A new technique is suggested for multimode fiber bandwidth prediction based on a preform profile. It allows one to calculate the output pulse distortion and allows the bandwidth of a fiber to be drawn dependent on the excitation conditions under which it will operate. It is shown that the accuracy of the bandwidth prediction for 1.5- to 2.5-km fibers is about 10%, the bandwidth being 1-1.5 GHz/km. To achieve this accuracy it is necessary that the excitation conditions and differential mode attenuation be exactly reproduced in the calculation. The profile variations along the length should not be considerable. The prediction technique was adapted to the P101 Preform Analyser (York Technology) and can replace alpha-approximation curve-fitting during routine manufacture of multimode preforms. 相似文献
This paper is devoted to relations between the Kurosh problem and the Shirshov height theorem. The central point and main
technical tool is the identity of algebraicity. The main result of this paper is the following. Let A be a finitely generated PI-algebra and Y be a finite subset of A. For any Noetherian associative and commutative ring {ie125-01}, let any factor of R ⊗ A such that all projections of elements from Y are algebraic over π(R) be a Noetherian R-module. Then A has bounded essential height over Y. If, furthermore, Y generates A as an algebra, then A has bounded height over Y in the Shirshov sense.
This paper also contains a new proof of the Razmyslov-Kemer-Braun theorem on radical nilpotence of affine PI-algebras. This
proof allows one to obtain some constructive estimates.
The main goal of the paper is to develop a “virtual operator calculus.” Virtual operators (pasting, deleting, and transfer)
depend not only on an element of the algebra but also on its representation.
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Translated from Fundamentalnaya i Prikladnaya Matematika, Vol. 13, No. 2, pp. 3–29, 2007. 相似文献
The cyclodimerization of norbornadiene-2,5 (NBD) catalyzed by the systems formed on the basis of bis(ηy3-allyl)nickel and organophosphorus compounds and the process kinetics are studied. The formation rate of all products follows
the overall second-order rate law: first order with respect to the catalyst and NBD. The addition of phosphines and phosphites
substantially decreases the reaction rate compared to that in nickel systems containing no organophosphorus additives. The
influence of the phosphine ligand structure and temperature on the ratio of the reaction products is studied. The blocking
of one coordination site on the nickel atom changes the process kinetics. The loss of two vacancies results in the loss of
the catalytic activity of the system. A mechanism explaining the stoichiometry and composition of the reaction products is
proposed. 相似文献
This work presents the experimental study of the isomeric ratio of 137mCe–137gCe produced in 138Ce(γ, n) 137m,gCe photonuclear reaction, in neutron capture reaction 136Ce(n, γ) 137m,gCe and in the two simultaneous reactions 138Ce(γ, n) 137m,gCe and 136Ce(n, γ) 137m,gCe in the mixed photon—neutron field by the activation method. The investigated samples were irradiated at the bremsstrahlung photon flux, in the epithermal and thermal-epithermal neutron beam and in the mixed photon-neutron field constructed at the electron accelerator Microtron MT-25 of the Flerov Laboratory of Nuclear Reaction, Joint Institute for Nuclear Research, Dubna, Russia. The results were analyzed, discussed and compared with those of other authors to examine the role of the channel effect in nuclear reaction and provide the nuclear data for theoretical model interpretation of nuclear reactions.
The diverse range of mass spectrometry (MS) instrumentation along with corresponding proprietary and nonproprietary data formats has generated a proteomics community driven call for a standardized format to facilitate management, processing, storing, visualization, and exchange of both experimental and processed data. To date, significant efforts have been extended towards standardizing XML-based formats for mass spectrometry data representation, despite the recognized inefficiencies associated with storing large numeric datasets in XML. The proteomics community has periodically entertained alternate strategies for data exchange, e.g., using a common application programming interface or a database-derived format. However, these efforts have yet to gain significant attention, mostly because they have not demonstrated significant performance benefits over existing standards, but also due to issues such as extensibility to multidimensional separation systems, robustness of operation, and incomplete or mismatched vocabulary. Here, we describe a format based on standard database principles that offers multiple benefits over existing formats in terms of storage size, ease of processing, data retrieval times, and extensibility to accommodate multidimensional separation systems. 相似文献
A fourth-generation rigid-chain pyridine-containing polyphenylene dendrimer is studied by inverse gas chromatography. Two
types of sorbates are investigated: C7-C11n-alkanes and C6H6-C6H5C5H11 alkylbenzenes. In the range 35−150°C, specific retention volumes of the indicated sorbates are measured and their solubility
coefficients are calculated. It is shown that aliphatic sorbates exhibit reduced solubility coefficients in the aromatic dendrimer
compared to those observed for aliphatic polymers and the earlier studied carbosilane dendrimer. At the same time, alkylbenzenes
are characterized by enhanced solubility coefficients and this effect is more pronounced for the first members of the homologous
series. An analysis of excess partial molar thermodynamic functions shows that π-electron interactions in the dendrimer and
among dendrimer and aromatic sorbates are responsible for the thermodynamic properties of the dendrimer under study. 相似文献
A series of potassium titanyl phosphate single crystals doped with zinc (KTP: Zn) is grown by spontaneous flux crystallization.
Their properties and the way the additive is implanted in the crystal lattice are studied. The inclusion of zinc atoms in
the KTP structure is evidenced by the data of chemical analysis and the results of studies of electrophysical properties (the
growth of conductivity and increase of relaxation anomalies). Precision X-ray diffraction studies of KTP: Zn single crystals
reveal changes in the channel of the structure which correlate with the physical properties of this crystal series. No substitution
of zinc atoms for titanium, phosphorus, or potassium atoms is found in the structure. Zinc atoms can be located at structural
defects, domain walls, and the crystal surface. 相似文献
Experimental data on the study of modifications of two types of the YBCO(123)-based composite tape under irradiation with
electrons with the energy of 23 MeV and 132Xe27+ (167 MeV), 84Kr17+ (107 MeV), and 40Ar8+ (48 MeV) ions in a wide range of irradiation doses are presented. It is shown that no changes in the HTS transition temperature
and critical current occurred under electron irradiation up to the dose D ≈ 10−4 disp/a (displacements per atom). The threshold dose of irradiation with 132Xe27+ ions, at which superconductivity disappears, is determined. In comparison with the initial value, the critical current of
40Ar8+ ions is found to increase by ≈18% in the zero magnetic field at T = 77 K. This effect can be explained by the pinning centers for Abrikosov vortices induced by relatively small ion irradiation
doses. High doses of heavy ions lead to partial or complete amorphization of a superconductor, which results first in a decrease
in the critical current and transition temperature and then in a total disappearance of superconductivity. X-ray diffraction
is used to study the changes in the crystal structure of the YBCO(123) superconductor under ion irradiation. 相似文献