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排序方式: 共有1019条查询结果,搜索用时 15 毫秒
71.
R. A. Corrêa J. J. Barroso 《International Journal of Infrared and Millimeter Waves》2000,21(6):1019-1029
The cylindrical waveguide with azimuthally periodic corrugations described by a sinusoidal function is analyzed. Relevant to magnetron and gyrotron interactions, TE-mode oscillations are treated by deriving a dispersion relation—linking the cut-off frequency and corrugation parameters—upon expansion of the field quantities in terms of space harmonics. From numerical examples, the present paper examines how the geometrical properties (area and perimeter) of the corrugated cross section relates with the cutoff frequencies of 2 and modes having one radial variation. The waveguiding system studied here with continuously corrugated azimuthal profile looks attractive to relativistic, slow-wave electron devices for it is more resistant to RF breakdown in comparison with traditional magnetron cavities with vane-type side resonators. 相似文献
72.
Mónica Schwarz M. Carmen Rodríguez Dominico A. Guillén Carmelo G. Barroso 《Journal of separation science》2009,32(11):1782-1790
Brandy and other aged distillates are a rich source of polyphenols. For brandies, contact with wood during ageing makes an important contribution to their polyphenols content. This paper describes the use of a previously devised ultra performance LC (UPLC) method to study the polyphenols content of Brandy de Jerez. UPLC is a new technique in LC offering several potential advantages, especially the reduction of time. Analyses of brandy performed by HPLC were repeated by UPLC. A special UPLC analytical column (Acquity UPLC BEH C18 column, 100×2.1 mm), with a particle size of 1.7 μm, forms part of this system. Using the UPLC system enabled the time needed for analysis to be reduced to one tenth of the time needed in the conventional HPLC system. In conclusion, the separation factor results of the UPLC were compared to those obtained using HPLC methods; this demonstrated that simple, high efficiency UPLC gradients are viable and advantageous substitutes for traditional analysis of polyphenols in brandy by HPLC. The method enabled 14 phenolic compounds to be identified and determined in 33 different commercial brandies, and this allowed them to be differentiated in function of quality. 相似文献
73.
Barroso A. Nogueira P. Romão J. C. 《Zeitschrift fur Physik C Particles and Fields》1986,32(2):243-248
Direct (nonresonant) 3-body decays of charmed mesons are calculated in chiral perturbation theory. The magnitudes of the 20 and 84 representations of the effective chiralSU(4)×SU(4) Lagrangian are determined from the measured 2-bodyD→Kπ rate. For decay modes which do not contain nonspectator contributions, the agreement of theoretical predictions with the data is satisfactory. Nevertheless, the large discrepancy between theory and experiment for decays which can proceed through theW-exchange orW-annihilation might imply the importance of nonperturbative corrections to the nonspectator diagram and the existence of final-state interactions. 相似文献
74.
Matteo Perini Federica Camin Luana Bontempo Andreas Rossmann Edi Piasentier 《Rapid communications in mass spectrometry : RCM》2009,23(16):2573-2585
The study focuses on the 2H/H, 13C/12C, 15N/14N, 18O/16O and 34S/32S values of defatted dry matter (DFDM) and on the 2H/H, 13C/12C and 18O/16O values of the fat fraction of meat samples from various lamb types reared in seven Italian regions, following different feeding regimes (forage, concentrate, milk). The 13C/12C (r = 0.922), 2H/H (r = 0.577) and 18O/16O (r = 0.449) values of fat and DFDM are significantly correlated, the fat values being significantly lower for C and H and higher for O than for DFDM values and the differences between the two fractions not being constant for different lamb types. The feeding regime significantly affected the 13C/12C, 15N/14N, 18O/16O and 2H/H of fat. The DFDM 2H/H, and 18O/16O values, excluding an outlier, are significantly correlated with the corresponding values in meteoric waters, thus allowing us to trace the variability of geoclimatic factors. 15N/14N is influenced by pedoclimatic conditions, whereas 34S/32S is influenced by the sea spray effect and the surface geology of the provenance area. By applying stepwise linear discriminant analysis only the 2H/H of fat was found not to be significant and 97.7% of the samples were correctly assigned to the lamb type and more than 90% cross‐validated. With the feeding regime, 97.7% of the samples were both correctly assigned and cross‐validated using a predictive model including 13C/12C, 15N/14N, 18O/16O, 34S/32S of DFDM and 18O/16O of fat. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
75.
76.
Let (ℋ
t
)
t≥0 be the Ornstein-Uhlenbeck semigroup on ℝ
d
with covariance matrix I and drift matrix −λ(I+R), where λ>0 and R is a skew-adjoint matrix and denote by γ
∞ the invariant measure for (ℋ
t
)
t≥0. Semigroups of this form are the basic building blocks of Ornstein-Uhlenbeck semigroups which are normal on L
2(γ
∞). We investigate the weak type 1 estimate of the Riesz transforms for (ℋ
t
)
t≥0. We prove that if the matrix R generates a one-parameter group of periodic rotations then the first order Riesz transforms are of weak type 1 with respect
to the invariant measure γ
∞. We also prove that the Riesz transforms of any order associated to a general Ornstein-Uhlenbeck semigroup are bounded on
L
p
(γ
∞) if 1<p<∞.
The authors have received support by the Italian MIUR-PRIN 2005 project “Harmonic Analysis” and by the EU IHP 2002-2006 project
“HARP”. 相似文献
77.
M. Fampa L. A. Barroso D. Candal L. Simonetti 《Computational Optimization and Applications》2008,39(2):121-142
In this paper, we present a bilevel programming formulation for the problem of strategic bidding under uncertainty in a wholesale
energy market (WEM), where the economic remuneration of each generator depends on the ability of its own management to submit
price and quantity bids. The leader of the bilevel problem consists of one among a group of competing generators and the follower
is the electric system operator. The capability of the agent represented by the leader to affect the market price is considered
by the model. We propose two solution approaches for this non-convex problem. The first one is a heuristic procedure whose
efficiency is confirmed through comparisons with the optimal solutions for some instances of the problem. These optimal solutions
are obtained by the second approach proposed, which consists of a mixed integer reformulation of the bilevel model. The heuristic
proposed is also compared to standard solvers for nonlinearly constrained optimization problems. The application of the procedures
is illustrated in case studies with configurations derived from the Brazilian power system. 相似文献
78.
79.
Ohne ZusammenfassungMit 5 Abbildungen. 相似文献
80.
Alessandro Gandini Dora Coelho Armando J.D. Silvestre 《European Polymer Journal》2008,44(12):4029-4036
The model Diels-Alder reaction of furfuryl acetate with N-methylmaleimide and the linear polymerization of the corresponding difunctional monomers were followed by both UV and 1H NMR spectroscopy. The results obtained from this study provided clear-cut indications about the most appropriate conditions to be applied in the preparation of novel macromolecular materials based in part on renewable resources and possessing thermoreversible, mendable and recycling features, among other properties. 相似文献