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71.
M.P. Estellita Lins A.C. Moreira da Silva C.A.K. Lovell 《European Journal of Operational Research》2007
The flexibility of weights assigned to inputs and outputs is a key aspect of DEA modeling. However, excessive weight variability and implausible weight values have led to the development of DEA models that incorporate weight restrictions, reflecting expert judgment. This in turn has created problems of infeasibility of the corresponding linear programs. We provide an existence theorem that establishes feasibility conditions for DEA multiplier programs with weight restrictions. We then propose a linear model that tests for feasibility and a nonlinear model that provides minimally acceptable adjustments to the original restrictions that render the program feasible. The analysis can be applied to restrictions on weight ratios, or to restrictions on virtual inputs or outputs. 相似文献
72.
We consider typical analytic unimodal maps which possess a chaotic attractor. Our main result is an explicit combinatorial formula for the exponents of periodic orbits. Since the exponents of periodic orbits form a complete set of smooth invariants, the smooth structure is completely determined by purely topological data (“typical rigidity”), which is quite unexpected in this setting. It implies in particular that the lamination structure of spaces of analytic unimodal maps (obtained by the partition into topological conjugacy classes, see [ALM]) is not transversely absolutely continuous. As an intermediate step in the proof of the formula, we show that the distribution of the critical orbit is described by the physical measure supported in the chaotic attractor. 相似文献
73.
P.J. Iunes G. Bigazzi J.C. Hadler Neto M.A. Laurenzi M.L. Balestrieri P. Norelli A.M. Osorio Araya S. Guedes C.A. Tello S. S.R. Paulo P.A.F.P. Moreira R. Palissari E.A.C. Curvo 《Radiation measurements》2005,39(6):665-668
Neutron dosimetry based on U and Th thin films was used for fission-track dating of the age standard Moldavite, the central European tektite, from the Middle Miocene deposit of Jankov (southern Bohemia, Czech Republic). Our fission-track age () agrees with a recent 40Ar/39Ar age, , based on several determinations on Moldavites from different sediments, including the Jankov deposit. This result indicates that the U and Th thin film neutron dosimetry represents a reliable alternative for an absolute approach in fission-track dating. 相似文献
74.
The transverse modes of a laser resonator comprising a near 90° roof-top mirror and a feedback mirror are studied theoretically. We relate this configuration to an almost plane roof-top resonator and apply the Fox and Li technique to compute the lowest-order symmetric and antisymmetric modes. The effects of perturbations to the vertex angle of the roof-top mirror, misalignments of the feedback mirror and curved feedback mirrors are examined. 相似文献
75.
We show that the Sal'nikov thermokinetic oscillator system has at least two limit cycles, an unstable one lying inside a stable one. The proof uses the elementary technique of Liénard's equation. 相似文献
76.
A. Righi J.P. Salvestrini P. Bourson R.L. Moreira M.D. Fontana 《Applied physics. B, Lasers and optics》1998,67(5):559-562
1-x RbxSO4 for x varying between 0 and 0.50 were investigated by an ac modulation method based upon the Sénarmont arrangement. The electro-optic
coefficient rc, and for the first time the coefficients r41 and r51 were determined with good accuracy in pure LiKSO4 around room temperature at a wavelength of 633 nm. The frequency dependence of the electro-optic coefficient rc was measured in the frequency range from 1 kHz up to 1 MHz. The values of the factor of merit ne
3rc of the mixed crystals LiK1-xRbxSO4 were obtained for the first time, for the concentrations x=0.05, 0.10, 0.20, and 0.50. The electro-optic properties are shown
to be affected by the random presence of the rubidium ions in this disordered system.
Received: 16 March 1998/Revised version: 2 June 1998 相似文献
77.
The composition of iron(III) precipitates prepared by different methods was investigated by Mossbauer and infrared spectrometry. The principal constituents were identified as α-FeOOH, β-FeOOH, α-Fe2O3, and the van der Giessen precipitate, α-Fe2O3· nH2O. Effects of chloride ion and formic acid on the products of precipitation were studied. 相似文献
78.
The indirect interaction between localized magnetic moments in insulators and semiconductors is investigated at T = 0°K. This interaction arises from virtual excitations of the valence electrons to the conduction band and is oscillatory as a function of distance. The passage from the case of small gap semiconductors to insulators is studied in detail, as a function of the energy gap and the effective masses. The Bloembergen-Rowland interaction is derived as a limiting case for insulators. Possible applications are also discussed. 相似文献
79.
The cashew apple is native to Brazil, but there is insufficient information regarding the nutritional properties of this fruit. The objective of this study was to evaluate the impact of high pressure processing (HPP) at room temperature (25 °C) on phenolic compound and ascorbic acid contents and antioxidant capacity of cashew apple juice. This study showed that HPP at 250 or 400 MPa for 3, 5 and 7 min did not change pH, acidity, total soluble solids, ascorbic acid or hydrolysable polyphenol contents. However, juice pressurized for 3 and 5 min showed higher soluble polyphenol contents. Antioxidant capacity, measured by the ferric-reducing antioxidant power method, was not altered by HPP, but when treated at 250 MPa for 3 min, it resulted in an increased value when 2,2-diphenyl-1-picrylhydrazyl was used. These data demonstrate that HPP can be used in the food industry for the generation of products with higher nutritional quality. 相似文献
80.
ABSTRACT A systematic investigation on the influence of the diffusion parameters (time and temperature) and initial titanium film thickness on the spectral characteristics of the LiNbO3 Raman modes is reported. Raman spectra are measured in the range 50–1000 cm?1 ~2 µm below the surface of the crystals. Broadening of the Raman lines and, therefore, crystal lattice disorder induced by the titanium ions are found to depend on the fabrication parameters. The disorder associated with the titanium ions near the surface of LiNbO3 is encoded in the broadening of the A1(TO1) Raman line. A linear relation between the A1(TO1) mode broadening and the Ti concentration is presented. The diffusion theory is used to explain the experimental data. Raman spectroscopy combined with diffusion theory can be used to estimate the evolution of the titanium surface concentration. 相似文献