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991.
V. T. Astrelin A. V. Burdakov V. S. Koidan K. I. Mekler P. I. Mel’nikov V. V. Postupaev M. A. Shcheglov 《Journal of Experimental and Theoretical Physics》1998,86(3):489-500
This paper presents the results of experiments on two-stage heating of a dense plasma by a relativistic electron beam in the
GOL-3 facility. A dense plasma with a length of about a meter and a hydrogen density up to 1017 cm−3 was created in the main plasma, whose density was 1015 cm−3. In the process of interacting with the plasma, the electron beam (1 MeV, 40 kA, 4 μs) imparts its energy to the electrons of the main plasma through collective effects. The heated electrons, as they disperse
along the magnetic field lines, in turn reach the region of dense plasma and impart their energy to it by pairwise collisions.
Estimates based on experimental data are given for the parameters of the flux of hot plasma electrons, the energy released
in the dense plasma, and the energy balance of the beam-plasma system. The paper discusses the dynamics of the plasma, which
is inhomogeneous in density and temperature, including the appearance of pressure waves.
Zh. éksp. Teor. Fiz. 113, 897–917 (March 1998) 相似文献
992.
H. Hommel A. Touhami A. Halli A. P. LeGrand 《Journal of Polymer Science.Polymer Physics》1995,33(16):2189-2198
EPR spectroscopy of labeled poly(ethylene oxide) (PEO) grafted on silica has been used to characterize the conformation and local dynamics of the chains. Grafted molecules of MW 2000 with grafting ratios of 0.045, 0.057, 0.126, and 0.42 molecules/nm2 were in contact with benzene. The mobility of the label was compared with that observed for solution of PEO from very diluted to highly concentrated and even bulk PEO. Thus, the concentration inside the grafted layer could be evaluated and also the thickness, which evolves rather linearly with the grafting ratio. © 1995 John Wiley & Sons, Inc. 相似文献
993.
H.-J. Scheibe D. Drescher A. Kolitsch A. Mensch 《Fresenius' Journal of Analytical Chemistry》1995,353(5-8):690-694
Morphology and structure of amorphous carbon films deposited with a pulsed arc source (LASER-ARC) have been studied using microscopical methods (SEM, TEM and AFM), electron diffraction and spectroscopical investigation (EELS). The parameters of the arc source and the deposition conditions (substrate temperature) influence morphology and structure of deposited amorphous carbon films. Especially the incorporation and growth of particles, embedded in the film have been investigated. By particle analysis using an optical microscope a majority of particles that is smaller than 500 nm has been determined. The morphology has been also demonstrated similar by AFM and TEM images. Their number and size of particles is strongly influenced by the deposition temperature. The structure of amorphous film is characterized by the EELS-spectra, but the particle structure was not detectable. 相似文献
994.
The solvent extraction of cobalt(II), nickel(II) and copper(II) using 2,4-pent-dione (Hacac) and 4-phenyl-2, 4-but-dione (Hbzac)
is carried out by varying the reagent concentration and pH of the aqueous phase. Each of these metals is quantitatively separated
(≈ 98%) from their binary mixtures with monovalent (Ag), divalent (Mn, Zn, Cd, Hg, Mg, Sn, Pb) and trivalent (Cr, Fe) metals.
The extraction constants are calculated from the metal distribution data using linear regression analysis. The extracted species
is MA2 in each case. A most significant result is separation of copper(II) from iron(III) which otherwise interferes when extracted
from the acidic medium. 相似文献
995.
The twisting power of chiral probes in nematics is interpreted in terms of a shape model, in which the surface elements of the solute molecules tend to align with the local director. The theoretical treatment is based on a previous approach, suitable for relating order parameters in nematics to molecular shape, and leads to the definition of a molecular pseudo-tensor whose orientational average determines the pitch and handedness of the helical macrostructures. Results of numerical calculations performed for distorted biphenyl and binaphthyl molecules are in agreement with the experimental results. 相似文献
996.
Summary A new method of evaluating the Tolman cone angle from X-ray structural data available from the Cambridge Crystallographic Data Base has been developed and a statistical analysis of the cone angles of the phosphines PPh3, PMe2Ph, PMePh2, PMe3, PEt3 and PCy3 (Cy = cyclohexyl) in transition metal complexes has been completed. 相似文献
997.
Examines the use of magnetic fields to functionally stimulate peripheral nerves. All electric fields are induced via a changing magnetic field whose flux is entirely confined within a closed magnetic circuit. Induced electric fields are simulated using a nonlinear boundary element solver. The induced fields are solved using duality theory. The accuracy of these predictions is verified by saline bath experiments. Next, the theory is applied to the stimulation of nerves using small, partially occluded ferrite and laminated vanadium permendur cores. Experiments demonstrate the successful stimulation of peripheral nerves in the African bullfrog with 11 mA, 153 mV excitations. These results offer a new vista of possibilities in the area of functional nerve stimulation. Unlike functional electric stimulation (FES), FMS does not involve any half cell reactions, and thus would not have the commensurate FES restrictions regarding balanced biphasic stimulation, strength duration balances, and oxidation issues, always exercising care that the electrodes remain in the reversible operating regime 相似文献
998.
The operation of (In,Ga)As quantum well lasers prepared on [112]-oriented GaAs substrates is reported. Threshold current densities as low as 187 A/cm2 for a 1.57 mm-long device have been obtained under pulsed-mode operation. The demonstration of laser action in a heterostructure grown on the [112]-oriented substrate is important for the design of blue-green light emitters by second harmonic generation 相似文献
999.
Baars J.W.M. Greve A. Hein H. Morris D. Penalver J. Thum C. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1994,82(5):687-696
The “Millimeter Radio Telescope” (MRT) is operated by the Institute for Radio Astronomy in the millimeter range (IRAM) and is located at 2850-m altitude in the Sierra Nevada, near Granada, Spain. It is a reflector antenna of 30-m diameter with a surface accuracy of 0.08 mm and a pointing accuracy of better than 2 arcsec. The telescope is equipped with sensitive receivers for the atmospheric windows between 0.8- and 7-mm wavelength. The authors describe the optics layout of the receiver and calibration system, which allows simultaneous observations at a number of frequencies. The special design aspects of the antenna, in particular the control of thermal deformations and the achievement of a high reflector and pointing accuracy are described. The authors compare the design computations with the characteristics of the telescope, derived from several years of operation and optimization. The success of the design is demonstrated by observational experience. The authors conclude the paper with a short review of some of the astronomical results obtained with the telescope 相似文献
1000.
The authors demonstrate, for the first time, a three node optically time division multiplexed network with a maximum capacity of 40 Gbit/s. Electro-optical switches were used for both `drop and insert' and demultiplexing, and electronic clock recovery provided synchronisation throughout the network 相似文献