1,815 research outputs found
Mechanical properties, wear and corrosion of boronized N80 tube steel
The effect of boronizing on mechanical properties, wear and corrosion of boronized N80 tube steel is studied. A dual-phase boride layer consisting of FeB and F₂B phases was formed on the surface of steel substrate in a hardness range of 1220 to1340 HV. A set-up to use less boriding agent and accelerate the pipe’s cooling process was designed. In order to meet the tensile properties of N80 steel required by API SPEC 5L, four cooling methods were employed. The fan-cooling with a graphite bar inside the boriding agent resulted in the highest mechanical properties, in accordance with the mechanical properties of API SPEC 5L. The boronized N80 steel showed a high wear resistance under dry sliding condition and excellent corrosion resistance in as-received oilfield water from Jilin oil field, Northeast China.Изучено влияние борирования на механические свойства, изнашивание и коррозию трубной стали N80. На поверхности стальной подкладки сформирован двухфазный боридный слой на основе FeB и F₂B с твердостью 1220...1340 HV. Разработаны способы для уменьшения количества компонента для борирования и ускорения охлаждения. Для обеспечения высоких механических характеристик при растяжении согласно спецификации API SPEC 5L использованы четыре метода охлаждения. Вентиляторное охлаждение с графитовым бруском внутри борированного реагента обусловило наиболее высокие механические характеристики. Борированная сталь выявила высокие износостойкость в условиях сухого трения и коррозийную прочность в воде нефтяного промысла в Китае в провинции Джулин.Вивчено вплив борування на механічні властивості, зношування та корозію трубної сталі N80. На поверхні сталевої підкладки сформовано двофазний боридний шар на основі FeB і F₂B з твердістю 1220...1340 HV. Розроблено способи для зменшення кількості компонента для борування та пришвидшення охолодження. Для забезпечення високих механічних характеристик за розтягу згідно зі специфікацією API SPEC 5L використано чотири методи охолодження. Вентиляторне охолодження з графітовим бруском всередині борувального реагента призвело до найвищих механічних характеристик. Борована сталь виявила високі зносотривкість за сухого тертя та корозійну міцність у воді з нафтового родовища в Китаї у провінції Джулін
Studies on La2-xPrxCayBa2Cu4+yOz (0.1 < x < 0.5) type mixed oxide superconductors
The La2-xPrxCayBa2Cu4+yOz (LaPrCaBCO) mixed oxides have been studied for
their structural and superconducting properties using X-ray diffraction (XRD),
d. c. resistivity, d. c. susceptibility and iodometric double titration. All
the LaPrCaBCO samples for x = 0.1 - 0.5, exhibit tetragonal crystalline
structure with P 4/mmm space group as determined by Rietveld analysis of the
X-ray diffraction data. With increasing x, enhancement in Tc is observed, which
is quite interesting for Pr substituted high Tc oxides. Maximum Tc ~ 58 K has
been observed for x = 0.5(La-2125 stoichiometry). The results of structural
studies and superconducting property measurements are presented in light of
increase in Tc in LaPrCaBCO system with increasing Pr concentration.Comment: 6 pages including 5 figures and 1 tabl
Continuous Truth II: Reflections
Abstract. In the late 1960s, Dana Scott first showed how the Stone-Tarski topological interpretation of Heyting’s calculus could be extended to model intuitionistic analysis; in particular Brouwer’s continuity prin-ciple. In the early ’80s we and others outlined a general treatment of non-constructive objects, using sheaf models—constructions from topos theory—to model not only Brouwer’s non-classical conclusions, but also his creation of “new mathematical entities”. These categorical models are intimately related to, but more general than Scott’s topological model. The primary goal of this paper is to consider the question of iterated extensions. Can we derive new insights by repeating the second act? In Continuous Truth I, presented at Logic Colloquium ’82 in Florence, we showed that general principles of continuity, local choice and local com-pactness hold in the gros topos of sheaves over the category of separable locales equipped with the open cover topology. We touched on the question of iteration. Here we develop a more gen-eral analysis of iterated categorical extensions, that leads to a reflection schema for statements of predicative analysis. We also take the opportunity to revisit some aspects of both Continuous Truth I and Formal Spaces (Fourman & Grayson 1982), and correct two long-standing errors therein
Representations of Conformal Nets, Universal C*-Algebras and K-Theory
We study the representation theory of a conformal net A on the circle from a
K-theoretical point of view using its universal C*-algebra C*(A). We prove that
if A satisfies the split property then, for every representation \pi of A with
finite statistical dimension, \pi(C*(A)) is weakly closed and hence a finite
direct sum of type I_\infty factors. We define the more manageable locally
normal universal C*-algebra C*_ln(A) as the quotient of C*(A) by its largest
ideal vanishing in all locally normal representations and we investigate its
structure. In particular, if A is completely rational with n sectors, then
C*_ln(A) is a direct sum of n type I_\infty factors. Its ideal K_A of compact
operators has nontrivial K-theory, and we prove that the DHR endomorphisms of
C*(A) with finite statistical dimension act on K_A, giving rise to an action of
the fusion semiring of DHR sectors on K_0(K_A)$. Moreover, we show that this
action corresponds to the regular representation of the associated fusion
algebra.Comment: v2: we added some comments in the introduction and new references.
v3: new authors' addresses, minor corrections. To appear in Commun. Math.
Phys. v4: minor corrections, updated reference
X-ray and ion emission studies from subnanosecond laser-irradiated SiO2 aerogel foam targets
In this experiment, a comparative study of ion and X-ray emission from both a SiO2 aerogel foam and a quartz target is performed. The experiment is performed using Nd:glass laser system operated at laser energy up to 15 J with a pulse duration of 500 ps with focusable intensity of 1013–1014 W/cm2 on target. X-ray fluxes in different spectral ranges (soft and hard) are measured by using X-ray diodes covered with Al filters of thickness 5 µm (0.9–1.56 keV) and 20 µm (3.4–16 keV). A 2.5 times enhancement in soft X-ray flux (0.9–1.56 keV) and a decrease of 1.8 times in hard X rays (3.4–16 keV) for 50 mg/cc SiO2 aerogel foam is observed compared with the solid quartz. A decrease in the flux of the K-shell line emission spectrum of soft X rays is noticed in the case of the foam targets. The high-resolution K-shell spectra (He-like) of Si ions in both the cases are analyzed for the determination of plasma parameters by comparing with FLYCHK simulations. The estimated plasma temperature and density are T c = 180 eV, n e = 7 × 1020 cm−3 and T c = 190 eV, n e = 4 × 1020 cm−3 for quartz and SiO2 aerogel foam, respectively. To measure the evolution of the plasma moving away from the targets, four identical ion collectors are placed at different angles (22.5, 30, 45, and 67.5°) from target normal. The angular distribution of the thermal ions are scaled as cosnθ with respect to target normal, where n = 3.8 and 4.8 for the foam and quartz, respectively. The experimental plasma volume measured from the ion collectors and shadowgraphy images are verified by a two-dimensional Eulerian radiative–hydrodynamic simulation (POLLUX code
Doping effect on the anomalous behavior of the Hall effect in electron-doped superconductor NdCeCuO
Transport properties of NdCeCuO single crystal films
are investigated in magnetic fields up to 9T at =(0.4-4.2)K. An analysis
of normal state (at ) Hall coefficient dependence on Ce
doping takes us to a conclusion about the existence both of electron-like and
hole-like contributions to transport in nominally electron-doped system. In
accordance with (x) analysis an anomalous sign reversal of Hall effect
in mixed state at may be ascribed to a flux-flow regime for two
types of carriers with opposite charges.Comment: 14 pages, 5 figure
Cosmokinetics: A joint analysis of Standard Candles, Rulers and Cosmic Clocks
We study the accelerated expansion of the universe by using the kinematic
approach. In this context, we parameterize the deceleration parameter, q(z), in
a model independent way. Assuming three simple parameterizations we reconstruct
q(z). We do the joint analysis with combination of latest cosmological data
consisting of standard candles (Supernovae Union2 sample), standard ruler
(CMB/BAO), cosmic clocks (age of passively evolving galaxies) and Hubble (H(z))
data. Our results support the accelerated expansion of the universe.Comment: PDFLatex, 15 pages, 12 pdf figures, revised version to appear in JCA
RVB Contribution to Superconductivity in
We view as electronically equivalent to (non-staggered) graphite
( layer) that has undergone a zero gap semiconductor to a superconductor
phase transition by a large c-axis (chemical) pressure due to layers.
Further, like the \ppi bonded planar organic molecules, graphite is an old
resonating valence bond (RVB) system. The RVB's are the `preexisting cooper
pairs' in the `parental' zero gap semiconducting (graphite) sheets that
manifests themselves as a superconducting ground state of the transformed
metal. Some consequences are pointed out.Comment: 4 pages, 2 figure, RevTex. Based on a talk given at the Institute
Seminar Week, IMSc, Madras (12-16, Feb. 2001
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