Деструкция полимерной изоляции и пороговые амплитуды импульсов тока различной временной формы для электрических проводов и кабелей в слабо– и сильноточных цепях устройств импульсной энергетики, электротехники и электроники

Goal. Development of engineering method for settlement of threshold amplitudes Impk of single-pulse current ip(t) of different temporal shapes for electric wires and cables with polyethylene (PET), polyvinylchloride (PVC) and rubber (R) half-length insulation, used in modern pulsed power engineering, electrical engineering and electronics in their low- and high-current circuits. Methodology. Basis of the theoretical and applied electrical engineering, electrical power engineering, electrophysics bases of technique of high-voltage and large pulsed currents, bases of low- and high-current electronics, measuring technique, electromagnetic compatibility and standardization. Results. Development of engineering method is executed on close calculation determination of threshold amplitudes Impk of single-pulse axial-flow current ip(t) of different temporal shapes for electric wires and cables with copper (aluminum) current-carrying parts and PET, PVC and R half-length insulation, used in the ow- and high-current circuits of pulsed electrical power engineering, electrical engineering and electronics. Electrothermal resistibility of half-length insulation of the examined cable and wire products (CWP), proper maximum to the possible temperatures of heating of current-carrying and insulating parts of the probed wires and cables and shutting out the offensive of the phenomenon destruction in the indicated insulation of CWP, was fixed based on this method. Calculation analytical correlations are obtained for finding in probed CWP of threshold numeral values of Impk amplitudes of pulses of current ip(t), time-varying both on aperiodic dependence of type τf/τp with duration of their front τf and duration of their pulses τp and by law of exponential attenuation sinewave. It is shown that at Imp>Impk destruction of their half-length insulation, resulting in the decline of service life of CWP, will come from the thermal overheat of current-carrying parts of the examined electric wires and cables. The examples of practical application of the offered method are resulted upon settlement for a radiofrequency coaxial cable RC 50-4-11 with middle sizes is easily soiled with continuous PET insulation of threshold amplitudes of Impk of standard aperiodic pulses of current ip(t) from nano-, micro- and millisecond temporal ranges of shape of τf/τp=5 ns/200 ns, τf/τp=10 μs/350 μs and τf/τp=7 ms/160 ms. It is shown that with the proper growth of parameter τp>>τf for flow on a continuous copper tendon and split copper shell of radiofrequency coaxial cable RC 50-4-11 with middle sizes is easily soiled indicated homopolar pulses of current ip(t) substantial diminishing of their threshold amplitudes of Impk (with 531,2 кА for the nanosecond pulse of current of type 5 ns/200 ns to 1.84 кА for the millisecond impulse of current of type of 7 ms/160 ms takes place). Originality. An engineering method is first developed for close settlement of threshold numeral values of Impk amplitudes of single-pulse axial-flow current ip(t) of arbitrary peak-temporal parameters for electric wires and cables with copper (aluminum) current-carrying parts and PET, PVC and R half-length insulation. Practical value. Application in electrical engineering practice of the offered engineering method for determination of threshold amplitudes Impk of the indicated pulses of axial-flow current ip(t) for the probed electric wires and cables will allow considerably to increase service life of examined CWP.Запропонована інженерна методика за розрахунковим визначенням порогових амплітуд Impk імпульсів струму ip(t) різної часової форми для електричних проводів і кабелів з поліетиленовою, полівінілхлоридною і гумовою ізоляцією, широко вживаних в галузі імпульсної енергетики, високовольтної сильнострумової техніки, вимірювальної техніки і електроніки, а також в системах імпульсного електроживлення, контролю, управління роботою і діагностики стану функціонування електротехнічних пристроїв різного загальногромадянського і військового призначення. В якості вихідного критеріального положення при виборі порогових амплітуд Impk імпульсів струму ip(t) довільних амплітудно-часових параметрів для вказаних проводів і кабелів була вибрана термічна стійкість їх поясної ізоляції, яка відповідає гранично допустимим короткочасним температурам нагріву мідних (алюмінієвих) і ізоляційних частин досліджуваних кабелів (проводів) і що не допускає настання явища деструкції в ізоляції даної кабельно-провідникової продукції. Приведені приклади практичного використання запропонованої методики за розрахунковим визначенням порогових амплітуд Impk стандартних аперіодичних імпульсів струму ip(t) часової форми 5 нс/200 нс, 10 мкс/350 мкс і 7 мс/160 мс для радіочастотного коаксіального середньогабаритного кабелю марки РК 50-4-11 зі суцільною поліетиленовою ізоляцією

Mass spectra of doubly heavy Omega_QQ' baryons

We evaluate the masses of baryons composed of two heavy quarks and a strange quark with account for spin-dependent splittings in the framework of potential model with the KKO potential motivated by QCD with a three-loop beta-function for the effective charge consistent with both the perturbative limit at short distances and linear confinement term at long distances between the quarks. The factorization of dynamics is supposed and explored in the nonrelativistic Schroedinger equation for the motion in the system of two heavy quarks constituting the doubly heavy diquark and the strange quark interaction with the diquark. The limits of approach, its justification and uncertainties are discussed. Excited quasistable states are classified by the quantum numbers of heavy diquark composed by the heavy quarks of the same flavor.Comment: 14 pages, revtex4-file, 3 eps-figures, 5 tables, typos correcte

Doubly heavy baryons in sum rules of NRQCD

The masses of baryons containing two heavy quarks and their couplings to the corresponding quark currents are evaluated in the framework of NRQCD sum rules. The coulomb-like corrections in the system of doubly heavy diquark are taken into account, and the contribution of nonperturbative terms coming from the quark, gluon and mixed condensates as well as the product of quark and gluon condensates, is analyzed. The higher condensates destroy the factorization of baryon and diquark correlators and provide the convergency of sum rule method. As a result the accuracy of estimates is improved.Comment: 17 pages, LATEX file and 6 eps-figure

Interplay of magnetization dynamics with a microwave waveguide at cryogenic temperatures

In this work, magnetization dynamics is studied at low temperatures in a hybrid system that consists of a thin epitaxial magnetic film coupled with a superconducting planar microwave waveguide. The resonance spectrum was observed over a wide magnetic field range, including low fields below the saturation magnetization and both polarities. Analysis of the spectrum via a fitting routine we develop allows the derivation of all magnetic parameters of the film at cryogenic temperatures, the detection of waveguide-induced uniaxial magnetic anisotropies of the first and the second order, and the uncovering of a minor misalignment of the magnetic field. A substantial influence of the superconducting critical state on the resonance spectrum is observed and discussed

Neutral H density at the termination shock: a consolidation of recent results

We discuss a consolidation of determinations of the density of neutral interstellar H at the nose of the termination shock carried out with the use of various data sets, techniques, and modeling approaches. In particular, we focus on the determination of this density based on observations of H pickup ions on Ulysses during its aphelion passage through the ecliptic plane. We discuss in greater detail a novel method of determination of the density from these measurements and review the results from its application to actual data. The H density at TS derived from this analysis is equal to 0.087 \pm 0.022 cm-3, and when all relevant determinations are taken into account, the consolidated density is obtained at 0.09 \pm 0.022 cm-3. The density of H in CHISM based on literature values of filtration factor is then calculated at 0.16 \pm 0.04 cm-3.Comment: Submitted to Space Science Review

Design, Commissioning and Performance of the PIBETA Detector at PSI

We describe the design, construction and performance of the PIBETA detector built for the precise measurement of the branching ratio of pion beta decay, pi+ -> pi0 e+ nu, at the Paul Scherrer Institute. The central part of the detector is a 240-module spherical pure CsI calorimeter covering 3*pi sr solid angle. The calorimeter is supplemented with an active collimator/beam degrader system, an active segmented plastic target, a pair of low-mass cylindrical wire chambers and a 20-element cylindrical plastic scintillator hodoscope. The whole detector system is housed inside a temperature-controlled lead brick enclosure which in turn is lined with cosmic muon plastic veto counters. Commissioning and calibration data were taken during two three-month beam periods in 1999/2000 with pi+ stopping rates between 1.3*E3 pi+/s and 1.3*E6 pi+/s. We examine the timing, energy and angular detector resolution for photons, positrons and protons in the energy range of 5-150 MeV, as well as the response of the detector to cosmic muons. We illustrate the detector signatures for the assorted rare pion and muon decays and their associated backgrounds.Comment: 117 pages, 48 Postscript figures, 5 tables, Elsevier LaTeX, submitted to Nucl. Instrum. Meth.

Possibility of Measuring the CP-Violation gamma-parameter in Decays of Xi_bc Baryons

The model-independent method based on the triangle ideology is implemented to extract the CKM-matrix angle gamma in the decays of doubly heavy baryons containing the charmed and beauty quarks. We analyze a color structure of diagrams and conditions for reconstructing two reference-triangles by tagging the flavor and CP eigenstates of neutral D mesons in the fixed exclusive channels. The characteristic branching ratios are evaluated in the framework of a potential model setting a parametric dependence on the hadronic matrix elements for the decay rates.Comment: 15 pages, LaTeX file, 8 eps-figures, title changed, typos correcte

The Structure of a Rigorously Conserved RNA Element within the SARS Virus Genome

We have solved the three-dimensional crystal structure of the stem-loop II motif (s2m) RNA element of the SARS virus genome to 2.7-Å resolution. SARS and related coronaviruses and astroviruses all possess a motif at the 3′ end of their RNA genomes, called the s2m, whose pathogenic importance is inferred from its rigorous sequence conservation in an otherwise rapidly mutable RNA genome. We find that this extreme conservation is clearly explained by the requirement to form a highly structured RNA whose unique tertiary structure includes a sharp 90° kink of the helix axis and several novel longer-range tertiary interactions. The tertiary base interactions create a tunnel that runs perpendicular to the main helical axis whose interior is negatively charged and binds two magnesium ions. These unusual features likely form interaction surfaces with conserved host cell components or other reactive sites required for virus function. Based on its conservation in viral pathogen genomes and its absence in the human genome, we suggest that these unusual structural features in the s2m RNA element are attractive targets for the design of anti-viral therapeutic agents. Structural genomics has sought to deduce protein function based on three-dimensional homology. Here we have extended this approach to RNA by proposing potential functions for a rigorously conserved set of RNA tertiary structural interactions that occur within the SARS RNA genome itself. Based on tertiary structural comparisons, we propose the s2m RNA binds one or more proteins possessing an oligomer-binding-like fold, and we suggest a possible mechanism for SARS viral RNA hijacking of host protein synthesis, both based upon observed s2m RNA macromolecular mimicry of a relevant ribosomal RNA fold

Heavy quarkonium: progress, puzzles, and opportunities

A golden age for heavy quarkonium physics dawned a decade ago, initiated by the confluence of exciting advances in quantum chromodynamics (QCD) and an explosion of related experimental activity. The early years of this period were chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in 2004, which presented a comprehensive review of the status of the field at that time and provided specific recommendations for further progress. However, the broad spectrum of subsequent breakthroughs, surprises, and continuing puzzles could only be partially anticipated. Since the release of the YR, the BESII program concluded only to give birth to BESIII; the $B$-factories and CLEO-c flourished; quarkonium production and polarization measurements at HERA and the Tevatron matured; and heavy-ion collisions at RHIC have opened a window on the deconfinement regime. All these experiments leave legacies of quality, precision, and unsolved mysteries for quarkonium physics, and therefore beg for continuing investigations. The plethora of newly-found quarkonium-like states unleashed a flood of theoretical investigations into new forms of matter such as quark-gluon hybrids, mesonic molecules, and tetraquarks. Measurements of the spectroscopy, decays, production, and in-medium behavior of c\bar{c}, b\bar{b}, and b\bar{c} bound states have been shown to validate some theoretical approaches to QCD and highlight lack of quantitative success for others. The intriguing details of quarkonium suppression in heavy-ion collisions that have emerged from RHIC have elevated the importance of separating hot- and cold-nuclear-matter effects in quark-gluon plasma studies. This review systematically addresses all these matters and concludes by prioritizing directions for ongoing and future efforts.Comment: 182 pages, 112 figures. Editors: N. Brambilla, S. Eidelman, B. K. Heltsley, R. Vogt. Section Coordinators: G. T. Bodwin, E. Eichten, A. D. Frawley, A. B. Meyer, R. E. Mitchell, V. Papadimitriou, P. Petreczky, A. A. Petrov, P. Robbe, A. Vair

Double volume reflection of a proton beam by a sequence of two bent crystals

The doubling of the angle of beam deflection due to volume reflection of protons by a sequence of two bent silicon crystals was experimentally observed at the 400 GeV proton beam of the CERN SPS. A similar sequence of short bent crystals can be used as an efficient primary collimator for the Large Hadron Collider