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1.
Sz.-Nagy's dilation theorem for a contraction on a Hilbert space has been extended by Mlak to the case of a contraction semigroup whose indices are the positive elements of a totally ordered discrete group. We generalize to this case the intertwining lifting theorem of Sz.-Nagy and Foias. Some previous interpolation results on ordered groups are obtained as consequences. 相似文献
2.
The low-temperature specific heat (LTSH) of the melt-quenched Ni81.5Px- B18.5?x amorphous alloy system, with 0 ? x ? 18.5, is presented. The decomposition of the LTSH into magnetic, lattice and electronic contributions shows that both Debye temperature θD and electronic specific heat coefficient decrease when the concentration of P increases.The electronic density of states N(EF), deduced from γ for various Ni-metalloid alloys, is plotted as a function of the average electronic concentration xZM, where x is the metalloid concentration and ZM is the chemical valence of M. Following Malozemoff et al.'s work, this plot is considered as a representation of the band structure and yields the change of the Fermi level with alloying. 相似文献
3.
Consider the following problem: given complex numbers a1, ...,an, find an L function f of minimum norm whose Fourier coefficientsck(f) are equal to ak for k between 0 and n. We show the uniquenessof this function, and we estimate its norm. The operator-valuedcase is also discussed. 2000 Mathematics Subject Classification30E05, 47A20, 47A56, 47A57. 相似文献
4.
L.F. KissV. Franco M. CsontosL. Péter C.F. CondeA. Conde T. KeményJ. Tóth L.K. VargaI. Bakonyi 《Journal of magnetism and magnetic materials》2011,323(6):699-707
The magnetoresistance (MR) was measured at 200, 250 and 300 K in magnetic fields up to B=12 T for a nanocrystallized Fe63.5Cr10Nb3Cu1Si13.5B9 alloy. Both the longitudinal (LMR) and transverse (TMR) component of the magnetoresistance decreased from B=0 to about 0.1 T. This could be ascribed to a giant MR (GMR) effect due to spin-dependent scattering of conduction electrons along their path between two Fe-Si nanograins via the non-magnetic matrix. Such a scattering may occur if the nanograin moments are not or only weakly coupled in the absence of a strong exchange coupling (due to the high Cr content in the matrix) and/or only weak dipole-dipole coupling is present (due to sufficiently large separations between the nanograins). For larger fields, the GMR saturated and a slightly nonlinear increase in MR with B was observed due to a contribution by the residual amorphous matrix. The anisotropic MR effect (AMR≡LMR−TMR) was negative for all fields and temperatures investigated. By measuring the MR of melt-quenched Fe100−xSix solid solutions with x=15, 18, 20, 25 and 28, the observed AMR could be identified as originating from the Fe-Si nanograins having a D03 structure. 相似文献
5.
Based upon certain key principal minors, a formula is given for the determinant of a nonsingular matrix in the case its inverse has a perfect elimination directed graph. The main result of [8] may be deduced from this formula. Our method allows us to construct a counterexample to a conjecture made in [8]. 相似文献
6.
The purpose of the present study was to provide a reliable value for the specific grain-boundary resistivity ρSGBR of Ni metal. New results are presented on the room-temperature electrical resistivity of nanocrystalline (nc) Ni metal samples produced by electrodeposition with various grain sizes. These resistivity data were compared with previous reports on nc-Ni and all results were analysed according to the procedure of Andrews [Phys. Lett. 19, 558 (1965)] who found that the resistivity increment due to grain boundaries is proportional to the grain-boundary surface area per unit volume which is, on the other hand, inversely proportional to the grain size. It is pointed out that the grain size directly accessible by transmission electron microscopy imaging is the relevant parameter for the evaluation of ρSGBR whereas the crystallite size deduced from X-ray diffraction line broadening leads to an underestimation of ρSGBR because coherency-breaking intragrain defects not contributing significantly to the resistivity also cause a line broadening. From the evaluation of the nc-Ni resistivity data at room temperature, we find that 4.45·10?16?Ω·m2?ρSGBR(Ni)?6.2·10?16?Ω·m2 and our upper bound agrees exactly with the most recent calculated value in the literature. 相似文献
7.
Sándor Kunsági-Máté Sándor Bakonyi László Kollár Bernard Desbat 《Journal of inclusion phenomena and macrocyclic chemistry》2009,64(3-4):283-288
The solvent effect on the kinetic energy distribution of p-cresol molecule was investigated by quantum-chemical (QM) method and molecular dynamics (MD) simulations, then the consequences were checked experimentally by photoluminescence (PL) and differential scanning calorimetry (DSC) methods. Results of QM calculations highlight the coupling of two vibrational normalmodes of p-cresol molecule in the presence of ethanol while no similar coupling was observed in methanol. MD simulations show that the normalmode coupling in ethanol is more pronounced at higher temperature and it is preferably based on the molecular friction of the cresol molecule with its environment. The theoretical observations were also proved experimentally. The dissociation rate of calixarene–phenol complexes were measured by DSC method. The decreased dissociation rate of the calixarene–phenol complexes observed in ethanol reflects the increased motion of the methyl groups of cresol units of calixarene in the ethanol solvent, a property which was predicted by the theoretical results. Our findings are applicable to many areas of chemistry where the formation and dissociation rates play important role: e.g., in the development of chemical molecular sensors or developing molecular containers for drugs towards pharmaceutical applications. 相似文献
8.
R. Risti? E. Babi? A. Kuršumovi? I.A. Figueroa I. Todd I. Bakonyi 《Journal of Non》2011,357(15):2949-2953
We provide new data for the stiffness, hardness, Debye temperatures and crystallization and glass transition temperatures for fourteen Ti-TL and Hf-TL amorphous alloys (TL = Ni,Cu) covering wide composition range (x(TL) ≤ 70). These data increase linearly with x, as was previously observed for Zr-TL glassy alloys. Thus, the strength of interatomic bonding (reflected in stiffness) in all TE-TL amorphous alloys (TE = Ti,Zr,Hf) increases with x for x ≤ 65. The actual variations of studied properties depend on TE, being feeble for TE = Ti. The approximately linear variation of mechanical, vibrational and thermal parameters with x enables one to estimate these parameters for pure amorphous TEs, but does not indicate compositions at which bulk metallic glasses (BMG) form in these alloy systems. The reduced glass transition temperature Trg is the property which roughly correlates with the formation of BMGs in glassy TE-TL alloys. 相似文献
9.
Marjaneh Jafari Fesharaki Gholam Reza Nabiyouni Júlia Dégi Lajos Pogány ádám Révész Imre Bakonyi László Péter 《Journal of Solid State Electrochemistry》2012,16(2):715-722
Codeposition of Ru and Co was studied at room temperature and at 50 °C with various Ru3+ and Co2+ concentrations in the electrolyte. The codeposition of Co and Ru proved to be anomalous since no pure Ru could be obtained
in the presence of Co2+ in the electrolyte, but a significant Co incorporation into the deposit was detected at potentials where the deposition of
pure Co was not possible. The composition of the deposits varied monotonously with the change of the concentration ratio of
Co2+ and Ru3+. The deposition of Ru was much hindered, and the current efficiency was a few percent only when the molar fraction of Co
in the deposit was low. Continuous deposits could be obtained only when the molar fraction of Co in the deposit was at least
40 at.%. The deposit morphology was related to the molar fraction of Co in the deposit. The X-ray diffractograms are in conformity
with a hexagonal close-packed alloy and indicate the formation of nanocrystalline deposits. Two-pulse plating did not lead
to a multilayer but to a Co-rich alloy. Magnetoresistance of the samples decreased with increasing Ru content. 相似文献
10.
Let be a compact abelian group having the property that its character group is totally ordered by a semigroup . We prove that every operator-valued function on of the form , such that the Hankel operator is bounded, has an essentially bounded extension with . The proof is based on Arveson's Extension Theorem for completely positive functions on -algebras. Among the corollaries we have a Carathéodory-Fejér type result for analytic operator-valued functions defined on such groups.