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951.
O.G. Kosareva N.A. Panov N. Akozbek V.P. Kandidov Q. Luo S.A. Hosseini W. Liu J.-F. Gravel G. Roy S.L. Chin 《Applied physics. B, Lasers and optics》2006,82(1):111-122
We demonstrate a three orders of magnitude increase and stability in the backscattered fluorescence signal from nitrogen molecules
by terawatt femtosecond laser pulse induced air filaments using a new method. The method is based on squeezing the initial
beam diameter using a telescope. The effect of laser shot-to-shot fluctuations was included in numerical simulations by a
random distribution of the initial intensity in both squeezed and non-squeezed beams. Statistical processing of the simulation
results shows that the average diameter of plasma channels as well as the total amount of free electrons generated in a bunch
of multiple filaments in air is larger in the squeezed beam. Shot-to-shot stability of the simulated plasma density increases
in the squeezed beam. The change of this plasma density with propagation distance is in good qualitative agreement with the
change of the range-corrected nitrogen fluorescence signal with distance.
PACS 42.65.Jx; 42.60.Jf; 42.68.Ay; 42.68.Wt 相似文献
952.
A. V. Kopylov I. V. Orekhov V. V. Petukhov A. E. Solomatin 《Physics of Atomic Nuclei》2006,69(11):1829-1832
Experiments sensitive to pp neutrinos from the Sun are very promising for precise measurement of the mixing angle ϑ
12. A νe
− scattering experiment (XMASS) and/or a charged-current experiment (indium detector) can measure the flux of electron pp neutrinos. One can find the total flux of pp neutrinos from a luminosity constraint after the contributions of 7Be and CNO neutrinos to the total luminosity of the Sun are measured. A radiochemical experiment utilizing a lithium target
has high sensitivity to the CNO neutrinos; thus, it has a good promise for precise measurement of the mixing angle and for
a test of the current theory of evolution of the stars.
The text was submitted by the authors in English. 相似文献
953.
V. S. Bilanych I. I. Makauz T. D. Mel’nichenko I. M. Rizak V. M. Rizak 《Physics of the Solid State》2006,48(11):2060-2064
The internal friction in Ge x As40 ? x S60 glasses is investigated in the temperature range 100 K-T g at infralow frequencies (10?3?10?1 Hz). It is shown that the concentration dependence of the internal friction of these materials changes as a result of the transformation of the dominant kinetic unit in dissipative processes of the relaxation and nonrelaxation types. It is established tha the change in the mechanism of internal friction in the Ge x As40 ? x S60 glasses leads to a jump in the activation energy of the α relaxation and to a local minimum in the frequency factor τ0. 相似文献
954.
A new version of the fast optically pumped magnetometer, an optically pumped balanced quantum magnetometer, built around a pair of symmetric transitions in the hyperfine structure of the 87Rb ground state is implemented for the first time. The noise-limited sensitivity of the prototype in terms of the variance is 6 pT for a measurement time of 0.1 s. The basic advantages of the new magnetometer are the absence of dead zones when it changes orientation relative to the magnetic field and an extremely low sensitivity to the drift of pumping parameters. 相似文献
955.
Inverse diffusion problems allow the diffusion coefficients to be determined from experimental concentration profiles. Solutions
of the inverse diffusion problem are unstable toward perturbations of the initial concentration profiles. By the example of
inverse diffusion problem solution for a model binary system it is demonstrated that the use of the production entropy to
minimize the discrepancy functional stabilizes the solution even for significant perturbations of the initial concentration
profile. The choice of the entropy production for the smoothing component of the discrepancy functional is physically adequate
to the formulated problem, and the entropy production can be used to solve inverse problems of heat and mass transfer.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 79–83, June, 2006. 相似文献
956.
957.
M. R. Darafsheh N. S. Karamzadeh A. R. Moghaddamfar 《Journal of Applied Mathematics and Computing》2006,21(1-2):437-450
IfG is a finite group, we define its prime graph Г(G), as follows: its vertices are the primes dividing the order ofG and two verticesp, q are joined by an edge, if there is an element inG of orderpq. We denote the set of all the connected components of the graph Г(G) by T(G)= {πi(G), fori = 1,2, …,t(G)}, where t(G) is the number of connected components of Г(G). We also denote by π(n) the set of all primes dividingn, wheren is a natural number. Then ¦G¦ can be expressed as a product of m1, m2, …, mt(G), where mi’s are positive integers with π(mi) = πi. Thesem i ’s are called the order components ofG. LetOC(G) := {m 1,m 2, …,m t (G)} be the set of order components ofG. In this paper we prove that, if G is a finite group andOC(G) =OC(M), where M is a finite simple group witht(M) ≥ 2, thenG is neither Frobenius nor 2-Frobenius. 相似文献
958.
Electron beam processing of poly(ethylene terephthalate) (PET) films is found to promote significant changes in the melting heat, intrinsic viscosity and polymer film-liquid (water, isooctane and toluene) boundary surface tension. These properties are featured with several maximums depending on the absorbed dose and correlating with the modification of PET surface functionality. Studies using adsorption of acid-base indicators and IR-spectroscopy revealed that the increase of PET surface hydrophilicity is determined by the oxidation of methylene and methyne groups. Electron beam treatment of PET films on the surface of N-vinylpyrrolidone aqueous solution provided graft copolymerization with this comonomer at optimum process parameters (energy 700 keV, current 1 mA, absorbed dose 50 kGy). 相似文献
959.
We discuss the spectral lineshapes of reflectance and modulated reflectance (MR) measurements on optoelectronic device structures such as epi-layers, quantum wells (QWs), vertical-cavity surface emitting-lasers (VCSELs) and resonant-cavity light-emitting diodes (RCLEDs). We consider the various methods for the extraction of built-in electric fields and band-gap energies from Franz-Keldysh oscillations (FKO), using the example of a tensilely strained InGaAs QW system, whose InGaAsP barriers yield strong FKO. We describe how critical point transition energies can be easily obtained by eye from Kramers-Kronig (KK) transforms of low field or QW modulation spectra, using the example of the modulated transmittance spectra of dilute-nitrogen InGaAsN p-i-n structures. We also discuss how the ordinary reflectivity spectrum, usually acquired at the same time as the MR signal, may also be exploited to extract layer thicknesses and compositions, and information about the active QW absorption spectrum in VCSEL and RCLED structures. 相似文献
960.
N.D. Tho N. Chau S.C. Yu H.B. Lee N.D. The L.A. Tuan 《Journal of magnetism and magnetic materials》2006
Effect of annealing on the soft magnetic properties of Fe73.5Si13.5B9Nb3Au1 amorphous ribbon has been investigated by means of structure examination, magnetoimpedance ratio (MIR) and incremental permeability ratio (PR) spectra measured in the frequency range of 1–10 MHz at a fixed current of 10 mA X-ray diffraction analysis showed that the as-cast sample was amorphous and it became nanocrystalline under a proper heat treatment. When annealing amorphous alloy at 530 °C for 30, 60, 90 min, soft magnetic properties have been improved drastically. Among the samples investigated, the sample annealed at 530 °C for 90 min showed the softest magnetic behavior. The MIR and PR curves revealed the desirable changes in anisotropy field depending upon annealing. 相似文献