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921.
922.
Katulka G.L. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1997,25(1):66-72
Theoretical calculations are performed with a one-dimensional (1-D), steady state, isothermal computer plasma model to define plasma output parameters for various input electrical energies and capillary radii of relevance to the electrothermal-chemical (ETC) propulsion concept. Three capillaries of 1.92, 4.75, and 7.0 mm radius, and a fixed length of 11.84 cm, were chosen for this study with input currents between 30 and 350 kA. Plasmas are categorized according to their total power and energy levels (based on a 3-ms pulse width) and are compared with respect to their resistance, exit pressure, and core plasma temperature. The input power ranges from 0.17 to 1.89 GW, for input energies from 0.49 to 5.80 MJ, which is considered suitable coverage for ETC ignition through ETC enhanced propulsion concepts. The study shows that the range of resistance, pressure, and temperature are 12.8-195 mΩ, 19.8-2000 MPa, and 2.9-13.5 eV, respectively, for the chosen capillary geometry. Flow conditions for plasma calculations include choked (no pressure boundary) and unchoked (450-MPa pressure boundary) for some calculations. Results from the computational model and interpretations from the perspective of capillary implementation into ETC propulsion concepts are also included 相似文献
923.
J. Odeurs R. Coussement C. L'abbé G. Neyens G.R. Hoy E.E. Alp W. Sturhahn T. Toellner C. Johnson 《Hyperfine Interactions》1998,113(1-4):455-463
A new time integrated method for the study of resonant nuclear scattering of synchrotron radiation in the forward direction
or in Bragg directions is introduced. This method gives in principle similar information as the well known time differential
method. A brief comparison of both methods is presented. The idea is to excite coherently the nuclei incorporated in two absorbers,
one moving with respect to the other. The fields radiated by the nuclei from both absorbers interfere and each time the nuclear
energy in one absorber matches, by Doppler modulation, the nuclear energy of the other, an extremum in the time integrated
intensity is observed. The results of the first experiments at the Advanced Photon Source at the Argonne National Laboratory
will be presented.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
924.
G. Marest A. Fontes M. Jeandin S. Fayeulle M. Vardavoulias M. Frainais 《Hyperfine Interactions》1998,112(1-4):39-42
Pearlitic grey iron was treated by means of a XeCl laser to remelt only a shallow layer. This process allows to modify the
heteregeneous surfaces of cast irons in order to improve their tribological behaviour. The energy density ranged from 0.3
to 3 J/cm2 and the number of shots from 4 to 40. It is shown that after laser irradiation austenite is formed in the melted layer; compressive
stresses at the surface were exhibited as well as the deposition of graphite and the formation of carbides. It is shown that
excimer laser processing highly decreases the coefficient of friction and the wear rate.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
925.
926.
We estimate the concentration functions of n-fold convolutions of one-dimensional probability measures. The Kolmogorov–Rogozin inequality implies that for nondegenerate distributions these functions decrease at least as O(n
–1/2). On the other hand, Esseen(3) has shown that this rate is o(n
–1/2) iff the distribution has an infinite second moment. This statement was sharpened by Morozova.(9) Theorem 1 of this paper provides an improvement of Morozova's result. Moreover, we present more general estimates which imply the rates o(n
–1/2). 相似文献
927.
In 1964 Davis and Adams established that the large increase of the thermal expansion and compressibility in the critical region
of the γ-to α-Ce phase transition occurs predominantly in the α phase. This provides strong evidence that a tricritical point
is realized in Ce. This also means that the aforementioned transition is not isomorphic and that α-Ce should have a distorted
fcc structure. A careful examination of Jayaraman’s data (1965) shows that a second-order transition line continues beyond
the tricritical point to the vicinity of a triple point on the melting curve. The phase boundary with the tricritical point
and the minimum of the melting curve are reconstructed within the framework of Landau theory.
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 2, 111–117 (25 January 1998)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
928.
929.
D. G. Pak 《Theoretical and Mathematical Physics》1998,116(2):947-955
We consider a three-dimensional bicovariant differential calculus on the quantum group SUq(2) that is compatible with the structure of gauge transformations. In the approach based on the global covariance with respect
to the stability subgroup U(1), we show that the gauge-covariant exterior differential algebra on SUq(2) is uniquely determined. We construct explicit representations of q-deformed Lie algebras in terms of differential operators.
Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 116, No. 2, pp. 265–276, August. 1998. 相似文献
930.
The reactions of IO radicals with CH3SCH3, CH3SH, C2H4, and C3H6 have been studied using the discharge flow method with direct detection of IO radicals by mass spectrometry. The absolute rate constants obtained at 298 K are the following: IO + CH3SCH3 → products (1): k1 = (1.5 ± 0.2) × 10?14; IO + CH3SH → products (2): k2 = (6.6 ± 1.3) × 10?16; IO + C2H4 →products (3): k3 < 2 × 10?16; IO + C3H6 → products (4): k4 < 2 × 10?16 (units are cm3 molecule?1 s?1). CH3S(O)CH3 and HOI were found as products of reactions (1) and (2), respectively. The present lower value of k1 compared to our previous determination is discussed. 相似文献