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91.
92.
da Costa Silva F. Barroso de Assis Fonseca S. Soares A.J.M. Giarola A.J. 《Antennas and Propagation, IEEE Transactions on》1991,39(9):1398-1404
The use of dyadic Green's functions and the moment method is explored for the solution of microstrip antenna problems on circular cylindrical substrates. The dyadic Green's functions of the electric type are obtained for a medium consisting of three cylindrical dielectric layers concentric with a perfectly conducting cylinder, and integral equations are developed for the evaluation of the electromagnetic fields. The effect of a dielectric overlay on the resonant frequency of a cylindrical-rectangular microstrip antenna is analyzed. The patch is directly fed by means of a microstripline printed along the cylinder axial direction. The results show that the effect of the dielectric overlay is substantial when its relative permittivity and thickness are increased, such that this effect has to be very carefully considered in the design of microstrip antennas 相似文献
93.
A. Fonseca K. Hernadi P. Piedigrosso J.-F. Colomer K. Mukhopadhyay R. Doome S. Lazarescu L.P. Biro P. Lambin P.A. Thiry D. Bernaerts J.B. Nagy 《Applied Physics A: Materials Science & Processing》1998,67(1):11-22
The quantities of deposited carbon were measured and the quality of the nanotubes was characterized by means of transmission
electron microscopy and scanning tunneling microscopy. The inner and outer diameters of the nanotubes were also measured and
the diameter distribution histograms were established. The multi-wall straight and coiled nanotubes were found to be quite
regular with an average inner (outer) diameter of 4–7 nm (15–25 nm) and with lengths up to 50 μm. The walls contain concentric
cylindrical graphene sheets separated by the graphitic interlayer distance. The single-wall nanotubes were found as bundles
of hundreds of aligned straight 1-nm-diameter nanotubes with lengths up to 1-μm.
The influence of various parameters such as the method of catalyst preparation, the nature and the pore size of the support,
the nature of the metal, the quantity of catalyst active particles, and the reaction conditions on the nanotubes formation
were studied. The numbers and dimensions of the catalyst active particles dispersed on the support were found to be of importance
in regulating the shape of the produced nanotubes. Following these results, a model of growth mechanism was suggested for
the nanotubes obtained by this method.
Received: 5 January 1998 相似文献
94.
A Global Method for Relaxation 总被引:3,自引:0,他引:3
Guy Bouchitté Irene Fonseca Luisa Mascarenhas 《Archive for Rational Mechanics and Analysis》1998,145(1):51-98
A new method for the identification of the integral representation of a class of functionals defined on (where represents the family of open subsets of Ω) is presented. Applications are derived, such as the integral representation of
the relaxed energy in corresponding to a functional defined in with a discontinuous integrand with linear growth; relaxation and homogenization results in are recovered in the case where bulk and surface energies are present.
(Accepted April 20, 1998) 相似文献
95.
V. Fonseca G. Mageras D. Son H. Dietl G. Eigen P. Franzini K. Han S.W. Herb J.E. Horstkotte R. Imlay C. Klopfenstein J. Lee-Franzini G. Levman E. Lorenz W. Metcalf F. Pauss L. Romero T. Zhao 《Nuclear Physics B》1984,242(1):31-50
We present a detailed study of the decays ?′ → π+π?? and ?′ → π0π0?, where the ? decays subsequently to e+e? or μ+μ?. The results are obtained from a sample of 146 000 ?′ decays observed with the CUSB detector at the Cornell Electron Storage Ring. We derive branching fractions of (18.9 ± 2.6)% for ?′ → π′π?? and (10.3 ± 2.3)% for ?′ → π0π0?, and determined partial widths for these decays. Invariant mass and angular distributions of both the π+π? and π0π0 systems are presented. We also set a limit on the branching fraction for ?′ → η? of less than 0.2% at the 90% confidence level. 相似文献
96.
97.
A three-body problem is studied that involves the scattering of a heavy particle from a bound state of a heavy and a light particle. For fairly large mass ratios we find many partial waves involved in the scattering with both elastic and inelastic resonances present. It is also found that virtually all of the breakup inelasticity is in the odd partial waves, if the heavy particles are identical bosons. The same problem is solved in the Born-Oppenheimer approximation and it is found that the effective potential between the heavy particles develops an imaginary part in the odd partial waves and thus gives a quantitative account of the three-body results including the inelasticity. The linear combination of nuclear orbitais method is applied to the same problem and is found to be inadequate. 相似文献
98.
Luís Felipe Gonçalves Fonseca 《代数通讯》2018,46(4):1630-1640
Let F be an infinite field and let Mn(F) be the algebra of n×n matrices over F endowed with an elementary grading whose neutral component coincides with the main diagonal. In this paper, we find a basis for the graded polynomial identities of Mn(F) with the transpose involution. Our results generalize for infinite fields of arbitrary characteristic previous results in the literature, which were obtained for the field of complex numbers and for a particular class of elementary G-gradings. 相似文献
99.
M. Conceição Fonseca Álvaro García-Sánchez Miguel Ortega-Mier Francisco Saldanha-da-Gama 《TOP》2010,18(1):158-184
In this paper we propose a comprehensive model for reverse logistics planning where many real-world features are considered
such as the existence of several facility echelons, multiple commodities, choice of technology and stochasticity associated
with transportation costs and waste generation. Moreover, we adopt a bi-objective model for the problem. First, the cost for
building and operating the network is to be minimized. Second, the obnoxious effect caused by the reverse network facilities
is also to be minimized. A two-stage stochastic bi-objective mixed-integer programming formulation is proposed, in which the
strategic decisions are considered in the first stage and the tactical/operational decisions in the second one. A set of different
scenarios is considered, and the extensive form of the deterministic equivalent problem is presented. This model is tested
with a case study based on some data from the Spanish province of Cordoba. Nondominated solutions are obtained by combining
the two different objectives and by using a general solver. 相似文献
100.