The influence of the electron thermal motion on the surface oscillating potential produced by traversal of a vacuum-plasma interface by a fast charged particle

The passage of a charged particle through a vacuum-plasma interface is considered. Expressions for a surface potential oscillating at the surface-wave frequency are found under conditions of mirror reflection of plasma electrons from the interface. It is shown that allowance for spatial dispersion eliminates a singularity appearing in the model of a cold plasma on the trajectory of particle motion in the near-surface oscillating potential. The possibility of measuring near-surface oscillating fields is discussed.Institute of Radio-Electronics, Armenian Academy of Science, Erevan. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 38, No. 12, pp. 1241–1249, December, 1995.     

Future contributions toJournal of Crystallographic and Spectroscopic Research

Future contributions toJournal of Crystallographic and Spectroscopic Research     

Cellulose-based fibers from liquid–crystalline solutions. II. Processing and morphology of acetate/butyrate esters

Fibers were spun from isotropic and anisotropic dimethylacetamide solutions of cellulose esters. Take-up speeds of the dry jet/wet spinning process varied. Water served as the coagulant. The mechanical properties of the fibers increased as spinning progressed from the isotropic to the anisotropic state of the solution. A trade-off in solubility and fiber properties was noted as the butyryl acetyl ratio decreased. Whereas high butyryl content enhances both overall solubility and the formation of liquid–crystalline solutions at lower concentration, it results in lower fiber modulus and strength. Morphology of the fibers depended on the coagulation rate which was influenced by the concentration of the sppinning solution. The level of orientation and crystallinity of the fibers increased somewhat when they were spun from liquid-crystalline solutions. © 1993 John Wiley & Sons, Inc.     

Parametric study of high energy plasmas for electrothermal-chemicalpropulsion applications

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     

Time‐integrated energy domain measurements with synchrotron radiation

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.     

Excimer Laser Processing of Grey Cast Iron: Microstructural and Tribological Characterization

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.     

Estimates for the Rapid Decay of Concentration Functions of n-Fold Convolutions

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).     

On the nature of the γ-α transition in cerium

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.