all the complexity of FeSC properties is encapsulated in their
electronic structure. For many compounds, this structure was determined in
numerous ARPES experiments and agrees reasonably well with the results of band
structure calculations. Nevertheless, the existing small differences may help
to understand the mechanisms of the magnetic ordering and superconducting
pairing in FeSC.Comment: Invited Revie
Experimentelle Untersuchung des Wärmeübergangs beim Sieden von R 22 und R 717 an verschiedenartigen Oberflächen in horizontalen Rohrbündelverdampfern
Beschrieben werden die Ergebnisse der experimentellen Untersuchungen des Wärmeübergangs beim Sieden von Kältemitteln an horizontalen Rohren mit verschiedenartigen Oberflächen. Die Heizwirkung der untersuchten Oberflächen wird verglichen. Desweiteren werden die Ergebnisse von Versuchen beschrieben, die sich mit den Verwendungseigenschaften der Wärmeübergangsflächen befassen: Hystereseerscheinungen im Bereich des nicht ausgebildeten Siedens; Einfluß glatter, untereinander angeordneter Rohre; Einfluß eines Horizontal-rohrbündels auf den Wärmeübergang einzeln ausgewählter Rohre in einer jeden waagrechten Reihe. Angegeben werden die Versuchsdaten, bei denen eine starke Zunahme (um mehr als das 2fache) auf die Wärmeübergangskoeffizienten in den oberen Reihen von Glattrohrbündeln festgestellt wurde, verglichen mit den unteren Reihen. Es wird nachgewiesen, daß der Intensivierungsgrad des Wärmeübergangs nach Aufbringen einer porösen Schicht mit zunehmender Anzahl horizontaler Rohrreihen im Bündel abnimmt
Einfluss der Oberflächenbeschaffenheit auf die Intensivierung des Siedens von Kältemitteln
Aufgrund der durchgeführten Untersuchung kann man folgende Schlußfolgerungen ziehen:
Verändert man die Art der Wärmeübergangsfläche, kann man eine Zunahme der Wärme-übergangszahl um das 5 – 7fache erreichen.
Kältemittel mit stark ausgeprägten wärmephysikalischen Eigenschaften wie R22 und Ammoniak verlangen ein spezielles Vorgehen bei der Auswahl der effektiven Wärmeüber-gangsfläche.
Die untersuchten Rohre mit porösem aufgedampftem Belag intensivieren den Siede-vorgang von Ammoniak nur schwach. Dafür bräuchte man Rohre mit anderen geo-metrischen Werten der Beläge. Es muß also weiter untersucht werden, wie Werkstoff des Belags und Standzeit der Oberfläche den Wärmeübergang beeinflussen
Hydrogen atom in crossed external fields reexemined by the moment method
Recurrence relations of perturbation theory for hydrogen ground state are
obtained. With their aid polarizabilities in constant perpendicular electric
and magnetic fields are computed up to 80th order. The high orders asymptotic
is compared with its quasiclassical estimate. For the case of arbitrary mutual
orientation of external fields a general sixth order formula is given.Comment: 11 pages, LaTeX, 2 figures (eps
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