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991.
Audrey A S G Lonni Ieda S Scarminio Lucas M C Silva Dalva T Ferreira 《Analytical sciences》2003,19(7):1013-1017
Phytochemical investigation of the aerial parts of three Baccharis species (Asteraceae family) was performed using HPLC and chemometric methods, with the objective of distinguishing between three morphologically very similar species: Baccharis genistelloides Persoon var. trimera (Less.) DC, B. milleflora (Less.) DC and B. articulata (Lam.) Persoon. With the help of Principal Component Analysis (PCA) and variance weights, it was possible to characterize the chromatographic profiles of the alcoholic extracts of the three species. Application of Soft Independent Modeling of Class Analogy (SIMCA) and K-Nearest Neighbor (KNN) methods on a training set of 74 extracts resulted in models that correctly classified all eight samples in an independent test set. 相似文献
992.
On the capacitated vehicle routing problem 总被引:1,自引:0,他引:1
We consider the Vehicle Routing Problem, in which a fixed fleet of delivery vehicles of uniform capacity must service known
customer demands for a single commodity from a common depot at minimum transit cost. This difficult combinatorial problem
contains both the Bin Packing Problem and the Traveling Salesman Problem (TSP) as special cases and conceptually lies at the
intersection of these two well-studied problems. The capacity constraints of the integer programming formulation of this routing
model provide the link between the underlying routing and packing structures. We describe a decomposition-based separation
methodology for the capacity constraints that takes advantage of our ability to solve small instances of the TSP efficiently.
Specifically, when standard procedures fail to separate a candidate point, we attempt to decompose it into a convex combination
of TSP tours; if successful, the tours present in this decomposition are examined for violated capacity constraints; if not,
the Farkas Theorem provides a hyperplane separating the point from the TSP polytope. We present some extensions of this basic
concept and a general framework within which it can be applied to other combinatorial models. Computational results are given
for an implementation within the parallel branch, cut, and price framework SYMPHONY.
Received: October 30, 2000 / Accepted: December 19, 2001 Published online: September 5, 2002
Key words. vehicle routing problem – integer programming – decomposition algorithm – separation algorithm – branch and cut
Mathematics Subject Classification (2000): 20E28, 20G40, 20C20 相似文献
993.
E. Casarejos P. Armbruster L. Audouin J. Benlliure M. Bernas A. Boudard R. Legrain S. Leray B. Mustapha S. Czajkowski T. Enqvist B. Fernandez J. Pereira M. Pravikoff F. Rejmund K. -H. Schmidt C. Stephan J. Taieb L. Tassan-Got C. Villagrasa C. Volant W. Wlazlo 《Physics of Atomic Nuclei》2003,66(8):1413-1420
The isotopic production cross sections of heavy residues in relativistic heavy-ion collisions have been investigated in inverse kinematics. The primary reaction products were fully identified in mass and atomic number prior to beta decay using the fragment separator FRS. The huge collection of data obtained helps in the understanding of the two main reaction mechanisms involved: fragmentation and fission. These data provide basic information for future radioactive ion beam facilities and for technical applications like intense neutron sources by means of spallation targets. 相似文献
994.
A transverse flow, transverse discharge cw CO2 laser in which de discharge is sustained by employing high repetition rate high voltage pulses has been developed. Pulser
sustained discharge through electrodes of innovative design provided uniform excitation at electrical input power densities
more than 10 W/cc. Laser output power more than 2.5 kW was obtained in a laser gas mixture consisting of 0.5 mbar of CO2, 16 mbar of N2 and 38.5 mbar of He. Design details and operational characteristics of this laser are presented. 相似文献
995.
996.
Yanfei Lü 《中国光学快报(英文版)》2007,5(6)
A new resonator design for doubly resonant continuous-wave (CW) intracavity sum-frequency mixing (SFM) is reported. 1.12 W of coherent radiation at 588 nm is generated by mixing 1062-nm Nd:GdVO4laser and 1319-nm Nd:YAG laser. The optical-to-optical conversion efficiency is up to 3.7%. 相似文献
997.
G.G.L. Nashed 《The European Physical Journal C - Particles and Fields》2007,49(3):851-857
An exact charged solution with axial symmetry is obtained in the teleparallel equivalent of general relativity. The associated metric has the structure function G(ξ)=1-ξ2-2mAξ3-q2A2ξ4. The fourth order nature of the structure function can make calculations cumbersome. Using a coordinate transformation we get a tetrad whose metric has the structure function in a factorizable form (1-ξ2)(1+r+Aξ)(1+r-Aξ) with r± as the horizons of Reissner–Nordström space-time. This new form has the advantage that its roots are now trivial to write down. Then, we study the singularities of this space-time. Using another coordinate transformation, we obtain a tetrad field. Its associated metric yields the Reissner–Nordström black hole. In calculating the energy content of this tetrad field using the gravitational energy-momentum, we find that the resulting form depends on the radial coordinate! Using the regularized expression of the gravitational energy-momentum in the teleparallel equivalent of general relativity we get a consistent value for the energy. 相似文献
998.
Let Top
0
be the category of topological T
0-spaces, QU
0
the category of quasi-uniform T
0-spaces, T : QU
0
→ Top
0
the usual forgetful functor and K : QU
0
→ QU
0
the bicompletion reflector with unit k : 1 → K. Any T-section F : Top
0
→ QU
0
is called K-true if KF = FTKF, and upper (lower)
K-true if KF is finer (coarser) than FTKF. The literature considers important T-sections F that enjoy all three, or just one, or none of these properties. It is known that T(K,k)F is well-pointed if and only if F is upper K-true. We prove the surprising fact that T(K,k)F is the reflection to Fix(TkF) whenever it is idempotent. We also prove a new characterization of upper K-trueness. We construct examples to set apart some natural cases. In particular we present an upper K-true F for which T(K,k)F is not idempotent, and a K-true F for which the coarsest associated T-preserving coreflector in QU
0
is not stable under K.
We dedicate this paper to the memory of Sérgio de Ornelas Salbany (1941–2005). 相似文献
999.
Small‐Angle Neutron Scattering has been performed from poly(ethylene oxide) in deuterated water at temperature ranging from 10 to 80 °C. A simple fitting model was used to obtain a correlation length and a Porod exponent. The correlation length L characterizes the average distance between entanglements in the semidilute region and is proportional to the individual coil sizes in the dilute region. L was found to increase with temperature in the semidilute region but it decreases with temperature in the dilute region. This decrease is the precursor to the single‐chain collapse which applies to very dilute polymer solutions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2196–2200, 2007 相似文献
1000.
M. G. Voronkov S. G. D’yachkova I. P. Lebedeva A. V. Evart L. G. Shagun 《Russian Journal of General Chemistry》2007,77(4):604-606
Alkylthiochloroacetylenes react with geminal (in ether) and vicinal (in THF) dithiols to form, respectively, functional 1,3-dithiolenes (yield 43%) or 1,3-dithiolanes (yield 34%). 相似文献